固定化酶催化合成CCK-8C-端三肽衍生物

报道胆囊收缩素（CCK-8）C-末端片段三肽衍生物外Hpac-Met_Asp(Cam为起始 原料，采用三种固定化酶--α-糜蛋白酶／Celite-545、木瓜蛋白酶／VA-Epoxy、 步酶促反应得到目标三肽化合物．对酶的专一性、酶的固定化、溶剂选择和合成条 件等进行了研究，比较了自由酶法与固定化酶法的结果．     

Enzymatic Synthesis of a CCK-8 Tripeptide Derivative

The enzymatic synthesis of CCK-8 tripeptide derivative Phae-Met-Asp(OMe)-Phe-NH2 is reported.Starting with Phac-Met-OCam,we have successfully synthesized the target tripeptide with three free or immobilized enzymes, α-chymotrypsin,papain and thermolysin in reasonable yields.The key steps in this synthesis were the coupling of Phac-Met-OCam and H-Asp(OMe)2 to from Met-Asp peptide bond catalyzed by α-chymotrypsin and the selective hydrolysis of α-ester of Phac-met-Asp(OMe)2 catalyzed by papain.     

四氢嘧啶类化合物的合成

以羰基衍生物,取代1,3-二羰基化合物,脲和硫脲为原料,经固定化青霉素酰化酶催化的Biginelli反应合成了22个四氢嘧啶类化合物（1a~1v）,其中1s和1v为新化合物,其结构经¹H NMR, ¹³C NHR和IR表征。研究了溶剂、反应温度、反应时间和物料比γ［n(苯甲醛) ：n(脲) ：n(乙酰乙酸乙酯)］对1a产率的影响。结果表明：在最佳反应条件（固定化青霉素酰化酶为催化剂,乙醇为溶剂,γ=1.0 ：1.5：1.0,于50 ℃反应6 h）下,1a产率最高（85%）。     

改性Ultrastable-Y分子筛固定化对非水相中脂肪酶拆分(R,S)-2-辛醇的影响

采用改性Ultrastable-Y分子筛固定Penicillium expansum PED-03 脂肪酶(PEL), 利用固定化PEL在非水相中对(R,S)-2-辛醇进行手性拆分, 考察了改性Ultrastable-Y分子筛固定化处理对PEL催化性能的影响. 结果表明, 与游离PEL及经其它载体固定化的PEL相比, 改性Ultrastable-Y分子筛固定的PEL所催化的拆分反应的转化率(c)和对映体过量值(ee)以及对映体选择性(E)均得到了较大提高. 经固定化处理后, PEL的最适反应温度明显升高, 适宜反应温度范围变宽, 其稳定性也得到了明显改善, 而适宜反应pH值则具有“记忆”性. 在间歇式反应器中利用Ultrastable-Y分子筛固定化PEL对(R,S)-2-辛醇进行手性拆分, 50 ℃反应24 h转化率(c)可达理论值的97.68%, 对映体过量值(ee)可达98.75%. 连续8批拆分反应的结果表明: 改性Ultrastable-Y分子筛固定化脂肪酶催化效率高、立体选择性强(平均E 值＞460), 且催化性能稳定, 显示了该固定化酶在(R,S)-2-辛醇的手性拆分方面具有良好的应用前景.     

13C NMR quantification of mono and diacylglycerols obtained through the solvent‐free lipase‐catalyzed esterification of saturated fatty acids

In the present investigation, we studied the enzymatic synthesis of monoacylglycerols (MAG) and diacylglycerols (DAG) via the esterification of saturated fatty acids (stearic, palmitic and an industrial residue containing 87% palmitic acid) and glycerol in a solvent‐free system. Three immobilized lipases (Lipozyme RM IM, Lipozyme TL IM and Novozym 435) and different reaction conditions were evaluated. Under the optimal reaction conditions, esterifications catalyzed by Lipozyme RM IM resulted in a mixture of MAG and DAG at high conversion rates for all of the substrates. In addition, except for the reaction of industrial residue at atmospheric pressure, all of these products met the World Health Organization and European Union directives for acylglycerol mixtures for use in food applications. The products were quantified by ¹³C NMR, with the aid of an external reference signal which was generated from a sealed coaxial tube filled with acetonitrile‐d3. After calibrating the area of this signal using the classical external reference method, the same coaxial tube was used repeatedly to quantify the reaction products. Copyright © 2012 John Wiley & Sons, Ltd.     

