A facile enzymatic process for the preparation of (s)-Naproxen ester prodrug in organic solvents

A facile enzymatic synthesis process has been developed to directly prepare the 4-morpholinoethyl ester prodrug of (s)-Naproxen from racemic Naproxen using lipases as the biocatalysts in the organic solvent. With the careful selection of lipase (Lipase MY) and reaction medium (cylohexane), a high enantiomeric ratio of 136 for the enzyme was obtained. A Ping-Pong Bi Bi mechanism with competitive inhibition by the alcohol was illustrated from the variation of initial rates with substrate concentrations.     

Study of vitamin ester synthesis by lipase-catalyzed transesterification in organic media

Immobilized lipase from Candida antarctica (Novozym 435) was used in organic media to catalyze esterifications of vitamins (ascorbic acid and retinol) from hydroxy acid. We described the synthesis of retinyl L-lactate by transesterification between retinol and L-methyl lactate with yield reaching 90% and the synthesis of ascorbyl L-lactate by transesterification between ascorbic acid and L-methyl lactate with yield reaching 80%. The kinetic study of the esterification of vitamins with L-methyl lactate in organic media has been carried out and agrees with ping-pong-ordered Bi-Bi when the initial vitamin concentration is low. When initial vitamin concentration is high, the kinetic is similar to a hybrid ping-pong-ordered Bi Bi or hybrid ping-pong-random Bi Bi mechanism. However, with high initial substrate concentration, change of the kinetic by other phenomena, such as interaction of substrates with molecular sieves, adsorption of the methanol formed, and decreases of substrate diffusion, could be considered. It is obvious that in these conditions, classical enzymology (i.e., Michaelian enzymology) cannot be used for the interpretation of results.     

脂肪酶在微乳液和微乳液凝胶中催化辛酸辛醇的酯化反应

脂肪酶在合成反应中具有很高的区域选择性和立体选择性 ,已广泛用于食品工业和药物工业[1,2 ] ,在有机介质中的脂肪酶催化反应已有较多研究[3 ,4 ] 。微乳液一般由表面活性剂、助表面活性剂、油和水等组份组成 ,它是一种热力学稳定、光学透明、宏观均匀而微观不均匀的体系 ,能提供酶催化所需要的巨大油 /水界面[5] 。而将脂肪酶增溶于油包水(Ｗ /Ｏ)微乳液中的纳米级“水池”中 ,可使酶以分子水平分散[6] ,图 1(ａ) ,从而可用来模拟细胞微环境中的反应。油包水微乳液中的酶可通过加入明胶而制成固定化酶 ,含明胶的微乳液凝胶 (ＭＢＧｓ)最早…     

Localization of bismuth radiotracer in rat kidney following exposure to bismuth

It has been proposed that alpha emitting 212Bi (t1/2 = 60 min) coupled to tumor-specific antibodies may be a useful radiotherapeutic agent. However, since Bi can accumulate in the kidney, it is necessary to characterize the factors influencing localization of Bi within this tissue in order to evaluate the potential for radiation damage to the renal system. In this study, the localization of Bi radiotracers was determined in kidneys of rats previously exposed and not exposed to mumole quantities of Bi. Following repeated injection of Bi (4 x 14 mumols (3 mg Bi)/kg bw) the element accumulated mainly in the kidney followed by liver, spleen, pancreas, bone, and brain. Kidney copper and liver zinc concentrations were higher in Bi-exposed rats than in non-exposed rats. Within the cytosol, in Bi-exposed rats, Bi radiotracer in the kidney was associated with a metallothionein-like protein (Mt). In contrast, non-exposed rats contained no detectable metallothionein-like proteins in the kidney and the Bi tracer was associated with the hemoglobin fraction of the cell. Thus, when Bi is administered in tracer quantities such as that incorporated for use as a radiopharmaceutical, no induction of, and association with, metallothionein-like proteins should occur. These results suggest that the potential nephrotic effects of 212Bi will be influenced by the individual's previous exposure to Bi-containing drugs, or other metallothionein-inducing insults.     

A Safe Organic/Inorganic Composite Anode for Sodium-Ion Batteries

Sodium-ion batteries (SIBs), based on hard carbon anodes and Na⁺-intercalation compound cathodes, have gained significant attention. Nonetheless, hard carbon anodes involve the storage of Na⁺ at a low potential, typically below 0.1 V (vs Na/Na⁺), which increases the risk of dendritic Na growth on the anode surface during overcharging. Herein, a safe organic/inorganic composite anode containing tetrasodium 3,4,9,10-perylenetetracarboxylate (Na₄PTC) and Metallic bismuth (Bi) with a weight ratio of 7:2, which exhibits an average potential of 0.7 V (vs Na⁺/Na) and a capacity of 150 mAh g⁻¹ is proposed. The electrode reaction involves a reversible coordination reaction within the organic host and alloying reactions within the metallic Bi component. Importantly, the organic component efficiently buffers the volume changes in Bi during the alloying reaction, while the metallic Bi enhances the electronic conductivity of the organic material. As a result, this composite anode shows high cycle stability and rate performance, even under high mass loadings ranging from 10 to 50 mg cm⁻². Furthermore, it is demonstrated that the Na-ion full cell, consisting of the composite anode and the Na₃V₂O₂(PO₄)₂F cathode, exhibits minimal capacity degradation over 100 cycles while maintaining a high areal capacity of 1.1 mA cm⁻².     

