酵母还原乙酰乙酸乙酯制备（S）-3-羟基丁酸乙酯的研究

研究了五种酵母催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的能力,筛选出催化性能较好的菌株酿酒酵母,并以该酵母为出发菌株进行紫外诱变筛选出催化性能更优良的菌株 LY7;另外还对菌株 LY7 催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的反应特性进行了研究。研究表明：采用 200g／L蔗糖作为碳源,初始乙酰乙酸乙酯浓度为 O.25mol/L,初始细胞浓度为 150g／L,反应温度为36℃时所得产物得率和对映体过剩值最高。     

柠檬酸改性USY催化纤维素合成乙酰丙酸乙酯

以0.2mol/L浓度的柠檬酸对超稳Y型(USY)分子筛进行脱铝改性,并对改性获得的脱铝超稳Y型分子筛(DUSY)催化纤维素合成乙酰丙酸乙酯(EL)进行试验研究。利用X线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、比表面积测试(BET)、吡啶吸附红外光谱(Py-IR)、氨气程序升温脱附(NH3-TPD)等对改性前后的USY进行表征。结果显示:柠檬酸改性能够丰富USY的多孔结构,增强Lewiss(L)酸位,提高催化纤维素合成EL的能力。此外,优化了DUSY催化纤维素合成EL的工艺条件,在纤维素加入量0.6 g、DUSY用量0.3 g、反应温度220℃、反应时间3 h的条件下,EL的产率达到36.1%,且DUSY可重复使用。进一步对DUSY催化不同碳水化合物合成EL进行比较,发现果糖、葡萄糖、蔗糖和菊糖转化合成的EL产率分别为50.7%、41.0%、47.9%和42.9%。     

超临界下有机酸对稻秆水解糖化的影响

采用间歇式反应器在超临界条件下,以有机酸（甲酸、乙酸和丙酸）为催化剂对稻秆进行水解糖化研究,重点考察反应温度、反应时间、固液比对还原糖产率的影响。实验表明：有机酸的加入有利于稻秆的水解糖化,稻秆水解速率和还原糖产量都有所提高,这种趋势在加入甲酸时最为明显;随着反应时间的延长,还原糖产量会逐渐减少;适当提高固液比有助于增加还原糖产量。稻秆超临界水解糖化的最佳条件：甲酸体积分数3％、固液比4：60（g／mL）、反应温度410℃、反应时间5min,在此条件下,还原糖产量最高,达6．65g／L。     

酵母还原乙酰乙酸乙酯制备(S)-3-羟基丁酸乙酯的研究*

研究了五种酵母催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的能力,筛选出催化性能较好的菌株酿酒酵母,并以该酵母为出发菌株进行紫外诱变筛选出催化性能更优良的菌株LY7;另外还对菌株LY7催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的反应特性进行了研究。研究表明:采用200g/L蔗糖作为碳源,初始乙酰乙酸乙酯浓度为0.25mol/L,初始细胞浓度为150g/L,反应温度为36℃时所得产物得率和对映体过剩值最高。     

酵母还原乙酰乙酸乙酯制备(S)-3-羟基丁酸乙酯的研究

研究了五种酵母催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的能力,筛选出催化性能较好的菌株酿酒酵母,并以该酵母为出发菌株进行紫外诱变筛选出催化性能更优良的菌株LY7;另外还对菌株LY7催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的反应特性进行了研究。研究表明:采用200g/L蔗糖作为碳源,初始乙酰乙酸乙酯浓度为0.25mol/L,初始细胞浓度为150g/L,反应温度为36℃时所得产物得率和对映体过剩值最高。     

深黄被孢霉中微生物油脂的提取工艺

采用微波细胞破胞法处理深黄被孢霉,并对破胞后的菌体进行甲醇萃取油脂过程的研究。通过测量细胞内蛋白质释放量,确定微波处理的较佳条件为微波强度420 W,反应2 min。对微波后菌体进行扫描电镜观察,菌丝出现孔洞和裂纹,结构完全被破坏,达到微波破胞的效果;再直接进行甲酯化反应,通过正交试验考察固液比、反应温度、KOH浓度以及反应时间对甲酯化得率的影响。结果表明微生物油脂甲酯化的最佳条件:固液比(g/mL)1∶5,温度50℃,KOH-甲醇质量分数2.5%,时间2 h,此条件下干菌含油率为51.3%。     

