title: Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces.
abstract: Two-dimensional alignment of shape-anisotropic colloids is ubiquitous in nature, ranging from interfacial virus assembly to amyloid plaque formation. The principles governing two-dimensional self-assembly have therefore long been studied, both theoretically and experimentally, leading, however, to diverging fundamental interpretations on the nature of the two-dimensional isotropic-nematic phase transition. Here we employ single-molecule atomic force microscopy, cryogenic scanning electron microscopy and passive probe particle tracking to study the adsorption and liquid crystalline ordering of semiflexible β-lactoglobulin fibrils at liquid interfaces. Fibrillar rigidity changes on increasing interfacial density, with a maximum caused by alignment and a subsequent decrease stemming from crowding and domain bending. Coexistence of nematic and isotropic regions is resolved and quantified by a length scale-dependent order parameter S(2D)(d). The nematic surface fraction increases with interfacial fibril density, but depends, for a fixed interfacial density, on the initial bulk concentration, ascribing the observed two-dimensional isotropic-nematic coexistence to non-equilibrium phenomena.
authors.affiliation: ETH Zurich, Department of Health Sciences and Technology, Laboratory of Food & Soft Materials, Schmelzbergstrasse 9, 8092 Zurich, Switzerland.
authors.forename: Sophia
authors.initials: S
authors.lastname: Jordens
authors.forename: Lucio
authors.initials: L
authors.lastname: Isa
authors.forename: Ivan
authors.initials: I
authors.lastname: Usov
authors.forename: Raffaele
authors.initials: R
authors.lastname: Mezzenga
mesh_terms: D000327:Adsorption; D000388:Air; D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure; D000818:Animals; D016880:Anisotropy; D002417:Cattle; D003198:Computer Simulation; D020285:Cryoelectron Microscopy; D003460:Crystallization; D007782:Lactoglobulins / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry; D046911:Macromolecular Substances; D018625:Microscopy, Atomic Force; D044367:Phase Transition; D014867:Water / Q000737:chemistry*
chemical_list: D000682:Amyloid; D007782:Lactoglobulins; D046911:Macromolecular Substances; D014867:Water