The first encapsulation of hydroxynitrile lyase from Hevea brasiliensis in a sol–gel matrix
摘要:
A straightforward process for the encapsulation of HbHNL under low methanol conditions has been developed. By adding a sol, prepared by hydrolysis of TMOS/MTMS at pH 2.8 with continuous removal of methanol, to a stirred solution of the enzyme in a buffer at pH 6.5, at least 65% of the activity of the free enzyme could be recovered after the encapsulation. The aquagels were successfully used in the synthesis of (S)-cyanohydrins. (C) 2004 Elsevier Ltd. All rights reserved.
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%.
Enzymatic Logic of Anthrax Stealth Siderophore Biosynthesis: AsbA Catalyzes ATP-Dependent Condensation of Citric Acid and Spermidine
作者:Daniel Oves-Costales、Nadia Kadi、Mark J. Fogg、Lijiang Song、Keith S. Wilson、Gregory L. Challis
DOI:10.1021/ja072391o
日期:2007.7.1
A unique combination of nonribosomal peptide synthetase (NRPS) and NRPS-independent siderophore (NIS) synthetase enzymes is known to be required for petrobactin biosynthesis in B. anthracis. Here it is shown that AsbA from B. anthracis, the first type A NIS synthetase to be biochemically characterized, catalyzes ATP-dependent regioselective condensation of citric acid with N8 of spermidine, but not
Petrobactin 是一种铁螯合铁载体,最初从 Marinobactercarbonoclastus 中分离出来,已被证明在缺铁条件下的生长和致命的生物恐怖主义剂炭疽芽孢杆菌的毒力中发挥重要作用。最近显示它不与铁钙蛋白结合,使其被指定为可以避开哺乳动物免疫系统的“隐形铁载体”。已知非核糖体肽合成酶 (NRPS) 和不依赖 NRPS 的铁载体 (NIS) 合成酶的独特组合是炭疽芽孢杆菌中石油杆菌素生物合成所必需的。此处显示来自炭疽芽孢杆菌的 AsbA,第一种被生化表征的 A 型 NIS 合成酶,催化柠檬酸与亚精胺的 N8 的 ATP 依赖性区域选择性缩合,但不与 N1-(3,4-二羟基苯甲酰基)-亚精胺.
Titanium(IV) and Vitamin C: Aqueous Complexes of a Bioactive Form of Ti(IV)
作者:Katherine M. Buettner、Joseph M. Collins、Ann M. Valentine
DOI:10.1021/ic301545m
日期:2012.10.15
the range pH 3–10, the aqueous speciation is characterized by the sequential appearance of the following complexes as a function of added base: Ti(asc)20 → Ti(asc)32- → Ti(asc)2(OH)22- → Ti(asc)(OH)42-. These species dominate the speciation at pH < 3, pH 4–5, pH ∼ 8, and pH > 10, respectively, with minimum log stability constants (β values) of 25.70, 36.91, 16.43, and −6.91. Results from electrospray
Structural, Luminescence, and NMR Studies of the Reversible Binding of Acetate, Lactate, Citrate, and Selected Amino Acids to Chiral Diaqua Ytterbium, Gadolinium, and Europium Complexes
作者:Rachel S. Dickins、Silvio Aime、Andrei S. Batsanov、Andrew Beeby、Mauro Botta、James I. Bruce、Judith A. K. Howard、Christine S. Love、David Parker、Robert D. Peacock、Horst Puschmann
DOI:10.1021/ja020836x
日期:2002.10.1
The nature of the ternary complexes formed in aqueousmedia at ambient pH on reversiblebinding of acetate, lactate, citrate, and selected amino acids and peptides to chiral diaqua europium, gadolinium, or ytterbium cationic complexes has been examined. Crystal structures of the chelated ytterbium acetate and lactate complexes have been defined in which the carboxylate oxygen occupies an "equatorial"
Some metal complexes of citric and tricarballylic acids
作者:N.C. Li、A. Lindenbaum、J.M. White
DOI:10.1016/0022-1902(59)80101-9
日期:1959.12
formation constants of several metalcomplexes of citrate and tricarballylate, and of the “hydrogen complexes”, i.e. complexes in which HA2− act as ligands, have been determined by a titrimetric method. For Mn(II), Cd(II), Zn(II) and Ni(II) complexes of citrate, the value of KMA/KKHA varies from 101·6 to 101·9, the ratio increasing with increasing value of KMA. The citrate complexes are more stable than the
已经通过滴定法确定了柠檬酸盐和三羧酸盐的几种金属配合物以及“氢配合物”(即HA 2−充当配体的配合物)的形成常数。对于柠檬酸盐的Mn(II),Cd(II),Zn(II)和Ni(II)配合物,K MA / K KHA的值在10 1·6到10 1·9之间变化,比率随值的增加而增加的K MA。如所预期的,柠檬酸盐复合物比相应的三碳酸酯复合物更稳定。柠檬酸的Co(II)和Mg配合物具有的还原电位对于直接极谱法来说太负了。在pH范围1·9至2·5中,已显示1:1的铀酰柠檬酸酯络合物是log K MA = 8·5的单体。