A Quantitative Examination of the Buoyant Behavior of Macromolecules of Known Molecular Weight in a Density Gradient at Equilibrium in the Ultracentrifuge

Author: Ifft, James Brown

Year: 1962

Degree: Dissertation (Ph.D.)

Advisor: Vinograd, Jerome Rubin

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/VKXK-ZC50

Abstract

The quantitative aspects of the method of sedimentation equilibrium in a density gradient with a purified protein of known molecular weight have been examined.

In order to quantitatively evaluate the results of density gradient experiments, the density distribution and the density gradient in the salt solution at equilibrium in the ultracentrifuge must be known. Calculations based on thermodynamic data were made to determine these quantities. The results of this work are given in Part I.

Because of the large hydrostatic pressures encountered during centrifugation, it was necessary to evaluate the effects of pressure on the results. In Part II, an experimental investigation of the changes in banding position of deoxyribonucleic acid (DNAY and tobacco mosaic virus (TMV) with pressure was made. A useful quantity involving the compressibilities of the solution and of the solvated macromolecule was obtained. The results agree with the thermodynamic theory presented.

An experimental investigation of bovine serum mercaptalbumin (BMA) in a variety of salt solutions was carried out. Part III presents the experimental techniques and the methods of calculation for such experiments. The net hydration of BMA was determined solely from the ultracentrifuge results. The extent of anion binding was independently determined to obtain the net hydration of the protein-salt complex and the density gradient required to calculate the solvated molecular weight.

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