Correlation between cellular localization and binding preference to RNA, DNA, and phospholipid membrane for luminescent ruthenium(II) complexes.

Because of their unique photophysical properties, sensitively depending on environment, ruthenium dipyridophenazine (dppz) complexes are interesting as probes for cellular imaging with fluorescence microscopy. Here three complexes derivatized with alkyl ether chains of varied length, which exhibit distinctly different cellular staining patterns by confocal laser scanning microscopy, are studied regarding their binding preference for rRNA compared with calf thymus DNA (ct-DNA) and phospholipid membranes. Co-staining with commercial RNA and membrane-specific dyes shows that whereas the least lipophilic complex exclusively stains DNA inside the nucleus, the most lipophilic complex preferentially stains membrane-rich parts of the cell. Interestingly, only the intermediate lipophilic complex shows intense staining of the RNA-rich nucleoli. The intracellular localizations of the probes correlate with their binding preferences concluded from spectroscopy measurements.