Characterization ofanovel deep-seamicrobial esterase EstC 10 and its use in the generation o f(R)-methyl 2-chloropropionate

A novel esterase Est C10 from B acillus sp. CX01 isolated from the deep sea of the Western Pacific Ocean and the functionalities of Est C10 was characterized. At present, the reports about the kinetic resolution of racemic methyl 2-chloropropionate were quite rare. So we developed deep-sea microbial esterase Est C10 as a novel biocatalyst in the kinetic resolution of racemic methyl 2-chloropropionate and generate( R)-methyl 2-chloropropionate with high enantiomeric excess(>99%) after the optimization of process parameters such as p H, temperature, organic co-solvents, surfactants, substrate concentration and reaction time. Notably, the optimal substrate concentration(80 mmol/L) of esterase Est C10 was higher than the kinetic resolution of another esterase, Est12-7(50 mmol/L). The novel microbial esterase Est C10 identified from the deep sea was a promising green biocatalyst in the generation of( R)-methyl 2-chloropropionate as well of many other valuable chiral chemicals in industry.

The Susceptibilities of Oxya chinensis(Orthoptera:Acridoidea) to Malathion and Comparison of the Esterase Properties from Three Collected Populations in Tianjin Area,China

The susceptibilities of Oxya chinensis to malathion were studied in three populations collected from outskirt of Tianjin, China, using bioassays and biochemical analysis. Populations were chosen to represent different exposure to insecticides： BDG （Beidagang; low exposure）, BD （Baodi; high exposure previously but low exposure now）, and JN （Jinnan; high exposure）. The results showed that the LD50 values of BD and JN populations were 3.95- and 12.02-fold and 3.64- and 10.07- fold higher than that of BDG population in females and males, respectively. The LD50 values in females were higher than those in males. The results of biochemical analysis indicated that the esterase （EST） activities in JN population were higher than those in BD and BDG populations. They showed that when α-NA, α-NB, and α-NA were used as substrates, females＇ EST activities of JN population were 1.11-, 1.30-, and 1.14-fold and 1.39-, 1.59-, and 1.54-fold higher than those of BD and BDG populations, respectively. When α-NA, α-NB, and β-NA were used as substrates, males＇ EST activities of JN population were 1.13-, 1.12-, and 1,00-fold and 1.20-, 1.14-, and 1.07-fold higher than those of BD and BDG populations, respectively. The results also showed that the specific activities of the females were higher than those of the males in the BD and JN populations, whereas the specific activities of the males were higher than those of the females in the BDG population. The results of bioassay were consistent with those of biochemical analysis. Thus, it was inferred that the elevated ESTs activities might play an important role in conferring the differences of susceptibility of O. chinensis to malathion in the three collected populations. Enzyme kinetic studies indicated that the Km and Vmax values were different among the three collected populations and between the females and the males. The observed changes in the kinetic parameters might be explained by differential expression patterns of isozymes so that the insect esterases have different affinities and maximum velocities toward the same substrate.

Study on Roast Reaction Kinetics of Baotou Concentrate of Rare Earth with 15% Na_2CO_3 Additions

The research on the mechanism of the roast reaction of Baotou concentrate of rare earth with 15% Na 2CO 3 additions was carried out through thermal, X ray diffraction and chemical analysis. Bastnaesite(RECO 3F) was first decomposed into REOF at 623～741 K, then Monazite(REPO 4) reacted with Na 2CO 3 was decomposed into RE 2O 3 and produced Ca 8Nd 2(PO 4) 6O 2 at 853～928 K. The kinetics parameters of the roast reaction were calculated. The results of the calculation were as follows: at 623～741 K, E =152 kJ·mol -1 , n =0 77, A =1 11×10 12 s -1 ·mol -1 , k =1 102( T =705 K), and at 853～928 K, E =232 kJ·mol -1 , n =1 16, A =1 11×10 9 s -1 ·mol -1 , k =1 07×10 -4 ( T =915 K). The equation of the mechanism of the roast reaction is F 1=-ln(1- α ) at 623～741 K and 853～928 K according to TG curves.

Revisiting Electrolyte Kinetics Differences in Sodium Ion Battery:Are Esters Really Inferior to Ethers?