聚ε-己内酯的微米硅球固定化猪胰脂肪酶促合成

本文采用微米硅球固定化猪胰脂肪酶为催化剂合成聚ε-己内酯, 以期获得具有较高分子量、 良好生物相容性和使用安全性的生物可降解医用高分子材料.     

Chemoenzymatic Synthesis of Cellular Adhesion Tripeptide RGD Precursor in Organic Media

IntroductionA characteristic tripeptide sequence Arg-Gly-Asp(RGD) that is found within fibronectin and other rela-ted adhesion molecules in extracellular matrices(ECM)has received considerable attention from researcherssince it was proved to be a recognit…     

Effect of lipase immobilization on resolution of (R, S)-2-octanol in nonaqueous media using modified ultrastable-Y molecular sieve as support

The lipase from Penicillium expansum PED-03 (PEL) was immobilized onto modified ultrastable-Y (USY) molecular sieve and the resolution of (R, S)-2-octanol was carried out in a bioreactor in nonaqueous media by the immobilized lipase. It was found that the conversion rate, enantiomeric excess (ee) value, and enantioselectivity (E) value of the resolution catalyzed by PEL immobilized on modified USY molecular sieve were much higher than those of the reaction catalyzed by free PEL and PEL immobilized on other supports. Immobilized on modified USY molecular sieve, the PEL exhibited obvious activity within a wider pH range and at a much higher temperature and showed a markedly enhanced stability against thermal inactivation, by which the suitable pH of the buffer used for immobilization could be “memorized.” The conversion rate of the reaction catalyzed by PEL immobilized on modified USY molecular sieve reached 48.84%, with excellent enantio-selectivity (avarege E value of eight batches >460) in nonaqueous media at “memorial” pH 9.5, 50°C for 24 h, demonstrating a good application potential in the production of optically pure (R, S)-2-octanol.     

Efficient <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase immobilization on Maghnite clay and application for the production of (<Emphasis Type="Italic">1R</Emphasis>)-(−)-Menthyl acetate

This work focused on the identification of natural, economical, and efficient supports for immobilization of Candida rugosa lipase (CRL) to catalyze the resolution of (±)-menthol. To this purpose, CRL has been immobilized on natural montmorillonite from Algeria (Maghnite-H), ion-exchange resins (Amberjet^®1200-H and Amberjet^®4200-Cl), and diatomaceous earth (Celite^®545). After a preliminary screening of supports, the immobilization of CRL led to a markedly improved enantioselectivity. Excellent enantioselectivity (E ≥ 134) was achieved by the four supported lipases (E = 68 for free enzyme). Compared to the three other supports tested, higher enantioselectivity was observed with Maghnite-H used as immobilization matrix. In this work, the effects of solvent, reaction time, and temperature, on the conversion as well as on enantioselectivity were investigated. The maximum of conversion (% C = 43%) with high enantiomeric excess of products (eep > 99) was obtained when the reaction is catalyzed by CRL immobilized on Maghnite-H at 30 °C for 24 h, and using toluene as selected solvent. Immobilized CRL on Maghnite-H exhibited good thermostability over a wide temperature range (30–90 °C) compared to the free one. These results suggest that CRL immobilized on Maghnite-H has good potential as biocatalyst for the production of (1R)-(?)-menthyl acetate.     

