1. The following results are extracted from last year's report, were obtained in collaboration with T. Scherer of Genentech. The concentration dependence of light scattering of solutions of two different monoclonal IgGs over a concentration range of up to over 150 g/L at several different salt concentrations ranging from 40 to 600 mM NaCl has been analyzed in the context of an effective hard particle model allowing for equilibrium self-association. The data are well fit by an effective hard sphere model that allows for the equilibrium association of monomeric IgG to form a dimer and a tetramer, pentamer, or hexamer, depending upon salt concentration. A report of this work has been accepted for publication. 2. The concentration dependence of static light scattering and sedimentation equilibrium of solutions of Dextran 70 has been measured. Both measurements have been found to yield essentially identical thermodynamic descriptions of the concentration dependence of the free energy of polymer solvation. The results show that as solute concentration increases, the free energy of solvation of additional dextran is substantially larger than that of Ficoll 70, which in turn is substantially larger than that of BSA, three macromolecules of comparable mass. Although self-interaction is predominantly repulsive in all three solutions, the magnitude of repulsion is largest for Dextran, the most extended of the three species, and smallest for BSA, the most compact.
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