title: Polymorphism complexity and handedness inversion in serum albumin amyloid fibrils.
abstract: Protein-based amyloid fibrils can show a great variety of polymorphic structures within the same protein precursor, although the origins of these structural homologues remain poorly understood. In this work we investigate the fibrillation of bovine serum albumin--a model globular protein--and we follow the polymorphic evolution by a statistical analysis of high-resolution atomic force microscopy images, complemented, at larger length scales, by concepts based on polymer physics formalism. We identify six distinct classes of coexisting amyloid fibrils, including flexible left-handed twisted ribbons, rigid right-handed helical ribbons and nanotubes. We show that the rigid fibrils originate from flexible fibrils through two diverse polymorphic transitions, first, via a single-fibril transformation when the flexible left-handed twisted ribbons turn into the helical left-handed ribbons, to finally evolve into nanotube-like structures, and second, via a double-fibril transformation when two flexible left-handed twisted ribbons wind together resulting in a right-handed twisted ribbon, followed by a rigid right-handed helical ribbon polymorphic conformation. Hence, the change in handedness occurs with an increase in the level of the fibril's structural organization.
authors.affiliation: Food & Soft Materials Science, Department of Health Scence & Technology, ETH Zurich , Schmelzbergstrasse 9, LFO E23, 8092 Zurich, Switzerland.
authors.forename: Ivan
authors.initials: I
authors.lastname: Usov
authors.forename: Jozef
authors.initials: J
authors.lastname: Adamcik
authors.forename: Raffaele
authors.initials: R
authors.lastname: Mezzenga
mesh_terms: D000465:Algorithms; D000682:Amyloid / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D005583:Fourier Analysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D043942:Nanotubes / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011110:Polymorphism, Genetic; D011208:Powders; D011487:Protein Conformation; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013696:Temperature
chemical_list: D000682:Amyloid; D011108:Polymers; D011208:Powders; D012710:Serum Albumin, Bovine