Spectroscopic analysis of the interaction between thiazolo[2,3-b]pyrimidine analogues and bovine serum albumin

The interaction between thiazolo[2,3-b]pyrimidine (TZPM) analogues and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and UV–Vis spectroscopy at two different temperatures (299 and 307 K) under imitated physiological conditions. The results indicate that both static quenching and dynamic quenching contribute to the fluorescence quenching of BSA by TZPM. The binding constant (Ka) and binding sites (n) were calculated from the obtained spectra. Based on the Förster non-radiation energy transfer theory, the average binding distance between BSA and TZPM was estimated. The synchronous fluorescence spectra indicate that the conformation of BSA has been changed. The comparison of binding potency of TZPM and BSA suggests that the substituents on the benzene ring enhance the binding affinity of TZPM and BSA. We investigated the possible sub-domains on BSA that bind TZPM by displacement experiments. Furthermore, to explore the effect of molecular structure on the binding, a study on quantitative structure–property relationship (QSPR) was performed, the quantitative relationship equation of R0, r and Ka were obtained. We observed that R0, r and Ka between BSA and TZPM is connected with the margin of the highest and the lowest occupied orbital energy (ΔE), dipole moment (μ), Molar Volume (Vm), Mole Mass (M).

Graphical abstractThe interaction between thiazolo[2,3-b]pyrimidine (TZPM) analogues and bovine serum albumin (BSA) was studied by fluorescence and UV–Vis spectroscopy. The quenching mechanism, binding constants, and binding distance were obtained. The synchronous fluorescence spectra indicated that the conformation of BSA has been changed. The comparison of binding potency of TZPM and BSA suggested that the substituents on the benzene ring enhance the binding affinity of TZPM and BSA.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We explored the interaction between BSA and TZPM by spectroscopic methods. ► The fluorescence quenching mechanism is combined quenching. ► The binding constants, binding sites and binding distances were calculated. ► The synchronous fluorescence indicated that the conformation of BSA has changed. ► The substituents on the benzene ring enhance the binding affinity of TZPM and BSA.