考虑电网结构脆弱性的配电网网架优化规划

基于复杂网络理论,从网络拓扑结构角度对配电网网架结构的脆弱性进行评估。建立了以配电网投资及运行费用最小、结构脆弱性指标最优为目标的配电网网架多目标优化规划模型。采用改进最小生成树算法,并将经济性指标的减少率和结构脆弱性指标的增长率之和作为迭代过程中的目标函数,将多目标问题转化为单目标进行求解,通过16节点算例验证了该方法在求解多目标配网优化规划问题中的可行性。算例结果表明,所建立的优化规划模型能够有效地评估配电网的结构脆弱性,并能求得结构稳定、经济性好的规划方案。     

维生素C的结构、性质及在烹调中的变化

本文主要阐述了维生素C的结构，性质及在烹调中的变化。     

Electrostatic effect on electron transfer between cytochrome b5 and cytochrome c

The binding and electron transfer between wild type, E44A, E56A, E44/56A, E44/48/56A/D60Aand F35Y variants of cytochrome b5 and cytochrome c were studied. When mixed with cytochrome c, the cytochrome b5E44/48/56A/D60A did not show the typical UV-vis difference spectrum of absorption, indicating that the alteration ofthe surface electrostatic potential obviously influenced the spectrum. The electron transfer rates of wild type cytochromeb5, its variants and cytochrome e at different temperature and ionic strength exhibited an order of F35Y > wild type >E56A > E44A > E44/48/56A/D60A. The enthalpy and entropy of the reaction did not change obviously, suggestingthat the mutation did not significantly disturb the electron transfer conformation. The investigation of electron transfer rateconstants at different ionic strength demonstrated that electrostatic interaction obviously affected the electron transfer pro-cess. The significant difference of Cyt b5 F35Y and E44/48/56A/D60A from the wild type protein further confirmed thegreat importance of the electrostatic interaction in the protein electron transfer.     

Structure of cytochrome c nitrite reductase.

The enzyme cytochrome c nitrite reductase catalyses the six-electron reduction of nitrite to ammonia as one of the key steps in the biological nitrogen cycle, where it participates in the anaerobic energy metabolism of dissimilatory nitrate ammonification. Here we report on the crystal structure of this enzyme from the microorganism Sulfurospirillum deleyianum, which we solved by multiwavelength anomalous dispersion methods. We propose a reaction scheme for the transformation of nitrite based on structural and spectroscopic information. Cytochrome c nitrite reductase is a functional dimer, with 10 close-packed haem groups of type c and an unusual lysine-coordinated high-spin haem at the active site. By comparing the haem arrangement of this nitrite reductase with that of other multihaem cytochromes, we have been able to identify a family of proteins in which the orientation of haem groups is conserved whereas structure and function are not.