title: Salt induced thermodynamic instability, concentration heterogeneity and phase transitions in lysozyme solutions.
abstract: The ESR spin label method was used to estimate an average distance between spin-labeled protein molecules at a concentration of 35mg/ml in solutions which contained 0 to 3M NaCl. Three NaCl concentration ranges, in which the distance between protein molecules varied markedly, were revealed: the distance increased in the range 0 to 0.15М NaCl, decreased in the range 0.3 М to 1.5 М NaCl and increased again in the range 1.5М to 3М NaCl. In lysozyme solutions, which contained 0.3 to 1.5М NaCl, solution heterogeneity was observed to increase gradually during 4 days because of the emergence of supramolecular organization in the form of clusters and aggregates. Viscous gel was formed immediately under salting-out conditions at 3М NaCl, and remained unchanged during 4 days. The results obtained are discussed on the basis of a theoretical and experimental phase diagram of lysozyme solution with an emphasis on analysis of continuous supercritical phase transitions which give rise to various types of dynamic and/or equilibrium protein clusters.
authors.affiliation: Institute of Biology, Karelian Research Center RAS, Pushkinskaya 11, 185910, Petrozavodsk, Russia. rozhkov@krc.karelia.ru
authors.forename: S P
authors.initials: SP
authors.lastname: Rozhkov
authors.forename: A S
authors.initials: AS
authors.lastname: Goryunov
mesh_terms: D004305:Dose-Response Relationship, Drug; D009113:Muramidase / Q000737:chemistry*; D044367:Phase Transition; D055550:Protein Stability / Q000187:drug effects; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions; D013816:Thermodynamics
chemical_list: D012996:Solutions; D012965:Sodium Chloride; D009113:Muramidase