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The evaluation of standard sedimentation coefficient in band sedimentation of macromolecules

โœ Scribed by Mauro Belli

Publisher
Wiley (John Wiley & Sons)
Year
1973
Tongue
English
Weight
971 KB
Volume
12
Category
Article
ISSN
0006-3525

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โœฆ Synopsis

Abstract

Standardization in the calculation of the sedimentation coefficient of macromolecules by means of band techniques is discussed. When a sample of macromolecules suspended in a solvent is layered on to a denser bulk solution, the macromolecules do not sediment in this solution alone, but sediment in a mixture of bulk solution and sample solvent. This is caused by the diffusion between sample solvent and bulk solution.

Experimental evidence of this process is shown during band sedimentation of ribosomes when the variation of the density and the viscosity along the cell is measured. The calculation shows that in the experimental conditions frequently used, standardization made in the usual way leads to a sedimentation coefficient which is largely overestimated; while standardization yields the correct coefficient if the diffusion effect of the sample solvent in to the bulk solution is taken into account, together with possible deuteration effects.

A method to calculate the standard coefficient with the aid of a computer is proposed.

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