Simultaneous Determination of Molecular Weights and Sedimentation Constants

Abstract

Within the last several years Archibald has indicated how molecular weights and sedimentation coefficients may be calculated from the ultracentrifuge data during the period of ap roach toward sedimentation equilibrium in a sector shaped cell. Applications of this method have been made to smat molecules by Porath and by Brown, Kritchevsky and Davies. Gutfreund and Ogston, and Baldwin have devised an independent method fqr the determination of sedimentation coefficients based on the flow of solute past a fixed surface in the cell, and have applied this to the study of polypeptides. In the present study we have correlated the two methods so that they may be applied simultaneously to the data obtained in a single experiment. The method employs phase-contrast schlieren optics of Wolter, Armbruster, Kossel and Strohmeier and Trautman and Burns. A two-coordinate comparator is used to measure diagrams from standard ultracentrifuge cells as well as from a boundary-forming cell described by Kegeles, and used here as a refractometer. We have found that both molecular weights and Sedimentation coefficients may be determined reliably within one hour of centrifugntion for raffinose and for bovine plasma albumin, by the proper choice of speed.

Pyruvate Dehyrogenase Component Subunit Structure of the Escherichia coli K 12 Pyruvate Dehydrogenase Complex

“…Capillary cells [29] or 12 mm double sector capillary cells were used for determinations of sedimentation coefficients ; sedimentation equilibrium measurements were performed in an Yphantis 6-channel cell, equipped with sapphire windows. All runs were performed a t 20".…”

Studies on Ovalbumin II. The Formation and Properties of S-Ovalbumin, a More Stable Form of Ovalbumin

“…was used. Values of 0 = (l/xc)(dc/dx), where x is the radial distance and c the concentration at a point in the cell, were determined from the photographed schlieren patterns by the integration method of Klainer and Kegeles (1955). A plot of 0 against x was extrapolated to give values of Om and Ob at the top and bottom menisci.…”

Studies on Mammalian and Human Pyruvate and Alpha-Ketoglutarate Dehydrogenation Complexes

“…The molecular weight was calculated at the meniscus with the equation proposed by Klainer and Kegeles (32).…”