The ether electrolytes usually outperform ester electrolytes by evaluating sodium-ion batteries(SIBs)rate performance,which is a near-unanimous conclusion of previous studies based on an essential configuration of the half-cell test.However,here we find that contrary to consensus,the ester electrolyte shows better Na storage capability than the ether electrolyte in full cells.An in-depth analysis of three-electrode,symmetric cell,and in situ XRD tests indicates that traditional half-cell test results are unreliable due to interference from Na electrodes.In particular,Na electrodes show a huge stability difference in ester and ether electrolytes,and ester electrolytes suffer more severe interference than ether electrolytes,resulting in the belief that esters are far inferior to ether electrolytes.More seriously,the more accurate three-electrode test would also suffer from Na electrode interference.Thus,a“corrected half-cell test”protocol is developed to shield the Na electrode interference,revealing the very close super rate capability of hard carbon in ester and ether electrolytes.This work breaks the inherent perception that the kinetic properties of ester electrolytes are inferior to ethers in sodium-ion batteries,reveals the pitfalls of half-cell tests,and proposes a new test protocol for reliable results,greatly accelerating the commercialization of sodium-ion batteries.

Adsorption Thermodynamics and Diffusion Kinetics of PX over Na Y Zeolite Synthesized by In-Situ Crystallization from Kaolin Microsphere

Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere(designated as Na Y/kaolin composites) separately, using a high precision intelligent gravimetric analyzer(IGA). The adsorption isotherms showed normal Langmuir type-Ⅰ behaviors. The increased adsorption heat with an increasing p-xylene coverage supported a mechanism of phase transition, diffusion and re-arrangement of p-xylene molecules during the adsorption process. The rearrangement seemed to be most pronounced at an adsorption loading of 2.13 and 2.29 mmol/g for Na Y zeolite and Na Y/kaolin composites respectively. Compared with Na Y zeolite, a 2—3 times higher in the diffusion coefficient of p-xylene was observed on Na Y/kaolin composites when the pressure was more than 50 Pa. Temperature-programmed desorption(TPD) of p-xylene on two samples from room temperature to 450 ℃ at a special loading has also been investigated by IGA. Results showed only single desorption peak appeared for Na Y zeolite, indicating that adsorption can only occur in the super-cage structure. Comparably, there were two different peaks for in-situ synthesized Na Y zeolite, corresponding to the two thermo desorption processes in both super-cage structure and the channels provided by kaolin, respectively.Key words:

Functional characterization of a novel microbial esterase identified from the Indian Ocean and its use in the stereoselective preparation of(R)-methyl mandelate

Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21(DE3) and further functionally characterized. Under optimal conditions(10 mmol/L substrate, p H 6.0, 2 h at 40 °C), this esterase can hydrolyze racemic methyl mandelate to( R)-methyl mandelate with very high optical purity(e. e. >99%) and yield(nearly 90%). Interestingly, the stereoselectivity of this esterase is opposite to that of two previously reported lipases that can generate( S)-methyl mandelate through the hydrolysis of racemic methyl mandelate. No organic solvents or other additives were required to optimize the optical purity and production of the fi nal chiral product(R)-methyl mandelate, which can potentially simplify the production procedure of( R)-methyl mandelate catalyzed by esterase.

Characterization of a Novel <i>Pseudomonas stutzeri</i>Lipase/Esterase with Potential Application in the Production of Chiral Secondary Alcohols

The search for new enzymes is facilitated by the rapidly growing number of genome sequences from different organisms. However, the discovery of functional proteins is still time intensive and complex alignments have to be performed. Herein, a genome database search identified a new, until now undescribed, putative lipase from Pseudomonas stutzeri strain A1501. The gene was cloned and expressed as functional protein in E. coli. A biochemical characterization provided an indication that the enzyme could be classified as an esterase with an alkaline pH optimum and a temperature optimum at 50&degC. The enzyme was able to perform the kinetic resolution of racemic esters and could therefore be an interesting candidate for chiral synthesis.

Kinetics and Thermodynamic Parameters of the CopperExchange on Na-montmorillonite Clay Mineral inSelected Solvents

The kinetics of Cu ion exchange on Na-montmorillonite clay mineral has been investigated at three temperatures, in three solvents: H2O, ethylene glycol and glycerol. Solvent effects on the reaction rate have been discussed. The thermodynamic activation parameters were calculated and discussed in terms of solvation effects. The determined isokinetic temperature indicates that the reaction is enthalpy controlled where the interaction between solvent and clay surface plays an important role. A reaction mechanism which describes the solvent effect on the rate of Cu ion exchange is proposed.

