钉螺谷草转氨酶的催化条件优化及对氯硝柳胺的敏感性

研究钉螺谷草转氨酶(GOT)的催化最适条件及对Niclosamide(NiC,氯硝柳胺)浸泡染毒的敏感性.取钉螺软体组织匀浆,将13000 r/min离心的上清液作为GOT酶液,用L25(56)正交设计和极(方)差分析GOT活性测定最适条件:酶液质量浓度0.2 g/L,底物浓度5 mmol/L,反应体系DH值7.5,反应温度45℃,反应时间60 min.与去氯水对照组相比较,1.5 mg/L NiC浸泡钉螺24、48 h,其软体GOT活性抑制率分别达25.98%、26.81%.结果说明GOT可能是NiC胁迫的防御性靶酶之一.     

氯硝柳胺和SX-Ⅰ染毒对钉螺可溶性蛋白的影响

用HPLC和分光光度法研究灭螺药物染毒对钉螺可溶性蛋白组分及其活性的作用.1.5 mg/L Nic和100 mg/LSX-Ⅰ分别浸泡染毒钉螺96 h,色谱分析其可溶性蛋白分别有20种和21种,与对照组的(22种)相近,其中诱导或抑制表达蛋白数分别为8种和5种;酶活力测定表明Nic和SX-Ⅰ染毒均抑制钉螺AchE、GOT、GPT活性.但Nic的抑制活性大于SX-Ⅰ,分别达47.34%、59.56%、81.39%.GPT对Nic的敏感性最高.     

鲫鱼和青虾GPT的动力学特性及对杀螺药物的敏感性

从鲫鱼和青虾肝脏中分离谷丙转氨酶(GPT),以比活力为指标,L25(56)正交试验与极差分析法研究TGPT酶活力测定的最适条件,测定YNic(氯硝柳胺)和CuSO4(硫酸铜)对GPT活力的影响.正交试验分析鲫鱼GPT活力测定最适条件:酶质量浓度2.0 g/L、底物浓度2.0 μmol/L、反应体系pH值7.0、反应温度30 ℃、反应时间55 min,青虾GPT活力测定最适条件酶质量浓度3.0 g/L、底物浓度0.5 μmol/L、反应体系pH值7.5、反应温度45 ℃和反应时间45 min.Nic和CuSO4对鲫鱼和青虾GPT活力均显示诱导作用,其0.002 g/L时对鲫鱼GPT的诱导率分别为641.01%和61.22%,对青虾的分别为45.99%和67.57%.研究结果表明:2种GPT活力测定条件相差较大,酶质量浓度和底物浓度影响作用最大.鲫鱼和青虾GPT对Nic和CuSO4敏感度高,推定GPT可能是Nic和CuSO4中毒的生化靶点之一.     

鲎血胶原蛋白酶解条件及其体外活性的研究

为了考察鲎血胶原蛋白(HXJ)酶解条件及其体外活性,以酶解后的肽得率为考察指标,在单因素的基础上,采用正交设计试验对酶解p H、酶解温度和底物浓度进行筛选,寻找HXJ的最佳酶解条件;对酶解后的HXJ进行体外α-葡萄糖苷酶和乙酰胆碱酶抑制活性测试,同时对其总抗氧化力和对DPPH自由基、羟自由基、超氧阴离子清除率进行测试。结果表明,HXJ的最佳酶解条件为:p H为7.0、温度为70℃、底物质量浓度为0.38 mg/m L、胰酶质量浓度为2.20 mg/m L、酶解时间为5 h,此时肽得率为36.50%;对α-葡萄糖苷酶和乙酰胆碱酯酶的最大抑制率分别为47.9%和97.5%;HXJ具有一定总抗氧化能力,对DPPH自由基、羟自由基和超氧阴离子的最大清除率分别为29.3%、97.3%和25.9%。HXJ能有效抑制α-葡萄糖苷酶和乙酰胆碱酯酶,具有较强的抗氧化活性。     