表面活性剂辅助提取首乌藤中的总黄酮

用表面活性剂辅助提取首乌藤中总黄酮,分别考察了表面活性剂的种类和质量浓度、液固比、提取温度和加热时间对总黄酮得率的影响,通过正交试验设计以优化工艺条件,结合对照实验最终确定最佳工艺条件:表面活性剂十二烷基磺酸钠(SDS)质量浓度3 g/L,液固比30 mL/g,提取温度90℃,加热时间2.5 h。此时总黄酮得率为6.0%。与其他提取方法相比,本方法具有成本低、得率高的特点。     

响应面法优化泡桐叶中熊果酸的超声波提取工艺

为探讨泡桐叶中熊果酸的超声波提取工艺,通过中心复合设计-响应面法研究乙醇浓度(X1)、液固比(X2)、超声波提取时间(X3)对泡桐叶中熊果酸提取得率的影响。结果表明,各因素对熊果酸得率的影响顺序为乙醇浓度(X1)超声波提取时间(X3)液固比(X2);超声波辅助提取泡桐叶中熊果酸的最优工艺条件为:乙醇浓度89%,液固比31 m L/g,超声时间37 min;在此条件下,熊果酸得率为14.80 mg/g,与预测值相近,二次回归模型预测性良好。     

面包酵母催化不对称合成4-氯-(R)-3-羟基丁酸乙酯

以4 氯乙酰乙酸乙酯为原料,以面包酵母为手性生物催化剂,选择性合成光学活性4 氯 (R) 3 羟基丁酸乙酯。经IR、GC MS、1HNMR和旋光度测定,表明所得产品的结构与预期的结构一致。分别考察了面包酵母用量、葡萄糖浓度、底物投入量、pH值、反应时间以及反应温度等因素对产品比旋光度的影响。结果表明,4 氯乙酰乙酸乙酯不对称生物还原反应的适宜条件为:面包酵母6 0 0g/L、葡萄糖2 0g/L、反应温度34℃、底物加量16mL/L、反应时间4 8h、pH为5 ,产品的比旋光度为[α]2 0D = 13 9°。     

K_2CO_3/γ-Al_2O_3催化棕榈油和甲醇酯交换反应制备生物柴油

采用浸渍法制备K2CO3/γ-Al2O3负载型固体碱催化剂,用X线衍射(XRD)和热质量分析法(DSC-TGA)表征催化剂的物化性质,考察催化剂在棕榈油和甲醇酯交换制备生物柴油中的反应性能。结果表明:活性组分已成功负载到载体γ-Al2O3上,且在高温焙烧过程中K2CO3和γ-Al2O3之间产生了相互作用;在K2CO3负载量22.6%、醇油摩尔比12∶1、反应时间3h、催化剂质量分数3%、反应温度65℃的条件下,甲酯产率最高可达91.6%。     

New preparations and molecular structures of cis-MCl2(Ph2PCH2PPh2)2, M = Ru,Os and trans-RuCl2(Ph2PCH2PPh2)2

