Allowance for radial dilution in evaluating the concentration dependence of sedimentation coefficients for globular proteins
- 99 Downloads
The accuracy with which the concentration dependence of the sedimentation coefficient, s = s 0(1 − kc), can be quantified for globular proteins by commonly used procedures has been examined by subjecting simulated sedimentation velocity distributions for ovalbumin to c(s)‒s analysis. Because this procedure, as well as its g(s)‒s counterpart, is based on assumed constancy of s over the time course of sedimentation coefficient measurement in a given experiment, the best definition of the concentration coefficient k is obtained by associating the measured s with the mean of plateau concentrations for the initial and final distributions used for its determination. The return of a slightly underestimated k (by about 3%) is traced to minor mislocation of the air‒liquid meniscus position as the result of assuming time independence of s in a given experiment. Although more accurate quantification should result from later SEDFIT and SEDANAL programs incorporating the simultaneous evaluation of s 0 and k, the procedures based on assumed constancy of s suffice for determining the limiting sedimentation coefficient s 0—the objective of most s‒c dependence studies.
KeywordsConcentration dependence Sedimentation coefficient Sedimentation velocity Ultracentrifugation
Support of this investigation by the award of an NSERC Discovery Grant (RGPIN-2017-04003) to TRP is gratefully acknowledged. DJS is a Senior Molecular Biology and Neutron Fellow supported by the Science and Technology Facilities Council (UK).
- Fujita H (1962) Mathematical theory of sedimentation analysis. Academic Press, New YorkGoogle Scholar
- Lamm O (1929) Die Differentialgleichung der Ultrazentrifugierun Arkiv för matematik, astronomi och fysik 21B:2, 1–4Google Scholar
- Rowe AJ (2005) Weak interactions: optical algorithms for their study in the AUC. In: Harding SE, Rowe AJ (eds) Scott DJ. Analytical ultracentrifugation: techniques and methods. Royal Society of Chemistry, Cambridge, pp 484–500Google Scholar
- Schuck P (2005) Diffusion-deconvoluted sedimentation coefficient distributions for the analysis of interacting and noninteracting protein mixtures. In: Harding SE, Rowe AJ (eds) Scott DJ. Analytical ultracentrifugation: techniques and methods, Royal Society of Chemistry, Cambridge, pp 26–50Google Scholar