丙二醛氧化对米糠蛋白结构及功能性质的影响

选取丙二醛（malondialdehyde，MDA）代表脂质过氧化反应中的活性次生氧化产物，借助蛋白质化学理论和谱学分析技术等手段，研究脂质过氧化产物对米糠蛋白结构和功能性质以及构效关系的影响。结果表明，米糠蛋白羰基含量随MDA氧化诱导浓度的增加而增大，而游离氨基含量逐渐减少。米糠蛋白α-螺旋和β-折叠含量随MDA氧化诱导浓度增加逐渐增大，β-转角结构和无规卷曲结构随之呈现逐渐降低的变化趋势。MDA氧化诱导的米糠蛋白色氨酸荧光λmax逐渐蓝移。低氧化诱导浓度下MDA对米糠蛋白亚基组成无显著影响，随着MDA氧化诱导浓度增加，分子质量为53、49、36、21、14 kDa的亚基归属条带均有所变浅，条带逐渐变窄，并且分子质量为36、21、14 kDa的亚基逐渐消失。随着MDA氧化诱导浓度的增大，米糠蛋白粒径、多分散指数、浊度及泡沫稳定性均随之逐渐增大，而氧化米糠蛋白溶解度、表面疏水性、乳化性、乳化稳定性和起泡性逐渐降低。

Effects of Oxidation by Malondialdehyde On the Structure and Function of Rice Bran Protein

The effect of malondialdehyde (MDA) as a representative reactive secondary oxidation product from lipid peroxidation reaction on the structure and functional properties of rice bran protein (RBP) as well as its structure-activity relationship was investigated by means of the theory of protein chemistry and spectroscopies. It was found that the carbonyl content of RBP increased with increasing MDA concentration, while the free amino content decreased gradually. Besides, the α-helix and β-sheet content of oxidized RBP increased with MDA concentration, whereas the opposite was true for the random coil and β-turn. The maximum absorption wavelength (λmax) of oxidized RBP was blue-shifted. The subunit composition of RBP was not significantly affected by low concentrations of MDA. With increasing the MDA concentration, the intensity of bands near 53, 49, 36, 21 and 14 kDa all decreased and the color became lighter; the 36, 21 and 14 kDa bands gradually disappeared. Increasing MDA concentration led to higher, particle size, polydispersity index (PDI), turbidity and foam stability but lower solubility, surface hydrophobicity, emulsifying capacity, emulsion stability and foamability of oxidized RBP.