EXCIMER FLUORESCENCE TO MONITOR TRANSITIONS OF THE ASSOCIATION-DISSOCIATION EQUILIBRIA INDUCED BY DILUTION OF PROTEINS COMPOSED OF SUBUNITS

Dilution is a simple method to induce shifts of the association-dissoc iation equilibria of protein subunits. Excimer fluorescence is useful to monitor changes of equilibria in dilute solution, which has been sh own in a well-characterized protein, actin. Actin was labeled with a f luorescent probe; N-(1-pyrenyl)iodoacetamide. When actin was diluted i n low ionic strength buffer, the relative excimer fluorescence decreas ed. This arose from the conformational drift of actin, which resulted in a change in the association-dissociation equilibria of actin subuni ts in the dilute solution. Since dilution effects are often observed i n other proteins, excimer fluorescence would be a useful sensitive tec hnique to detect shifts of association-dissociation equilibria in dilu te solution.