Figure 2. Chemical structures of photoconvertible cyanine dyes.

(a) Photoconversion of SYTO62 in the presence of NaN₃ (left) or D₂O (right). The curves are normalized for visualization purposes; however, we observed quenching of the green fluorescence by ~63% with NaN₃ (3.3 or 33.3 mM) and enhancement of the green fluorescence by ~31% with D₂O (45%). (b) Left: The backbone structure of SYTO red dyes (US Patent 20090068672), for which red-to-green photoconversion was observed. Right: Proposed structure of SYTO 62 based on LC-MS (MW = 550 g/mol), ¹H, ¹³C, gCOSY and DEPT NMR. Data on chemical analyses are available upon request. (c) Chemical structures of Cyanine 3 and Cyanine 5 (provided by Lumiprobe), for which photoconversion was not observed. (d) Chemical structures of Cyanine 3.5 and Cyanine 5.5 (provided by Lumiprobe), for which red-to-blue photoconversion was observed.