Hydrolysis rates of alkyl and aryl sulfinamides: evidence of general acid catalysis

Sulfinamides are important in enantioselective synthesis, as rare post-translational modifications of proteins and as isosteres of the amide bond. Little is known about the rates of hydrolysis for aliphatic sulfinamides or the mechanism of hydrolysis. In this Letter, we show that sulfinamides hydrolyse by predominantly a non-specific acid/base catalysis with phosphate buffer but by varying the buffer concentration, it was possible to determine the hydrolysis rates of a range of sulfinamides with water through non-linear least squares regression.     

酶催化脂肪族聚酯的合成

脂肪族聚酯是一种可生物降解的新型高聚物,可通过化学催化、发酵和酶催化来合成.酶催化合成聚酯是一种新型的环境友好绿色化学技术,可以在温和条件下高效的合成聚酯,有着传统聚合方法难以比拟的优势.尤其是特种酶的应用,为传统方法难以合成的聚酯,开辟了一条新的合成途径.本文综述了脂肪酶催化缩聚、酯交换、内酯开环聚合等聚酯合成方法,并讨论了反应参数(如溶剂、温度、酶和单体的浓度)对反应的影响.     

尿素酶固载于纳米二氧化钛多孔膜上的尿素生物传感器

在钛丝基体上沉积一层纳米二氧化钛(TiO2)多孔膜,然后直接将尿素酶吸附在TiO2膜上。基于TiO2膜的pH响应,发展了一种廉价的、易于微型化的pH敏尿素酶传感器。采用石英微天平、红外光谱和紫外可见光谱等手段研究尿素酶在TiO2膜上的物理固载行为。由于纳米TiO2在紫外光下光自洁特性可获得高度洁净的表面,石英微天平研究表明在光自洁后的TiO2膜上尿素酶的吸附具有很好的重复性和稳定性,吸附量为0.22mmol/g,吸附平衡常数k为3.15×105L/mol。采用电位法测定了尿素酶/TiO2复合膜电极的性能及其影响因素,在1.0 mmol/L pH 7~8 PBS,35℃,尿素的响应范围为8.5×10-5~1.5×10-1mol/L,相关系数r为0.993 7,检出限为6×10-5mol/L。     

Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors

The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H₂O₂ formed during the enzymatic process. This paper is dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday.     

单分子酶学研究进展

源于20世纪90年代的单分子显微成像技术成功实现了对单分子酶的催化过程实时监控,此后单分子酶学的研究进入了快速的发展时期,发现了多种酶的新单分子行为及反应机制。单分子酶学的研究能够发现隐藏于整体平均水平下的单个酶分子的个体行为,揭示了酶与底物作用的动态变化,加深了人们对各种生化反应的理解。     

脂肪酶催化开环聚合的研究进展

酶是一种绿色、安全、高效、专一的生物催化剂,在反应中具有能耗小、可循环利用和选择性高等优点,更重要的是酶催化聚合能够制备传统的化学催化无法(或难以)实现的聚合物,具有一定的工业化前景。本文简述了酶催化的发展历程、机理以及其制备特殊结构和功能聚合物材料的特点,特别是脂肪酶催化下的开环聚合相对于缩聚反应来说,具有反应条件温和、分子量和结构可控性好等优势,因此重点描述脂肪酶催化开环聚合在合成不同拓扑结构(线型、支化、交联)聚合物中的研究进展。     

Enzyme-catalyzed asymmetric domino aza-Michael/aldol reaction for the synthesis of 1,2-dihydroquinolines using pepsin from porcine gastric mucosa

An unprecedented enzyme-catalyzed asymmetric domino aza-Michael/aldol reaction of 2-aminobenzaldehyde and a,b-unsaturated aldehydes is achieved. Pepsin from porcine gastric mucosa provided mild and efficient access to diverse substituted 1,2-dihydroquinolines in yields of 38%–97% with 6%–24%enantiomeric excess(ee). This work not only provides a novel method for the synthesis of dihydroquinoline derivatives, but also promotes the development of enzyme catalytic promiscuity.     

Hydrostatic Pressure Studies Distinguish Global from Local Protein Motions in C−H Activation by Soybean Lipoxygenase‐1

The proposed contributions of distinct classes of local versus global protein motions during enzymatic bond making/breaking processes has been difficult to verify. We employed soybean lipoxygenase‐1 as a model system to investigate the impact of high pressure at variable temperatures on the hydrogen‐tunneling properties of the wild‐type protein and three single‐site mutants. For all variants, pressure dramatically elevates the enthalpies of activation for the C−H activation. In contrast, the primary kinetic isotope effects (KIEs) for C−H activation and their corresponding temperature dependencies remain unchanged up to ca. 700 bar. The differential impact of elevated hydrostatic pressure on the temperature dependencies of rate constants versus substrate KIEs provides direct evidence for two distinct classes of protein motions: local, isotope‐dependent donor–acceptor distance‐sampling modes, and a more global, isotope‐independent search for productive protein conformational sub‐states.