Water Activity Dependence of Lipases in Non-aqueous Biocatalysis

Eleven lipases are tested and it was found that lipases can be divided into three types according to water activity dependence. The first type is lipase that has low water activity dependence and works in a low water activity, its performance changes little with the change of water activity. The optimum water activity is 0.19 and Newlase F (Rhizopus niveus), lipase FAP-15 (Rhizopus oryzae) belong to this type. The second type is lipase that has medium water activity dependence and its performance changes with the change of water activity. Most lipases belong to this type and the optimum water activity in this type is about 0.60. The third type is lipase that has a high water activity dependence and works only in a high water activity (a _w  > 0.75). WGL (wheat germ) belongs to this type and the optimum water activity is 0.90. The relationship between enantioselectivity and water activity is also discussed and the enantioselectivity seems to be independent of water activity. And we also compared the two control methods of water activity, it was found that the method which add solid salt hydrates to the reaction mixture (method II) is more stable and effective throughout the reaction than the method that pre-equilibrate via the vapor phase (method I). The addition concentration of salt hydrates is also investigated and the optimum concentration is 1 g/l.     

不同活性焦载体对V2O5/AC催化剂脱硫活性的影响

活性焦载体的选择是制备高活性烟气脱硫催化剂的关键.以四种煤制活性焦(AC)为载体,制得了系列V2O5/AC催化剂.通过脱硫活性评价、催化氧化能力测试和孔结构分析表明,AC表面的高活性氧化位较少,担载V2O5使AC表面产生了新的高活性氧化位,其脱硫活性显著提高;V2O5在具有高比表面积和较大孔容的载体上分散性较好,能够形...     

Transferase and hydrolase activities of phospholipase D from the roots ofAconitum arcuatum

The phospholipase D fromAconitum arcuatum has been studied. The optimum pH values have been determined: 6.3 for the hydrolase activity and 8.0 for the transferase activity. Calcium ions activate the phospholipase D: the hydrolase activity most strongly at 8 and 30 µmole and the transferase activity at 30 µmole. The hydrolase activity of the phospholipase D is not activated by low concentrations of sodium dodecyl sulfate, while the transferase activity is activated to a considerable degree. The results obtained are compared with those on the activation of cabbage phospholipase D.     

Endo- and aminopeptidase activities of rat cathepsin H.

Employing soluble denatured protein substrates and their derivatives, the proteolytic activity of rat cathepsin H was investigated. The enzyme showed aminopeptidase activity which sequentially released amino acid from the N-terminal of the substrate. The aminopeptidase activity did not act on N alpha-acetylated peptides and showed moderate ionic-strength dependence when methionyl-methylcoumarylamide was employed as a substrate. These results indicate that the activity essentially requires an N-terminal free amino group of the substrate and recognizes it electrostatically to some extent. On the other hand, the enzyme was also indicated to exhibit endopeptidase activity by employing appropriate N alpha-acetylated peptide substrates. In contrast to the aminopeptidase activity, the endopeptidase activity showed rather strict specificity, preferring hydrophobic residues at P2 and P3 sites. Because of the broad specificity and high efficiency of the aminopeptidase activity, it was difficult to directly observe endopeptidase activity in the digestion of large peptide substrates with a free alpha-amino terminal. Thus, this is the first experimental evidence that indicates endopeptidase activity by assigning internal peptide bonds cleaved by this activity. From this data, we proposed a model of the binding site of this enzyme.     

Effect of Support and Acidity of Catalyst on the Direct Oxidation of Ethylene to Acetic Acid

The selective oxidation of ethylene to acetic acid was investigated on Pd-acid/ support catalyst system. The catalytic activity is influenced strongly by the acidity of the catalyst. The stronger the catalyst acidity the higher the catalytic activity. The nature of the support also influences the activity of the catalyst substantially. The catalyst has highest activity when it exhibits highest acidity on silica.     

Interpretation of the measurement results near the detection limit in gamma-ray spectrometry using Bayesian statistics

The requirement that the true value of an activity cannot be negative is used for the transformation of raw observed values, which can be positive or negative, into the expected activity values. The probability distribution of the activity values is a truncated Gaussian distribution, and the expected value and the variance of the activity values are derived from the observed value and its standard deviation. It has been shown that the standard deviation of the activity values is smaller than the standard deviation of the observed value and that the ratio of the standard deviation of the activity values and the expected value is less than unity. Since the expected activity value is larger than the original observed value, and the standard deviation of the activity values is smaller than the standard deviation of the observed value, the additional information, that the activity cannot be negative, leads to an improvement in the result. However, since the expected activity value depends on the standard deviation of the observed value, conservatively assessed standard deviation lead to a bias of the expected activity values.     

