Evaluation of pyrene fluorescence quenching in biological membranes

The redistribution between two excited forms of pyrene accompanying a change in the intramembrane probe concentration yields a set of fluorescence spectra that intersect at a single common (isobestic) point. Infensities of monomer and excimer fluorescence (Im and Ie, respectively) are related by a linear dependence: Ie+kIm=Is. The coefficient k depends on the membrane type and temperature. Fluorescence intensity at the isobestic point (Ii) along with the proportional quantity Is reflect the total steady-state level of excited pyrene forms and do not depend on the excimerization degree (Ie/Im ratio), and can be used when estimating the quenching degree of pyrene fluorescence in biological membranes.