Targeting β-cell failure could prevent, delay or even partially reverse Type 2 diabetes. However, development of such drugs is limited as the molecular pathogenesis is complex and incompletely understood. Further, while β-cell failure can be modeled experimentally, only some of the molecular changes will be pathogenic. Therefore, we used a novel approach to identify molecular pathways that are not only changed in a diabetes-like state but also are reversible and can be targeted by drugs. INS1E cells were cultured in high glucose  for 72 h or HG for an initial 24 h followed by drug addition  for the remaining 48 h. RNAseq (Illumina TruSeq), gene set enrichment analysis (GSEA) and pathway analysis  were used to identify changes in molecular pathways. HG decreased function and increased apoptosis in INS1E cells with drugs partially reversing these effects. HG resulted in upregulation of 109 pathways while drug treatment downregulated 44 pathways with 21 pathways in common. Interestingly, while hyperglycemia extensively upregulated metabolic pathways, they were not altered with drug treatment, rather pathways involved in the cell cycle featured more heavily. GSEA for hyperglycemia identified many known pathways validating the applicability of our cell model to human disease. However, only a fraction of these pathways were downregulated with drug treatment, highlighting the importance of considering druggable pathways. Overall, this provides a powerful approach and resource for identifying appropriate targets for the development of β-cell drugs.  At the time of diagnosis, patients have usually already lost over 50% of their β-cell function and this continues to decline.1–4 Along with this decline in function, there is also a continuous decline in β cell mass, mainly due to an increase in apoptosis.5 Clinically, this manifests as a requirement for additional therapies to maintain adequate glycemic control.6 Thus, the most efficient way to treat T2D would be to prevent or delay the onset of the disease by halting or slowing the progression of β-cell failure. Further, as β-cell dysfunction in T2D can be viewed as reversible, at least in the early years of the disease (<10 y),7 pharmacological interventions aimed at protecting the β-cells can potentially be used to restore, or at least prevent further loss of, β-cell function in subjects with diagnosed T2D which would result in better patient outcomes.β-Cell dysfunction, a combination of reduced β-cell secretory function and reduced β-cell mass, is an absolute requirement for the development of Type 2 diabetes (T2D).9 This could be due to the inability of these medications to target the root causes of the disease, especially the progressive decline in β-cell mass and function.11 In fact, no pharmacological agent has yet been shown to be capable of changing the natural course of β-cell dysfunction.12The increasing prevalence of T2D has led to different approaches in the discovery of new therapeutic targets for the treatment of hyperglycemia. Currently, there are several different drugs available; however, achieving and maintaining long-term glycemic control are still challenging with only 50% of the patients able to meet target glycemic levels.13 What is clear is that β-cell failure is not a simple process but involves many different stressors, and despite much research it is not clear which pathway is disrupted first.13 However, even though several pathways are involved it has been suggested that given the likely overlap, crosstalk and convergence between pathways, targeting a single molecule could still affect multiple stressor pathways and have beneficial effects on β-cells.13 What is common for all of these pathways however is the upstream stressors of increased metabolic load and insulin resistance (demanding increased insulin release)13 each of which can be modeled experimentally by inducing chronic hyperglycemic stress. In fact, it has been suggested that initiating therapies aimed against β-cell glucose toxicity in the early stages of the disease will be of the utmost importance in treating and preventing T2D.14 It has also been suggested that the appropriate therapy needs to be selected based on the molecular mechanisms of glucose toxicity.15 However, given that the full molecular mechanisms of glucose toxicity are complicated and yet to be elucidated, this is very difficult. In addition, while hyperglycemia is bound to result in extensive molecular changes within the β-cell, only some of these changes will be involved in the pathology of β-cell failure. Therefore, identifying which changes are important to target therapeutically remains a challenge.Stressors on the β-cell thought to contribute to decreased β-cell function and mass include inflammatory stress, endoplasmic reticulum (ER) stress, metabolic/oxidative stress, amyloid stress and stressed islet integrity.16–22In complex disease like T2D, there are many genes involved which affect biological function in groups rather than alone. Therefore it may be more effective to understand the signaling pathways involved in the pathological mechanisms rather than individual genes. Other studies have used pathway-based genetic approaches to obtain interesting and relevant pathway outcomes linked to complex diseases such polycystic ovary syndrome, bipolar disorder, coronary artery disease, Crohn’s disease, hypertension, rheumatoid arthritis, Type 1 diabetes, and T2D illustrating the potential of a pathway-based approach in characterizing and identifying novel pathways associated with complex disease.23–26 Finding out what pathways are involved in a disease and identifying which of these pathways are affected in each patient may provide more understanding of T2D and could lead to new strategies for diagnosing, treating and preventing disease. However, whether these pathways are altered as a result of the disease or are involved in the pathogenesis of the disease can be difficult to determine. Further, whether these can be effectively targeted pharmacologically, and result in an improvement in the disease state is uncertain. Hence, in this study, we have taken a new approach to this type of analysis. Here we looked at the pathways that are not only changed in a diabetes-like state but are also reversible and can be targeted by drugs. To our knowledge, this is the first study of this kind, which looks at both induction and reversal of dysfunction. This study therefore provides a novel insight into the transcriptional changes accompanying dysfunction of β-cells as well as the successful reversal of dysfunction.Previous studies have identified pathways associated with T2D by comparing nondiabetic and diabetic subjects.We propose that by using a cocktail of drugs that can successfully treat β-cells undergoing hyperglycemic stress, we can not only prolife the global transcriptomic changes that occur under hyperglycemic conditions but also identify those changes that are reversible pharmacologically. By identifying the pathways that reverse with successful treatment of β-cells, we suggest that this can contribute to target drug design efforts to overcome the current difficulty in identifying drugs that have an overall beneficial effect to protect β-cells in T2D.INS 1E cells were treated with Roswell Park Memorial Institute 1640 medium (Gibco Thermo Fisher) supplemented with 10% heat-inactivated fetal bovine serum (Gibco Thermo Fisher), 1% sodium pyruvate, 0.05 mM 2-mercaptoethanol, 1% HEPES and 1% penicillin and streptomycin containing either standard 11.1 mM glucose  treatment) or 20 mM glucose (as a high glucose (HG) treatment). It should be noted that a glucose concentration of 11.1 mM is considered normal in culture of β-cells and islets.For reversal of the HG effects, a cocktail of agents  was added in the final 48 h of the 72-h treatment.27 Insulin measurements were normalized to cell number, determined by the CyQUANT Assay (Molecular Probes) as per the manufacturer’s directions.INS-1E cells were first reset to their basal state by incubation for 30 min with 2 mM glucose Krebs–Ringer bicarbonate HEPES (KRBH) buffer. The buffer was then changed to KRBH containing either 2 mM glucose  or 20 mM glucose (stimulated) for 45 min and the supernatant collected for insulin measurement using the Mouse Insulin Ultra-Sensitive ELISA kit (Alpco Diagnostics).Caspase-3/7 activity was measured using the Caspase-glo 3/7 assay kit (Promega Biosciences) as per manufacturer’s instructions.p < .05 considered significant.Twenty  independent experiments, each with triplicate repeats, was performed. Insulin secretion and apoptosis data were normally distributed and were compared by two-way analysis of variance using least significant difference post hoc analysis with n = 20) were collected in TRIzol reagent (Invitrogen), RNA extracted by chloroform/ethanol extraction followed by purification using RNeasy Mini columns (Qiagen). The quality and quantity of the RNA were determined using the Agilent Bioanalyzer (Agilent Technologies) and RNA 600 Nano Assay kit (Agilent).28 Samples with an RNA Integrity Number (RIN) value ≥7 were deemed sufficient quality for RNAseq .Treated INS1E cells (Samples were prepared using the Illumina TruSeq RNA Sample Preparation Kit v2 (Illumina) using TruSeq RNA Sample Preparation v2 LS protocol and 15 indexed adapters as per the manufacturer’s instructions. Verification of the size of PCR enriched fragments was performed using Agilent 2100 Bioanalyzer (Agilent Technologies) and a DNA 1000 chip. To quantify the prepared libraries, qPCR was used according to the Illumina qPCR Quantification Protocol Guide. Indexed DNA samples were normalized to 10 nM and the DNA templates were pooled together for cluster generation in four batches of 15 samples. Next-generation sequencing was then performed using lllumina’s HiSeq 2500 (San Diego).https://basespace.illumina.com). Quality control of the raw sequence data was performed using the BaseSpace app FastQC Version 1.0.0.29 One sample was not of sufficient quality and was excluded from further analysis, while all other samples exceeded the minimum quality value and were well above Q30 . The sequences were trimmed to remove adapter sequences using FASTQ Toolkit Version: 2.0.0 by BaseSpace Labs30 and then aligned against the reference genome (Rattus norvegicus UCSC rn5 (RefSeq gene annotations)) using TopHat Alignment app by Illumina.31 Quantification or Fragments Per Kilobase of transcript (FPKM) estimation of the reference genes and transcripts were performed using Cufflinks 2.32 The data discussed in this publication have been deposited in NCBI’s Gene Expression Omnibus33 and are accessible through GEO Series accession number GSE218540 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE218540).RNAseq data analysis was performed using Illumina BaseSpace cloud computing environment (n = 19–20) was first corrected using software packages developed in version 2.6.0 of Bioconductor and R version 2.10.135 and adjusted for false discovery rate (FDR). The resulting data were then analyzed using the GSEA software developed by the Broad Institute as per their instructions36 using treatment group  as a categorical label and the platforms Reactome, KEGG and Biocarta. Using a permutation test with 1,000 repetitions, the cutoff of significance level p-values was chosen as <0.05 for the significant pathways with any gene sets that had <10 genes and >500 genes being excluded to avoid inflated scores for small gene sets and inaccurate normalization for larger gene sets. From this analysis, genes were ranked based on their magnitude of the difference in expression between the phenotypic states. The key scores for this analysis were as follows: (1) Normalized Enrichment Score (NES): the degree to which a set of genes is overrepresented with the magnitude of the increment dependent on the correlation of the gene to the phenotype normalizing to the size of the gene set, (2) FDR corresponding to each NES to correct for gene set size and multiple hypotheses testing. An FDR ≤0.25 is recommended by the software developers to identify significantly associated gene sets.37 The gene sets with an FDR <0.25 were considered for the NG vs HG analysis and an FDR <0.3 for HG vs HG + drugs . As the final step, each pathway was classified based on its function as identified in Reactome and manually assigned to functional classes.RNAseq data  before they lose too much β-cell functional mass that the treatment would not be effective. Therefore, we aimed to use a cell model where early dysfunction has been induced, but some function still remains. INS-1E cells were cultured in HG (20 mM) to induce dysfunction. After 24 and 48 h in HG, GSIS was reduced by 38 ± 3.7% and 61 ± 9.6%, respectively . The dec39 Exendin-4 is a GLP-1 receptor agonist that can directly increase insulin secretion and proliferation40 while NaS is an anti-inflammatory agent that has also been shown to have direct, positive effects on islets.41 Thus, while this combination of drugs is not routinely used in patients, each of the drugs acts via a different mechanism to protect β-cells. Therefore, by using the combination of these drugs the resultant pathway findings would be more likely to be representative of the overall function of the cells rather than showing the effect of a single drug.Several drugs were screened for their ability to reverse dysfunction. The final cocktail and the concentrations used (50 nM exendin-4 and 250 μM NaS) were selected so that each drug had an intermediate effect on cell function and/or apoptosis and the effect of one drug would not be predominant (250 μM metformin). This was to ensure that the resultant pathway results would not