Evaluation of association constants from fluorescence data: A corrected method

Abstract

An equation is proposed for the evaluation of partition or association constants from fluorescence properties (such as spectrum shape or anisotropy) whose values are not linearly related to the solute distribution. The proposed procedure is applied to the binding of pyrene to beta-cyclodextrin (employing the I-1/I-3 relationship and fluorescence anisotropy) and to the association of pyrene to dioctadecyldimethylammonium small unilamellar vesicles (sonicated) and large unilamellar vesicles (injected). The results obtained in the latter system indicate that the pyrene partition constant between the vesicles and the aqueous medium is nearly 10 times larger in the small vesicles.