The title compounds were made by reacting bis(diphenylphosphino)methane (dppm) with reduced solutions of OsCl₆^4? and Ru₂OCl₁₀^4?. The crystal and molecular structures of these compounds have been determined form three-dimensional X-ray study. The cis-isomers crystallize with one CHCl₃ per molecule of the complex. All three compounds crystallize in the monoclinic space group P2₁/n with unit cell dimensions as follows: Cis-OsCl₂(dppm)₂·CHCl₃: a = 13.415(4) Å, b = 22.859(4) Å, c = 16.693(3) Å, β = 105.77(3)°, V = 4926(3) ų, Z = 4. cis-RuCl₂(dppm)₂·CHCl₃: a = 13.442(3) Å, b = 22.833(7) Å, c = 16.750(4) Å, β = 105.53(2)°, V = 4953(3) ų, Z = 4. trans-RuCl₂(dppm)₂: a = 11.368(7) Å, b = 10.656(6) Å, c = 18.832(12) Å; β = 103.90(6)°, V = 2213(7) ų; Z = 2. The structures were refined to R = 0.044 (R_w = 0.055) for cis-OsCl₂(dppm)₂·CHCl₃; R = 0.065 (R_w = 0.079) for cis-RuCl₂(dppm)₂·CHCl₃ and R = 0.028 (R_w = 0.038) for trans-RuCl₂(dppm)₂. The complexes are six coordinate with stable four-membered chelate rings. The PMP angle in the chelate rings is ca. 71° in each case.     

Achiral internucleoside linkages: CH2-CH2-NH and nH-CH2-CH2 linkages

The synthesis of CH₂-CH₂-NH and NH-CH₂-CH₂ internucleoside linkages are described. Antisense oligonucleosides containing these dimer modifications hybridized to the sense sequence. Furthermore incorporation of these backbone modifications enhanced the nuclease resistance of the antisense strand.     

Crystal structures of MoCl2(O)(O2)(OPMePh2)2 and mixtures of MoCl2(O2)(OPPh3)2 and MoCl2(O)(O2)(OPPh3)2: allylic alcohol isomerization studies using MoCl2(O)(O2)(OPMePh2)2

Adding one equivalent of H₂O₂ to compounds of stoichiometry MoCl₂(O)₂(OPR₃)₂, OPR₃ = OPMePh₂ or OPPh₃, leads to the formation of oxo-peroxo compounds MoCl₂(O)(O₂)(OPR₃)₂. The compound MoCl₂(O)(O₂)(OPMePh₂)₂ crystallized with an unequal disorder, 63%:37%, between the oxo and peroxo ligands, as verified by single-crystal X-ray diffractometry, and can be isolated in reasonable yields. MoCl₂(O)(O₂)(OPPh₃)₂, was not isolated in pure form, co-crystallized with MoCl₂(O)₂(OPPh₃)₂ in two ratios, 18%:82% and 12%:88%, respectively, and did not contain any disorder in the arrangement of the oxo and peroxo groups. These complexes accomplish the isomerization of various allylic alcohols. A mechanism of this reaction has been constructed based on ¹⁸O isotopic studies and involves exchange between the alcohol and metal bonded O atoms.     

Ntal/Lab/Lat2

Non-T cell activation linker (NTAL)/linker for activation of B cells (LAB), now officially termed LAT2 (linker for activation of T cells 2) is a 25-30kDa transmembrane adaptor protein (TRAP) associated with glycolipid-enriched membrane fractions (GEMs; lipid rafts) in specific cell types of hematopoietic lineage. Tyrosine phosphorylation of NTAL/LAB/LAT2 is induced by FcvarepsilonRI aggregation and Kit dimerization in mast cells, FcgammaRI aggregation in monocytes, and BCR aggregation in B cells. NTAL/LAB/LAT2 is also expressed in resting NK cells but, unlike the related TRAP, LAT, not in resting T cells. As demonstrated in monocytes and B cells, phosphorylated NTAL/LAB/LAT2 recruits signaling molecules such as Grb2, Gab1 and c-Cbl into receptor-signaling complexes. Although gene knock out and knock down studies have indicated that NTAL/LAB/LAT2 may function as both a positive and negative regulator of mast cell activation, its precise role in the activation of these and other hematopoietic cells remains enigmatic.     

