γ射线和电子束辐照对牛血清蛋白结构的影响

Effects of γ Rays and Electron Beam Irradiation on Bovine Serum Albumin Structure

为比较γ射线和电子束对牛血清辐照灭菌后蛋白损伤的差异,将牛血清辐照0~50 k Gy后,测定蛋白浓度、浊度、疏水性以及纯化后白蛋白的二级结构、热稳定性和分子量大小的变化。结果表明,牛血清辐照后蛋白浓度下降,浊度和疏水性上升,电子束辐照的变化幅度低于γ射线。以10 k Gy剂量为转折点,白蛋白的α螺旋含量先升后降,β折叠含量先降后升,变化范围分别为0%~15.2%和40.6%~52.4%。自由卷曲含量始终呈上升趋势。牛血清辐照后白蛋白组分的DSC图出现放热杂峰,出峰时间延长,γ射线辐照的峰温随剂量增加（77.4℃升至79.1℃）而升高,电子束辐照的趋势相反。照后白蛋白在GPC图中出现分布加宽的杂峰。这说明射线和电子束作用使牛血清同时发生交联和降解反应,破坏白蛋白二级结构,牛血清蛋白分子出现疏水基团外露,浊度增加,以及浓度下降的现象。常温辐照时电子束与γ射线效果差异不明显。

To compare differences in bovine serum protein damage following sterilization by γ rays and electron beam irradiation, bovine serum was irradiated with 0~50 kGy and protein concentration, turbidity, and hydrophobicity were determined. The secondary structure and thermal stability of the albumin purified from this bovine serum were analyzed. The results showed that the protein concentration decreased, and the turbidity and hydrophobicity increased. And the changes induced by electron beam irradiation were smaller than those induced by γ rays. At the threshold dosage of 10 kGy, the α-helical content of albumin had increased and thereafter decreased, and β-fold content first decreased and thereafter increased, with ranges of change of 0~15.2% and 40.6~52.4%, respectively. The content of random coils always showed an increasing trend. After irradiation, the DSC plot of the albumin fraction from the bovine serum showed an exothermic peak with a prolonged time, and the peak temperature increased with increased dose（77.4 ℃ to 79.1 ℃）; electron beam irradiation showed the opposite trend. In the GPC plot, the miscellaneous albumin peaks exhibited widening after irradiation. This shows that the interaction between the radiation and the electron beam causes crosslinking reactions and degradation of bovine serum, which disrupts the secondary structure of albumin and exposes the hydrophobic groups of bovine serum albumin to the exterior, increasing turbidity and decreasing concentration. No significant difference between the electron beam and γ rays was found at normal temperatures.