simply represent the effects of one drug but be more representative of the functional state of the cells. Metformin, a common treatment for T2D acting on the liver to reduce glucose production, has also been shown to have a direct effect on β-cells and islets to increase viability and function.The final cell model is represented in There were clear differences in overall gene expression in cells treated with HG compared to those treated with NG . When ceGSEA was then performed on all genes to allocate them into gene sets based on their known functions. No pathways were significantly reduced with HG treatment compared to NG, but 109 pathways were significantly increased . To get a better understanding of these gene set pathways, they were then mapped into functional classes. These 109 pathways could be mapped into seven functional classes: ‘cellular processes/cell cycle,’ ‘metabolism,’ ‘signal transduction,’ ‘apoptosis,’ ‘neuronal systems,’ ‘human diseases’ and ‘extracellular matrix’ . The maj‘metabolism,’ ‘signal transduction,’ ‘apoptosis,’ ‘neuronal systems,’ ‘extracellular matrix,‘immune responses’ and ‘cellular stress’ . These pathways were then mapped into functional classes revealing significant changes in genes involved in the control of several aspects of β-cell function such as, ‘cellular processes/cell cycle,’  stress’ .Of the 109 pathways enriched with HG and the 44 pathways downregulated by drug treatment, 21 pathways were common . There wCell Cycle pathway show that the vast majority of genes in this pathway were upregulated with HG vs LG . Of these, 13 pathways were common. HG vs LG  and downHG vs LG .Figure ’ show that almost all genes were upregulated with HG . Treatment with drugs resulted in only five metabolism pathways being downregulated , four of which were reversing the effect of HG . These p with HG  and down with HG .Figure ’ and the ‘DARPP 32 events pathway’ . Eight pathways were downregulated with drugs  with two pathways in common, the ‘insulin pathwaypathway’ . Again, pathway’  and downpathway’ .Figure ’) in common . Two pathways were downregulated with HG + drugs  with one pathway , two significantly downregulated with HG + drugs  with one in common . Almost  with HG  and down with HG .Figure This study attempted to tackle the issue of finding appropriate drug targets for the protection of β-cells in a novel way. We suggest that obtaining a comprehensive view of transcriptional changes associated with β-cell dysfunction and restoration of function, we could identify those pathways that are druggable. Ultimately this information could contribute to drugs that improve β-cell function and survival. The analysis revealed several pathways associated with β-cell function which have important roles in various functions such as cellular processes, metabolism, signal transduction, apoptosis, neuronal systems and human diseases. Interestingly HG induced global upregulation of pathways associated with β-cell function but did not result in downregulation of pathways. Further, successful drug treatment only resulted in downregulation of pathways, some of which were reversing the effects of HG. Cellular processes and metabolism were the top functional class identified by HG vs NG analysis, whereas cellular processes and signal transduction were the top functional class regulated in the reversal group. Therefore, the reversal group showed a shift from the metabolic pathways toward signal transduction and other cellular functions.Many of the gene sets identified by the HG vs NG GSEA analysis did not appear in the HG + drugs vs HG analysis. This is expected as the most important implication of this study was to select out the pathways that are simply regulated by HG from those that are more likely to play a role in the function and health of the β-cell. Thus, it is likely that only those pathways that are vitally relevant to the function and health of β-cell would have been reversed with the successful drug treatment. Moreover, this disparate transcriptional response could also imply that there may be some differences in the mechanisms that lead to the induction of β-cell dysfunction compared to the reversal of dysfunction, or in other words, the drug combination may have acted on the cells in a different way to improve cell function and viability. However, some of the pathways are also common in both analyses suggesting the drugs may had some direct effects to reverse pathways altered by HG.‘Cellular Processes/Cell Cycle’ was the most highly represented functional class among both analysis (HG vs NG and HG + drugs vs HG). The majority of these pathways are associated with cell division, proliferation and survival. Several of these pathways were upregulated in the HG phenotype which have previously known functions in β-cell proliferation and insulin secretion.42–45 The upregulation of these pathways suggests that β-cells are attempting to enter the cell cycle, possibly to expand mass to compensate for the demands of hyperglycemia. A similar effect is seen in response to an insulin resistant state such as obesity or pregnancy, where β-cell mass expands to adjust with the increased insulin demand partly due to β-cell proliferation.46–48 Multiple cell cycle pathways were restored with drugs suggesting that the increased demand may be partially restrained.‘Metabolism.’ This is expected as β-cells are highly metabolically active and hyperglycemia has previously been shown to alter the expression of genes involved in multiple metabolic pathways from normal β-cell glucose metabolism.49–52 There were also several pathways upregulated by HG involved in gene expression (involving PGCA1 and RNA polymerase III) as well as overall RNA and protein metabolism. This is consistent with the large transcriptional changes that were observed in HG vs NG and also indicates an increase in protein production in response to these changes. This could also indicate increased protein synthesis for growth in response to HG.53 Importantly, there were increases in pathways involving glucose metabolism, as would be expected under HG conditions. Moreover, pathways associated with fatty acid and triglyceride biosynthesis and metabolism of lipids and lipoproteins, were also upregulated validating previous studies showing an adaptive response of chronic exposure of β-cells to HG by inducing glycolytic and lipogenic genes in conjunction with glycogen and triglyceride deposition, as well as increased anaplerosis and altered lipid partitioning.54The second major functional class identified by our study was 26 our data suggest that there may be other functional pathways which may play a greater role in improving β-cell function than the previously appreciated metabolic pathways. Moreover, Webb et al., in their study to identify genes involved in insulin secretion and synthesis by pancreatic β-cells, suggested that glucose metabolism may play a lesser role in improving β-cell function,26 which concurs with our current findings. Overall, while several studies have focused on identifying targets to modify changes in the metabolic pathways in diabetes,55 our study demonstrates that targeting metabolic pathways may not be an ideal way to improve β-cell function and viability.Surprisingly, compared to the number of metabolic pathways affected with, only a fraction of metabolic pathways were reversed with the drugs. This could suggest that the upregulation of several metabolic pathways in the HG vs LG group associated with metabolism could be mainly due to the orchestration of general effects of HG rather than its actual role in the pathology of the disease. Thus, drugs that target these pathways may not be greatly beneficial in treating β-cell dysfunction. However, the reversal of some metabolic pathways with HG + drugs treatment suggests that the drugs that can improve β-cell function could eventually restore the dysfunctionality in metabolism caused by HG. This is crucial information as to our knowledge no previous studies have demonstrated the effect of the reversal of dysfunction on these pathways. Thus, although metabolism has been demonstrated to be uniquely important in β-cell function,56 Similarly, ‘DARPP 32 events pathway is a key component of the insulin signaling pathway which is responsible for bridging the initial insulin-stimulated phosphorylation cascade with the ultimate dephosphorylation of insulin sensitive substrates.57 However, there is little information available for the DARPP32 pathway in β-cells. DARPP32 (dopamine- and cyclic-AMP-regulated phosphoprotein) is a neuronal phosphoprotein, which is an inhibitor of protein phosphatase 1 (PP1). The presence of DARPP32 in β-cell has been previously studied by Lilja et al., where they indicated its potential role in the regulation of PP1 activity in pancreatic β-cell stimulus-secretion coupling.58 However, it is still unclear how this plays a role in β-cell function. Hence our study proposes a likely role of DARPP32 events pathway in the restoration of β-cell function which warrants further investigation.Our study demonstrated that several ‘signal transduction pathways’ were also upregulated with HG treatment mainly involved in β-cell insulin secretion, cell differentiation, proliferation and survival. The upregulation of these pathways in our HG treated group suggests a possible attempt of these cells to maintain appropriate β-cell mass, insulin production and survival in response to hyperglycemia. However, only ‘Insulin Pathway’ and ‘DARPP32 Events’ were reversed with our drug treatment. The reversal of these pathways with our drug treatment suggests that these pathways are druggable and can be possible targets to improve β-cell and viability. The insulin pathway is not just crucial for insulin exocytosis but is also a positive regulator of β-cell mass and is equally crucial for protection against β-cell apoptosis.59–63 In T2D, β-cell mass is progressively decreased due to an increase in apoptosis.63–65 Hence, identification of pathways involved in cellular stress and apoptosis and targeting them with drugs could improve cell viability and thereby delay the progression of T2D. This study identified one pathway which was reversed with drug treatment, ‘BAD,’ suggesting that this pathway could perhaps be a potential target for improving cell viability. BAD, a proapoptotic Blc2 protein, has been considered as a multifunctional protein which could modulate both cell survival and cell death pathways.66 In pancreatic β-cells, BAD has been shown to have physiological role in the regulation of insulin secretion and β-cell mass.67 However, under HG condition, Bad expression is significantly upregulated.68 Moreover, evidence suggests that BAD plays an important role in HG-induced β-cell death in cultured human islets.69 The reversal of the BAD pathway with our drug treatment possibly suggests the druggability of the pathway for improving β-cell health.Our study also showed that cellular stress and apoptosis pathways were upregulated under the HG condition. These pathways have been heavily studied in β-cell dysfunction.70 Inhibition of NOS1 has shown to increase ER stress and activate JNK, therefore activation of NOS could protect β-cells from stress and apoptosis induced by glucolipotoxicity.65 Hence, upregulation of ‘NOS1 pathway’ with HG in our study could represent an adaptive response to glucotoxicity. This is supported by a previous study that demonstrated that NOS1 activation in glucolipotoxic condition is an adaptive response to protect β-cells from stress and apoptosis.65 Hence, modulation of the NOS1 pathway could possibly be beneficial for restoring β-cell viability/health.Lastly, our study showed the NOS1 pathway was significantly upregulated with HG and successfully reversed with the drug treatment. NOS1  has previously shown to have important role in normal β-cell function.Our GSEA analysis between control groups (HG vs NG) identified many known pathways, which validated the applicability of our cell model to human disease and the directionality of our current study. This group is important in providing clues to the pathogenesis of human T2D and may be of predictive value in efforts aiming at conferring β-cell protection against apoptosis, impaired regenerative capacity, and functional suppression occurring in diabetes. However, the novelty of this study was the inclusion of the reversal group (HG + drugs) that could provide valuable information on the pathways which can actually be modified by and targeted with drugs. The most interesting findings of this study were the conflicting evidence to the previous studies that focus on the metabolic pathways to restore insulin secretion and β-cell function. Features we found to be associated with restoration of β-cell function do not directly link to the metabolic pathways, instead we believe the alteration in the metabolic pathways could be a separate effect due to the prolonged hyperglycemic condition.Moreover, our study demonstrated the genome-wide integration of β-cell function at the level of transcript abundance and validates the efficacy of expression profiling in identifying gene sets/pathways involved in β-cell dysfunction and reversal of dysfunction. Overall, the described results demonstrate the widespread integration of important biological processes in β-cells and illustrates the complex dynamics of whole-cell adaptation to changes in glucose levels and the possibility of reversing this effect using drug treatments. Additionally, these findings demonstrating reversible pathways that are associated with resorted β-cell function may provide clues to the pathogenesis and possible drug targets for human T2D.Click here for additional data file.


