Studies on Interaction of Tyrosine with DNA by Fluorescence Spectra

Abstract

The fluorescence spectral characteristics of tyrosine in the presence of DNA and the interaction between them have been investigated. In the presence of salmon sperm DNA (SM DNA) the fluorescence intensity of tyrosine was strongly quenched with red shifts of excitation and emission peaks. In a neutral phosphate buffer, F ₀ /F of tyrosine was linear with the concentration of SM DNA from 7.80 × 10⁻⁶ to 1.25 × 10⁻⁴ mol L⁻¹, with a detection limit of 1.18 × 10⁻⁷ mol L⁻¹. The enhancement of UV absorbance of tyrosine was also observed. The interaction model between tyrosine and DNA was found to be a groove binding with additional confirmation by fluorescence polarization and KI quenching experiments. The pH and salt effects on the fluorescence properties were also investigated. The intrinsic binding constant and the binding site number were determined to be 2.24 × 10⁶ L mol⁻¹ in base pairs and 0.81 according to the newly deduced fluorescence equation.

Keywords:

• Tyrosine
• DNA
• Fluorescence quenching
• The groove model

Acknowledgments

This work was supported by the National Natural Science Foundation of China, the Excellent Teacher Program of MOE, P.R. China, the Teaching and Research Award Program for Outstanding Young Teachers in High Education Institutes of MOE, P.R. China, and the Key Project of Hunan Normal University.