固氮酶中N2键合位的研究

用乙烯作为株针，从Ｎ＿２还原Ｈ＿２和体系的总电子数可以看出，乙烯不能与Ｎ＿２在固氮酶体系中相竞争，表明Ｎ＿２在固氮酶中的键合位很可能是蛋白键合ＦｅＭｏ－ｃｏ笼内的６Ｆｅ［μ＿６（η￣２，ε＿４）］模式和３Ｆｅ＋ｌＭｏ［μ＿４（η￣３，ε＿１）模式。而不是笼口的２Ｆｅ模式，     

FeMo－co模拟物体系的性能表征

根据蛋白键合ＦｅＭｏ－ｃｏ的Ｋ－Ｒ模型，合成了两个ＦｅＭｏ－ｃｏ模拟物的体系，这两个体系的可见光谱和Ｍｏ／Ｆｅ／Ｓ组成都接近于天然分离的ＦｅＭｏ－ｃｏ．模拟物体系经柠檬酸盐缓冲液稀释后，再与ＵＷ４５的组份１组合，都表现出高乙炔还原活性．     

氧缺位铁酸锰分解CO2成C的研究

空气氧化湿法制备的ＭｎＦｅ２Ｏ４在Ｈ２还原下，生成氧缺位铁酸锰ＭｎＦｅ２Ｏ４－δ，利用ＸＲＤ和Ｍｏｓｓｂａｕｅｒ谱等技术，对它的性质（还原性，晶格常数稳定性）进行了详细地研究，考查了在氧缺位铁酸锰（ＭｎＦｅ２Ｏ４－δ，δ〉１）及ＭｎＯ－ＦｅＯ固溶体下ＣＯ２分解成Ｃ的活性，结果表明能够有效地分解ＣＯ２成Ｃ，并且在反应以后自身转变成为化学计量的ＭｎＦｅ２Ｏ４，ＭｎＯ４－ＦｅＯ分解ＣＯ２以后，一部分变成     

FeMo—co模拟物体系的性能表征

根据蛋白键合ＦｅＭｏ－ｃｏ的Ｋ－Ｒ模型，合成了两个ＦｅＭｏ－ｃｏ模拟物的体系，这两个体系的可见光谱和Ｍｏ／Ｆｅ／Ｓ组成都接近于天然分离的ＦｅＭｏ－ｃｏ。模拟物体系经柠檬酸盐缓冲液稀释后再与ＵＷ４５的组份Ⅰ组合，都表现出高乙炔还原活性。     

Fe—TPPS3配合物电化学研究（Ⅱ）

用吸收光谱法和单扫描极谱法研究了Ｆｅ＾２＋与三磺基四苯基卟啉水溶性配合物在５．２〈ｐＨ〈５．９的ＨＡｃ－ＮａＡｃ底物中的性质。实验表明Ｆｅ＾２＋与ＴＰＰＳ３在该介质条件下，９０℃加热１５ｍｉｎ即可反应完全，确定了产物的组成比为１：１，Ｈ＾＋参与了这种电活性配合物的电极反应，ｐＨ对电活物性质的还原峰电流和峰电位影响明显；在ＴＰＰＳ３过量情况下，还原峰电流与Ｆｅ＾２＋的浓度成正比，可作为一种测定２铁的     

一种双核铁（Ⅲ）配合物的合成,表征,电化学性质及？…

合成了双核铁（Ⅲ）配合物Ｎａ２（Ｆｅ２（μ－ＯＡｃ）２（ＩＤＡ２）．５Ｈ２Ｏ（Ｉ）其中ＯＡｃ为乙酸根（ＣＨ３ＣＯＯ＾－）ＩＤＡ为亚氨基二乙酸根（ＨＮ（ＣＨ２ＣＯＯ＾－）２通过元素分析,摩尔电导,紫外可见光谱,红光光谱等方法对该配合物进行了表征,研究了它的电化学性质,并采用微量热法测定了其催化水解ＡＴＰ的动力学参数（Ｋｍ＝（２．８９８±０．１９５）×１０＾－４ｍｏｌ．Ｌ＾－１,ｋ２＝（４．６１７±０     

