Discrimination of DNA and RNA in cells by a vital fluorescent probe: lifetime imaging of SYTO13 in healthy and apoptotic cells.

Background: Of the few vital DNA and RNA probes, the SYTO dyes are the most specific for nucleic acids. However, they show no spectral contrast upon DNA or RNA binding. We show that fluorescence lifetime imaging using two-photon excitation of SYTO13 allows differential and simultaneous imaging of DNA and RNA in living cells, as well as sequential and repetitive assessment of staining patterns.