title: Oligomerization and phase separation in globular protein solutions.
abstract: We have chemically crosslinked a globular protein, gamma IIIb-crystallin, to produce a system of well-defined oligomers: monomers, dimers, trimers and a mixture of higher n-mers. Gel electrophoresis, size exclusion chromatography, quasielastic light scattering spectroscopy, and electrospray ionization mass spectrometry were used to characterize the oligomers formed. The liquid-liquid phase separation boundaries of the various oligomers were measured. We find that at a given concentration the phase separation temperature strongly increases with the molecular weight of the oligomers. This phase behavior is very similar to previous findings for gamma II-crystallin, for which oxidation-induced oligomerization is accompanied by an increase in the phase separation temperature. These findings imply that for phase separation, the detailed changes of the surface properties of the proteins are less important than the purely steric effects of oligomerization.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge 02139-4307, USA.
authors.forename: N
authors.initials: N
authors.lastname: Asherie
authors.forename: J
authors.initials: J
authors.lastname: Pande
authors.forename: A
authors.initials: A
authors.lastname: Lomakin
authors.forename: O
authors.initials: O
authors.lastname: Ogun
authors.forename: S R
authors.initials: SR
authors.lastname: Hanson
authors.forename: J B
authors.initials: JB
authors.lastname: Smith
authors.forename: G B
authors.initials: GB
authors.lastname: Benedek
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents; D003459:Crystallins / Q000737:chemistry* / Q000302:isolation & purification*; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D008027:Light; D008301:Maleimides; D013058:Mass Spectrometry; D008970:Molecular Weight; D011487:Protein Conformation; D012542:Scattering, Radiation; D012996:Solutions; D013438:Sulfhydryl Compounds / Q000032:analysis
chemical_list: D003432:Cross-Linking Reagents; D003459:Crystallins; D008301:Maleimides; D012996:Solutions; D013438:Sulfhydryl Compounds; C075594:1,6-bismaleimidohexane