Ultracentrifugation, analytical calculation

With this relationship for all samples was calculated from ninh This M is used for evaluating the reaction data. The ultracen rifuge (u.c measurements were carried out in a Spinco model E analytical ultracentrifuge, with 0.4% solutions in 90% formic acid containing 2.3 M KCl. By means of the sedimenta- ion diffusion equilibrium method of Scholte (13) we determine M, M and M. The buoyancy factor (1- vd = -0.086) necessary for tSe calculation of these molecular weights from ultracentrifugation data was measured by means of a PEER DMA/50 digital density meter. 

When a cesium chloride solution is spun in an ultracentrifuge, a density gradient is formed. The position of DNA in the gradient is determined by its G + C content, which can be calculated from the relative position of a second DNA of known density. Determinations are generally made in an analytical ultracentrifuge, but a preparative ultracentrifuge will also serve for this purpose. 

Centrifugation data from measurements with an analytical ultracentrifuge are useful for characterizing glycoenzymes. Pure gly-coenzymes yield symmetrical patterns when examined by this procedure. Sedimentation measurements can be made at several concentrations of the enzyme, and a number of physical constants characteristic of the molecule can be calculated from these data. On the basis of such measurements and calculations, it was determined that chloroperoxidase, which contains carbohydrate, is homogeneous with respect to molecular size,21 and it was concluded that the carbohydrate component in the preparation of chloroperoxidase studied is chemically linked to the protein. 

This model is in accordance with the results from gradient sedimentation experiments in the analytical ultracentrifuge, which indicate an oblate overall shape of the enzyme. It was calculated that the oblate ellipsoid looks like a discus of 330 A in diameter and 46 A in thickness (58). Revision of the calculations for a molecular mass of 1 69 MDa gave slightly corrected values of 322 A in diameter and 54 A in thickness (Schmidt B, personal communication). 

Durchschlag H, Zipper P (2005) Calculation of Volume, Surface, and Hydration Properties of Biopolymers. In Scott DJ, Harding SE, Rowe AJ (eds) Analytical Ultracentrifugation Techniques and Methods. Royal Society of Chemistry, Cambridge UK, pp 389 31... 

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