二甲双胍对乙酰胆碱酯酶活性影响的研究

利用试剂盒法探究不同浓度二甲双胍对乙酰胆碱酯酶(AChE)活性的影响。以人的血清作为酶源,氯化乙酰硫代胆碱为底物,建立体外筛选模型,计算酶的相对活性(B/B0%)和绘制Lineweaver-Burk (L-B)双倒数图。在浓度为0.003～0.122μmol/mL的盐酸二甲双胍作用下,测得酶的相对活性(B/B0%)在100%以上,随着二甲双胍浓度的增大,酶活力均逐渐增加。在盐酸二甲双胍良好的浓度线性范围内(0.003～0.122μmol/mL)对乙酰胆碱酯酶活性呈现激活作用,其激活机理表现为混合性效应。本项目的研究可以为今后采用二甲双胍治疗与乙酰胆碱酯酶活性相关疾病方面的研究提供理论依据。     

固定化乙酰胆碱酯酶的制备及其在中药抑制剂筛选中的应用

采用固定化酶的方法从治疗阿尔茨海默病的常用中药中筛选出具有乙酰胆碱酯酶(acetylcholinesterase, AChE)抑制活性的品种。结果表明,AChE能较好的固定在修饰羧基的磁珠表面,在酶浓度8 mg/mL、固定时间4 h、缓冲液pH5.0、固定温度20℃的条件下,固定的AChE具有最佳的酶固载量及酶活性;将所合成的固定化酶与高效液相色谱-质谱(LC-MS/MS)技术相结合,成功筛选出石菖蒲、川芎、茯苓、当归等4味具有较好AChE抑制活性的药材。     

乳酸菌发酵液对单胺氧化酶活性抑制率的测定

以犬脲胺为底物,从大鼠肝脏提取单胺氧化酶(MAO)粗酶,建立了一个酶反应体系,从而测定乳酸菌发酵产物对单胺氧化酶活性的相对抑制率。结果表明,几株乳酸菌的脱脂乳发酵液均具有对单胺氧化酶的抑制活性,其中干酪乳杆菌LC2W的脱脂乳发酵液对MAO抑制率最高,其抑制MAO-A和MAO-B活性的半数抑制率IC50分别为51.9,46.8 mg/m L。     

中华猕猴桃水提液清除羟自由基以及抑制酪氨酸酶活性的研究

以Fenton反应产生羟自由基,测定中华猕猴桃水提液清除羟自由基的能力。以L-酪氨酸和L-多巴为底物,测定中华猕猴桃水提液对酪氨酸酶单酚酶和二酚酶活力的影响以及抑制动力学。实验结果表明:中华猕猴桃水提液对羟自由基有较好的清除作用,当水提液质量浓度为1.0 g/L时,羟自由基清除率达到了95.57%。中华猕猴桃水提液对酪氨酸酶单酚酶和二酚酶的活性均有较好的抑制作用,其半数抑制浓度(IC_(50))分别为0.28和0.35 g/L。动力学研究表明,中华猕猴桃水提液对酪氨酸酶二酚酶的抑制作用属于可逆过程,其抑制作用表现为混合型抑制。     

乳酸菌发酵液对单胺氧化酶活性抑制率的测定

以犬脲胺为底物,从大鼠肝脏提取单胺氧化酶(MAO)粗酶,建立了一个酶反应体系,从而测定乳酸菌发酵产物对单胺氧化酶活性的相对抑制率。结果表明,几株乳酸菌的脱脂乳发酵液均具有对单胺氧化酶的抑制活性,其中干酪乳杆菌LC2W的脱脂乳发酵液对MAO抑制率最高,其抑制MAO-A和MAO-B活性的半数抑制率IC50分别为51.9,46.8 mg/m L。     

酶法拆分N-乙酰-D,L-蛋氨酸转化条件优化

重组大肠杆菌BL21/pET22b-argE表达的N-乙酰鸟氨酸脱酰基酶(NAOase)可用于脂肪族氨基酸的手性拆分.水解N-乙酰-D,L-氨基酸中的L-型底物,N-乙酰-D,L-蛋氨酸为其最合适的底物.为了确定NAOase拆分N-乙酰-D,L-蛋氨酸合适的转化条件,考察了反应温度、pH值、Co2+浓度、转化时间、底物浓度和加酶量对产物的影响.结果表明,合适的反应条件为37℃,pH值7.0,Co2+ 1 mmol/L,转化时间20 min,底物浓度150 mmol/L,菌泥5 g/L.在上述反应条件下,N-乙酰-D,L-蛋氨酸的转化率可达81.4%.     

