Department of Chemistry, National Institute of Technology Meghalaya, Shillong-793003, Meghalaya, India.
Phys Chem Chem Phys. 2020 Jan 29;22(4):2212-2228. doi: 10.1039/c9cp05301h.
In this work, the interaction of a bioactive tea polyphenol (-)-epigallocatechin gallate (EGCG) with bovine hemoglobin (BHb) along with its anti-oxidative behavior and the anti-glycation property have been explored using multi-spectroscopic and computational techniques. The binding affinity for EGCG towards BHb was observed to be moderate in nature with an order of 104 M-1, and the fluorescence quenching mechanism was characterized by an unusual static quenching mechanism. The binding constant (Kb) showed a continuous enhancement with temperature from 3.468 ± 0.380 × 104 M-1 at 288 K to 6.017 ± 0.601 × 104 M-1 at 310 K. The fluorescence emission measurements along with molecular docking studies indicated that EGCG binds near the most dominant fluorophore of BHb (β2-Trp37, at the interface of α1 and β2 chains) within the pocket formed by the α1, α2 and β2 chains. The sign and magnitude of the thermodynamic parameters, changes in enthalpy (ΔH = +17.004 ± 1.007 kJ mol-1) and in entropy (ΔS = +146.213 ± 2.390 J K-1 mol-1), indicate that hydrophobic forces play a major role in stabilizing the BHb-EGCG complex. The micro-environment around the EGCG binding site showed an increase in hydrophobicity upon ligand binding. The binding of EGCG with BHb leads to a decrease in the α-helical content, whereas that of the β-sheet increased. FTIR studies also indicated that the secondary structure of BHb changed upon binding with EGCG, along with providing further support for the presence of hydrophobic forces in the complexation process. Molecular docking studies indicated that EGCG binds within the cavity of α1, α2, and β2 chains surrounded by residues such as α1- Lys99, α1-Thr134, α1-Thr137, α1-Tyr140, α2-Lys127 and β2-Trp37. Molecular dynamics simulation studies indicated that EGCG conferred additional stability to BHb. Furthermore, moving away from the binding studies, EGCG was found to prevent the glyoxal (GO)-mediated glycation process of BHb, and it was also found to act as a potent antioxidant against the photo-oxidative damage of BHb.
在这项工作中，使用多光谱和计算技术研究了一种具有生物活性的茶多酚（-）-表没食子儿茶素没食子酸酯（EGCG）与牛血红蛋白（BHb）的相互作用及其抗氧化和抗糖化性质。观察到 EGCG 与 BHb 的结合亲和力为中等强度，其顺序为 104 M-1，荧光猝灭机制为不寻常的静态猝灭机制。结合常数（Kb）随温度的升高而连续增强，从 288 K 时的 3.468 ± 0.380×104 M-1 增加到 310 K 时的 6.017 ± 0.601×104 M-1。荧光发射测量和分子对接研究表明，EGCG 结合在 BHb（β2-Trp37，位于α1 和β2 链之间的最主要荧光团附近）位于由α1、α2 和β2 链形成的口袋内。热力学参数的符号和大小、焓变（ΔH = +17.004 ± 1.007 kJ mol-1）和熵变（ΔS = +146.213 ± 2.390 J K-1 mol-1）表明疏水相互作用在稳定 BHb-EGCG 复合物中起主要作用。配体结合后，EGCG 结合部位周围的微环境疏水性增加。EGCG 与 BHb 的结合导致α-螺旋含量减少，而β-折叠含量增加。FTIR 研究还表明，BHb 的二级结构在与 EGCG 结合后发生变化，同时为复合物形成过程中存在疏水相互作用提供了进一步的支持。分子对接研究表明，EGCG 结合在由α1-Lys99、α1-Thr134、α1-Thr137、α1-Tyr140、α2-Lys127 和β2-Trp37 等残基包围的α1、α2 和β2 链的空腔内。分子动力学模拟研究表明，EGCG 赋予 BHb 额外的稳定性。此外，除了结合研究之外，还发现 EGCG 可以防止乙二醛（GO）介导的 BHb 糖化过程，并且它还可以作为一种有效的抗氧化剂来抵抗 BHb 的光氧化损伤。
