Self‐association of β‐lactoglobulin A in acid solution. I. Translational diffusion coefficients

Abstract

SynopsisWe report measurements of the diffusion coefficient of p-lactoglobulin A (BLG-A) a t pH = 5.60 and 4.58 in 0.10 ionic strength acetate buffer by the techniques of analog photocurrent signal correlation and digital single-clipped photon correlation. At a concentration of 21 mg/ml and a pH of 4.58, the self-association of 0-lactoglobulin can be represented by a simple dimer-octamer equilibrium model. We determined the translational diffusion coefficient of the dimer and that of the octamer using the scattering results of Kumosinski and Timasheff in a dimer-octamer mixture. Our analysis shows that the dimer OLG-A does not change its size if the pH is varied from 5.60 to 4.58 and both species remain constant in size for temperature changes from 3.5" to 25°C Hydrodynamically, the octamers behave like closed-packed spheres with an effective radius of about 45 A according to the Stokes-Einstein relation.

A light-scattering characterization of membrane vesicles

“…where now Tr = 1/(2 <D> K2) instead of l/(<D>K2) and terms including 62 are assumed negligible. When the small scatterer (small x) limit is considered in expression 17, the expression reduces to that used by Chen et al (16) in QELS intensity autocorrelation studies of suspensions of meningococcal polysaccharides and by Chu et al (17) in QELS studies of lactoglobulin suspensions.…”