Multispectral and molecular docking investigations on the interaction of primethamine/trimethoprim with BSA/HSA

Primethamine (PMA) and trimethoprim (TMP) were investigated as traditional coccidiostats on the binding of bovine serum albumin (BSA) and human serum albumin (HSA) by multispectral and molecular docking techniques. The Stern-Volmer plots and time-resolved fluorescence measurement declared that PMA/TMP quenching the intrinsic fluorescence of BSA/HSA was static quenching process. The binding constants (K_a) and binding sites (n) were calculated at different temperatures. Meanwhile, thermodynamic parameters showed electrostatic forces played a leading role in the interaction of PMA/TMP with BSA/HSA. Some metal ions such as K⁺, Mg²⁺, Cu²⁺, Ca²⁺, Zn²⁺ and Fe³⁺ had no effects on the binding system. The UV-vis absorption spectra confirmed that the interaction between PMA/TMP and BSA/HSA did happen. The analyses of synchronous fluorescence, FT-IR and circular dichroism spectra illustrated that PMA/TMP changed the secondary structures of BSA/HSA. According to Förster non-radiative energy transfer theory, the binding distance between PMA/TMP and BSA/HSA was calculated. The binding location of PMA/TMP to BSA/HSA was identified as sub-domain IIA, which was further confirmed by molecular docking.Communicated by Ramaswamy H. Sarma.