P2X2, P2X2–2 and P2X5 receptor subunit expression and function in rat thoracolumbar sympathetic neurons

The present study investigated the pharmacological properties of excitatory P2X receptors and P2X(2) and P2X(5) receptor subunit expression in rat-cultured thoracolumbar sympathetic neurons. In patch-clamp recordings, ATP (3-1000 microM; applied for 1 s) induced inward currents in a concentration-dependent manner. Pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS; 30 microM) counteracted the ATP response. In contrast to ATP, alpha,beta-meATP (30 microM; for 1 s) was virtually ineffective. Prolonged application of ATP (100 microM; 10 s) induced receptor desensitization in a significant proportion of sympathetic neurons in a manner typical for P2X(2-2) splice variant-mediated responses. Using single-cell RT-PCR, P2X(2), P2X(2-2) and P2X(5) mRNA expression was detectable in individual tyrosine hydroxylase-positive neurons; coexpression of both P2X(2) isoforms was not observed. Laser scanning microscopy revealed both P2X(2) and P2X(5) immunoreactivity in virtually every TH-positive neuron. P2X(2) immunoreactivity was largely distributed over the cell body, whereas P2X(5) immunoreactivity was most distinctly located close to the nucleus. In summary, the present study demonstrates the expression of P2X(2), P2X(2-2) and P2X(5) receptor subunits in rat thoracolumbar neurons. The functional data in conjunction with a preferential membranous localization of P2X(2)/P2X(2-2) compared with P2X(5) suggest that the excitatory P2X responses are mediated by P2X(2) and P2X(2-2) receptors. Apparently there exist two types of P2X(2) receptor-bearing sympathetic neurons: one major population expressing the unspliced isoform and another minor population expressing the P2X(2-2) splice variant.     

Spin trapping of the azidyl radical in azide/catalase/H2O2 and various azide/peroxidase/H2O2 peroxidizing systems

The azidyl radical is formed during the oxidation of sodium azide by the catalase/hydrogen peroxide system, as detected by the ESR spin-trapping technique. The oxidation of azide by horseradish peroxidase, chloroperoxidase, lactoperoxidase, and myeloperoxidase also forms azidyl radical. It is suggested that the evolution of nitrogen gas and nitrogen oxides reported in the azide/catalase/hydrogen peroxide system results from reactions of the azidyl radical. The azide/horseradish peroxidase/hydrogen peroxide system consumes oxygen, and this oxygen uptake is inhibited by the spin trap 5,5-dimethyl-1-pyrroline-N-oxide, presumably due to the competition with oxygen for the azidyl radical. Although azide is used routinely as an inhibitor of myeloperoxidase and catalase, some consideration should be given to the biochemical consequences of the formation of the highly reactive azidyl radical by the peroxidase activity of these enzymes.     

The oxidative stress response in Enterococcus faecalis: relationship between H2O2 tolerance and H2O2 stress proteins

The hydrogen peroxide (H₂O₂) stress response in Enterococcus faecalis ATCC19433 was investigated. A 2·4 mmol l⁻¹ H₂O₂ pretreatment conferred protection against a lethal concentration (45 mmol l⁻¹) of this agent. The relatively high concentrations of H₂O₂ used for adaptation and challenge treatments in Ent. faecalis emphasised the strong resistance towards oxidative stress in this species. Various stresses (NaCl, heat, ethanol, acidity and alkalinity) induced weak or strong H₂O₂ cross-protection. This paper describes the involvement of protein synthesis in the active response to lethal dose of H₂O₂, in addition to the impressive enhancement of synthesis of five H₂O₂ stress proteins. Combined results suggest that these proteins might play an important role in the H₂O₂ tolerance response.     

Generation of H2O2 in Brain Mitochondria

Generation of H2O2 by rat brain mitochondria using succinate and glycerol-1-phosphate as substrates has been demonstrated. Earlier workers were unable to detect this activity in sucrose-Tris buffer. We found that this was due to a lag in the expression of activity in sucrose medium. Using phosphate buffer (50 mM), good rates are now obtained. Generation of H2O2 by rat brain mitochondria required the presence of antimycin A and was dependent on the substrates succinate and glycerol-1-phosphate. Low rates were obtained with NAD+-linked substrates and none with choline, glutamate, and NADH. The Km and Vmax values for H2O2 generation were considerably lower than the corresponding values for the respective dehydrogenase activity, measured by dye reduction. Oxygen-radical scavengers inhibited H2O2 generation, suggesting oxygen radical involvement. Depletion of ubiquinone from mitochondria resulted in loss of H2O2 generation. Reconstitution of such depleted particles with ubiquinone restored the capacity to generate H2O2 in a concentration-dependent manner. Levels of H2O2 production were found to be maximal in cerebellum. Brain mitochondria from rabbit, hamster, mouse, and guinea pig also have the capacity to generate H2O2 on oxidation of glycerol-1-phosphate.     

