天然橡胶中蛋白质二级结构及热变性

Secondary structure and thermal denaturation of protein in natural rubber

采用三级中红外光谱(一维中红外光谱、变温去卷积中红外光谱和二维中红外光谱)开展了天然橡胶(NR)及其含有蛋白质的二级结构研究。实验发现,NR蛋白质二级结构的红外吸收模式主要包括ν无规则卷曲、νβ-折叠、να-螺旋和νβ-转角。在293~393 K的温度范围内,随着测试温度的升高,NR蛋白质β-转角二级结构含量略有增加,β-折叠二级结构和无规则卷曲二级结构含量略有减少,而α-螺旋二级结构含量基本不变。结果表明,蛋白质二级结构对热的敏感程度及官能团变化快慢顺序都存在着较大的差异性,蛋白质β-转角二级结构最先改变,且变化早于α-螺旋二级结构。热扰动因素下,蛋白质β-转角二级结构改变则是整个NR蛋白质二级结构改变的关键步骤。本研究拓展了三级中红外光谱在NR中蛋白质二级结构及热变性的研究范围。

The study of natural rubber(NR)and its secondary structure containing proteins was carried out using tertiary mid infrared spectroscopy(one-dimensional MIR,temperature dependent deconvolution MIR,and two-dimensional MIR).The experiment found that the infrared absorption modes of the secondary structure of NR protein mainly includedνRandom-crimping,νβ-Sheet,να-Helix andνβ-Turning.With the test temperature increasing from 293 K to 393 K,the content of the NR proteinβ-Turning secondary structure of slightly increased,and the content ofβ-Turning and Random-crimping secondary structure decreased slightly,while the content ofα-Helix secondary structure was basically unchanged.The thermal denaturation of NR protein secondary structure was further studied by two-dimensional MIR.The results indicated that the sensitivity of the secondary structure of NR protein to heat and the sequence of the change of functional groups were quite different.Theβ-Turning secondary structure changed firstly and earlier thanα-Helix secondary structure.Under thermal disturbance,the proteinβ-Turning secondary structure changer was the key step of the secondary structure change of the whole NR protein.This study expanded the research scope of the tertiary MIR in the secondary structure and thermal denaturation of protein secondary structure in NR.