Comparative Study of Malathion Toxicity and General Esterases in Larvae and Adults from a Field Population of Oxya chinensis (Thunberg) (Orthoptera: Acridoidea)

The susceptibility of Oxya chinensis to malathion was compared in larvae and adults from a field population, collected from Jinyuan outskirt, Shanxi Province. The results showed that Oxya chinensis was more susceptible to malathion in the adult stage than in the larval stage. The LD50 values for malathion susceptibility of Oxya chinensis were 4.94 and 2.44 mg g-1 body weight in the larvae and adults respectively. The results indicated that the larvae were 2.02-fold less susceptible to malathion than the adults. The general esterases and the kinetics were characterized and compared between the two life stages and between females and males. Larval preparations of Oxya chinensis were more active than adult preparations in females and males. The larvae showed 1.18-, 1.49-, and 1.17- fold higher specific activities than the adults in females with α-NA, α-NB and β-NA respectively. In males, the ratios were 1.34-, 1.70-, and 1.06-fold. Female preparations were more active than those of males in the adults. The reverse results were observed in the larvae where male preparations were more active than female preparations. Kinetic studies showed that Km values of general esterases hydrolyzing α-NA, α-NB, and β-NA in the adult stage were 1.36-, 1.32- and 1.39-fold respectively, higher than those in the larval stage in females. In males, the ratios were 1.24-, 2.14-, and 1.20-fold. The esterase from male insects had a higher affinity (lower Km value) to the substrate than those from females. The results also showed that the Vmax values of general esterase hydrolyzing α-NA, α-NB, and β-NA in the two stages were similar. From the results of bioassays and biochemical analyses, it has been inferred that a higher level of resistance to malathion in larvae than in adults would appear to result from differences in the expression of resistance mechanisms in these two life stages. Enhanced esterase activities appeared to play a major role in resistance to malathion in both larvae and adults. From the analysis of inhibition in vitro, the esterases in the two life stages were B-type, and carboxylesterases were predominant enzymes in the composition of the esterases in the two stages.

Kinetic Process and Conductivity of Ag^+ Ion Exchange for Polycrystalline Na-β"-Al_2O_3

This paper reports the kinetic process of Ag ion exchange for the polycrystalline Na-β'-Al2O3.The interdiffusion coefficients in the process of Ag+ and Na+ ion exchange have been calculated with an 'one dimensional double side diffusion model'. Microstructures of the samples were observed and analysed by XRD, EMPA, SEM. The results of the conductivity measurements for samples with Na+, Ag+ and Na+-Ag+ mobile ions are presented and explained

Sr和 Na在AI-Si合金中的变质行为及机理的研究

研究了Ｓｒ、Ｎａ在ＡＩ－Ｓｉ熔体中的氧化动力学，应用原子杂化轨道理论分析了Ｓｒ、Ｎａ与ＡＩ－Ｓｉ熔体的作用机理。研究结果表明，Ｓｒ比Ｎａ具有更长的变质有效期，其原因是Ｓｒ比Ｎａ具有更加稳定的原子杂化轨道，而并非完全由工艺因素决定。

绞股蓝总苷对大鼠心、脑Na^+,K^+-ATP酶的抑制作用及其动力学分析

目的观察绞股蓝总苷对心、脑微粒体Na+,K-ATP酶活性的抑制作用及动力学分析。方法采用离心法制备大鼠心、脑组织微粒体酶,以比色法测定Na+,K-ATP酶活力,通过酶动力学研究方法分析绞股蓝总苷对心、脑微粒体Na+,K-ATP酶活性的抑制作用。结果绞股蓝总苷体外可逆性抑制大鼠心、脑微粒体Na+,K-ATP酶活性,并呈浓度依赖性,且对脑微粒体Na+,K-ATP酶的抑制作用较强,其IC50分别为(58.79±8.25)、(52.07±6.25)mg/L。降低Na+,K+浓度或增加ATP浓度则增强其抑制酶活性作用。酶动力学分析显示,绞股蓝总苷对微粒体Na+,K-ATP酶的作用近似Na+的竞争性拮抗剂、底物ATP的反竞争性抑制剂、K+的混合性抑制剂。结论绞股蓝总苷通过抑制心、脑Na+,K-ATP酶活性而发挥其强心作用和中枢抑制作用。

