Absorption and fluorescence properties of some basic dyes complexing with nucleosides or nucleic acids.

The absorption and fluorescence spectra of some basic dyes were measured in the pre­ sence of large excess of adenosine or nucleic acids. The visible absorption band of dye shifts to longer wavelengths than that in free dye solution. The fluorescence spectral shape and peak posi­ tion remain unchanged on the addition of nucleoside or nucleic acid, while the fluorescence inten­ sity is enhanced or quenched to some extent depending on the nature of dyes. These results give us some information about the binding nature of basic dyes to nucleosides or nucleic acids.