Use of synchronously excited fluorescence to assess the accumulation of membrane potential probes in yeast cells

Evaluation of emission spectra of fluorescent probes used for the monitorin g of membrane potential in microbial cells can be greatly facilitated by us ing synchronously excited spectroscopy (SES). This method permits the suppr ession of undesirable spectrum components (contributions due to scattered l ight or cell autofluorescence) and leads to considerable increase in monito red emission intensity and to narrowing of spectral peaks. It allows an eff icient fractional decomposition of the probe fluorescence spectra into thei r free and bound dye fluorescence components. The usefulness of the method was tested by monitoring the accumulation of the fluorescent membrane poten tial probe diS-C-3(3) in yeast cells, which serves as a qualitative measure of the membrane potential.