Investigation the interaction of Daphnin with human serum albumin using optical spectroscopy and molecular modeling methods

The interaction between Daphnin with human serum albumin has been studied for the first time by spectroscopic methods including fluorescence quenching technology, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The results of fluorescence titration revealed that Daphnin can quench the intrinsic fluorescence of HSA by static quenching and there is a single class of binding site on HSA. In addition, the studies of CD spectroscopy and FT-IR spectroscopy showed that the protein secondary structure changed with increases of α-helices at the drug to protein molar ratio of 2. Furthermore, the thermodynamic functions ΔH0 and ΔS0 for the reaction were calculated to be 11.626 kJ mol−1 and 118.843 J mol−1 K−1 according to Van’t Hoff equation. The thermodynamic parameters (ΔH0 and ΔS0) and the molecular modeling study indicated that hydrophobic force played an important role to stabilize the Daphnin–HSA complex, and Daphnin could bind within the subdomain IIA of the HSA.

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► The interaction of HSA and Daphnin was studied by spectroscopic methods.
► The fluorescence quenching mechanism is static quenching.
► The interaction is driven mainly by hydrophobic force.
► The binding constants and thermodynamic parameters were calculated.
► The binding of Daphnin to HSA induced changes in the secondary structure of HSA.