Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland 20892-0830, USA.
Two new applications of the recently developed technique of composition gradient static light scattering (CG-SLS) are presented. 1), The method is demonstrated to be capable of detecting and quantitatively characterizing reversible association of chymotrypsin and bovine pancreatic trypsin inhibitor in a solution mixture and simultaneously occurring reversible self-association of chymotrypsin at low pH in the same mixture. The values of equilibrium constants for both self- and heteroassociation may be determined with reasonable precision from the analysis of data obtained from a single experiment requiring <15 min and <1 mg of each protein. 2), Analysis of the results of a single CG-SLS experiment carried out on Ftsz, a protein that self-associates to form linear oligomers of indefinite size in the presence of guanosine diphosphate, yields the dependence of the equilibrium constant for monomer addition upon oligomer size.