The kinetic mechanism of the major form of ox kidney aldehyde reductase with d-glucuronic acid

The steady-state kinetics of the major form of ox kidney aldehyde reductase with d-glucuronic acid have been determined at pH7. Initial rate and product inhibition studies performed in both directions are consistent with a Di-Iso Ordered Bi Bi mechanism. The mechanism of inhibition by sodium valproate and benzoic acid is shown to involve flux through an alternative pathway.     

Alcoholysis catalyzed by Candida antarctica lipase B in a gas/solid system obeys a Ping Pong Bi Bi mechanism with competitive inhibition by the alcohol substrate and water.

The kinetics of alcoholysis of methyl propionate and n-propanol catalyzed by Candida antarctica lipase B supported onto silanized Chromosorb P was studied in a continuous solid/gas reactor. In this system the solid phase is composed of a packed enzymatic sample and is percolated by nitrogen as carrier gas, which simultaneously carries substrates to the enzyme while removing reaction products. In this reactor the thermodynamic activity of substrates and effectors can be perfectly adjusted allowing kinetic studies to be performed under different operating conditions. The kinetics obtained for alcoholysis were suggested to fit a Ping Pong Bi Bi mechanism with dead-end inhibition by the alcohol. The values of all apparent kinetic parameters were calculated and the apparent dissociation constant of enzyme for gaseous ester was found very low compared with the one obtained for liquid ester in organic medium, certainly due to the more efficient diffusion in the gaseous phase. The effect of water thermodynamic activity was also investigated. Water was found to act as a competitive inhibitor, with a higher inhibition constant than n-propanol. Thus alcoholysis of gaseous methyl propionate and n-propanol catalyzed by C. antarctica lipase B was found to obey the same kinetic mechanism as in other non-conventional media such as organic liquid media and supercritical carbon dioxide, but with much higher affinity for the substrates.     

Wax ester synthesis by lipase-catalyzed esterification with fungal cells immobilized on cellulose biomass support particles

Esterification reactions between long-chain alcohol and oleic acid were performed for producing wax esters. The reaction can be catalyzed efficiently by cell-bound lipase of Rhizopus niveous fungal cells immobilized within cellulose biomass support particles. Carrying out the reaction in a solvent-free system is feasible by adding a molecular sieve for dehydration purposes. To optimize the yield, addition of a molecular sieve should be performed gradually during the whole course starting from the beginning of the reaction. The influence of reaction conditions such as temperature and substrate concentrations on reaction rates and yields were investigated; however, this reaction system is under the influence of both internal and external mass transfer resistance. Conducting the reaction in an organic solvent system with hexane or heptane as the solvent can eliminate diffusional effects. Reaction kinetics were subjected to detailed study in this system. The kinetics of the reaction can be represented satisfactorily by a Ping-Pong Bi Bi mechanism with deadend inhibition by alcohol.     

Bi‐Based Metal‐Organic Framework Derived Leafy Bismuth Nanosheets for Carbon Dioxide Electroreduction

Electroreduction of carbon dioxide (CO₂) into high‐value and readily collectable liquid products is vital but remains a substantial challenge due to the lack of highly efficient and robust electrocatalysts. Herein, Bi‐based metal‐organic framework (CAU‐17) derived leafy bismuth nanosheets with a hybrid Bi/Bi? O interface (Bi NSs) is developed, which enables CO₂ reduction to formic acid (HCOOH) with high activity, selectivity, and stability. Specially, the flow cell configuration is employed to eliminate the diffusion effect of CO₂ molecules and simultaneously achieve considerable current density (200 mA cm^?2) for industrial application. The faradaic efficiency for transforming CO₂ to HCOOH can achieve over 85 or 90% in 1 m KHCO₃ or KOH for at least 10 h despite a current density that exceeds 200 mA cm^?2, outperforming most of the reported CO₂ electroreduction catalysts. The hybrid Bi/Bi? O surface of leafy bismuth nanosheets boosts the adsorption of CO₂ and protects the surface structure of the as‐prepared leafy bismuth nanosheets, which benefits its activity and stability for CO₂ electroreduction. This work shows that modifying electrocatalysts by surface oxygen groups is a promising pathway to regulate the activity and stability for selective CO₂ reduction to HCOOH.     

