Novel electrocatalytic procedure for the oxidation of alcohols, aldehydes, cyclic ketones, and carbon-hydrogen bonds adjacent to olefinic or aromatic groups
Simultaneous Quantification of Metabolites Involved in Central Carbon and Energy Metabolism Using Reversed-Phase Liquid Chromatography−Mass Spectrometry and in Vitro <sup>13</sup>C Labeling
作者:Wen-Chu Yang、Miroslav Sedlak、Fred E. Regnier、Nathan Mosier、Nancy Ho、Jiri Adamec
DOI:10.1021/ac801693c
日期:2008.12.15
Comprehensive analysis of intracellular metabolites is a critical component of elucidating cellular processes. Although the resolution and flexibility of reversed-phase liquid chromatography−mass spectrometry (RPLC−MS) makes it one of the most powerful analytical tools for metabolite analysis, the structural diversity of even the simplest metabolome provides a formidable analytical challenge. Here we describe a robust RPLC−MS method for identification and quantification of a diverse group of metabolites ranging from sugars, phosphosugars, and carboxylic acids to phosphocarboxylics acids, nucleotides, and coenzymes. This method is based on in vitro derivatization with a 13C-labeled tag that allows internal standard based quantification and enables separation of structural isomer pairs like glucose 6-phosphate and fructose 6-phosphate in a single chromatographic run. Calibration curves for individual metabolites showed linearity ranging over more than 2 orders of magnitude with correlation coefficients of R2 > 0.9975. The detection limits at a signal-to-noise ratio of 3 were below 1.0 μM (20 pmol) for most compounds. Thirty common metabolites involved in glycolysis, the pentose phosphate pathway, and tricarboxylic acid cycle were identified and quantified from yeast lysate with a relative standard deviation of less than 10%.
Designed four-helix bundle catalysts—the engineering of reactive sites for hydrolysis and transesterification reactions of p-nitrophenyl esters
作者:Lars Baltzer、Kerstin S Broo、Helena Nilsson、Jonas Nilsson
DOI:10.1016/s0968-0896(98)00218-1
日期:1999.1
designed that catalyze the hydrolysis and transesterification reactions of p-nitrophenylesters by a cooperative nucleophilic and general acid mechanism. The catalysts consist of two 42-residue peptides that fold into helix-loop-helix motifs and dimerise. They have previously been shown to recognize anionic and hydrophobicsubstrates and to follow saturation kinetics. The catalytic entity is a HisH(+)-His
l-Amino acid ligase catalyzes the formation of an α-peptide bond from unprotected l-amino acids in an ATP-dependent manner, and this enzyme is very useful in efficient peptide production. We performed enzyme purification to obtain a novel l-amino acid ligase from Bacillus subtilis NBRC3134, a microorganism producing peptide-antibiotic rhizocticin. Rhizocticins are dipeptide or tripeptide antibiotics and commonly possess l-arginyl-l-2-amino-5-phosphono-3-cis-pentenoic acid. The purification was carried out by detecting l-arginine hydroxamate synthesis activity, and a target enzyme was finally purified 1,280-fold with 0.8% yield. The corresponding gene was then cloned and designated rizA. rizA was 1,242 bp and coded for 413 amino acid residues. Recombinant RizA was prepared, and it was found that the recombinant RizA synthesized dipeptides whose N-terminus was l-arginine in an ATP-dependent manner. RizA had strict substrate specificity toward l-arginine as the N-terminal substrate; on the other hand, the substrate specificity at the C-terminus was relaxed.
