Novel intercalators of pyrylium dye into double-stranded DNA.

Discovery is reported of novel intercalators without fused ring systems, pyrylium and thiopyrylium salt. 2-Methyl-4,6-bis-(N,N-dimethylaminophenyl) pyrylium salt 1 (Fig. 1) is, in particular, virtually non-fluorescent in aqueous solution, but form highly fluorescent complexes with double-stranded DNA (dsDNA), which yield more than 400 fold fluorescence enhancement at the peak emission. We report the synthesis, absorption and fluorescence properties of 1 and its thiopyrylium derivative 2 in comparison with other pyrylium 3, thiopyrylium 4 dyes and typical intercalator, ethidium bromide(EB). Compound 1 shows the absorption maximum at 540 nm and the red shift (about 40 nm) in the presence of dsDNA in similar to EB. The enhancement of fluorescence emission excited by visible light is extremely sensitive to the concentration of dsDNA comparing to that of EB. The thiopyrylium salt 2 with absorption maximum at 575 nm shows the similar profile in the absorption spectral shift and fluorescence enhancement to that of 1, when the dye binds to dsDNA.