Nonphotochemical hole burning spectroscopy of a mitochondrial selective rhodamine dye molecule in normal and cancerous ovarian surface epithelial cells

Results are presented of nonphotochemical hole burning experiments on the mitochondrial dye rhodamine 800 (MitoFluor Far Red 680, Molecular Probes) incubated with two human ovarian surface epithelial cell lines: OSE(tsT)-14 normal cells and OV 167 carcinoma (cancer) cells. This dye is believed to be selective for the plasma and inner membranes of the mitochondria. Importantly, the dispersive (distributed) growth kinetics of zero-phonon holes were found to be significantly different with the OV 167 line exhibiting the higher burn efficiency. This may reflect greater structural heterogeneity of that line. Equally interesting is that the permanent dipole moment change (Δμ) for the S₀ → S₁ transition of the dye is markedly different for the two cell lines, the Δμ value for the carcinoma cell line being a factor of 1.5 higher. Discussion of this finding in terms of membrane potentials is given.