室温钠硫电池硫正极催化剂的研究进展

室温钠硫电池因其正负极材料丰富的自然资源、低廉的成本和优异的能量密度被视为极具竞争力的电化学储能系统。然而,严重的穿梭效应和缓慢的反应动力学是制约室温钠硫电池可持续发展和实际应用的两大障碍。在硫正极中引入适当的催化剂被广泛证明是一种可以抑制多硫化物的穿梭效应并促进其氧化还原动力学的有效策略,并在近年来成为了该领域的研究焦点。本文从材料设计和优化的角度入手,首先总结了在室温钠硫电池硫正极中被报道的金属、金属氧化物、金属硫化物、金属氮化物、金属碳化物、MXenes、金属单原子及其他在内的各种主流催化剂,并讨论了调节催化剂的吸附和催化性质的各种有效调节策略,包括尺寸缩减、缺陷工程、电化学钠化及异质结工程等。最后,针对室温钠硫电池正极用催化剂的研究现状指出了其未来的发展趋势,并基于室温钠硫电池面临的重大挑战,从基础理论研究和实用化设计两个层面展望了其未来的发展方向。

几种人参皂甙对大鼠肾脏微粒体Na^+,K^+-ATP酶的抑制作用

人参皂甙Rg组、Rb组、Rg_1、Rb_1对大鼠肾脏微粒体Na^+,K^+—ATP酶均有抑制作用,IC_(50)分别为402,74μg/ml,15和50μmol/L。Rb组、Rg_1和Rb_1的抑酶作用可逆;增加K^+可竞争性拮抗Rg_1和Rb_1的抑酶作用,但Na^+对此作用无明显影响。动力学研究表明,Rg_1和Rb_1抑制Na^+,K^+—ATP酶,对底物ATP似为反竞争性抑制剂。

外源EBR对NaCl胁迫下紫花苜蓿幼苗微量元素吸收及叶绿素荧光动力学参数的影响

为明确外源2,4-表油菜素内酯(2,4-epibrassinolide,EBR)诱导紫花苜蓿(Medicago sativa L.)幼苗抗盐性的效果及其可能的生理调节机制,采用营养液水培法,以紫花苜蓿品种‘中苜3号’和‘陇中苜蓿’为材料,研究Na Cl胁迫下施用外源EBR对紫花苜蓿幼苗微量元素吸收及叶片PSⅡ功能、电子传递速率和光能分配的影响。结果表明:150 mmol·L^(-1) Na Cl胁迫下,苜蓿幼苗不同器官(叶片、茎秆、根系)中的Cu^(2+)含量显著升高,Fe^(2+)、Mn^(2+)、Zn^(2+)含量和Fe^(2+)/Na+、Mn^(2+)/Na+、Cu^(2+)/Na+、Zn^(2+)/Na+显著降低,无机离子的吸收、运输和分配等代谢平衡被打破;同时Na Cl胁迫造成苜蓿幼苗叶片PSⅡ反应中心受损,天线耗散、反应中心耗散增加,光合能力下降。Na Cl胁迫下,施用0.1μmol·L^(-1)外源EBR后,苜蓿幼苗不同器官(叶片、茎秆、根系)中的Cu^(2+)含量显著降低,Fe^(2+)、Mn^(2+)、Zn^(2+)含量及Fe^(2+)/Na+、Mn^(2+)/Na+、Cu^(2+)/Na+、Zn^(2+)/Na+显著升高,幼苗体内无机离子的吸收、运输得到有效调控,Na+和Fe^(2+)、Mn^(2+)、Cu^(2+)、Zn^(2+)等阳离子间的拮抗作用减小;苜蓿幼苗叶片的F_0、NPQ显著降低,F_m、F_v/F_0、F_v/F_m、ФPSⅡ、F_v′/F_m′、q P和ETR显著升高,苜蓿幼苗叶片吸收的光能用于光化学反应部分(P)增加、天线色素耗散部分(D)和反应中心过剩光能部分(E)降低。说明外源EBR能够促进Na Cl胁迫下苜蓿幼苗对无机离子的选择性吸收、运输和分配,维持体内的离子代谢平衡,通过提高光合电子传递效率,降低天线热耗散和反应中心过剩光能,维持较高的PSⅡ光化学活性,进而平衡激发能在PSⅠ、PSⅡ之间的分配,降低Na Cl胁迫对PSⅡ反应中心的损伤程度,有效缓解Na Cl胁迫对苜蓿幼苗所造成的伤害。

