The effects of substrate orientation on the mechanism of a phosphotriesterase
作者:Colin J. Jackson、Jian-Wei Liu、Michelle L. Coote、David L. Ollis
DOI:10.1039/b512399b
日期:——
While the underlying chemistry of enzyme-catalyzed reactions may be almost identical, the actual turnover rates of different substrates can vary significantly. This is seen in the turnover rates for the catalyzed hydrolysis of organophosphates by the bacterial phosphotriesterase OpdA. We investigate the variation in turnover rates by examining the hydrolysis of three classes of substrates: phosphotriesters, phosphothionates, and phosphorothiolates. Theoretical calculations were used to analyze the reactivity of these substrates and the energy barriers to their hydrolysis. This information was then compared to information derived from enzyme kinetics and crystallographic studies, providing new insights into the mechanism of this enzyme. We demonstrate that the enzyme catalyzes the hydrolysis of organophosphates through steric constraint of the reactants, and that the equilibrium between productively and unproductively bound substrates makes a significant contribution to the turnover rate of highly reactive substrates. These results highlight the importance of correct orientation of reactants within the active sites of enzymes to enable efficient catalysis.
Reactivity of the insecticide chlorpyrifos-methyl toward hydroxyl and perhydroxyl ion. Effect of cyclodextrins
作者:Raquel V. Vico、Rita H. de Rossi、Elba I. Buján
DOI:10.1002/poc.1502
日期:2009.7
The reactivity of Chlorpyrifos‐Methyl (1) toward hydroxyl ion and the α‐nucleophile, perhydroxyl ion was investigated in aqueous basic media. The hydrolysis of 1 was studied at 25 °C in water containing 10% ACN or 7% 1,4‐dioxane at NaOH concentrations between 0.01 and 0.6 M; the second‐order rate constant is 1.88 × 10−2 M−1 s−1 in 10% ACN and 1.70 × 10−2 M−1 s−1 in 7% 1,4‐dioxane. The reaction with
在含水碱性介质中研究了毒死rif甲基(1)对羟基离子和α-亲核试剂,全羟基离子的反应性。在25°C的条件下,于NaOH浓度介于0.01和0.6 M之间的水溶液中,在含有10%ACN或7%1,4-二恶烷的水中研究 1的水解;二阶速率常数为1.88×10 -2中号-1 小号-1在10%ACN和1.70×10 -2中号-1 小号-1在7%的1,4-二恶烷。在7%1,4-二恶烷/ H 2中,在9.14至12.40的pH范围内研究了与H 2 O 2的反应 O; 二阶速率常数HOO的反应-离子是7.9 中号-1 小号-1而中性ħ 2 ö 2不竞争作为亲核试剂。在所有情况下,观察到定量形成的3,5,6-三氯-2-吡啶醇(3),表明存在S N 2(P)途径。水解反应受到α-,β-和γ-环糊精的抑制,表现出饱和动力学。γ-环糊精产生更大的抑制作用。与过氧化氢的反应被α-和β-环糊精(β-CD),而γ-环糊
Experimental and computational determination of Brønsted coefficients for equilibrium transfer of the<i>O</i>,<i>O</i>-dimethyl phosphorothioyl group between oxyanion nucleophiles
作者:David R. Edwards、Christopher I. Maxwell、Robert W. Harkness、Alexei A. Neverov、Nicholas J. Mosey、R. Stan Brown
DOI:10.1002/poc.1903
日期:2012.3
phosphorothioate, pKaHOAr of 7.14) is linear over the entire range of phenoxides employed (5.53 ≤ pKaNu ≤ 12.38), the reaction for phenoxidenucleophiles displacing phenoxide leaving groups is probably concerted. The obtained data allow one to calculate, for a symmetrical transitionstate involving 2,4,5‐trichlorophenoxide as a nucleophile and leaving group, an approximately 60% P–OAr cleavage and about 40% P–Nuc
Photoinduced Decarboxylative Phosphorothiolation of <i>N</i>-Hydroxyphthalimide Esters
作者:Yu Guo、Ying Luo、Shiqiang Mu、Jian Xu、Qiuling Song
DOI:10.1021/acs.orglett.1c02300
日期:2021.9.3
protocol for the synthesis of phosphorothioates is developed by employing the Ir-catalyzed decarboxylative phosphorothiolation of N-hydroxyphthalimide esters. This novel synthesis method utilizes carboxylic acids as raw material, which is stable, cheap, and commercially available. Scope studies show that this reaction has good compatibility of functional groups. Notably, both the synthesis of steric hindrance
通过采用N-羟基邻苯二甲酰亚胺酯的 Ir 催化脱羧硫代磷酸酯,开发了一种可见光诱导的硫代磷酸酯合成方案。这种新的合成方法以羧酸为原料,稳定、廉价且可商购。范围研究表明该反应具有良好的官能团相容性。值得注意的是,空间位阻硫代磷酸酯的合成和一些生物活性化合物的后期修饰都成功实现。
Adsorption and degradation of methyl parathion (MP), a toxic organophosphorus pesticide, using NaY/Mn0.5Zn0.5Fe2O4 nanocomposite
作者:Sina Yekta、Meysam Sadeghi
DOI:10.1007/s11164-017-3203-1
日期:2018.3
(0.5 g), and initial pesticide concentration (15 mg/L) were studied and optimized for the reaction. Reaction kinetic status was surveyed using a first order model. The values of the half-life ( T 1/2) and rateconstant ( k ) were 54.6 min and 0.0127 min−1, respectively. The products of the degradation reaction between methyl parathion and NaY/Mn0.5Zn0.5Fe2O4 were dimethyl phosphorothioic acid (DMPA)
在这项研究中,NaY / Mn 0.5 Zn 0.5 Fe 2 O 4作为一种新型的纳米复合吸附剂在有机磷农药甲基对硫磷(MP,O,O-O-二甲基O- 对 硝基苯基硫代磷酸酯)的吸附和降解中 的适用性,被调查。通过SEM-EDAX,TEM,XRD,FTIR,VSM和N 2 -BET技术对制备的样品进行表征。通过31 P核磁共振(31 PNMR)光谱研究和评估了几种实验因素,如接触时间,吸附剂剂量和甲基对硫磷的初始浓度对这种农药的去除效率的影响。31PNMR光谱表明,在某些优化条件下,NaY / Mn 0.5 Zn 0.5 Fe 2 O 4纳米复合物理想地除去了甲基对硫磷。研究并优化了接触时间(80分钟),吸附剂剂量(0.5 g)和农药初始浓度(15 mg / L)等因素。使用一级模型调查反应动力学状态。半衰期( T 1/2)和速率常数( k )的值分别为54.6min和0.0127min -1。甲基对硫磷与NaY