两种拟除虫菊酯农药及混合制剂对鲫鱼乙酰胆碱酯酶活性影响

以淡水鲫鱼脑、肌肉和肝脏中乙酰胆碱酯酶(AChE)为酶源,以高效氯氰菊酯和甲氰菊酯为抑制剂,采用酶抑制法测定2种农药对AChE活性影响;将2种农药按不同比例混配,研究混配制剂对AChE活性的影响.结果表明:2种农药单剂施用及按不同比例混合施用时均对鲫鱼脑部AChE活性有促进作用,随高效氯氰菊酯所占比例增加,混合制剂对鲫鱼脑部AChE活性的促进作用逐渐增强,最高增强率为138.03%,与单剂施用时抑制率相当;对于鲫鱼肌肉,高效氯氰菊酯及甲氰菊酯单独施用的抑制率分别为28.58%和8.92%,混剂中高效氯氰菊酯与甲氰菊酯混配比例为3:1时,抑制率最高为39.45%;对于鲫鱼肝脏AChE,混剂中高效氯氰菊酯与甲氰菊酯混配比例为1:2时抑制率最高为52.27%.     

Free radical-scavening activity of phenolics by reversed-phase TLC

A method was developed to measure the radicalscavenging activity of compounds separated by reversed-phase TLC (RP-TLC) using phenolic acids as model analytes. TLC separation was followed by dipping the plate in a 0.04% (wt/vol) solution of 1,1-diphenyl-2-picrylhydrazyl (DPPH) in methanol. The compounds possessing radical-scavenging activity were detected as bright yellow bands against a purple background. A video documentation system based on a CCD video camera was used for the detection and quantification of the activity. The developed RP-TLC-DPPH method was compared to the widely used spectrophotometric DPPH assay. The results obtained by the two methods correlated well, apart from syringic acid, ascorbic acid, and n-propyl gallate, which proved to be outliers in the regression analyses. The correlation coefficient, after, excluding outliers, was r ²=0.923. The RP-TLC-DPPH method was applied for the measurement of free radical-scavenging activity of rapeseed meal fractions. A total of 10 separated zones with free radical-scavening activity were detected, with R _f values ranging from 0.04 to 0.85. The results show that the method can be used for the effective fractionation and analysis of potential antioxidative compounds in natural extracts.     

SO_4~(2-)/TiO_2 催化合成甲基丙烯酸甲氧基乙酯

沉淀-浸渍法制备了固体超强酸SO_4~(2-)/TiO_2催化剂,利用该催化剂合成了甲基丙烯酸甲氧基乙酯。考察了浸渍酸Hp_2SO_4浓度和焙烧温度对催化剂活性的影响,X射线衍射(XRD)分析确定催化剂为锐钛矿晶型结构。采用电子自旋共振(ESR)对催化剂进行了分析与表征,ESR波谱能够检测出催化剂空位或缺陷数量即催化剂活性的强弱,结合相关催化反应的转化率,最终确定了浸渍酸的较佳浓度为0.75 mol/L,最佳焙烧温度为450℃。研究了催化剂的重复使用性能,发现催化剂循环使用2次后活性下降明显,ESR初步分析表明其主要原因是由于催化剂表面积碳和吸附了有机物而导致的。     

Aromatization of n-hexane on Mo2C catalysts

The deposition-precipitation method was used to prepare gold catalysts based on different supports. Their catalytic activities for combustion of carbon monoxide (CO) and formaldehyde (HCHO) were investigated. All these catalysts showed good activity for the two reactions and the Au/CeO₂-a catalyst exhibited the highest activity for the two reactions. Furthermore, catalysts derived from the as-precipitate hydroxides exhibited higher activity than that from corresponding oxide supports. The BET, XRD, TEM and XPS were carried out. The results indicated that the gold dispersed more homogeneous on the as-precipitate hydroxide supports than that on the corresponding oxide supports.     

