College of Food Science & Engineering, Qingdao Agricultural University, Qingdao, P. R. China.
J Sci Food Agric. 2023 Aug 30;103(11):5364-5375. doi: 10.1002/jsfa.12611. Epub 2023 Apr 26.
Whey protein-epigallocatechin gallate (WP-EGCG) covalent conjugates and non-covalent nanocomplexes were prepared and compared using Fourier-transform infrared spectra. The effect of pH (at 2.6, 6.2, 7.1, and 8.2) on the non-covalent nanocomplexes' functional properties and the WP-EGCG interactions were investigated by studying antioxidant activity, emulsification, fluorescence quenching, and molecular docking, respectively.
With the formation of non-covalent and covalent complexes, the amide band decreased; the -OH peak disappeared; the antioxidant activity of WP-EGCG non-covalent complexes was 2.59- and 2.61-times stronger than WP-EGCG covalent conjugates for 1-diphenyl-2-picryl-hydrazyl (DPPH) and ferric reducing ability of plasma (FRAP), respectively (particle size: 137 versus 370 nm). The antioxidant activity (DPPH 27.48-44.32%, FRAP 0.47-0.63) was stronger at pH 6.2-7.1 than at pH 2.6 and pH 8.2 (DPPH 19.50% and 26.36%, FRAP 0.39 and 0.41). Emulsification was highest (emulsifying activity index 181 m g , emulsifying stability index 107%) at pH 7.1. The interaction between whey protein (WP) and EGCG was stronger under neutral and weakly acidic conditions: K (5.11-8.95 × 10 L mol ) and K (5.11-8.95 × 10 L mol s ) at pH 6.2-7.1. Binding constants (pH 6.2 and pH 7.1) increased with increasing temperature. Molecular docking suggested that hydrophobic interactions played key roles at pH 6.2 and pH 7.1 (∆H > 0, ∆S > 0). Hydrogen bonding was the dominant force at pH 2.6 and pH 8.2 (∆H < 0, ∆S < 0).
Environmental pH impacted the binding forces of WP-EGCG nanocomplexes. The interaction between WP and EGCG was stronger under neutral and weakly acidic conditions. Neutral and weakly acidic conditions are preferable for WP-EGCG non-covalent nanocomplex formation. © 2023 Society of Chemical Industry.
采用傅里叶变换红外光谱法制备了乳清蛋白-表没食子儿茶素没食子酸酯（WP-EGCG）共价轭合物和非共价纳米复合物，并进行了比较。通过研究抗氧化活性、乳化、荧光猝灭和分子对接，分别考察了 pH（2.6、6.2、7.1 和 8.2）对非共价纳米复合物功能特性和 WP-EGCG 相互作用的影响。
随着非共价和共价复合物的形成，酰胺带减少；-OH 峰消失；WP-EGCG 非共价复合物的抗氧化活性比 WP-EGCG 共价轭合物对 1-二苯基-2-苦基肼（DPPH）和血浆铁还原能力（FRAP）分别强 2.59-2.61 倍（粒径：137 对 370nm）。在 pH 6.2-7.1 时，抗氧化活性（DPPH 27.48-44.32%，FRAP 0.47-0.63）强于 pH 2.6 和 pH 8.2（DPPH 19.50%和 26.36%，FRAP 0.39 和 0.41）。在 pH 7.1 时，乳化效果最佳（乳化活性指数 181m g ，乳化稳定性指数 107%）。在中性和弱酸性条件下，乳清蛋白（WP）和 EGCG 之间的相互作用更强：在 pH 6.2-7.1 时，K（5.11-8.95×10 L mol ）和 K（5.11-8.95×10 L mol s ）。结合常数（pH 6.2 和 pH 7.1）随温度升高而增加。分子对接表明，在 pH 6.2 和 pH 7.1 时，疏水力起关键作用（∆H>0，∆S>0）。在 pH 2.6 和 pH 8.2 时，氢键是主要作用力（∆H<0，∆S<0）。
环境 pH 影响 WP-EGCG 纳米复合物的结合力。在中性和弱酸性条件下，WP 和 EGCG 之间的相互作用更强。中性和弱酸性条件有利于 WP-EGCG 非共价纳米复合物的形成。© 2023 化学工业协会。
