Quasielastic laser scattering which utilizes the techniques of digital photon correlation and optical interferometry together with conventional methods will be used to investigate: 1. Molecular interactions, chemical equilibrium, and reaction kinetics of beta-lactoglobulin. An investigation of the translational diffusion coefficients of the monomer, dimer and octamer under appropriate pH, ionic strength and temperature conditions will be made. Then, by combining with measurements of the rotational diffusion coefficients of the dimer and the octamer, we get to check on the shape of the n-mers and their degree of hydration. Finally, with our knowledge of the equilibrum constant, degree of hydration, effects of charges (ionic strength and pH), size and shape and molecular weight of the system, we plan to study the association reactions by means of electrophoretic light scattering using the differential heterodyne technique. 2. Molecular interactions of Nucleohistone. Histone fractions and DNA (phage and calf thymus) will be studied separately as well as the nucleohistones. Both approaches, assembling the complex from histone fractions and DNA and disassembling purified chromatin, will be utilized. In the initial phase, we plan to study the DNA/histone complex from known combination of DNA and histone fractions.