Na型蛭石中2Na^+=Pb^(2+)离子交换过程的动力学研究

通过实验探讨了Na型蛭石在不同的Pb2+溶液浓度和不同的温度下的2Na+=Pb2+离子交换动力学关系,实验结果表明:蛭石中2Na+=Pb2+离子交换很快,0.5min以内交换吸附率已达70%~80%以上,达到交换平衡的时间与溶液的起始浓度和交换时的温度有关,原液浓度越大达到平衡所需要的时间越长,温度越高交换越快;蛭石中2Na+=Pb2+离子交换过程受粒内扩散控制;动力学方程符合克-金-布扩散(粒内扩散)方程;计算出了蛭石中2Na+=Pb2+离子交换过程的表观活化能E′a的平均值为25.21kJ/mol;推导出了蛭石中2Na+=Pb2+离子交换过程的动力学方程为:1-2/3α-(1-α)2/3=k0r-02exp-25 R.21.

DNA具酯酶活性的酶动力学初步研究

在发现绿豆、蜘蛛和小牛胸腺ＤＮＡ有促进乙酸萘酯水解的酯酶活性并建立ＤＮＡ酯酶活性测定方法的基础上，对具酯酶活性的ＤＮＡ进行了ｐＨ、酶反应速度、ＤＮＡ浓度以及各种金属离子影响的酶动力学实验，观察到ｐＨ的影响、酶反应速度及ＤＮＡ浓度曲线与一般酶反应动力学曲线相似，并且具有底物特异性．认为ＤＮＡ的酯酶活性具有“酶”

Na基膨润土对重金属离子Pb^(2+)吸附的研究

研究了吸附时间、吸附剂浓度、体系pH值、离子强度、温度、动力学、热力学等不同影响因素在Na基膨润土对Pb吸附过程中的影响。实验结果证明,Na基膨润土可在较短时间内完成对Pb的吸附,假二级动力学速率方程很好地模拟了相关数据。随着体系吸附剂浓度的增加,提供了更多的吸附点位,从而促进了Na基膨润土对Pb的吸附。较低的p H反应体系有利于Pb的吸附。热力学数据证明,Na基膨润土对Pb的吸附是一个吸热过程,较高的温度促进了吸附过程的进行。

钠离子电池正极材料Na3V2(PO4)2O2F的控制合成与电化学性能优化

采用简单的水热合成法制备氟磷酸钒氧钠(Na_3V_2(PO_4)_2O_2F,简写为NVPOF),通过调节水热反应溶液的pH值和反应温度等关键参数,有效调节NVPOF的颗粒尺寸和均匀性,优化其电化学性能。研究结果显示,性能最优的NVPOF的合成条件是:pH值为7.00±0.05,水热反应温度为170℃。在该条件下合成的NVPOF正极材料具有优异的电化学性能,表现为0.1C(1C=130 mA·g^(-1))的倍率下放电比容量可达123.2 mAh·g^(-1),且在20C的高倍率下仍可实现85.9 mAh·g^(-1)的比容量,在1C下循环200圈后其容量保持率为96.2%,表明该材料具有高容量、优异的倍率和循环性能。所制备的NVPOF颗粒为纳米尺度且具有很高的均匀性,可缩短Na^+的传输路径从而缩短其传输时间,且NVPOF晶体结构具有高稳定性,是一类具有高性能的钠离子电池正极材料。

Three-Dimensional Self-assembled Hairball-Like VS4 as High-Capacity Anodes for Sodium-Ion Batteries

Sodium-ion batteries(SIBs)are considered to be attractive candidates for large-scale energy storage systems because of their rich earth abundance and consistent performance.However,there are still challenges in developing desirable anode materials that can accommodate rapid and stable insertion/extraction of Na+and can exhibit excellent electrochemical performance.Herein,the self-assembled hairball-like VS4 as anodes of SIBs exhibits high discharge capacity(660 and 589 mAh g−1 at 1 and 3 A g−1,respectively)and excellent rate property(about 100%retention at 10 and 20 A g−1 after 1000 cycles)at room temperature.Moreover,the VS4 can also exhibit 591 mAh g−1 at 1 A g−1 after 600 cycles at 0°C.An unlike traditional mechanism of VS4 for Na+storage was proposed according to the dates of ex situ characterization,cyclic voltammetry,and electrochemical kinetic analysis.The capacities of the final stabilization stage are provided by the reactions of reversible transformation between Na2S and S,which were considered the reaction mechanisms of Na–S batteries.This work can provide a basis for the synthesis and application of sulfur-rich compounds in fields of batteries,semiconductor devices,and catalysts.