Sr2FeMoO6庞磁电阻陶瓷材料的微结构分析

研究了在钙钛矿结构Ｓｒ２ＦｅＭｏＯ６陶瓷中存在的多种不同的有序晶格结构。如Ｆｅ－Ｍｏ在简单钙钛矿结构ＡＢＯ３中的Ｂ位无序分布,Ｆｅ－ＭｏＢ位空间排列的ＮａＣｌ型有序分布的钙钛矿结构及在ｃ轴方向具有３倍简单钙钛矿结构周期的层状超结构等。结果表明：通过正确选择Ｓｒ２ＦｅＭｏＯ６陶瓷材料的微结构,可望大大提高其磁电阻性能。     

纺锤型γ－FeOOH的合成及其热分析研究

采用空气氧化ＦｅＳＯ４与Ｎａ２ＣＯ３作用生成的Ｆｅ（ＣＯ３）ｘ（ＯＨ）２（１－ｘ）悬浮液体系，通过稀土离子Ｙ３＋的掺杂合成出均匀纺锤型铁黄γ－ＦｅＯＯＨ微晶．由ＤＴＡ－ＴＧ和ＸＲＤ分析得出γ－ＦｅＯＯＨ随温度升高，发生如下相变过程：γ－ＦｅＯＯＨ→γ－Ｆｅ２Ｏ３→α－Ｆｅ２Ｏ３．本文还对γ－ＦｅＯＯＨ的脱水过程机制和以γ－ＦｅＯＯＨ为中间体经热处理制备的纺锤形γ－Ｆｅ２Ｏ３磁性能作了初步探讨．     

加压排代色谱法分离纯化~(55,59)Fe制备无载体~(60)Co和~(54)Mn的工艺研究

研究了用加压排代色谱法从堆照产物Ｆｅ中分离出无载体放射性同位素６０Ｃｏ，５４Ｍｎ及纯化５５，５９Ｆｅ．以ＤＴＰＡ作排代剂，Ｈ＋为阻滞离子，研究了阻滞离子、排代剂ｐＨ、线性流速及柱比等工艺条件对分离效果的影响．其最佳工艺条件为：ｃＤＴＰＡ＝０．０５ｍｏｌＬ－１，ｃＶｃ＝０．０５～０．１０ｍｏｌＬ－１；ｐＨ＝６．０～８．０；线性流速为７．５～１０ｃｍｍｉｎ－１；柱温：７０℃；柱比大于０．５．     

MTPEA非对映酰胺核磁共振化学位移不等性的研究

本文通过四个光学活性羧酸作为手性衍生化试剂研究了２－甲氧基－２－三氟甲基－２－苯基乙胺（ＭＴＰＥＡ）非对映酰胺中某些特征基团在不同ＮＭＲ中的化学位移不等性．ＭＴＰＥＡ非对映酰胺中所选择的探针基团在１Ｈ、１９Ｆ和１３ＣＮＭＲ中的化学位移差值分别为：０．０２～０．１６４（△δＯＭｅ）；０．０９５～０．５９９（△δＣＦ３）；０．３９～０．７４（△δＮＨＣＨ２）ｐｐｍ．     

Construction and characterization of double mutants in nitrogenase of<Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis>