我国鼎湖山小皮伞属的分类研究

本文报道了广东鼎湖山小皮伞属(Marasmius Fr．)的34个种,其中新种4个,国内新记录20个。新种为拟花味小皮伞(M·pseudo-euosmus Zheng et Bi sp nov.),近刚毛小皮伞(M. subsetiger Bi et Zheng sp. Nov.),脐状小皮伞(M．Umbilieatus Bi et Zheng sp．nov．)及 近血红小皮伞(M. subaimaru Bi sp．nov.)。     

Ping Pong Bi Bi机制的非稳态酶动力学分布函数图论研究

以非稳态酶动力学的布尔函数图形方法,来研究一类PingPongBiBi机制的非记酶动力学问题,推导出此类反应的非稳态酶动力学方程,并对此动力学方程进行了讨论,分析了此类PingPongBiBi机制酶反应体系的非稳态酶动力学方程。     

Random Bi Bi机制的非稳态酶动力学布尔函数图论研究

本文以非稳态酶动力学的布尔函数图形方法^[1],来研究一类Random Bi Bi机制的非稳态酶动力学问题,推导同此类反应的非稳态酶动力学方程,并对此动力学方程进行了讨论,分析了此类Random Bi Bi机制酶反应体系的非稳态酶动力学方程。     

In vivo cellular uptake of bismuth ions from shotgun pellets

Shotgun pellets containing bismuth (Bi) are widely used and may cause a rather intense exposure of some wild animals to Bi. A Bi shotgun pellet was implanted intramuscularly in the triceps surae muscle of 18 adult male Wistar rats. Another group of 9 animals had a Bi shotgun pellet implanted intracranially in the neocortex. Eight weeks to 12 months later the release of Bi ions was analysed by autometallography (AMG) of tissue sections from different organs (brain, spinal cord, kidney, liver, testes). In the group with intramuscular Bi shotgun pellets no AMG staining could be found for the first 2-4 months; 6 months after exposure Bi was traced in the kidney. Twelve months after the implantation the kidneys were heavily loaded and Bi was also traced in testosterone-producing Leydig cells, in glial cells and in neurons of brain and spinal cord. In the central nervous system (CNS) motor neurons were the most loaded. In rats with intracranially implanted shotgun pellets a massive uptake of Bi was observed involving both glia and neurons throughout the brain. The cells close to the shotgun pellet had the highest uptake. The animals showed a pronounced Bi uptake in the ependyma cells lining the ventricular system and in the cubic epithelia covering the choroid plexus. Dissemination of Bi ions to the rest of the body was demonstrated by AMG tracing of Bi accumulations in the tubular cells of the kidney. These findings emphasize that metallic Bi, including shotgun pellets, represents sites of intense Bi pollution if implanted or shot into a living organism, and further that such metallic Bi bodies, if they enter the CNS, cause a spread of Bi ions throughout it.     

广东省杯伞属的分组及三个新种

本文报道了广东地区杯伞属Clitocybe(Fr.)Staude的3个新种及5个国内新记录。3个新种是:拟褶杯伞Clitocybe pseudo-phyllophila Bi et zheng,sp.nov.,鳞杯伞Clitocybe furfuracea Bi sp.nov以及亚白杯伞Clitocybe subcandicans Bi sp.nov.。并附与种和种所属分组的检索表。     

广东小菇属的分类研究

本文报道了广东省小菇属 Mycena(Pers.ex Fr.)s.F.Gray 的21个种,其中新种3个,国内新记录种4个以及新组合1个。新种是鼎湖小菇 Myce-na dinghuensis Bi sp.nov.,近细小菇 Mycena subgracilis Bi sp.nov.以及亚长刺小菇 Mycena sublongiseta Bi sp.nov.。新组合为拟安络小菇 Mycena pseudo-androsacea(Bull.ex Fr.)Bi comb.nov;新记录种是:唯一小菇 Mycena insignis Smith,狭褶小菇 Mycena leptophylla(Pk.)Sacc.,粗糙孢小菇 Mycena trachyspora Rea 以及特洛伊小菇 Mycena,tro-jana Murr.。     

胆碱脱氢酶的动力学性质

本文对增溶胆碱脱氢酶的稳态初速度及产物抑制动力学做了。底物胆碱和ＰＭＳ的相互影响：变化一个底物的浓度,另一个底物的Ｋｍ及Ｖｍａｘ均变化。该酶的产物三甲胺 地 制表现为对底物胆碱非竞争性而地ＰＭＳ竞争性,在胆碱饱和的情况下,三甲胺乙醛对酶的抑制仍表现为对ＰＭＳ竞争性。这些结果表明增溶胆碱脱氢酶的催化机制搂双底物双产物乒乓机制。１－ＰＣ与９－ＡＣ对增溶胆碱脱氢酶均有抑制作用,且均为混和型抑制,Ｋ１分别     