BackgroundLonger post-polypectomy surveillance intervals are associated with increased colorectal neoplasia detection at surveillance in some studies. We investigated this association to inform optimal surveillance intervals.MethodsPatients who underwent colonoscopy and post-polypectomy surveillance at 17 UK hospitals were classified as low/high risk by baseline findings. We compared detection rates of advanced adenomas , high risk findings , or colorectal cancer (CRC) at surveillance colonoscopy by surveillance interval . Risk ratios (RRs) were estimated using multivariable regression.ResultsOf 11 214 patients, 7216 (64 %) were low risk and 3998 (36 %) were high risk. Among low risk patients, advanced adenoma, HRF, and CRC detection rates at first surveillance were 7.8 %, 3.7 %, and 1.1 %, respectively. Advanced adenoma detection increased with increasing surveillance interval, reaching 9.8 % with a 6-year interval (Ptrend < 0.001). Among high risk patients, advanced adenoma, HRF, and CRC detection rates at first surveillance were 15.3 %, 10.0 %, and 1.5 %, respectively. Advanced adenoma and CRC detection rates (Ptrends < 0.001) increased with increasing surveillance interval; RRs  for CRC were 1.54 (0.68–3.48), 4.44 (1.95–10.08), and 5.80 (2.51–13.40) with 3-, 4-, and 5-year intervals, respectively, versus an interval of < 18 months.ConclusionsMetachronous neoplasia was uncommon among low risk patients, even with long surveillance intervals, supporting recommendations for no surveillance in these patients. For high risk patients, a 3-year surveillance interval would ensure timely CRC detection. Colorectal cancer (CRC) can be prevented by removing premalignant polyps (PMPs)National surveillance guidelines classify patients’ risk by baseline polyp characteristics. The UK, US, and European Society of Gastrointestinal Endoscopy (ESGE) guidelines were updated in 2020No data exist on the effects of surveillance interval length on long-term post-polypectomy CRC outcomes. A randomized controlled trial examining CRC incidence with different surveillance intervals is underway, although results are not expected before 2029Our retrospective study used routine data from 17 UK hospitals on patients undergoing colonoscopy with polypectomy from 1984 to 2010 (87 % from 2000 to 2010). We used this cohort in previous studies examining long-term CRC incidence post-polypectomyTo be included, hospitals had to have electronic endoscopy and pathology records for colonic examinations for ≥ 6 years before the study start (2006). We searched endoscopy databases for patients with colonic examinations before the end of 2010 and pathology databases for colorectal lesions. We entered endoscopy and pathology data into a database. When the same polyp was described in multiple records, we combined data using rule hierarchies to create summary values for size, histology, and locationWe examined patients’ records to identify the first adenoma diagnosis, defined as “baseline.” The “baseline visit” included all examinations performed at baseline to completely examine the colon and remove detected lesions, sometimes spanning multiple days.To be included, patients had to have a colonoscopy and ≥ 1 adenoma at baseline. We excluded patients with the following: CRC or colectomy at/before baseline; Lynch syndrome or family history of familial adenomatous polyposis; polyposis, juvenile polyps, or hamartomatous polyps; inflammatory bowel disease or colitis; colorectal carcinoma in situ reported in registry data > 3 years pre-baseline; or examinations with no date recorded. We additionally excluded, from analysis, patients with insufficient information for risk classification by the UK (2020) guidelineWe collected data on colonic examinations performed after the baseline visit through 2016, combining them into surveillance visitsFor patients undergoing an examination > 6.5 years after their previous visit, we did not include this as surveillance because we thought it more likely that the patient was re-presenting with symptoms. We chose this cutoff based on the longest interval (5 years) recommended in the 2002 UK guideline (most examinations in our dataset occurred during the era of these guidelinesWe classified patients’ risk following the UK (2020) guidelineWe examined the proportion of high risk patients who were also classified as high risk by the ESGE (2020) guideline, which defines high risk patients as those with any serrated polyp (or adenoma) ≥ 10 mm or with (high grade) dysplasia, or ≥ 5 adenomasPrimary outcomes were incident advanced adenomas, HRFs, and CRC detected at first and second surveillance, ascertained using pathology data. Additionally, we obtained data on CRC diagnoses from the National Health Service (NHS) Central Register, National Services Scotland, and NHS Digital through 2016/17 (Scotland/England); any CRCs recorded in these databases but not in pathology data were included as outcomes.Advanced adenomas were adenomas ≥ 10 mm, with tubulovillous/villous histology, or with high grade dysplasia. HRFs were ≥ 2 PMPs, of which ≥ 1 was a serrated polyp (or adenoma) ≥ 10 mm or with (high grade) dysplasia; ≥ 5 PMPs; or ≥ 1 large (≥ 20 mm) nonpedunculated PMP, based on the UK (2020) guidelineWe defined CRCs as colorectal adenocarcinomas, including cancers with unspecified morphology located between the rectum and cecum (assumed adenocarcinomas), but not those located anally (assumed squamous cell carcinomas). In situ cancers were not included.Ethics approval for our original study involving patients included in the present study was granted by the Royal Free Research Ethics Committee (REC). Further ethics approval for protocol extension was granted by the London – Hampstead REC and the Health Research Authority . Approval for the processing of patient-identifiable information without consent was originally granted by the Patient Information Advisory Group (PIAG) under Section 60 of the Health and Social Care Act 2001 (re-enacted by Section 251 of the NHS Act 2006), and subsequent amendments/annual reviews were approved by the HRA-Confidentiality Advisory Group (reference PIAG 1–05[e]/2006).We used chi-squared tests to compare baseline characteristics between low risk and high risk patients, and to examine associations between baseline characteristics and interval length to first surveillance.Pvalues of < 0.05, and considering sex, age, PMP number and size, adenoma histology and dysplasia, proximal polyps, year of baseline visit, and family history of cancer/CRC. We included interval length, our main variable of interest, in all models. Tests for trend were conducted for interval length.Within risk groups, we calculated detection rates  of advanced adenomas, HRFs, and CRC at surveillance as the proportion of patients with ≥ 1 of the specified outcome detected. We examined detection rates by interval length from baseline, using univariable modified Poisson regression to calculate risk ratios (RRs) and 95 %CIs. We calculated RRs adjusted for baseline characteristics independently associated with increased detection of advanced adenomas, HRFs, or CRC at first surveillance using multivariable modified Poisson regression. Such characteristics were identified from models including all patients, using backward stepwise selection based on Wald tests to retain variables withFor high risk patients, we examined detection rates of advanced adenomas, HRFs, and CRC at second surveillance by interval from first surveillance, stratifying by presence of HRFs at the first surveillance. There were too few outcomes to perform regression analysis.We did not compare detection rates between the risk groups because this would not serve our aim of examining the effect of interval within each group.When calculating advanced adenoma and HRF detection rates at surveillance, we excluded PMPs detected in the same/adjacent colonic segment to baseline PMPs ≥ 15 mm seen at least twice within the preceding 3 years  because these were likely to have been incompletely resected at baseline and under polypectomy site surveillance; their inclusion would confound associations between interval length and neoplasia detection at surveillanceWhen calculating CRC detection rates at surveillance, we excluded CRCs assumed to have arisen from incompletely resected baseline PMPs, namely those detected in the same/adjacent colonic segment to a baseline PMP ≥ 15 mm seen at least twice within the preceding 5 years . This approach was taken to account for improvements in endoscopic resection over the past decade, so that our data reflect contemporary practiceIn additional analyses, we assessed the robustness of our results to our choice of reference group and interval cutoff, assigning patients with an interval of 3 years as the reference group and using a cutoff of 4.5 years. We performed additional analyses to assess the effect of adjusting for clustering by hospital in all models.We conducted analyses in Stata/IC V.13.1From 33 011 patients, we excluded 126 with CRC or colectomy at/before baseline, or with a condition associated with elevated CRC risk, 2859 with no baseline colonoscopy, 15 whose baseline visit was after 2010, 12 with colorectal carcinoma in situ > 3 years pre-baseline, 2 with examinations with no date recorded, and 2 without adenomas . AdditiA comparison of baseline characteristics among surveillance attenders compared with non-attenders is described elsewherePtrend < 0.001), but not HRFs (multivariablePtrend = 0.06), at first surveillance. Baseline characteristics that were independently associated with detection rates were: age, PMP number and size, adenoma histology, proximal polyps, and family history of cancer/CRC for advanced adenomas; sex, PMP number and size, proximal polyps, and year of baseline visit for HRFs; and age and proximal polyps for CRC .Examining all patients together, the interval from baseline was independently associated with detection rates of advanced adenomas and CRC (multivariableTable 2 s).Among low risk patients, the median time from baseline to first surveillance was 3.0 years (interquartile range [IQR] 2.0–4.1). Baseline characteristics associated with shorter intervals included age ≥ 65 years, 1 or 4 PMPs, PMPs ≥ 10 mm, adenomas with tubulovillous/villous histology or high grade dysplasia, and baseline visits performed pre-2005. Intervals were generally longer in patients with a family history of cancer/CRC than in those without (Ptrend < 0.001), reaching 9.8 % at an interval of 6 years. Detection of HRFs or CRC did not increase with increasing interval length, remaining < 5 % and < 2 %, respectively, with all interval categories   .Table 3 s).Among high risk patients, the median time from baseline to first surveillance was 2.1 years (IQR 1.1–3.2). Baseline characteristics associated with shorter intervals