Two mutants in nitrogenase of Klebsiella pneumoniae are constructed by site-directed mutagenesis and gene replacement procedure, which express the nitrogenases with Lysine and Glutamine substituting for α-Glutamine 190 and α-Histidine 194 respectively (Kp-Q α190 K and Kp-Hα194 Q). The above two substitutions are respectively introduced into a nifV mutant (expressing a citrate-containing nitrogenase) and sequentially two double mutants are obtained (Kp-Q α190 K-nifV and Kp-H α194 Q-nifV). All four mutants exhibit strict Nif phenotype under the N2-fixation condition and fail to grow diazotrophically. Altered nitrogneases are effectively depressed and the C2H2 reduction analysis shows that the double substitutions in Kp-Q α190 K-nifV abolish cell C2H2 reduction activity, but Kp-H α194 Q-nifV cells maintain a C2H2 reduction activity at 10% of that of wild type. Whole cell C2D2 reduction by all four mutants in comparison to the wild type and nifV mutant is also detected. The results show that only single α-Gln^194 substitution does not perturb the stereospecificity of protonation of C2D2. These results indicate that the α-Glutamine 190 and its combination with homocitrate are essential to the catalytic activity of nitrogenase and it is proposed that α-Glutamine 190 and its combination with homocitrate are involved in the proton and/or electron transfer to FeMoco. The nitrogenases from these double mutants will be useful in further analysis of the entry of the proton and/or electron to FeMoco and the substrate binding sites.     

花生根瘤菌共生吸氢和固氮的某些特性

用花生根瘤菌某些Hup~+和Hup~-菌株作回接,有接种的植株其根瘤数比对照多。所试菌株在共生条件下表现吸氢和乙炔还原活性。离体根瘤 72 h内其吸氧活性表现起初较低,随后逐渐升高,而后又逐渐下降;但乙炔还原活性则随时间的延长逐渐下降。根瘤吸氢依赖于氧并受CO的抑制。10％外源分子氢可提高乙炔还原活性20～60％。不同生长期的吸氢和乙炔还原活性以盛花期为最高。     

固氮鱼腥藻(Anabaena azotica Ley HB686)氮固定的能量和还原剂来源

某些外源碳水化合物提高固氮鱼腥藻的固氮能力.在光照和5%氧浓度条件下,分子氢促进固氮作用.光合抑制剂、呼吸链抑制剂和解偶联剂均抑制固氮酶活性,若同时加入葡萄糖,DCMU的抑制作用被解除,而对DBMIB和解偶联剂的作用影响甚微.固氮鱼腥藻固氮作用的还原剂与光合作用产生的碳化合物有关,能量主要由循环光合磷酸化供给.     

固氮鱼腥藻HB686固氮_放氢与谷氨酰胺合成酶的关系

固氮鱼腥藻HB686(Anabaena azotica HB686)的固氮和放氢被氨抑制与蛋氨酸砜亚胺(MSX)解除氨抑制的作用呈平行关系.谷氨酰胺能抑制固氮和放氢,而对谷氨酰胺合成酶(GS)和吸氢酶却有激活作用.固氮血腥藻在Mg~(2+)介质中的乙炔还原活性和放氢量皆比在Mn~(2+)介质中的高,而GS的活性则相反.不同波长的光照射对固氮、放氢和GS活性有不同的影响.     

Simulation for the primary electronic donor of photosystem Ⅱ in vitro

Histidine coordinated to Chl a is a distinct characteristic of Chl a in vivo. By using histidine analogue of 1-methylimidazole (C4H6N2) and measuring the UV/vis absorption, CD and MCD spectra of the interaction between C4H6N2 and Chl a in CCl4, we have obtained that: (ⅰ) In pure CCl4 solvent, Chl a molecule is in five-coordinate state, and two Chl a molecules form an asymmetric compact-dimer with strong coupling interaction. We propose that the two Chl a molecules are connected by two unequally coordinated Mg-O bonds (the two oxygen atoms come from the C== O of C131 keto and C17 ester, respectively); (ⅱ) when the molar ratio of C4H6N2/Chl a is 0.5 or 1 (corresponding to 2Chl a·1C4H6N2 and 2Chl a·2C4H6N2, respectively), significant changes have been observed in the absorption, CD and MCD spectra, which indicate that the Chl a remains in dimer form, but the coupling interaction between them reduces greatly. We postulate that C4H6N2 replaces the ligation of C== O of C17 ester and C131 keto to Mg atoms sequentially. The two Chl a molecules linked by two weakly interacted Mg...O bonds form a relaxed-dimer. The structure of the model is essentially similar to that of the primary electronic donor, P680, of photosystem Ⅱ in high plants and algae.     