Lipase-catalyzed synthesis of palmitanilide: Kinetic model and antimicrobial activity study

Enzymatic syntheses of fatty acid anilides are important owing to their wide range of industrial applications in detergents, shampoo, cosmetics, and surfactant formulations. The amidation reaction of Mucor miehei lipase Lipozyme IM20 was investigated for direct amidation of triacylglycerol in organic solvents. The process parameters (reaction temperature, substrate molar ratio, enzyme amount) were optimized to achieve the highest yield of anilide. The maximum yield of palmitanilide (88.9%) was achieved after 24 h of reaction at 40 °C at an enzyme concentration of 1.4% (70 mg). Kinetics of lipase-catalyzed amidation of aniline with tripalmitin has been investigated. The reaction rate could be described in terms of the Michaelis–Menten equation with a Ping–Pong Bi–Bi mechanism and competitive inhibition by both the substrates. The kinetic constants were estimated by using non-linear regression method using enzyme kinetic modules. The enzyme operational stability study showed that Lipozyme IM20 retained 38.1% of the initial activity for the synthesis of palmitanilide (even after repeated use for 48 h). Palmitanilide, a fatty acid amide, exhibited potent antimicrobial activity toward Bacillus cereus.     

Kinetic model of 1,3-specific triacylglycerols alcoholysis catalyzed by lipases

A new model of enzymatic 1,3-specific alcoholysis of triacylglycerols has been developed. The irreversibility of the acyl bounds cleavage in glycerides, a reversible monoglycerides isomerization and an irreversible enzyme deactivation have been assumed. The Ping Pong Bi Bi mechanism with competitive inhibition by alcohol has been applied to describe rates of acyl bonds cleavage. The enzymatic propanolysis and iso-propanolysis of triacetin and tricaprylin catalyzed by immobilized lipase B from Candida antarctica (Novozym 435) have been investigated to verify the model. Good agreement between experimental data and calculations has been obtained. It was shown that the rate of tricaprylin alcoholysis is higher than the triacetin alcoholysis and that the rate of iso-propanolysis reactions are higher than propanolysis. The irreversible enzyme deactivation affects the conversion of glycerides whereas the competitive alcohol inhibition may be neglected. Empirical correlations of rates for monoglycerides isomerization and enzyme deactivation have been proposed.     

Biocatalytic synthesis of vitamin A palmitate using immobilized lipase produced by recombinant Pichia pastoris

In this work, the Candida antarctica lipase B (CALB), produced by recombinant Pichia pastoris , was immobilized and used to synthesize vitamin A palmitate by transesterification of vitamin A acetate and palmitic acid in organic solvent. The reaction conditions including the type of solvent, temperature, rotation speed, particle size, and molar ratio between the two substrates were investigated. It turned out that the macroporous resin HPD826 serving as a carrier showed the highest activity (ca. 9200 U g^?1) among all the screened carriers. It was found that the transesterification kinetic of the immobilized CALB followed the ping pong Bi‐Bi mechanism and the reaction product acetic acid inhibited the enzymatic reaction with an inhibition factor of 2.823 mmol L^?1. The conversion ability of the immobilized CALB was 54.3% after 15 cycles. In conclusion, the present work provides a green route for vitamin A palmitate production using immobilized CALB to catalyze the transesterification of vitamin A acetate and palmitic acid.     

Human protein N-terminal acetyltransferase hNaa50p (hNAT5/hSAN) follows ordered sequential catalytic mechanism: combined kinetic and NMR study

N(α)-acetylation is a common protein modification catalyzed by different N-terminal acetyltransferases (NATs). Their essential role in the biogenesis and degradation of proteins is becoming increasingly evident. The NAT hNaa50p preferentially modifies peptides starting with methionine followed by a hydrophobic amino acid. hNaa50p also possesses N(ε)-autoacetylation activity. So far, no eukaryotic NAT has been mechanistically investigated. In this study, we used NMR spectroscopy, bisubstrate kinetic assays, and product inhibition experiments to demonstrate that hNaa50p utilizes an ordered Bi Bi reaction of the Theorell-Chance type. The NMR results, both the substrate binding study and the dynamic data, further indicate that the binding of acetyl-CoA induces a conformational change that is required for the peptide to bind to the active site. In support of an ordered Bi Bi reaction mechanism, addition of peptide in the absence of acetyl-CoA did not alter the structure of the protein. This model is further strengthened by the NMR results using a catalytically inactive hNaa50p mutant.