title: On the crucial importance of the pH for the formation and self-stabilization of protein microgels and strands.
abstract: Stable suspensions of protein microgels are formed by heating salt-free β-lactoglobulin solutions at concentrations up to about C = 50 g·L(-1) if the pH is set within a narrow range between 5.75 and 6.1. The internal protein concentration of these spherical particles is about 150 g·L(-1) and the average hydrodynamic radius decreases with increasing pH from 200 to 75 nm. The formation of the microgels leads to an increase of the pH, which is a necessary condition to obtain stable suspensions. The spontaneous increase of the pH during microgel formation leads to an increase of their surface charge density and inhibits secondary aggregation. This self-stabilization mechanism is not sufficient if the initial pH is below 5.75 in which case secondary aggregation leads to precipitation. Microgels are no longer formed above a critical initial pH, but instead short, curved protein strands are obtained with a hydrodynamic radius of about 15-20 nm.
authors: Polymères, Colloïdes, Interfaces, UMR CNRS Université du Maine, 72085 Le Mans cedex 9, France.
authors: Tuan
authors: T
authors: Phan-Xuan
authors: Dominique
authors: D
authors: Durand
authors: Taco
authors: T
authors: Nicolai
authors: Laurence
authors: L
authors: Donato
authors: Christophe
authors: C
authors: Schmitt
authors: Lionel
authors: L
authors: Bovetto
mesh_terms: D000818:Animals; D002417:Cattle; D002627:Chemistry, Physical; D002850:Chromatography, Gel; D005782:Gels / Q000737:chemistry* / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D008027:Light; D046529:Microscopy, Electron, Transmission; D009391:Nephelometry and Turbidimetry; D010316:Particle Size; D011489:Protein Denaturation; D012492:Salts / Q000737:chemistry; D053838:Scattering, Small Angle; D012996:Solutions; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D005782:Gels; D007782:Lactoglobulins; D012492:Salts; D012996:Solutions