Characterization of a FeMo cofactor-deficient MoFe protein from a nifE-deleted strain （DJ35） of Azotobacter vinelandii

A MoFe protein （△nifE Av1） with a purity of ～80% was purified from a nifE-deleted mutant of Azotobacter vinelandii DJ35. Compared with MoFe protein purified from wild-type strain OP （OP Av1）, △nifE Av1 had the same subunits composition, and had immune reaction with antibody to OP Av1, but its relative mobility in anaerobic native polyacrylamide gel electrophoresis （PAGE） was a little larger than that of OP Av1. Metal analysis showed that Mo and Fe contents of △nifE Av1 both apparently decreased. When complemented with OP Fe protein, △nifE Av1 had no C2H2-reduction activity, but it could be in vitro activated by FeMoco extracted from OP Av1. The circular dichroism （CD） spectrum of △nifE Av1 at ～450 nm was similar to that of OP Av1, while the EPR signal at g≈3.7 was absolutely silent, and the signal intensities at g≈4.3 and 2.0 decreased by 75% and 50%, respectively. The results indicated that △nifE Av1 purified from DJ35 was a FeMoco-deficient but P-cluster-containing MoFe protein.     

Phospholipid flippase associates with cisplatin resistance in plasma membrane of lung adenocarcinoma A549 cells

The fusion of the liposomes containing N-(7-nitro-2, 1, 3-benzoxadiazol-4-yl)-i ,2-hexadecanoylSn-glycero-3-1abeled phosphatidylethanolamine (NBD-PE) with A549 and A549/DDP cells was performed, and the activity of the phospholipid flippase in the plasma membrane of the cells was measured by fluorescence intensity change of NBDPE in the outer membrane. When A549 or A549/DDP cells containing N BD-PE were incubated at 37 C for 0, 30, 60 and 90 min, the fluorescence intensities in the outer membrane of the cells were 0%, 1.4%, 2.9% and 7.8% for A59cells, and 0%, 10.5 %, 15. 5 % and 18.3 % for A549/DDP cells respectively, demonstrating that the phospholipid flippase was distributed in the plasma membrane of As49 cells, but its activity in the drug-resistant A549/DDP cells was much higher than that in the A549 cells. When the A549/DDP cells were incubated with a multidrug resistance reverse agent, verapamil, for 60 min at 37C, the results showed that the NBD-PE in outer membrane decreased by 25.0% compared with the control's. Furthermore, when A549/DDP cells were incubated with 25 μmol/L cisplatin, which is a specific anticancer drug, the flippase activity decreased by 31.6%, and it further decreased with the increase of cisplatin concentration, suggesting that phospholipid flippase in the membrane might be related to the cisplatin-resistance of human lung adenocarcinoma cancer cells.     

Enhancement of Aminoacylase Activity by Sodium Citrate

IntroductionEnzyme activation is a common phenomenon inbiological studies. Many experiments havesuggested that enzyme activation is caused by theconformational change of the enzyme activesites[14 ] . Other papers have showed that theenhancement of enzyme activity is associated withsecondary or tertiary structural changes[5] .This study analyses aminoacylase (N-acylamino acid amidohydrolase,EC3 .5 .1 .1 4) ,adimeric protein,consisting of two identicalsubunits each with an active site. The zin…     

分子筛催化剂制备条件对催化转化NO的影响

采用浸渍法制备Cu_Na_ZSM_5催化剂 ,用C3H6 作还原剂 ,考察了贫燃条件下不同Cu2 +担载量、不同硅铝的量比和不同焙烧温度对Cu_Na_ZSM_5催化剂上选择还原NO的活性影响 ,并与Cu_SAPO_1 1、Cu_SAPO_34和Cu_Al2 O3进行比较 .实验结果表明 ,硅铝量比为2 5、担载Cu2 +的质量分数为 3%、 5 0 0℃焙烧制得的Cu_Na_ZSM_5分子筛催化剂具有较好的催化活性 ,反应温度为 350℃时 ,NO转化率高达 94. 3% .