鸡卵黄免疫球蛋白的mPEG修饰及其稳定性研究

研究了单甲氧基聚乙二醇(mPEG)对鸡卵黄免疫球蛋白(IgY)的化学修饰，并通过傅里叶变换红外光谱、圆二色光谱和荧光光谱分析比较了修饰前后IgY的稳定性。首先用N-羟基琥珀酰亚胺活化的单甲氧基聚乙二醇(NHS-mPEG)对IgY进行化学修饰，确定了mPEG的最佳修饰条件，即IgY与mPEG摩尔比为1∶10、pH值为7、反应时间为1 h，所得产物mPEG-IgY修饰率为20.56%，活性保持率为87.62%。其次通过光谱分析法对IgY以及mPEG-IgY的热稳定性和酸碱稳定性进行了研究。结果表明，70 ℃温育120 min后，IgY的α-Helix，β-sheet，β-Turn，Random各二级结构含量由14.5%，42.1%，6.2%，37.2%变为1.6%，55.25%，5.8%，37.5%;mPEG-IgY的各二级结构含量由12.9%，42.7%，6.3%，38.1%变为3.1%，50.5%，7.2%，39.2%。同样酸碱处理后，mPEG-IgY比修饰前IgY所引起的二级结构变化更小。因此可以推断出IgY经过mPEG修饰后对温度、酸碱处理所引起的变性有着更强的稳定性。

Study on the Stability of Chicken Egg Yolk Immunoglobulin (IgY)Modified with mPEG

The objective of the present paper was to study the effect of monomethoxypolyethlene glycol (mPEG) modification on the stability of chicken IgY and compare the stability of the modification products by Fourier transform infrared spectroscopy (FTIR), CD spectrooscopy and fluorescence spectroscopy. NHS-mPEG was used to modify IgY after mPEG was activated with N-hydroxysuccinimide (NHS). The optimal reaction condition for modification was 1∶10 molar rate of IgY to mPEG at pH 7, reaction for 1 h, and the product was obtained with modification rate of 20.56% and activity reservation of 87.62%. In addition, the thermal and pH stability of IgY and mPEG-IgY was compared by spectroscopic methods. The results showed that the α-helix, β-sheet, β-turn, and random content of IgY changed from 14.5%, 42.1%, 6.2% and 37.2% to 1.6%, 55.25%, 5.8% and 37.5%, while mPEG changed from 12.9%, 42.7%, 6.3% and 38.1% to 3.1%, 50.5%, 7.2% and 39.2%, respectively, after incubating for 120 min at 70 ℃. For the treatment with acid-base, similarly, the structure changes of mPEG-IgY were smaller than IgY. Thus, it is indicated that IgY modified by mPEG had greater stable properties.