Heat of supersaturation-limited amyloid burst directly monitored by isothermal titration calorimetry.
Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. Although the structural features of amyloid fibrils have become increasingly clearer, knowledge on the thermodynamics of fibrillation is limited. Furthermore, protein aggregation is not a target of calorimetry, one of the most powerful approaches used to study proteins. Here, with β2-microglobulin, a protein responsible for dialysis-related amyloidosis, we show direct heat measurements of the formation of amyloid fibrils using isothermal titration calorimetry (ITC). The spontaneous fibrillation after a lag phase was accompanied by exothermic heat. The thermodynamic parameters of fibrillation obtained under various protein concentrations and temperatures were consistent with the main-chain dominated structural model of fibrils, in which overall packing was less than that of the native structures. We also characterized the thermodynamics of amorphous aggregation, enabling the comparison of protein folding, amyloid fibrillation, and amorphous aggregation. These results indicate that ITC will become a promising approach for clarifying comprehensively the thermodynamics of protein folding and misfolding.
['Ikenoue|Tatsuya|T|', 'Lee|Young-Ho|YH|', 'Kardos|József|J|', 'Yagi|Hisashi|H|', 'Ikegami|Takahisa|T|', 'Naiki|Hironobu|H|', 'Goto|Yuji|Y|']
D000682:Amyloid D000686:Amyloidosis D002151:Calorimetry D006358:Hot Temperature D006801:Humans D018625:Microscopy, Atomic Force D017510:Protein Folding D055550:Protein Stability D020836:Protein Structure, Quaternary D011994:Recombinant Proteins D012996:Solutions D013816:Thermodynamics D001613:beta 2-Microglobulin
enthalpy change metastability solubility thermodynamic stability thioflavin T