中文摘要：

酶的热稳定性问题一直是生物科学领域的研究热点。构建氨基酸网络，从系统水平上研究酶热稳定性的影响因素是阐明嗜热酶耐热机制的重要途径。作者以超氧化物歧化酶（iron superoxide dismutase，Fe．SOD）的空间三维结构信息为基础，构建了不同类型的氨基酸相互作用网络。通过分析氨基酸网络的网络参数，发现热稳定性高的Fe-SOD氨基酸网络的平均度、平均连接强度及同配系数均高于常温的Fe-SOD氨基酸网络，而嗜热Fe-SOD氨基酸网络的特征路径长度小于常温的Fe-SOD氨基酸网络。此外，通过改变滑动窗口大小研究氨基酸网络中分子间相互作用区域范围，发现热稳定性高的Fe—SOD氨基酸网络中二级结构内部分子间连接紧密，二级结构之间及结构域之间的连接也较频繁。这些现象表明，嗜热Fe—SOD酶致密的内部结构缩短了氨基酸之间的距离，这更有利于稳定酶结构的作用力（如氢键和盐桥）的形成。实验结果进一步表明，通过研究氨基酸网络的网络参数可以阐述酶结构和功能之间的关系。

英文摘要：

There has been considerable interest in thermostability of thermophilic proteins in the field of biological science. Constructing amino acid networks is an important method to clarify the factors＇ influence on thermophilic enzyme resistant mechanism from the system level. Here, the authors constructed different types of iron superoxide dismutase （Fe-SOD） amino acid networks based on its three-dimensional structure. By analyzing the network properties of Fe-SOD amino acid networks, it was found that thermophilic Fe-SOD amino acid networks had greater average degree, stronger average strength and higher Pearson correlation coefficient than mesophilic Fe-SOD amino acid networks, and thermophilic Fe-SOD amino acid networks had shorter characteristic path length than mesophilic Fe-SOD amino acid networks. Moreover, through the analysis of intermolecular interaction range by changing slide windows size, it was observed that in thermophilic Fe-SOD amino acid networks, the molecules in secondary structure connections were much tighter and connections between secondary structures or domains were more frequent than mesophilic Fe-SOD. These results indicate that the tighter structure in thermophilic Fe-SOD make amino acids closer to each other, which helps to build new hydrogen bonds and salt bridges and keep Fe-SOD structure more stable. The results further show that the study of network properties of amino acid networks can help to find more relationships between protein structure and function.