included age ≥ 65 years, ≥ 5 PMPs, PMPs ≥ 20 mm, adenomas with high grade dysplasia, proximal polyps, and baseline visits performed pre-2000. Intervals were typically longer among those with tubular adenomas at baseline (Ptrend < 0.001); no such trend was seen for HRFs (multivariablePtrend = 0.31)  . For ad= 0.31) . For CR= 0.31) . The de= 0.31) .Among high risk patients who, at first surveillance, were free of CRC and had no HRFs detected (n = 3547) , 2008 . The meAmong high risk patients who, at first surveillance, were free of CRC but had HRFs detected (n = 393) , 262 6. The meInterpretation of our results did not change when we used patients with a 3-year interval as the reference group, applied an interval cutoff of 4.5 years, or adjusted for clustering by hospital (data not shown).This is the largest study investigating associations between post-polypectomy surveillance interval length and detection rates of colorectal neoplasia at surveillance, involving > 11 000 patients with ≥ 1 surveillance visit. Classifying patients’ risk following the UK (2020) surveillance guidelineAmong low risk patients, CRC detection rates at first surveillance did not vary by interval from baseline, remaining < 2 % even with intervals of 6 years. Advanced adenoma detection rates at first surveillance increased with increasing interval length but remained < 10 %. A yield of 10 % for advanced PMPs has been suggested as a minimum threshold to justify surveillanceAmong high risk patients, the likelihood of detecting CRC at first surveillance increased with increasing interval length. As the interval extended from < 18 months to 2 years, the CRC detection rate increased, but remained < 2 %. A greater increase in CRC detection rate occurred as the interval extended beyond 3 years; with adjustment, the detection rates with an interval of 4 years (3 %) and 5 years (4 %) were four and six times greater, respectively, than with an interval of < 18 months. This indicates that the recommended 3-year interval would help ensure timely CRC detection, preventing progression to advanced stages. Any additional benefit from a shorter interval would be small because CRC detection rates were low with intervals < 3 years. Detection of advanced adenomas among high risk patients increased with increasing interval, although even at 3 years the advanced adenoma yield (15 %) was sufficient to justify surveillance at this interval.According to the UK (2020) guideline, patients with HRFs at first surveillance should undergo another colonoscopy after 3 years, whereas those with no HRFs can cease surveillanceIn contrast to these expectationsAlthough we applied the UK risk criteriaWe had to decide at what point after baseline (or first surveillance) was it more likely that patients were attending examinations because of symptoms rather than for surveillance. As most examinations occurred during the era of the 2002 UK guidelineIn our study of post-polypectomy patients classified as “intermediate-risk” by the UK (2002) guidelineNo data exist on the effects of surveillance interval on long-term post-polypectomy CRC outcomes. Therefore, while our findings support recommendations for surveillance at 3 years in high risk patients, it remains unknown whether a 3-year interval is superior to longer intervals in terms of long-term protection against CRC. A randomized controlled trial examining long-term CRC incidence with different surveillance intervals will help address this knowledge gapOur study has limitations due to its observational and retrospective nature. We were unable to classify the risk of ~1800 patients owing to missing information on baseline polyp characteristics. Classification of serrated polyps was complicated by the evolution in detection and terminology used for these polyps over the study duration. We had incomplete data on reasons for attendance at follow-up examinations and so counted examinations performed within ≤ 6.5 years after the previous visit as surveillance; this might have captured some examinations performed for symptoms. However, our results were robust to changes in our chosen interval cutoff. Some patients might have undergone surveillance at hospitals not included in our study. We had insufficient data to estimate adenoma detection rates for the endoscopists performing the examinations. Associations between interval and neoplasia detection at surveillance might be confounded by baseline characteristics, although we reduced this likelihood by multivariable adjustment. As high risk patients attended first surveillance after a median of 2 years, observed detection rates at first surveillance with intervals of ≥ 3 years are likely to be lower than if intervals more closely aligned with UK (2020) recommendationsStudy strengths include the large size and wide coverage of the UK. We had detailed information on characteristics at baseline colonoscopy, and findings at first and second surveillance, with few missing data. The wide variation in surveillance intervals, owing to the study’s observational and retrospective nature, enabled examination of neoplasia detection rates at many different surveillance intervals; this feature is unique and unlikely to be seen in future studies when adoption of surveillance guidelines is more widespread. Our findings are applicable to contemporary practice because all analyzed patients had a complete baseline colonoscopy.Metachronous advanced neoplasia at surveillance was uncommon among low risk patients, even with surveillance intervals extending to 6 years, supporting recommendations for no surveillance in these patients. For high risk patients, whose likelihood of having CRC detected at first surveillance increased with increasing interval length, particularly as the interval extended beyond 3 years, surveillance at 3 years would help to ensure timely detection of CRC.


Subsequently, a Cu layer was electrodeposited on top of the metallic interdigitated electrodes. The CuO nanowire arrays (core) were obtained by thermal oxidation in air of the Cu layer. Afterwards, a ZnO thin film (shell) was deposited by RF magnetron sputtering covering the surface of the CuO nanowires. The morphological, structural, compositional, optical, electrical and photoelectrical properties of the CuO nanowire arrays and CuO–ZnO core–shell nanowire arrays grown on metallic interdigitated electrodes were investigated. The performances of the devices were evaluated by assessing the figures of merit of the photodetectors based on self-connected CuO–ZnO core–shell heterojunction nanowire arrays grown on the metallic interdigitated electrodes. The radial p–n heterojunction formed between CuO and ZnO generates a type II band alignment that favors an efficient charge separation of photogenerated electron–hole pairs at the CuO–ZnO interface, suppressing their recombination and consequently enhancing the photoresponse and the photoresponsivity of the photodetectors. The electrical connections in the fabricated photodetector devices are made without any additional complex and time-consuming lithographic step through a self-connecting approach for CuO–ZnO core–shell heterojunction nanowire arrays grown directly onto the Ti/Pt metallic interdigitated electrodes. Therefore, the present study provides an accessible path for employing low dimensional complex structures in functional optoelectronic devices such as photodetectors.An original photodetector system based on self-connected CuO–ZnO radial core–shell heterojunction nanowire arrays grown on metallic interdigitated electrodes, operating as visible-light photodetector was developed by combining simple preparation approaches. Metallic interdigitated electrodes were fabricated on Si/SiO Visible-light photodetectors are an important class of optoelectronic devices, finding applications in communication, wearable devices, biological imaging, environmental research, molecular sensing, etc.9.An important characteristic of scientific and technical evolution is related to packing more functionalities in devices. Consequently, nanomaterials and nanotechnology become key elements in the development of many areas including materials science, electronics, computer science, energy, environment or life sciences. Electronic and optoelectronic devices such as field effect transistors, light emitting diodes, photodetectors or solar cells are faster, smaller, energy efficient and cost-effective using nanostructures or nanostructured materials as building blocks9. Nanowires represent a distinctive category of 1D nanostructures, thoroughly investigated due to their highly anisotropic shape (diameters of 1–100 nm and lengths up to tens of micrometers), being suitable for applications in different areas such as optoelectronics, spintronics, photocatalisys, sensing, biotechnology, etc.13. Semiconductor nanowires have been widely explored as novel building blocks for advanced miniaturized optoelectronic devices, easily finding applications in field effect transistors15, solar cells16, light emitting diodes17, photodetectors19, photoelectrochemical water splitting20, etc. Different from bulk materials and thin films, owed to their high surface-to-volume ratio and large specific surface area, semiconductor nanowires are expected to enhance light confinement and photosensitivity in photodetectors21. However, one main challenge in semiconductor nanowires is related to the impact of the high density of surface states on their electrical properties as a consequence to the quantum-confined geometry. These point defects may act as nonradiative carrier traps that can decrease the electrical conductivity and limit the nanowire based photodetector performances22. Recently, two components based heterostructures have stimulated tremendous research efforts due to their potential use in obtaining improved optoelectronic devices compared to their single material counterparts23. A successful path to improve and fine tune the optoelectronic performances of the nanowires is to develop radial core–shell heterojunction nanowires which combine the features of two different semiconductor materials in order to enhance their individual properties, the core–shell architecture leading to advanced band engineering capability24. Hence, in the last years, core–shell heterojunction nanowires based on metal oxides emerged as promising new materials capable of encoding new and advanced functionalities that are essential for the next generation miniaturized nanowire based photodetectors26. Accordingly, various core–shell heterojunctions were used in order to fabricate photodetectors based on single  or on arrays  of radial core–shell nanowires. In spite of considerable efforts and progress made by researchers in fabricating semiconductor nanowire based photodetectors, there are still challenges that needs