To solve the problem of mulberry juice colour instability caused by ultraviolet radiation, we proposed the addition of mannoprotein (MP) to improve the stabilization of mulberry juice colour. First, the purified mulberry anthocyanins extracted (MAE) were identified by UFLC–MS, and their purity was determined by liquid-phase peak area normalization. The interaction mechanism between MP and MAE at different pH values was systematically investigated by Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and molecular docking. After conjugation with MAE, the secondary structure of MP changed slightly. The fluorescence quenching of MP by MAE was dose dependent. Thermodynamic analysis showed that the main interaction forces at pH 3.2 were hydrogen bonding and van der Waals forces, while the main force at pH 7.4 was hydrophobic forces. The molecular docking results verified the good binding properties of MP with cyanidin-3-O-glucoside (C3G) and cyanidin-3-O-rutinoside (C3R).

中文翻译：

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桑葚花色苷与酵母甘露糖蛋白相互作用机制研究

针对紫外线照射导致桑葚汁颜色不稳定的问题，我们提出添加甘露糖蛋白（MP）来提高桑葚汁颜色的稳定性。首先，通过UFLC-MS对纯化的桑葚花青素提取物（MAE）进行鉴定，并通过液相峰面积标准化确定其纯度。通过傅里叶变换红外(FTIR)光谱、圆二色性(CD)光谱、荧光光谱和分子对接等方法系统研究了不同pH值下MP和MAE之间的相互作用机制。与MAE缀合后，MP的二级结构略有变化。 MAE 对 MP 的荧光猝灭呈剂量依赖性。热力学分析表明，pH 3.2时主要相互作用力为氢键和范德华力，而pH 7.4时主要相互作用力为疏水力。分子对接结果验证了MP与花青素-3-O-葡萄糖苷(C3G)和花青素-3-O-芸香苷(C3R)良好的结合特性。