Study of the Interaction Between Coenzyme Q10 and Human Serum Albumin: Spectroscopic Approach

UV–vis absorption, fluorescence, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopic methods were employed to reveal the mechanism of the binding between coenzyme Q 10 (CoQ 10 ) and human serum albumin (HSA) under simulated physiological conditions (pH = 7.4). The binding parameters were calculated by the fluorescence quenching method. The results demonstrate that the fluorescence quenching of HSA by CoQ 10 is mainly static quenching due to the formation of HSA–CoQ 10 complexes, and the number of binding sites ( n ) is equal to 1. The thermodynamic parameters (Δ H 0  = −43.18 kJ·mol −1 , Δ S 0  = −47.05 J·mol −1 ·K −1 , Δ G 0  = −29.15 kJ·mol −1 ) indicate that the enthalpy-driven binding process is favorable, and the main binding forces between CoQ 10 and HSA are hydrogen bonds and van der Waals forces. The competitive experiments using different site markers indicate that subdomain IIA (site I) of HSA is the primary binding site for CoQ 10 . The average binding distance ( r ) between HSA and CoQ 10 is 4.29 nm, which was estimated according to the Förster’s theory of non-radiation energy transfer. In addition, the UV–vis absorption, synchronous fluorescence, three-dimensional fluorescence, 8-anilino-1-naphthalenesulfonic acid fluorescence, CD spectra, and FT-IR spectroscopy data show slight conformational changes of HSA in the presence of CoQ 10 . These findings provide valuable binding information between HSA and CoQ 10 , which may be beneficial to pharmacokinetics research and could be used to design the dosage form of CoQ 10 .