to be overcome, mostly related to material properties tuning and device architecture engineering, leaving room for new research.Nowadays, the rapid development and implementation of Internet of Things (IoT) using new and advanced technologies have inspired researchers to develop visible-light photodetectors based on one dimensional (1D) nanomaterials32. Amidst metal oxides, CuO is a p-type semiconductor with specific parameters including a narrow band gap (1.2–2 eV) and a high optical absorption in the visible range39. ZnO is a n-type semiconductor with a wide direct band gap (3.37 eV), large exciton binding energy (60 meV) at room temperature, and high electron mobility (up to 200 cm2 V−1 s−1)14. By joining CuO and ZnO into a radial core–shell nanowire configuration, a type II heterojunction is formed, leading to a structure suitable for advanced photodetectors with broad detection range40. The staggered gap type II heterojunction promotes an efficient charge separation of photogenerated electron–hole pairs along the CuO–ZnO interface, generating a built-in electric field and consequently enhancing the light absorption efficiency40. Until now, only a few approaches were used to obtain CuO–ZnO core–shell heterojunction nanowire arrays, the cores consisting in CuO nanowires and the shell being a ZnO thin film entirely covering the surface of the CuO nanowires43. Thus, the CuO nanowires (core) were prepared by thermal oxidation in air44, while the ZnO thin film shell was obtained by radio-frequency (RF) magnetron sputtering28, thermal decomposition43 or atomic layer deposition44. Moreover, we recently fabricated p–n radial heterojunction diodes based on single CuO–ZnO core–shell nanowires behaving as photodetectors28.Some metal oxides are low cost and non-toxic semiconductor materials that can be easily prepared by different pathways. The bandgap of such metal oxides can be tuned during their synthesis allowing tailored light absorption from the UV up to IR spectral domains, thus making them suitable for applications as photodetectors46.Metallic interdigitated electrodes are often employed as a platform for detecting devices due to their low Ohmic drop, increased signal to noise ratio and fast detection speed given by their alternating “finger-like” architecture with gaps typically in the micrometer range2 substrates using a conventional photolithography process; (ii) a Cu layer was electrodeposited on top of the metallic interdigitated electrodes; (iii) CuO nanowire arrays (core) were prepared by thermal oxidation in air of the Cu layer; and (iv) ZnO thin film shell was deposited by RF magnetron sputtering, covering the surface of the CuO nanowires. The morphological, structural, compositional and optical properties of the CuO nanowire arrays and CuO–ZnO core–shell nanowire arrays grown on metallic interdigitated electrodes were evaluated. Afterwards, the electrical and photoresponse properties of the photodetector devices were assessed in dark and under illumination. The figures of merit of the fabricated photodetectors were estimated, their performances being compared with state-of-the-art core–shell nanowire arrays based photodetectors. The reported devices have a major advantage: the electrical connections in the fabricated photodetectors are obtained without any additional complex and time-consuming lithographic steps due to the self-connected CuO–ZnO core–shell heterojunction nanowire arrays grown directly onto the Ti/Pt metallic interdigitated electrodes. The current work represents a step-forward on the research for next generation miniaturized visible-light photodetectors based on core–shell heterojunction nanowire arrays.In the current study, we aim to develop a new type of photodetector system based on self-connected CuO–ZnO core–shell heterojunction nanowire arrays grown on metallic interdigitated electrodes, in order to explore their potential application in visible-light photodetectors. The nanowire based photodetector system was developed using the following preparation steps: (i) metallic interdigitated electrodes were fabricated on Si/SiO2SO4·5H2O and H2SO4) were bought from Merck and used as received without further purification. Deionized water was provided by a Millipore water purification system. The n-type doped Si/SiO2 wafers having a diameter of 3 inch were acquired from Si-Mat Silicon Materials. The titanium (99.995% purity), platinum (99.99% purity) and zinc oxide (99.999% purity) sputtering targets having a diameter of 2 inch were purchased from Kurt J. Lesker Company Ltd. (UK).The chemical reagents used in the copper electrodeposition  were firstly cleaned in order to remove the contaminants. Further, an UV sensitive resist bought from MicroChemicals GmbH was spin coated on the surface of the Si/SiO2 wafers. Afterwards, the wafer coated with a thin layer of photoresist is thermally treated on a hotplate and then UV irradiated through a photomask. The resist covered Si/SiO2 wafers are developed using a developer acquired from MicroChemicals GmbH. After this process, a thin film of Ti (thicknesses of ≈ 10 nm) and Pt (thicknesses of ≈ 100 nm) were deposited by RF magnetron sputtering on the surface of the developed Si/SiO2 wafers. Subsequently, the remained photoresist on the Si/SiO2 wafers was stripped-off using a lift-off process in order to obtain Si/SiO2 wafers patterned with Ti/Pt metallic interdigitated electrodes.In the first step, a conventional photolithographic process was employed to obtain Si/SiO2 substrates  in order to obtain single Si/SiO2 substrates patterned with Ti/Pt metallic interdigitated electrodes that are used further as working electrodes in the electrochemical deposition process of the Cu film. The deposition bath contains 220 g/l Cu2SO4·5H2O and 32 g/l H2SO4. The electrodeposition process was performed using a VoltaLab PGZ100 potentiostat, in a two-electrode configuration, consisting in a copper foil (2 cm × 2 cm × 2 mm) as anode and the Pt thin film of the Ti/Pt metallic interdigitated electrodes as the working electrode (cathode).In the second step, Ti/Pt/Cu metallic interdigitated electrodes are fabricated on Si/SiOThe main stages in the process of fabricating the photodetector system based on metallic interdigitated electrodes with self-connected CuO–ZnO core–shell heterojunction nanowire arrays are sketched in Fig. 28. Thus, the diced Si/SiO2 substrates patterned with Ti/Pt/Cu metallic interdigitated electrodes were placed on a ceramic substrate and introduced into a convection oven (Nabertherm GmbH) were the Cu film is thermally oxidized at 450 °C for 12 h in the ambient pressure. The second step is focused on the preparation of the CuO–ZnO core–shell nanowire arrays on top of the metallic interdigitated electrodes. Thus, the surface of the as prepared CuO nanowire arrays was uniformly covered by a thin film of ZnO by employing radio-frequency (RF) magnetron sputtering . The following parameters were applied in the deposition process: 5.4 × 10–3 mbar pressure in the sputtering chamber, 100 W RF power applied on the magnetron and Ar atmosphere as the working gas. Two deposition times, 20 and 30 min, were used in order to investigate the influence of the ZnO shell thickness on the photoelectrical properties of the fabricated devices. The investigated samples were labelled as follows: CuO_MIE , CuO-ZnO_MIE_1  and CuO-ZnO_MIE_2 .The first step is to grow CuO nanowire arrays on top of the metallic interdigitated electrodes. The top copper layer of the electrode system is thermally oxidized in air, in a simple and effective approach by applying similar experimental parameters as in our previous workThe morphology and the crystalline structure of the Ti/Pt metallic interdigitated electrodes with self-connected CuO nanowire and CuO–ZnO nanowire arrays were investigated using a Zeiss Merlin Compact field emission scanning electron microscope (FESEM) and a Bruker AXS D8 Advance instrument with Cu Ka radiation, λ = 0.154 nm X-ray diffractometer (XRD). The elemental composition of the metallic interdigitated electrodes was assessed by energy dispersive X-ray spectroscopy (EDX) in SEM using a Zeiss Evo 50 XVP scanning electron microscope (SEM) with an energy dispersive X-ray analysis (EDX) Quantax Bruker 200 as accessory The morphology, atomic structure and local chemical composition of the CuO and CuO–ZnO nanowires were evaluated with a high-resolution transmission electron microscope Cs probe-corrected JEM ARM 200F analytical electron microscope (TEM) including EDX elemental mapping in scanning transmission electron microscopy (STEM) and selected area electron diffraction (SAED). The optical reflectance spectra of the Ti/Pt metallic interdigitated electrodes with self-connected CuO nanowire and CuO–ZnO nanowire arrays were recorded with a Perkin–Elmer Lambda 45 UV–Vis spectrophotometer equipped with an integrating sphere.2.The current–voltage characteristics, in dark and under illumination, of the photodetector system based on metallic interdigitated electrodes with self-connected CuO–ZnO core–shell heterojunction nanowire arrays were measured in the ambient pressure and temperature using a Keithley 2400 Source Meter and a Oriel VeraSol-2 Class AAA LED Solar Simulator which has 19 independently controlled LED wavelengths from 400 to 1100 nm. The solar simulator was calibrated with an NREL certified KG5 filtered Si reference diode to an irradiation intensity of 100 mW/cmThe morphological properties of the CuO_MIE, CuO–ZnO_MIE_1 and CuO–ZnO_MIE_2 samples were investigated by FESEM, the results being illustrated in Fig. At lower magnification, the FESEM images of the samples show that the metallic interdigitated electrodes are uniformly covered by CuO nanowire arrays Fig. a,b or byAdditionally, it can be noticed that the RF magnetron sputtering process had as a result a uniform and conformal coverage (without any agglomerations or irregularities) of the pristine CuO nanowires with the ZnO thin film shell Fig. . Hence, The structural and optical properties were evaluated directly on the as obtained self-connected nanowire arrays grown on metallic interdigitated electrodes, being presented in Figs. 2 versus the photon energy (E) for all the samples: CuO_MIE  = 0.23 nm. The TEM image of a single CuO–ZnO nanowire , high-resolution transmission electron microscopy (HRTEM) and EDX mapping in STEM were carried out on the pristine CuO nanowires and CuO–ZnO core–shell nanowires. In order to perform the TEM investigations CuO nanowires and CuO–ZnO core–shell nanowires were harvested from the Ti/Pt/Cu metallic interdigitated electrodes by ultrasonication in ultrapure isopropyl alcohol to obtain a suspension of nanowires. The nanowires were placed on TEM grids by directly drop casting droplets of nanowires suspensions onto their surface. Thus, the