[10] Light scattering and differential refractometry

This chapter presents the basic principles to discuss the problems and to describe the practical techniques involved in performing light scattering and differential refractometry measurements on multicomponent systems and to describe some of the instrumentation available for angular measurements. Among the techniques available for the characterization of macromolecules in solution, a particularly useful one is light scattering. With this method, it is possible to determine at relatively low protein concentration the molecular weight, the degree of association, interactions with solvent components, and, if the macromolecule is large enough, its size and general shape. When the dimensions of a particle become comparable to the wavelength of the incident radiation, interference occurs among the radiations scattered from individual elements within the particle. In the case of light scattering, this effect becomes significant when the maximal dimension of a particle becomes of the order of λ/10. As the wavelength of the incident radiation is of the order of 4000Å, this means that particle dimensions must attain 400Å to be resolved by light scattering.