title: Unconventional salt trend from soft to stiff in single neurofilament biopolymers.
abstract: We present persistence length measurements on neurofilaments (NFs), an intermediate filament with protruding side arms, of the neuronal cytoskeleton. Tapping mode atomic force microscopy enabled us to visualize and trace at subpixel resolution photoimmobilized NFs, assembled at various subunit protein ratios, thereby modifying the side-arm length and chain density charge distribution. We show that specific polyampholyte sequences of the side arms can form salt-switchable intrafilament attractions that compete with the net electrostatic and steric repulsion and can reduce the total persistence length by half. The results are in agreement with present X-ray and microscopy data yet present a theoretical challenge for polyampholyte interchain interactions.
authors.affiliation: Departments of Materials and Physics, University of California—Santa Barbara, Santa Barbara, California 93106, United States. roy@mrl.ucsb.edu
authors.forename: Roy
authors.initials: R
authors.lastname: Beck
authors.forename: Joanna
authors.initials: J
authors.lastname: Deek
authors.forename: Myung Chul
authors.initials: MC
authors.lastname: Choi
authors.forename: Taiji
authors.initials: T
authors.lastname: Ikawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Watanabe
authors.forename: Erwin
authors.initials: E
authors.lastname: Frey
authors.forename: Philip
authors.initials: P
authors.lastname: Pincus
authors.forename: Cyrus R
authors.initials: CR
authors.lastname: Safinya
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D007382:Intermediate Filaments / Q000187:drug effects* / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D008968:Molecular Conformation; D012492:Salts / Q000494:pharmacology*
chemical_list: D001704:Biopolymers; D012492:Salts