Synthesis, structure and properties of TTF-carboxylate bridged paddlewheel dirhodium complexes, Rh2(BuCO2)3(TTFCO2) and Rh2(BuCO2)2(TTFCO2)2

Reaction of tetrathiafulvalene carboxylic acid (TTFCO₂H) with paddlewheel dirhodium complex Rh₂(Bu^tCO₂)₄ yielded TTFCO₂-bridged complexes Rh₂(Bu^tCO₂)₃(TTFCO₂) (1) and cis- and trans-Rh₂(Bu^tCO₂)₂(TTFCO₂)₂ (cis- and trans-2). Their triethylamine adducts [1(NEt₃)₂] and cis-[2(NEt₃)₂] were purified and isolated with chromatographic separation, and characterized with single crystal X-ray analysis. Trans-[2(NEt₃)₂] is not completely separated from a mixture of cis- and trans-[2(NEt₃)₂], but its single crystals were obtained from a solution of the mixture. A three-step quasi-reversible oxidation process was observed for 1 in MeCN. The first two steps correspond to the oxidation of the TTFCO₂ moiety and the last one is the oxidation of the Rh₂ core. The oxidation of cis-2 is observed as a two-step process with very similar E_1/2 values to those of the first two processes for 1. Both 1⁺ and cis-2²⁺ in MeCN at room temperature show isotropic ESR spectra with a g value of 2.008 and a_H = 0.135 mT for two equivalent H atoms and a_H = 0.068 mT for one H atom. The redox and ESR data of cis-2 suggest that the intramolecular interaction between the TTF moieties is very small.     

Kinetic studies on the reactions of HCl with trans-[MoL(CNPh)(Ph2PCH2CH2PPh2)2] (L=N2, H2 or CO)

The kinetics of the reactions between anhydrous HCl and trans-[MoL(CNPh)(Ph₂PCH₂CH₂PPh₂)₂] (L=CO, N₂ or H₂) have been studied in thf at 25.0 °C. When L=CO, the product is [MoH(CO)(CNPh)(Ph₂PCH₂CH₂PPh₂)₂]⁺, and when L=H₂ or N₂ the product is trans-[MoCl(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]. Using stopped-flow spectrophotometry reveals that the protonation chemistry of trans-[MoL(CNPh)(Ph₂PCH₂CH₂PPh₂)₂] is complicated. It is proposed that in all cases protonation occurs initially at the nitrogen atom of the isonitrile ligand to form trans-[MoL(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]⁺. Only when L=N₂ is this single protonation sufficient to labilise L to dissociation, and subsequent binding of Cl⁻ gives trans-[MoCl(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]. At high concentrations of HCl a second protonation occurs which inhibits the substitution. It is proposed that this second proton binds to the dinitrogen ligand. When L=CO or H₂, a second protonation is also observed but in these cases the second protonation is proposed to occur at the carbon atom of the aminocarbyne ligand, generating trans-[MoL(CHNHPh)(Ph₂PCH₂CH₂PPh₂)₂]²⁺. Addition of the second proton labilises the trans-H₂ to dissociation, and subsequent rapid binding of Cl⁻ and dissociation of a proton yields the product trans-[MoCl(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]. Dissociation of L=CO does not occur from trans-[Mo(CO)(CHNHPh)(Ph₂PCH₂CH₂PPh₂)₂]²⁺, but rather migration of the proton from carbon to molybdenum, and dissociation of the other proton produces [MoH(CO)(CNPh)(Ph₂PCH₂CH₂PPh₂)₂]⁺.