TEM image of a single CuO nanowire Fig. a exhibitire Fig. c evidencire Fig. c. The SAire Fig. d confirmire Fig. . MoreoveA major advantage of the photodetector system developed in the current study consists in the fact that the electrical connections are achieved without any additional complex and time-consuming lithographic contacting step due to the self-connected CuO–ZnO core–shell heterojunction nanowire arrays grown directly onto the Ti/Pt metallic interdigitated electrodes. A schematic representation with the fabricated photodetector is depicted in Fig. 49. In addition, the electron affinities and work functions of CuO and ZnO are 52. The schematic representation of the band diagram after joining the two semiconductor materials into a radial CuO–ZnO core–shell heterojunction in the nanowires under illumination is depicted in Fig. The current–voltage characteristics of the self-connected CuO nanowire arrays grown on metallic interdigitated electrodes in dark conditions and under illumination with different spectral intervals  are presented in Fig. Taking into account the values of the bandgaps and electron affinities of the CuO and ZnO, the conduction band offset  and decay time (τd) of the photodetectors were estimated based on the enlarged time-dependent photoresponse  being evidenced in Fig. The performances of the photodetectors can be assessed by determining the most important figures of merit of the optoelectronic devices: responsivity (R), specific detectivity (D*) and external quantum efficiency (EQE). Responsivity represents the generated photocurrent per unit of the incident light power on the effective illuminated area of a photodetector. Detectivity is a key parameter that characterizes the ability of a photodetector to detect weak signals from noise.54:The figures of merit of a photodetector can be estimated using the following equations2 for each sample and the above equations, the figures of merit of the two type of photodetectors were estimated to be: 12.3 A/W and 5.34 × 1013 Jones for CuO–ZnO_MIE_1 and 26.3 A/W and 5.85 × 1013 Jones for CuO–ZnO_MIE_2, respectively. Additionally, the external quantum efficiency parameter was calculated for the 400 nm wavelength, being 13.34% for CuO–ZnO_MIE_1 and 38.75% for CuO–ZnO_MIE_2, respectively. The performances of the photodetectors fabricated in the current study were presented in a comparative manner with the performances of state-of-the-art core–shell nanowire arrays based photodetectors, being illustrated in Table Taking into account that the effective illuminated area is 0.49 mm13 Jones for CuO–ZnO_MIE_1 and 26.3 A/W and 5.85 × 1013 Jones for CuO–ZnO_MIE_2, respectively. Furthermore, the rise and decay times of the photodetectors were τr = 0.5 s and τd = 0.5 s. The major advantage of the fabricated photodetectors consists in the fact that the electrical connections are made in a straightforward manner  avoiding complex and time-consuming lithographic steps. The current study highlights that such photodetectors based on self-connected CuO–ZnO core–shell heterojunction nanowire arrays can have a potential impact on the development of the future nanoscale optoelectronic devices.In summary, the present work reports a novel visible-light photodetector system based on self-connected CuO–ZnO radial core–shell heterojunction nanowire arrays grown on metallic interdigitated electrodes. It was demonstrated that the radial p–n heterojunction formed in the CuO–ZnO core–shell nanowires enhances the photoresponse and photoresponsivity of the photodetectors. The nanowire based photodetectors were fabricated using simple and cost-effective preparation methods, such as photolithography, electrodeposition, thermal oxidation in air and RF magnetron sputtering. The morphological properties evidence a diameter of 80 nm for the CuO–ZnO_MIE_1 core–shell nanowires and 90 nm for the CuO–ZnO_MIE_2 core–shell nanowires. The structural characterization revealed a monoclinic phase for the CuO nanowires and a hexagonal wurtzite phase for the ZnO thin film shell. The band gap values of the CuO–ZnO core–shell nanowire arrays were estimated in the range of 1.5–1.6 eV based on the reflectance data. The electrical and photoresponse measurements proved that the photodetectors based on self-connected CuO–ZnO radial core–shell heterojunction nanowire arrays grown on metallic interdigitated electrodes operate as visible-light photodetector with the following figures of merit: 12.3 A/W and 5.34 × 10Supplementary Figures.


The first serial synchrotron crystallographic structure of apo PTP1B is reported and the conformational heterogeneity at several allosteric sites is compared with that seen in prior structures. Room-temperature X-ray crystallography provides unique insights into protein conformational heterogeneity, but obtaining sufficiently large protein crystals is a common hurdle. Serial synchrotron crystallography (SSX) helps to address this hurdle by allowing the use of many medium- to small-sized crystals. Here, a recently introduced serial sample-support chip system has been used to obtain the first SSX structure of a human phosphatase, specifically protein tyrosine phosphatase 1B (PTP1B) in the unliganded (apo) state. In previous apo room-temperature structures, the active site and allosteric sites adopted alternate conformations, including open and closed conformations of the active-site WPD loop and of a distal allosteric site. By contrast, in our SSX structure the active site is best fitted with a single conformation, but the distal allosteric site is best fitted with alternate conformations. This observation argues for additional nuance in interpreting the nature of allosteric coupling in this protein. Overall, our results illustrate the promise of serial methods for room-temperature crystallography, as well as future avant-garde crystallography experiments, for PTP1B and other proteins. Although most X-ray crystallography is performed with the sample at cryogenic temperature (cryo), data collection at elevated temperatures including room temperature (RT) offers unique insights into protein conformational heterogeneity and function . PTP1B is the archetypal protein tyrosine phosphatase, playing a key role in cellular regulation, cell-growth signaling and signal transduction by removing phosphate groups from phosphorylated tyrosine residues. Dysregulation of PTP1B function has been attributed to a number of human pathologies and has led to PTP1B becoming a validated therapeutic target  are from multitemperature crystallography of PTP1B, which indicated the existence of an extensive allosteric network spanning several promising sites in the protein  and data-collection temperature . Despite being described in the PDB metadata as being collected at 277 K, the diffraction data for PDB entry 2cm2 were actually collected at 93.15 K as per the crystallographic statistics presented in the accompanying manuscript  structure of PTP1B, demonstrating the feasibility of this method for this protein. We use two different processing pipelines and obtain very similar results with both, demonstrating the robustness of processing data from the SSX chips used here. Our data set allows us to draw comparisons to other existing structures with regard to the conformational ensemble of truly apo PTP1B. As may be expected, our model is broadly similar to the dozens of ligand-bound cryo structures and the smaller set of RT structures in different conditions. However, despite its moderate resolution relative to past single-crystal structures, our data set also indicates a degree of allosteric decoupling that adds nuance to the previously reported paradigm of allostery in this protein  grown overnight at 37°C with shaking. Starter cultures were subsequently used to inoculate 1 L growth cultures of LB + kanamycin , induced with 100 µM isopropyl β-d-1-thiogalactopyranoside and grown for a further 4 h at 37°C. Cell pellets were harvested via centrifugation and stored at −80°C until needed, or immediately sonicated (on ice) for 10 min with 10 s on/off at an amplitude of 50%.PTP1B was expressed and purified as reported previously  using a NaCl gradient (0–200 mM), with the protein eluting around 200 mM NaCl. Size-exclusion chromatography was subsequently performed on a Superdex 75 size-exclusion column  in crystallization buffer . Purity was assessed by SDS–PAGE and the protein was found to be pure and contamination-free.PTP1B WT* was initially purified via cation exchange on an SP FF 16/10 HiPrep column  in lysis buffer  and were incubated at 4°C. Crystals grew within 24 h and continued growing for a few more days, reaching final sizes of ∼50–100 µm.WT* PTP1B was used at 40 mg mL2.3.et al.  per crystal of <35.1 kGy using RADDOSE-3D  on the ID7B2 (FlexX) beamline for macromolecular X-ray science at the Cornell High Energy Synchrotron Source (MacCHESS), Ithaca, New York, USA. Crystal-loaded MiTeGen SSX sample supports were mounted on the ID7B2 endstation goniometer and rastered through the X-ray beam. The sample support was rastered in steps of 20 µm between likely crystal positions. At each such position six data frames were collected, and four blank frames were then collected during transit to the next position. The six data frames consisted of either 0.2° or 0.5° oscillations depending on the chip, with a total oscillation of either 1.2° or 3.0° collected per wedge. Initial data quality and resolution limits were assessed at ID7B2 using the 2.4.XDS  for each wedge. See Supplementary Fig. S2 for the list of steps run by xds_par. Space group P3121 was explicitly enforced. Subsequent scaling and merging of integrated intensities across all wedges across all used chips was performed using XSCALE. XDSCONV was used to convert the unmerged XSCALE.HKL file to a merged .hkl file and then to a merged .mtz file, which was used for subsequent processes.For the DIALS pipeline, data were imported using dials.import followed by spot-finding using dials.find_spots. A custom Python script was used to identify wedges as sets of consecutive frames with at least 20 identified diffraction spots, excluding blank images (see above), with the result stored in a single .expt and .refl file. Data for all wedges were indexed using dials.index with the flags joint_index=false and beam.fix=all detector.fix=all. The results were refined using dials.refine, and dials.split_experiments was run using refined.