5] The determination of the partial specific volume of proteins by the mechanical oscillator technique

Abstract

Publisher Summary The partial specific volume of a solute is a characteristic parameter that can be used in investigations of protein associations and changes in conformation, as well as in studies on protein solvent interactions and various other intermolecular interactions. It provides information needed for the determination of particle mass by means of ultracentrifugation and small-angle X-ray scattering. The precision density measurement in the apparatus described in the chapter is based on the determination of the natural frequency of an electronically excited, mechanical oscillator, its effective mass being composed of its own unknown mass and the well-defined, but also unknown, volume of the sample under investigation. To assure that this volume be well defined, the oscillator is made of a hollow, U-shaped glass tube that can be filled with the liquid sample. The mode of vibration is that of a bending-type oscillator. The positions of its vibrating nodes, which in fact determine the limits of the volume of sample taking part in the motion, is kept stable by the abrupt change in the cross-section of the glass tubes.