l-氨基酸连接酶以依赖 ATP 的方式催化未受保护的 l-氨基酸形成 α-肽键,这种酶对高效生产多肽非常有用。我们进行了酶纯化,从生产多肽抗生素根肿灵的微生物枯草芽孢杆菌(Bacillus subtilis NBRC3134)中获得了一种新型 l-氨基酸连接酶。根瘤菌素是一种二肽或三肽抗生素,通常含有 l-精氨酰-l-2-氨基-5-磷酰基-3-顺式戊烯酸。通过检测精氨酰羟氨酸盐合成活性进行纯化,最终纯化出目标酶 1280 倍,产率为 0.8%。然后克隆了相应的基因,并将其命名为 rizA,rizA 的长度为 1 242 bp,编码 413 个氨基酸残基。研究人员制备了重组 RizA,发现重组 RizA 能以 ATP 依赖性方式合成 N 端为 l-精氨酸的二肽。RizA对N端底物精氨酸具有严格的底物特异性,而对C端的底物特异性则比较宽松。
New insights into the intercalation chemistry of Al(OH)3
作者:Gareth R. Williams、Saul J. Moorhouse、Timothy J. Prior、Andrew M. Fogg、Nicholas H. Rees、Dermot O'Hare
DOI:10.1039/c0dt01790f
日期:——
This paper reports a number of recent developments in the intercalation chemistry of Al(OH)3. From Rietveld refinement and solid-state NMR, it has been possible to develop a structural model for the recently reported [MIIAl4(OH)12](NO3)2·yH2O family of layered double hydroxides (LDHs). The M2+ cations occupy half of the octahedral holes in the Al(OH)3 layers, and it is thought that there is complete ordering of the metal ions while the interlayer nitrate anions are highly disordered. Filling the remainder of the octahedral holes in the layers proved impossible. While the intercalation of Li salts into Al(OH)3 is facile, it was found that the intercalation of MII salts is much more capricious. Only with Co, Ni, Cu, and Zn nitrates and Zn sulfate were phase-pure LDHs produced. In other cases, there is either no reaction or a phase believed to be an LDH forms concomitantly with impurity phases. Reacting Al(OH)3 with mixtures of MII salts can lead to the production of three-metal MII–MII′–Al LDHs, but it is necessary to control precisely the starting ratios of the two MII salts in the reaction gel because Al(OH)3 displays selective intercalation of M nitrate (Li > Ni > Co ≈ Zn). The three-metal MII–MII′–Al LDHs exhibit facile ion exchange intercalation, which has been investigated in the first energy dispersive X-ray diffraction study of a chemical reaction system performed on Beamline I12 of the Diamond Light Source.
本文报告了 Al(OH)3 插层化学的一些最新进展。通过里特维尔德细化和固态核磁共振,可以为最近报道的 [MIIAl4(OH)12](NO3)2-yH2O 层状双氢氧化物(LDHs)家族建立一个结构模型。M2+ 阳离子占据了 Al(OH)3 层八面体空穴的一半,人们认为金属离子完全有序,而层间硝酸根阴离子则高度无序。事实证明,不可能填满层中剩余的八面体孔。虽然锂盐很容易插层到 Al(OH)3 中,但我们发现 MII 盐的插层却更加反复无常。只有钴、镍、铜和锌的硝酸盐和硫酸锌才能生成相纯的 LDH。在其他情况下,要么没有发生反应,要么认为是 LDH 的相与杂质相同时形成。将 Al(OH)3 与 MII 盐混合物反应可生成三金属 MII-MII′-Al LDH,但必须精确控制反应凝胶中两种 MII 盐的起始比例,因为 Al(OH)3 对硝酸 M 有选择性插层作用(锂 > 镍 > 钴 ≈ 锌)。三金属 MII-MII′-Al LDHs 表现出简便的离子交换插层,钻石光源 I12 光束线首次对化学反应体系进行了能量色散 X 射线衍射研究。
Reduction of maleate and fumarate by the anion radical
作者:Osnat Schutz、Dan Meyerstein
DOI:10.1016/j.tetlet.2005.12.042
日期:2006.2
The radicalanion CO2.- reacts with fumarate and maleate at pH 5.3 mainly via electron transfer. The final products are a mixture of (−O2CCH2–)2, trans-(−O2CCH)2 and products with higher molecular weight. At higher pHs, the yield of fumarate and succinate decreases. The results suggest that though the radicalanions formed by the reduction of fumarate and maleate have different structures, the final
自由基阴离子CO2-与富马酸酯和马来酸酯在pH 5.3下主要通过电子转移反应。最终产物是混合物(- Ò 2 CCH 2 - )2,反式- (- Ò 2 CCH)2和产品具有更高的分子量。在较高的pH值下,富马酸酯和琥珀酸酯的产率降低。结果表明,尽管由富马酸酯和马来酸酯还原形成的自由基阴离子具有不同的结构,但最终产物可能是相同的。