微生物谷氨酰胺转胺酶的研究进展

谷氨酰胺转胺酶(蛋白质-谷氨酸-γ-谷氨酰胺转胺酶EC2．3．2．13,TG)能催化蛋白质分子内或分子间的酰基转移反应,通过形成交联键改善蛋白质的功能性质。其酶活测定方法采用比色法,荧光法、偶联法、放射标记法目前只用于动物TG酶的活性测定;MTG(微生物谷氨酰胺转胺酶)作为胞外酶,从其发酵液中分离纯化MTG主要是用离子交换、凝胶层析、高效液相色谱、超滤等方法;MTG可用于肉食品、大豆蛋白和小麦制品等的加工。     

The Effects of PdZn Crystallite Size on Methanol Steam Reforming

Exceptional activity and selectivity of Pd/ZnO catalysts for methanol steam reforming have been attributed to the formation of PdZn alloy. In this paper, we evaluated the crystallite size effects of PdZn alloy on methanol steam reforming. An organic preparation method was used to avoid the complexity from the alteration of ZnO morphology typically associated with the conventional aqueous preparation method. Both Pd loading and reduction temperature (>350 °C) were used to vary the crystallite size of PdZn alloy. Experimental activity studies and transmission electron microscope (TEM) characterizations indicated that formation of large sized PdZn crystallites exhibit high reactivity and low CO selectivity during methanol steam reforming.     

Effects of conductive polyaniline (PANI) preparation and platinum electrodeposition on electroactivity of methanol oxidation

A modified galvanostatic method, termed the ‘pulse galvanostatic method’ (PGM) was used to synthesize nanofibular polyaniline (PANI). In contrast to granular PANI prepared by the conventional galvanostatic method (GM), nanofibular PANI has better conductivity and higher specific surface area. The nanofibular PANI electrode modified by Pt microparticles, at the same Pt loading, exhibits a considerably higher electrocatalytic activity on the methanol oxidation than that of the granular PANI electrode modified by Pt microparticles. Furthermore, the PGM method can be used as a good method for Pt microparticle electrodeposition. The composite electrode composed of PANI and Pt microparticles has the best electrocatalytic activity in the experimental range. The effects of Pt loading and methanol concentration, on the electrocatalytic activity for methanol oxidation have also been researched.     

Catalytic efficiency of signal peptidase I of Escherichia coli is comparable to that of members of the serine protease family

A method for estimating the activity of bacterial signal peptidase I (SPase I) was used to determine its activation energy (E[act]). Pro- OmpA-nuclease A, a hybrid secretory precursor, was purified to homogeneity under denaturing conditions and used as a substrate. This substrate was used to determine the activity of SPase I at different temperatures. The results show that the conformation of the mature domain of the substrate pro-OmpA-nuclease A has no discernible effect on the activity of SPase I. The activity data at a range of temperatures were then used to determine the activation energy using the Arrhenius equation. We have estimated E(act) to be 10.4 +/- 0.6 kcal/mol. This work indicates that SPase I is as catalytically efficient as the His-Ser-Asp family of proteases.      

茉莉花茎多糖的分离纯化及抗氧化作用研究

用优化超声法提取茉莉花茎多糖,通过单因素实验和正交实验,研究料液比、超声功率、超声提取温度和超声作用时间对茉莉花茎多糖提取效果的影响。利用Fenton反应原理,测定茉莉花茎多糖清除羟基自由基活性能力。超声提取法的优化工艺条件为:料液比(g∶mL)1∶35,提取温度50℃,超声功率180W,作用时间40min。茉莉花茎多糖的得率为6.02%。抗氧化性试验显示茉莉花茎多糖对羟基自由基的清除作用显著。茉莉花茎多糖具有较强的抗氧化活性,可为茉莉花茎药材资源的综合利用开发提供科学依据。