Efficient synthesis of cefadroxil in [Bmim][NTf2]‐phosphate cosolvent by magnetic immobilized penicillin G acylase

For the first time, cefadroxil was synthesized from 7‐Amino‐3‐desacetoxycephalosporanic acid and d ‐hydroxyphenylglycine methyl ester in [Bmim][NTf₂]‐phosphate cosolvent capable of dissolving the substrates using the penicillin G acylase (PGA) immobilized on the micrometer‐size magnetic polymer microspheres having high activity of 2,083 U/g. The high synthesis/hydrolysis (S/H) ratio of 1.12 was achieved with 79.0% yield, where only the S/H ratio of 0.19 and yield of 20.0% was obtained using free PGA under the identical optimum reaction conditions. Cefadroxil had been synthesized efficiently in [Bmim][NTf₂]‐phosphate cosolvent by the magnetic immobilized PGA, which illuminated that there are two very critical and essential designs, that is, effective support and suitable solvent system by PGA, in enzymatic synthesis of cefadroxil. Obviously, there is great potential for the magnetic immobilized PGA and ionic liquid solvent in application to biocatalysis.     

TEMPO/固载化席夫碱铜配合物共催化剂在分子氧氧化苯甲醇过程中的催化性能

通过大分子反应,将苯甲醛(BA)和邻氨基苯酚(AP)形成的双齿席夫碱配基键合在交联聚甲基丙烯酸缩水甘油酯(CPGMA)微球表面,形成固载有席夫碱配基的载体微球BAAP-CPGMA,再通过与铜盐的配位螯合反应,制备了固载有席夫碱铜配合物的微球[Cu(BAAP)2]-CPGMA.将该固载化铜配合物与均相的2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)构成共催化体系TEMPO/[Cu(BAAP)2]-CPGMA,应用于分子氧氧化苯甲醇的催化氧化过程.我们考察了该共催化体系的催化性能,并探索研究了催化氧化机理.实验结果表明,共催化体系TEMPO/[Cu(BAAP)2]-CPGMA可在温和条件下(室温、常压的氧气)高效地将苯甲醇氧化为苯甲醛(选择性100%,苯甲醛产率93%),并具有良好的循环使用性能.     

Free energy landscape for glucose condensation reactions

Ab initio molecular dynamics and metadynamics simulations were used to determine the free energy surfaces (FES) for the acid catalyzed β-D-glucose condensation reaction. Protonation of C1-OH on the β-D-glucose, breakage of the C1-O1 bond, and the formation of C1 carbocation is the rate-limiting step. The effects of solvent on the reaction were investigated by determining the FES both in the absence and presence of solvent water. It was found that water played a critical role in these reactions. The reaction barrier for the proton-catalyzed glucose condensation reaction is solvent induced because of proton's high affinity for water. During these simulations, β-D-glucose conversion to α-d-glucose process via the C1 carbocation was also observed. The associated free energy change and activation barrier for this reaction were determined.     

用嗜热菌蛋白酶催化合成天冬甜精并同时进行DL-苯丙氨酸甲酯的光学拆分

以DL-苯丙氨酸甲酯作原料,利用嗜热菌蛋白酶和固定化嗜热菌蛋白酶催化合成了天冬甜精,经拆分得到D-苯丙氨酸甲酯。实验结果表明,不仅天冬甜精产率高,而且D-苯丙氨酸甲酯的回收率好,光学纯度高。     

Proton transfer in nanoconfined polar solvents. 1. Free energies and solute position

The reaction free energy curves for a model phenol-amine proton-transfer system in a confined CH3Cl solvent have been calculated by Monte Carlo simulations. The free energy curves, as a function of a collective solvent coordinate, have been obtained for several fixed reaction complex radial positions (based on the center-of-mass). A smooth, hydrophobic spherical cavity was used to confine the solvent, and radii of 10 and 15 A have been considered. Quantum effects associated with the transferring proton have been included by adding the proton zero-point energy to the classical free energy. The results indicate the reaction complex position can be an important component of the reaction coordinate for proton-transfer reactions in nanoconfined solvents.     

