title: Amyloid-like fibrils formed from intrinsically disordered caseins: physicochemical and nanomechanical properties.
abstract: Amyloid-like fibrils are studied because of their significance in understanding pathogenesis and creating functional materials. Amyloid-like fibrils have been studied by heating globular proteins at acidic conditions. In the present study, intrinsically disordered α-, β-, and κ-caseins were studied to form amyloid-like fibrils at pH 2.0 and 90 °C. No fibrils were observed for α-caseins, and acid hydrolysis was found to be the rate-limiting step of fibrillation of β- and κ-caseins. An increase of β-sheet structure was observed after fibrillation. Nanomechanic analysis of long amyloid-like fibrils using peak-force quantitative nanomechanical atomic force microscopy showed the lowest and highest Young's modulus for β-casein (2.35 ± 0.29 GPa) and κ-casein (4.14 ± 0.66 GPa), respectively. The dispersion with β-casein fibrils had a viscosity more than 10 and 5 times higher than those of κ-casein and β-lactoglobulin, respectively, at 0.1 s(-1) at comparable concentrations. The current findings may assist not only the understanding of amyloid fibril formation but also the development of novel functional materials from disordered proteins.
authors.affiliation: Department of Food Science and Technology, University of Tennessee in Knoxville, USA. qzhong@utk.edu.
authors.forename: Kang
authors.initials: K
authors.lastname: Pan
authors.forename: Qixin
authors.initials: Q
authors.lastname: Zhong
mesh_terms: D000143:Acids / Q000737:chemistry; D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism; D055119:Elastic Modulus; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012212:Rheology; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000143:Acids; D000682:Amyloid; D002364:Caseins; D007782:Lactoglobulins