Quantitative Characterization of the Interaction between Sucrose and Native Proteins via Static Light Scattering

Abstract

Compatible osmolytes, such as sucrose, are small organic compounds that are synthesized in cells to protect proteins and other macromolecules from the effect of osmotic stress. Our present work is to quantitatively characterize the interactions between native globular proteins and sucrose, which has long been known to stabilize proteins against denaturation by heat or chaotropes, and has been shown to attenuate structural fluctuations in native proteins. The composition-dependent static light scattering of binary mixtures of each of four dilute globular proteins--bovine serum albumin (BSA), ovalbumin, ovomucoid, soybean trypsin inhibitor (STI), and sucrose were measured over a broad range of sucrose concentrations. A conventional analysis of the dependence of excess light scattering of a single macrosolute in a continuum solvent yields unphysical results. Then the analysis is based upon multicomponent scattering theory, treating sucrose as well as protein as a scattering species, and is shown to yield reliable information about the nature and magnitude of solute-solute interactions in protein-sucrose mixtures. The results could be satisfactorily accounted for by an effective hard particle model that indicates the nature of the underlying interactions between sucrose and each protein.