固定化过氧化氢酶的制备及其抗氧化作用

以烟用醋酸纤维的生物化学改性为目标,研究了以壳聚糖为载体时,吸附交联固定化过氧化氢酶的条件,并考察了固定化酶的性质。结果表明,固定化的最佳条件为:加酶量(酶活2×104C IU/m l)6m l,3%壳聚糖20m l,乙二醛浓度6%(w/v),交联剂用量100m l,吸附时间0.5 h,交联时间2.5h,酶活收率可达42.9%。过氧化氢酶固定化后,动学参数Km值为61.7mmol/L;对活性氧具有较好清除作用。     

Diffusion and reaction in an immobilized enzyme starch saccharification catalyst

Effectiveness factors were predicted from measurements of basic parameters made on single oligosaccharides, and the prediction was compared to experimental effec tiveness factors for the reaction of each oligosaccharide in the immobilized enzyme catalyst. Kinetic parameters were obtained for the hydrolysis of each oligosaccharide catalyzed by soluble glucoamylase, and were fit with a subsite model equation capable of generalization to all sizes of oligosaccharide. Diffusion coefficients in free solution were determined from movement out of a capillary tube. Spatial characteristics of the immobilized enzyme bed were obtained from pulse response experiments, allowing the calculation of effective diffusivities. Experimental effectiveness factors plotted against modulus were in reasonable agreement with the predictions.     

脂肪酶直接与硅胶混合催化无溶剂酯化反应的研究

用硅胶作为载体，以癸酸与己醇的酯化反应作为模型，将脂肪酶和底物直接与硅胶混合，用于无溶剂体系催化酯化反应．结果表明体系中水的含量、底物用量比以及反应时间均对酯化反应有较大影响．在该体系中，脂肪酶催化酯合成反应的速度显著增加，反应2h后．转化率可以达到90％以上．而且沉积在硅胶上的脂肪酶可以反复使用多次．     

Application of the aldehyde reactions for the endpoint detection in the catalytic thermometric titration of acids

Exothermic reaction of formaldehyde polymerization in alcoholic medium which is catalyzed by diluted solutions of strong bases was used for catalytic thermometric endpoint indication in titrations of organic acids. The amounts of 7.80–23.10 mg of various organic acids were determined with a relative standard deviation less than 0.9%. The developed method was successfully applied also to determination of free acid content (formic acid) in aqueous solutions of formaldehyde of various manufacturers.Also investigated were the possibilities of the application of two new indicator reactions in catalytic thermometric titrimetry: the exothermic reactions of aldolic addition of both benzaldehyde and acetophenone, and benzaldehyde and methylethylketone, which are catalyzed in alcoholic medium by diluted solutions of strong bases.The influence of concentration of indicator reaction components, the solvent and the titrant, on the shape of catalytic thermometric curves was explored.The obtained results were compared to those of potentiometry and other standard methods.     

One-pot synthesis and resolution of chiral allylic alcohols

Substituted α,β-unsaturated ketones were selectively reduced to the corresponding allylic alcohols under mild reaction conditions. The allylic alcohols thus obtained were kinetically resolved by lipase catalyzed transesterification in the same pot to afford chiral allylic alcohols in excellent enantioselectivity. Various lipases were screened for this one-pot transesterification of allylic alcohols. Effects of different solvent have also been studied under these conditions. Pseudomonas cepacia lipase immobilized on ceramic particles (PS-C) and on diatomaceous earth (PS-D) catalyzes this transesterification in diisopropyl ether in a highly efficient manner.     

底物,水量对脂肪酶不对称拆分萘普生的影响

选择了一种便于底物－产物分离的微水－有机两相体系,将对Ｓ－（＋＿萘普生酯有高度对映体选择性的ＣＣＬ脂肪酶固定于硅藻土上。合成了了一种能提高酶催化反应速度的激活的酯－萘普生氯乙酯。