该论文采用多光谱、表面等离子共振和分子对接，研究虾青素（Astaxanthin，AST）立体异构体与牛血清白蛋白（Bovine Serum Albumin，BSA）的相互作用机制。研究发现，AST异构体均结合于BSA亚结构域Ⅱ A和Ⅲ A的交界处，并且对蛋白质的构象没有明显影响。AST异构体对BSA具有相似的结合亲和力（左旋AST 4.17×10-7 mol/L，右旋AST 3.91×10-7 mol/L）和结合动力学（慢结合、慢解离），然而在较高浓度下（0.35~1.78 μmol/L）左旋AST的最高结合响应值均高于右旋AST。此外，左旋和右旋AST与BSA相互作用的焓变ΔH分别为-175.09和-149.42 kJ/mol，熵变ΔS分别为-502.72和-417.65 J/(mol•K)，负值的ΔH和ΔS表明AST-BSA发生结合的主要相互作用力是氢键和范德华力。分子对接显示左旋AST与Lys504、Thr190残基形成键长为2.0 Å、2.7 Å的氢键，而右旋AST与Arg435残基形成键长为2.9 Å的氢键。这项研究有助于阐明AST立体异构体与BSA的结合机制，并为AST异构体在血液循环中潜在的药代动力学提供重要的理论指导信息。

The mechanisms underlying the interaction between the two optical isomers of astaxanthin (AST) and bovine serum albumin (BSA) were investigated based on multiple spectroscopic, surface plasmon resonance, and molecular docking analyses. Both AST isomers were found to bind to BSA at the junction of subdomains IIA and IIIA, in the absence of any significant effects on protein conformation. The two isomers had similar binding affinities [4.17×10-7 mol/L for (3S,3’S)-AST and 3.91×10-7 mol/L for (3R,3’R)-AST for] and kinetic binding processes (slow binding, slow dissociation) for BSA. However, at higher concentrations (0.35~1.78 μmol/L), the highest binding response values obtained for (3S,3’S)-AST were higher than those for (3R,3’R)-AST. In addition, the change in enthalpy (ΔH) for the interactions between (3S, 3’S)-AST and (3R, 3’R)-AST and BSA were -175.09 and -149.42 kJ/mol, respectively, and the corresponding changes in entropy (ΔS) were -502.72 and -417.65 J/(mol•K). The negative values obtained for ΔH and ΔS indicate that hydrogen bonds and van der Waals forces were the main forces underlying the AST-BSA interactions. Molecular docking analysis revealed that (3S,3’S)-AST formed 2.0 Å and 2.7 Å hydrogen bonds with the Lys504 and Thr190 residues in BSA, respectively, whereas (3R,3’R)-AST formed a 2.9 Å hydrogen bond with the Arg435 residue. Our findings in this study contribute to elucidating the mechanisms associated with the binding of AST optical isomers to BSA, and will provide important theoretical guidance for the potential pharmacokinetics of AST isomers in blood circulation.

国家自然科学基金项目（ 32172195）；广东省自然科学基金项目（2021A1515012158）