TMRE (Tetramethylrhodamine ethyl ester, perchlorate) and TMRM are preferred dyes for quantitative measurements of membrane potentials using the Nernst equation. The dyes do not form aggregates in cell membranes and have minimal interaction with membrane proteins. Thus, the transmembrane distribution of the dyes is directly related to the membrane potential according to the Nernst equation. Biotium also offers TMRE, 2 mM in DMSO as a ready to use stock solution.    &lamba;Ex/&lamba;Em (MeOH) = 549/574 nm  Red solid soluble in DMSO, DMF or EtOH  Store at 4°C and protect from light  C26H27ClN2O7  MW: 515  [115532-52-0]