* files to create split_*.refl and split_*.expt files for individual wedges. Within a separate directory for each wedge, dials.integrate was run. Successfully integrated wedges were scaled and merged using xia2.multiplex , completeness (min_completeness=0.95) and resolution (d_min=2.40). The resulting merged .mtz file was used for subsequent processes.For the B values were obtained by running phenix.table_one with the merged data, and some statistics not initially provided by XDS were obtained by running phenix.merging_statistics with the final unmerged data from XSCALE.For Table 12.5.Phaser  via .pml scripting.The structure was solved using molecular replacement via 2.6.8du7. Raw diffraction images are available from SBGrid at https://doi.org/10.15785/SBGRID/961.Model coordinates and structure factors have been deposited in the Protein Data Bank as PDB entry 3.et al., 2021Supplementary Fig. S1). Using this system on the ID7B2 beamline at MacCHESS, we loaded six chips with PTP1B crystals in the previously characterized P3121 space group . Both pipelines yielded similar numbers of successfully processed wedges across the six chips, with no discernible pattern as to which wedges or chips were best processed by either method (Supplementary Table S1). The overall ‘hit rate’ for XDS was ∼10%, with 129 successfully processed wedges for XDS (and similar for DIALS) out of a total of 1297 collected wedges. This efficiency could likely be improved with experimental optimization, which was not performed here.To ensure that our data were processed robustly, we used two pipelines in parallel, XSCALE_ISOCLUSTER , a metric based on unit-cell parameters , with no noticeable differences in the key structural sites featured throughout this manuscript. These observations suggest a nonzero but relatively low level of non-isomorphism with limited impact on the structural state of PTP1B.Analysis of the correlation coefficients between all of the unmerged wedges with XDS and for DIALS. These data sets both have similarly good overall statistics after scaling and merging . We therefore focused on the XDS model for the remainder of this work.We therefore used all successfully processed wedges for g Table 1. We theng Table 1. The XDSUsing this final model, we next inspected the conformational ensemble of the protein at several key sites Fig. 2.b), which is known to dominate in solution , arguing against this interpretation of the data. Some residual density is detectable below the WPD loop and may be attributable to the complex water network of the active site . An attempt to model the ordered conformation results in detectable but weak electron-density support  and inflated B factors of >100 Å2 (compared with ∼40–60 Å2 for the more fully ordered α7 in PDB entry 1sug).A second key site is the α7 helix, which has been established by a variety of methods as a key allosteric hub in PTP1B . These conformations have a similar occupancy in the refined model , suggesting that they are approximately isoenergetic in our experimental conditions. Omit maps of either conformation result in convincing difference density features, confirming the simultaneous presence of both states in the crystal .A third key site in the protein, Loop 16, is the eponymous loop of the reported allosteric L16 site , which have open/closed alternate conformations for the WPD loop, open/closed alternate conformations for the L16 site and a quasi-ordered partial-occupancy α7  as used in our study, and were crystallized under similar conditions, including pH. Further, they were found to belong to the same space group as our SSX structure, with extremely similar unit-cell dimensions. PDB entries 7rin and 6b8x do differ in the fact that the crystals used to obtain PDB entry 6b8x include a high concentration of glycerol, subsequently leading to glycerol molecules bound to the active site. Despite the fact that glycerol bound to the active site of PTP1B may bias the conformational ensemble of the protein, PDB entry 6b8x still adopts a nearly identical conformation to the apo structure PDB entry 7rin. The more discernible conformational heterogeneity of these previous structures compared with our structure may be related to their higher resolution (1.74 Å for PDB entry 6b8x and 1.85 Å for PDB entry 7rin) compared with our SSX structure (2.40 Å). Nevertheless, the differences between our SSX structure and previous RT WT (or similar) structures of PTP1B suggest that the active-site WPD loop and the allosteric L16 site may not be as strictly coupled as previously imagined.These observations from our SSX structure are in contrast to the previous report of an allosteric network in PTP1B with coupled opening of the WPD loop, opening of the L16 site and disordering of the α7 helix , yet features a single-conformation open WPD loop, an open L16 site and a disordered α7  relative to the other aforementioned structures (P3121). However, upon a closer inspection of the PDB metadata compared with the crystallographic statistics presented in the manuscript, the data for PDB entry 2cm2 were actually collected at ∼93 K and not at 277 K as reported in the PDB. Unfortunately, the P212121 PTP1B data set from the same study that was collected at 277 K was not deposited in the PDB. It therefore remains unknown whether the different space group, unit cell and crystal contacts seen in PDB entry 2cm2 may explain its collapsed conformational ensemble at these sites, and whether these features would carry over at elevated temperatures. Unfortunately, structure factors are not available for PDB entry 2cm2, so we cannot interrogate its electron-density map for signs of ‘hidden’ unmodeled alternate conformations  and the latter is disordered . However, Loop 16 adopts both open and closed conformations , suggesting that coupling between the L16 site and the other two areas may not be as tight as previously hypothesized. This reframing is reminiscent of how the active-site side-chain network of the proline isomerase CypA was previously viewed as thoroughly coupled  when compared with previous single-crystal structures (<2 Å), although this could likely be improved by optimizing our crystals for serial diffraction, which we did not undertake. Secondly, although the unit cell and the crystal contacts in our structure are the same as in PDB entries et al., 2020et al., 2021et al., 2018et al., 2020et al., 2009In closing, we look forward to the ongoing development of serial crystallography approaches to enable powerful interrogations of functional motions in PTP1B and other systems, including time-resolved X-ray crystallography with on-chip mixing (Mehrabi https://doi.org/10.15785/SBGRID/961X-ray diffraction data from protein tyrosine phosphatase 1B, source of 8du7 structure: room-temperature serial synchrotron crystallographic structure of apo PTP1B, 8du7PDB reference: 10.1107/S2053230X22011645/rs5005sup1.pdfSupplementary Table and Figures. DOI:


The commonly used Franck–Condon (FC) approximationis inadequatefor explaining the electronic spectra of compounds that possess vibrationswith substantial Herzberg–Teller (HT) couplings. Metal-basedtetrapyrrole derivatives, which are ubiquitous natural pigments, oftenexhibit prominent HT activity. In this paper, we compare the condensedphase spectra of zinc–tetraphenylporphyrin (ZnTPP) and zinc–phthalocyanine(ZnPc), which exhibit vastly different spectral features in spiteof sharing a common tetrapyrrole backbone. The absorption and emissionspectra of ZnTPP are characterized by a lack of mirror symmetry andnontrivial temperature dependence. In contrast, mirror symmetry isrestored, and the nontrivial temperature-dependent features disappearin ZnPc. We attribute these differences to FC–HT interference,which is less pronounced in ZnPc because of a larger FC componentin the dipole moment that leads to FC-dominated transitions. A singleminimalistic FC–HT vibronic model reproduces all the experimentalspectral features of these molecules. These observations suggest thatFC–HT interference is highly susceptible to chemical modification. Similar reports exist for other aromaticssuch as benzene,19 anthracene,28 phenanthrene,27 pentacene,29 and porphyrin.23 Veryfew instances of the systematic inclusion of finite-temperature HTeffects exist in the literature.31 Our recent work32 identifiedanalytical symmetry arguments dictating the trends of FC–HTinterference within the normal mode approximation and reported numericalcalculations incorporating temperature dependence and homogeneousbroadening.32 Non-Condon signatures werealso recently found in excitation energy transfer34 as well as electron transfer36 dynamics. A theoreticalstudy by Zhang et al.34 suggested that non-Condon vibroniccoupling plays a central role in facilitating electronic–vibrationalenergy transfer and enhancing the quantum yield in contrast to FCvibronic coupling. Thus, in addition to traditional FC vibronic features,an intuitive understanding of HT signatures in molecular spectra isnecessary to recognize the dynamical consequences of non-Condon effects.Despite early characterization, the interference of FC and HT termsin vibronic spectra, and especially its modulation by condensed phaseenvironments and finite temperatures, still lack a clear understanding.Craig and SmallIn this paper, we investigate two metal-based tetrapyrrole derivatives,zinc–tetraphenylporphyrin (ZnTPP) and zinc–phthalocyanine(ZnPc), that share similar chemical structures but yield vastly differentmolecular spectra. Using a single minimalistic theoretical model,we show that the interference of FC and HT signatures can lead tomirror-asymmetric and nontrivially temperature-dependent spectralfeatures in ZnTPP, which are entirely absent in ZnPc because of adominant FC transition.max = 5.7 × 105 M–1 cm–1) at ∼23700cm–1 and a weaker band (εmax =2.5 × 104 M–1 cm–1) at λmax ∼ 18000 cm–1.These bands are known as B (or Soret) and Q bands, respectively. Inspite of similarities in the tetrapyrrole skeleton with ZnTPP, theabsorption spectrum of ZnPc has a drastically different appearance.The B band (∼29450 cm–1) is much weaker (εmax = 7.3 × 104 M–1 cm–1) and blue-shifted compared to that of ZnTPP. On theother hand, the Q band (∼14900 cm–1) in ZnPcis ∼10 times more intense (εmax = 2.97 ×105 M–1 cm–1) and red-shiftedcompared to that in ZnTPP. A closer look at the Q band region showsa contrast in vibronic structure. While the Q (0–0) peak appearsto be most intense in ZnPc, the 0–1 vibronic peak is the mostintense in the Q band of ZnTPP, with a weak appearance of a Q (0–2)vibronic peak.The absorption spectra of ZnTPP andZnPc 1a ina 3Dh4 symmetry, areusually understood by using Gouterman’s four-orbital model.37 The HOMOs have a1u and a2u symmetries whereas the LUMOs have eg (x/y) symmetry, as illustrated in 1u and a2u orbitals are nearly degenerate. The large interactionbetween the two lowest energy orbital excitations (x and By); the excitations nearly cancelout (nearly forbidden electronic transition) to form weak Q bands(Qx and Qy). In contrast, the degeneracy between the a1u and a2u orbitals is broken in ZnPc. The addition of the benzo groupat the β position and substitution of a carbon atom with anelectronegative nitrogen