Spectroscopic insights on the interaction between 4-(3,4 dimethoxyphenyl)-6-hydroxy-2- methylpyrimidine-5-carbonitrile and tryptophan.

Abstract

The interaction between 4-(3,4-dimethoxyphenyl)-6-hydroxy-2-methylpyrimidine-5-carbonitrile (DMPHMPC) and tryptophan (Trp) has been explored by fluorescence and Uv-visible studies. The formation of DMPHMPC-Trp complex leads to the fluorescence quenching of Trp was induced by DMPHMPC and evaluated by spectrofluorimetry. The fluorescence mechanism of Trp due to DMPHMPC is static in nature as analyzed by temperature effect study. Stern-Volmer quenching constants (Ksv) between DMPHMPC and Trp at three different temperatures 303, 308 and 313 K were obtained to be 9.12 x 10-3 , 4.07 x 10-3 and 1.63 x 10-3 L mol-1 , respectively which detected that the binding mechanism between DMPHMPC and Trp is predominantly static in nature. The calculated binding constants were 3.96 x 10-4 , 3.61 x 10-4 and 2.85 x 10-4 L mol-1 , respectively. The numbers of binding sites were 1.01, 0.92 and 0.91. Enthalpy change (ΔH) and Entropy change (ΔS) has positive value which indicates that hydrophobic interactions played a major role in the binding mechanism. Synchronous fluorescence suggesting that DMPHMPC bonded to Trp and placed in the close vicinity of Trp. Whereas the binding distance (r) between DMPHMPC and Trp was obtained to be 4.46 nm by Forster's theory of nonradiative energy transfer .