Light scattering of bovine serum albumin solutions: Extension of the hard particle model to allow for electrostatic repulsion

Abstract

SynopsisThe light scattering of bovine serum albumin (BSA) has been measured at protein concentration up to 90 g/L and at pH values between 4.4 and 7.6. The dependence of scattering on both protein concentration and pH may be quantitatively accounted for by a simple extension of the hard-sphere model for protein solutions [Ross, P. D. & Minton, A. P. (1977) J. Mol. Biol. 112,4374521 allowing for electrostatic repulsions between molecules. According to the extended model, the radius of the effective hard spherical particle representing BSA varies with the net electrical charge of the BSA molecule in a manner which may be calculated from electrostatic theory.

Automated measurement of the static light scattering of macromolecular solutions over a broad range of concentrations

“…The concentration dependence of the logarithm of the activity coefficient is obtained by modeling the protein molecule as an effective hard spherical particle [7]: (4) where φ denotes the fraction of volume occupied by protein, given by (5) and v eff is the specific volume of the effective hard spherical particle 2 . The infinite power series indicated in equation (4) is truncated after five terms since test calculations indicated convergence over the measured range of concentration.…”

“…2 We note that v eff is defined equal to the specific volume of a hard spherical particle whose interparticle interactions best mimic that of the actual protein under a particular set of experimental conditions. When protein molecules interact via repulsive electrostatic interactions the effective hard particle appears larger than the actual molecule [1,7,17].…”

“…However, such corrections cannot account quantitatively for the behavior of solutions at concentrations exceeding ca 50 g/L [5,6]. A semi-empirical treatment of nonideal behavior referred to as the effective hard particle model [1,7] has proven useful in accounting quantitatively for the concentration dependence of all three colligative properties of protein solutions at concentrations up to several hundred g/L [5,8]. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication.…”

Rigorous analysis of static light scattering measurements on buffered protein solutions

“…(3) [21]. This effective size is determined as the effective specific volume v eff , from which the second virial coefficient is calculated as B 22 = 4M 2 v eff .…”

Characterization of Protein-Protein Interactions via Static and Dynamic Light Scattering

“…In many cases a protein's nonspecific interactions may be modeled as those of hard, impenetrable spheres, albeit with an effective specific volume v eff different from that of the molecule's actual specific volume, resulting in a virial expansion containing only one independent parameter describing the non-ideality (Minton & Edelhoch, 1982):…”