固氮酶及合成氨Fe催化剂中N2的络合位

用乙烯为探针研究了固氮酶中Ｎ２的键合位，结果表明，乙烯不能与Ｎ２在固氮酶体系中相竞争，提出Ｎ２在固氮酶中键合位很可能是蛋白键合ＦｅＭｏ－ｃｏ笼内６Ｆｅ位的μρ（η＾２，ε４）ｔ ３Ｆｅ＋１Ｍｏ位的μ４（η＾３，ε）方式，而不是笼口２Ｆｅ位的μ２（η＾２）方式，在合成氨Ｆｅ催化剂中Ｎ２的络事方式可能是μ６（η＾３，ε３ ）。     

Use of mobile phase 18-crown-6 to improve peak resolution between mono- and divalent metal and amine cations in ion chromatography

It is difficult to quantify NH4+ by ion chromatography in the presence of high concentrations of Na+ due to peak overlap. The Dionex IonPac CS15 column, which contains phosphonate, carboxylate, and 18-crown-6 functional groups, was originally developed to overcome this problem. We have found that the addition of 18-crown-6 to the eluent promotes improved peak resolution between Na+ and NH4+ even at concentrations as high as 60,000 to 1 using this column. Its use also improves the separation of alkali and alkaline earth metal and amine cations. Mobile phase 18-crown-6 increased the retention times of CH3NH3+, NH4+, and K+, and decreased the retention time of Sr2+. The retention times of Li+, Na+, Mg2+, Ca2+, (CH3)2NH2+, and (CH3)3NH+ were not affected. This method makes possible the direct analysis of ammonia from nitrogenase, the enzyme responsible for biological nitrogen fixation. The resolution of the NH4+ peak from the Na+ and Mg2+ peaks improved from zero resolution to values of 6.19 and 5.65, respectively. This technique considerably reduces the analysis time of NH4+ in the presence of high concentrations of Mg2+ and Na+ over traditional indophenol measurements.     

Studies on Chem icalCom position ofIron-m olybdenum Cofactor fromNitrogenase by Fluorescence Analysis

ＩｎｔｒｏｄｕｃｔｉｏｎＮｉｔｒｏｇｅｎａｓｅｆｒｏｍａｖａｒｉｅｔｙｏｆＮ２－ｆｉｘｉｎｇｏｒｇａｎｉｓｍｓｉｓｃｏｍｐｏｓｅｄｏｆｔｗｏ－ｃｏｍｐｏｎｅｎｔｐｒｏｔｅｉｎ，ＭｏＦｅ－ｐｒｏｔｅｉｎａｎｄＦｅ－ｐｒｏｔｅｉｎ．Ｆｅ－ｐｒｏｔｅｉｎｃｏｎｔａｉｎｓａｓｉｎｇｌｅＦｅ４Ｓ４－ｃｌｕｓｔｅｒ，ｗｈｉｃｈｈａｓｔｈｅｆｕｎｃｔｉｏｎｏｆｔｒａｎｓｆｅｒｉｎｇｅｌｅｃｔｒｏｎｓｆｒｏｍｄｏｎｏｒｔｏＭｏＦｅ－ｐｒｏｔｅｉｎ．ＭｏＦｅ－ｐｒｏｔｅｉｎｃｏｎｔａｉｎｓＰ－ｃｌｕｓｔｅｒｐａｉ…     

[Fe2{SeC6H2‐2,4,6‐Ph3}2{N(SiMe3)2}2] and [Fe2{SeC6H2‐2,4,6‐Ph3}4], the First Three‐Coordinate Selenolatoiron Complexes

In a controlled manner , half or all the bis(trimethylsilyl)amido ligands of 1 can be replaced by selenolato ligands, resulting in the first selenolatoiron complexes 2 and 3 with three‐coordinate iron centers. They are stabilized by secondary metal–framework bonds (here metal–carbon) and could, since they are coordinatively unsaturated, possibly serve as model compounds of the FeMo cofactor of nitrogenases.