New methods in sedimentation analysis using the analytical ultracentrifuge.

A general procedure was laid down for estimating precise molecular weights by ultracentrifugation equilibrium using schlieren optical system. The phase plate diaphragm was checked against the knife edge of the schlieren optical system, and it was observed that the results using both the diaphragms are quite similar. The temperature indicating and control system of the MSE ultracentrifuge was also checked by running sedimentation velocity experiments at a wide range of temperatures, and it was found that the results of such experiments on s20,w are consistent, and are independent of temperature to the range studied. When similar experiments were performed on the Beckman Model E, the results were temperaure dependent. The new methods (Rowe and Rowe Method II and III) yielded excellent results. The method II provides satisfactory results for ideal systems using presmoothed data of concentration or concentration gradient as a function of distance from the axis of rotation. The method III provides acceptable results of Mo from data of a single sedimentation equilibrium experiment for both ideal and non-ideal systems. For both the methods to work it is essential to smooth the data with the help of fourier series, which is devised by incorporating it in the programs used by the digital computer. Procedures were also developed to determine Mo values by using hand smoothed data (instead of fourier smoothed data) with the desk computer. these procedures have made it possible to get comparable results of MO from a single photograph taken at equilibrium with any optical system without the cost of digital computer. Finally it is concluded that the new methods can be used for the estimation of precise values of molecular weights from a data of single experiment obtained by using any optical system.