Neurofilament networks: Salt-responsive hydrogels with sidearm-dependent phase behavior.
BACKGROUND
Neurofilaments (NFs) - the neuron-specific intermediate filament proteins - are assembled into 10nm wide filaments in a tightly controlled ratio of three different monomer types: NF-Low (NF-L), NF-Medium (NF-M), and NF-High (NF-H). Previous work on reconstituted bovine NF hydrogels has shown the dependence of network properties, including filament alignment and spacing, on the subunit composition.


METHODS
We use polarized optical microscopy and SAXS to explore the full salt-dependent phase behavior of reconstituted bovine NF networks as a function of various binary and ternary subunit ratios.


RESULTS
We observe three salt-induced liquid crystalline phases: the liquid-ordered B(G) and N(G) phases, and the disordered I(G) phase. We note the emergent sidearm roles, particularly that of NF-H in driving the parallel to cross-filament transition, and the counter-role of NF-M in suppressing the I(G) phase.


CONCLUSIONS
In copolymers of NF-LH, NF-H shifts the I(G) to N(G) transition to nearer physiological salt concentrations, as compared to NF-M in copolymers of NF-LM. For ternary mixtures, the role of NF-H is modulated by the ratio of NF-M, where beneath 10wt.% NF-M, NF-H drives the transition to the disordered phase, and above which NF-H increases interfilament spacing.


GENERAL SIGNIFICANCE
Understanding the role of individual subunits in regulating the network structure will enable us to understand the mechanisms that drive the dysfunction of these networks, as observed in diseased conditions.
['Deek|Joanna|J|', 'Chung|Peter J|PJ|', 'Safinya|Cyrus R|CR|']
D000818:Animals D002021:Buffers D002417:Cattle D020100:Hydrogels D007382:Intermediate Filaments D050866:Liquid Crystals D008859:Microscopy, Polarization D016900:Neurofilament Proteins D044367:Phase Transition D011487:Protein Conformation D053838:Scattering, Small Angle D014961:X-Ray Diffraction
Neurofilament Network Salt-responsive Hydrogel Sidearm-dependent Liquid crystal