atom at the meso position of the tetrapyrrolering cause relative stabilization of a2u compared a1u in ZnPc. Therefore, the interaction between the two lowestenergy orbital excitations is reduced in ZnPc compared to that inZnTPP  and emission (1297 cm–1) spectra (a differenceof 106 cm–1), creating an impression of significantdifferences between ground and excited potential energy curvatures.Intriguing differences are revealed by comparison of room temperature(∼295 K) absorption and fluorescence spectra of the two compounds(–1), unlike the 0–1 peak, which shows onlya small (∼20 cm–1) shift. Second, the disparityin energy gaps between 0−0 and 0–1 peaks in absorptionand emission spectra is larger at lower temperatures compared to roomtemperature (265 cm–1 at 95 K vs 106 cm–1 at room temperature). Third, in the absorption spectrum, the relativeintensity of the 0–1 band compared to the 0–0 band growswith increasing temperature. None of these three features appear inZnPc (–1) and familiarblue-shift of all absorption peaks and a red-shift of emission peaksare observed with increase in temperature. These gradual small shiftsare common and generally reflect the temperature dependence of theStokes shift.39 They mayalso contain solvatochromic shifts resulting from the change in solventpolarity with temperature.38Nontrivial behaviors also appear in the temperature dependenceof the ZnTPP spectra 2a. With  inZnPc 2b. Rathe32 Expanding the transitiondipole moment (in the direction of the applied electric field) alongthe normal mode coordinates q ≡ {qk} about a particular geometry {qkeq} of the molecule, we writek(1) is the first derivativeof the dipole moment along the particular mode. The FC approximationinvolves a truncation at the zeroth-order, electronic dipole termμ(0); thus, FC transitions follow Kasha’srule,41 producing mirror-image symmetrybetween absorption and emission spectra.38 This approximation holds well for ZnPc  band, which otherwise shows very weak FC activity withsmall Huang–Rhys (HR) factors caused by the rigid structureof the π-conjugated tetrapyrrole ring.44 The absorptionspectra of monomeric metalloporphyrin complexes in the Q band regionwere recently discussed in detail.23 TheQ band is derived from numerous modes in the low-frequency band andnumerous 0 → 1 transitions (600–1500 cm–1) among HT active modes in the higher-frequency peak. On the basisof previous studies of porphyrin complexes and our previous FC–HTanalysis,32 it is reasonable to hypothesizethat the nontrivial features and temperature dependence in the ZnTPPspectra arise from FC–HT interferences. However, the HT pathwaycannot be assumed to vanish in ZnPc, given the chemical similarityof the chromophores. The FC–HT model should thus not only accountfor the asymmetries and temperature dependence of the ZnTPP spectrabut also  recover the absence of HT effects in ZnPc. In what follows,we construct such a model. Note that our goal is not to simulate thespectra of ZnTPP or ZnPc but to capture the essential spectral featuresof both molecules by using a single minimalistic approach with thesmallest possible number of explicit FC–HT active vibrationalmodes.The inadequacy of the FC approximation is commonin porphyrin-basedmolecules.–1  calculationshave underestimated the HR factors of porphyrin vibrations.20 The chosen values of HR factors (0.05–0.15)are typical but larger than values reported based on DFT calculations.In addition, (0), while a bulk of the 0–1peak intensity arises from HT interactions alone. Moreover, the Bband is known to determine the strength of HT coupling through intensityborrowing. Overall, the experiment therefore suggests at least anorder of magnitude difference in the μ(1)s/μ(0) values (parameter s has the dimension of length) of the two compounds which is furthersubstantiated in the (iii) much larger ratio of 0–0 to 0–1peak intensity in ZnPc compared to ZnTPP. Thus, we set the value ofμ(0) to be 10 times larger in “set II”(∼ZnPc) compared to its value in “set I” (∼ZnTPP),leaving all other parameters, including the relative interactionsof the electronic states with the three discrete vibrations, unchanged.Last, we model the solvent and other normal mode vibrations of thecomplexes using a dissipative Ohmic bath45 that recently produced excellent agreement with pump–probeexperiments for closely related cofacial porphyrin dimers.46 All model parameters are summarized in the tableshown in We use three discrete vibrations at 100, 1200, and 1400cm(1)s/μ(0) values from “set I” of –1 modes. Our previous work32 showed that the direction of interference foreach vibronic transition is reversed between absorption and emissionspectra; that is, if a peak has amplified intensity through constructiveinterference in absorption, destructive interference and reduced intensityare observed in emission, and vice versa. Moreover, the vibronic transitionson either side of the 0–0 line are either all amplified orall diminished, depending on the relative signs of μ(0) and μk(1).32 Because theHT couplings of the two high-frequency modes are opposite in sign,the 1200 cm–1 mode shows absorption dominance inthe 0–1 peak, while the 1400 cm–1 peak ismore pronounced in emission. As a result, the model spectra capturethe feature of different energy gaps between the 0–0 and 0–1peaks observed in the experiment.Linear spectra 4a calcul48 However, when modes are FC–HT active,a change in temperature modifies the spectral asymmetry through differentialinterference patterns in transitions that originate from higher vibrationalquanta.32 First, the disparity (–1) and emission spectra (150 cm–1) hints at thepresence of a low-frequency HT mode. Our model captures the asymmetricthermal shifts qualitatively through the inclusion of the 100 cm–1 mode with a very weak HT coupling, such that combinationsbetween this mode and the Ohmic bath produce 42 and 65 cm–1 shifts in the theoretical absorption and emission spectra, respectively(–1) have beenidentified earlier in ZnTPP from low-temperature fluorescence experimentsand characterized as torsional motions of the phenyl groups.44 A DFT calculation20 on free-base porphyrin found an HT-active mode at 150 cm–1. The 0–1 bands also exhibit different thermal shifts in absorptionand emission spectra. The 80 and 28 cm–1 shiftsobserved in the theoretical absorption and emission spectra (–1) observedin the experiment  are given by the reorganizationenergy of the vibrational modes and the bath.isparity 2a betweeectively4a. Modes spectra 4a are inperiment 2a. This –1) that are of similar intensitiesin the absorption spectrum, such that the increase in homogeneousbroadening with temperature leads to an overall increase in intensityof the 0–1 band. In contrast, the two peaks in emission havedifferent intensities and therefore show no temperature dependence.Note that this effect is much more pronounced in the experimentalspectra, possibly due to the involvement of many more FC–HTactive modes23 in the 0–1 region.The ability of our simple model to qualitatively reproduce all trendsobserved in the experimental spectra of ZnTPP over a range of temperaturessuggests that these nontrivial spectral features arise from FC–HTinterference.Finally, our model also qualitatively captures the temperature-inducedchange in the intensity ratios of the 0–1 and 0–0 peaksin the absorption spectrum. This effect arises from two peaks (at1200 and 1400 cm–1) due to the quenchingof FC–HT interference. These shifts are also in excellent agreementwith the experimental shifts .Next, we turn to the ZnPc spectra predicted byour model whichinvolves a reasonable increase  of the FC componentof the dipole moment parameter which, as discussed earlier, is motivatedby the relative intensities of the 0–0 and 0–1 peaksin the experimental spectra and leads to less prominent HT features.The spectra 4b obtainOverall, this study shows that asmall modification in chemicalstructure can cause significant changes in the interference of FCand HT interactions and therefore result in vastly different molecularspectra. The condensed phase spectral signatures of ZnTPP and ZnPcas well as their contrasting temperature dependences are capturedby a minimalistic FC–HT vibronic model. We find that the dominanceof the FC-allowed pathway nearly quenches the dipole interferencesin ZnPc, largely recovering the mirror symmetry relationship in ZnPcspectra consistent with the FC approximation. In contrast, a weakQ band transition that encourages significant vibronic intensity borrowingfrom the B band, leads to intricate patterns of FC–HT interferencesthat give rise to intriguing temperature-dependent characteristicsin ZnTPP spectra. The intuitive understanding of FC–HT spectralfeatures presented in this work will aid future studies of non-Condonvibronic coherence-mediated energy and charge transfer dynamics incoupled chromophore systems.


Gowan et al. Nature Communications 10.1038/s41467-021-21469-w (2021)To reconstruct past sea levels, for estimating changes in global ice volume, it is necessary to obtain evidence from biofacies that rely on in situ fossil material and that grew at specific, shallow-water depths close to the oceans shorelines during their life span. At such sites, a time series is also necessary for estimating the exact timing of the lowest sea level by determining geological sequences and the dating has to be made on the in situ fossil organisms themselves.1 (hereafter EJG21) presented a new global ice sheet reconstruction for the last 80,000 years spanning the time period of the Last Glacial Maximum (LGM: around ca. 20 ka) and marine isotope stage 3 (MIS3: 57–30 ka). The reconstructed global ice volume relied on a simple ice model constrained by near-field ice volumes derived from glacio-geological evidence. The two main conclusions arising involved the magnitude of the global mean sea level during the LGM and during MIS 3. Firstly, their LGM sea level at −116 m is significantly shallower than previously reported values 5. Secondly, EJG21’s MIS3 sea level is also much shallower than most other records suggest  and geochemical analyses4 of the 583 cm core KH11-1GC6 confirmed a local LGM sea level of −120 m  is −118 m  by 20–80 m than previously reported. Important constraints for the MIS 3 GMSL come from both uplifted and submerged coral reef terraces in Papua New Guinea (PNG), a tectonically-active site, that has been extensively studied with corals from terrace surfaces and drill cores and were mass-spectrometric uranium/thorium dated  Expedition 310 also indicate GMSL at −65 to −75 m12. These results contradict those tabled by EJG21 . Unfortunately, the EJG21 study leads to an additional and unnecessary confusion rather than to a convergence of views.In conclusion, the paper by EJG21 argued that they have solved the missing ice problem of the LGM