玉米醇溶蛋白的磷酸化修饰及结构研究

玉米醇溶蛋白广泛应用于食品、医药、生物材料、纺织工业等领域，但蛋白不溶于水的性质限制了其应用范围。为改善其性质，本文用磷酸化修饰玉米醇溶蛋白，测定磷酸化修饰前后玉米醇溶蛋白的黏度、等电点、酸、碱稳定性等物理性质；用圆二色谱研究磷酸化修饰前后蛋白的二级结构和三级结构变化，用示差扫描量热法（DSC）测定蛋白的热稳定性。结果表明：Zein蛋白在80%乙醇溶液中的等电点（PdI）为pH 5.97，粒径为1436 nm。经磷酸化修饰后，蛋白与磷酸盐以O-磷酸键和N-磷酸键结合，酸性条件（pH 5.0）主要以O-磷酸键结合为主，中性及碱性（pH 7.0和9.0）条件下主要以N-磷酸键结合。同时，蛋白的黏度增加，等电点酸性漂移，α-螺旋结构含量降低，玻璃态转化温度升高。
Zein has widespread applications in food, medicine, biological materials, and the textile industry, but its use is limited to some degree due to the insolubility in water. To overcome this drawback, zein was phosphorylated by POCl3 and its physical properties of modified zein, such as viscosity, isoelectric point, as well as stability in acid and alkali were determined. Secondary and tertiary structures of zein before and after phosphorylation were measured by circular dichroism (CD), while thermal stability was determined using differential scanning calorimetry (DSC). The results showed that in 80% ethanol solution, the isoelectric point (PdI) of zein was at pH 5.97 and particle size was 1436 nm. Post modification, phosphate was combined with zein by O- and N- phosphate bonds, which mainly formed O-phosphate bonds under acidic conditions (pH 5.0) and N-phosphate bonds under neutral and alkaline conditions (pH 7.0 and 9.0). In addition, the viscosity of modified zein increased, the isoelectric point showed acidic shift, α-helix structure content reduced, and glass transition temperature increased.