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Updated: May 15, 2026

Structural Studies of Macromolecules in Solution using Small Angle X-Ray Scattering
Published on: November 5, 2018
A potential for overestimating the absolute magnitudes of second virial coefficients by small-angle X-ray scattering
David J Scott1, Trushar R Patel, Donald J Winzor
1National Center for Macromolecular Hydrodynamics, School of Biosciences, University of Nottingham, Sutton Bonington, UK. david.scott@nottingham.ac.uk.
Abstract:
Theoretical consideration is given to the effect of cosolutes (including buffer and electrolyte components) on the determination of second virial coefficients for proteins by small-angle X-ray scattering (SAXS)-a factor overlooked in current analyses in terms of expressions for a two-component system. A potential deficiency of existing practices is illustrated by reassessment of published results on the effect of polyethylene glycol concentration on the second virial coefficient for urate oxidase. This error reflects the substitution of I(0,c3,0), the scattering intensity in the limit of zero scattering angle and solute concentration, for I(0,0,0), the corresponding parameter in the limit of zero cosolute concentration (c3) as well. Published static light scattering results on the dependence of the apparent molecular weight of ovalbumin on buffer concentration are extrapolated to zero concentration to obtain the true value (M2) and thereby establish the feasibility of obtaining the analogous SAXS parameter, I(0,0,0), experimentally.
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