Enhanced fluorescence of 4-(p-dimethylaminostyryl)pyridinium salts in the presence of biological macromolecules

Abstract

The fluorescence quantum yields of two cationic styrylpyridinium dyes, trans-4-(p-N,N-dimethylaminostyryl)-N-vinylbenzylpyridinium chloride (1) and trans-4-(p-N,N-dimethylaminostyryl)-N-phenethylpyridinium bromide (2), increase dramatically in the presence of low concentrations of DNA with slight blue shifts (4 and 8 nm, respectively) of the emission maxima. These spectral changes suggest that the dyes are interacting with double helical DNA. Dyes 1 and 2 display similar enhancements in fluorescence in the presence of proteins, such as bovine serum albumin, with blue shifts in the emission maxima of 28 and 33 nm, respectively, suggesting that they also interact with proteins. Equilibrium association constants in the order of 10⁴ l mol⁻¹ were determined for the binding of 1 and 2 to bovine serum albumin. This family of dyes may be useful for the fluorescence detection of very low concentrations of DNA and proteins, and for the fluorescence staining of DNA and proteins in electrophoresis gels.