Interfacial activity of metal ion extractant

The interfacial activity of metal ion extractants is discussed. The interfacial tension isotherms are processed by matching the Szyszkowski equation, and estimation of selected parameters to discuss the interfacial activity of extractants. Results are presented in comprehensive tables and figures. The interfacial activity depends mainly on three different parameters; type of extractant, acidity of the aqueous phase and organic diluent. Strongly acidic extractants and protonated amine reagents exhibit the highest interfacial activity. The solvating reagents and non-protonated amines are on the opposite side of the scale, while the chelating reagents are somewhere in the middle. The acidity of the aqueous phase affects the interfacial activity of extractants, mainly by the ionisation (protonation and dissociation) of extractant molecules. Solvating diluents always decrease the interfacial activity of extractants.     

From activity cliffs to activity ridges: informative data structures for SAR analysis

The extraction of SAR information from structurally diverse compound data sets is a challenging task. One of the focal points of systematic SAR analysis is the search for activity cliffs, that is, structurally similar compounds having large potency differences, from which SAR determinants can be deduced. The assessment of SAR information is usually based on pairwise similarity and potency comparisons of data set compounds. As a consequence, activity cliffs are mostly evaluated at a compound pair level. Here, we present an extension of the activity cliff concept by introducing "activity ridges" that are formed by overlapping "combinatorial" activity cliffs between participating compounds, giving rise to ridge-like structures in activity landscapes. Activity ridges are rich in SAR information. In a systematic analysis of 242 compound data sets, we have identified well-defined activity ridges in 71 different sets. In addition, an information-theoretic approach has been devised to characterize the structural composition of activity ridges. Taken together, our results show that activity ridges frequently occur in sets of active compounds and that different categories of ridges can be distinguished on the basis of their structural content. The computational identification of activity ridges provides access to compound subsets having high priority for SAR analysis.     

新型水溶性钴酞菁的制备及其催化氧化硫醇的性能

采用丁二酸酐、顺丁烯二酸酐对四氨基钴酞菁进行改性后制得两种新型水溶性钴酞菁衍生物, 测试了这两种改性钴酞菁对巯基乙醇的催化氧化性能, 并考察了溶液pH值、温度和时间对催化氧化活性的影响, 结果表明, 在pH＝11时, 两种改性钴酞菁对巯基乙醇的催化氧化性能最好;随着温度的升高, 催化氧化性能提高.     

先锋褐煤焦的铁催化CO2脉冲气化

利用脉冲反应技术研究了先锋褐煤焦ＣＯ２气化反应的铁催化作用，并考察了铁负载量，催化剂前体和制备方法对化活性的影响。研究结果表明，催化剂前体为Ｆｅ（ＮＯ３）３时活性最高ＦｅＣ６Ｈ５Ｏ７次之，ＦｅＣｌ３最小。离子交换制备方法可显著提高ＦｅＣｌ３催化活性，这些因素主要表现在对煤焦表现催化剂浓度的影响，铁对碳化聚丙烯腈的Ｃ 气化具有异常高的催化活性，其活的种可能为铁碳化合物。     

Polymer-supported bases. 7. Nucleophilic acyl rearrangements catalyzed by polymer-supported aminopyridine or imidazole bases

Polymer-supported aminopyridine or imidazole catalysts were effective for acyl rearrangements of O-acylated substrates to C-acylated products. Some of the aminopyridine catalysts, which had much higher activity than the imidazole catalyst, exhibited high activity comparable to that of the corresponding soluble catalyst, 4-N, N-dimethylaminopyridine. The activity of the immobilized aminopyridines was studied as a function of the percentage of ring substitution, spacer-chain length, and solvents. The affinity of the substrates for the immobilized catalysts played an important role for the rearrangements. The increased catalytic activity resulted from the increased affinity of the substrates for the catalysts. The activity of the immobilized bases decreased gradually owing to the reaction of the active site with the products as the catalysts were used repeatedly. The treatment of the used catalysts with nucleophiles restored the activity to some extent. The activity decrease can be minimized by shortening a contact time between the catalysts and the products.     

The relationship between the chemical structures of dihydropyrazine derivatives and DNA strand-breakage activity

Dihydropyrazine, a compound derived from sugars, possesses DNA strand-breakage activity. The relationship between the activity as assayed using pBR 322 ccc-DNA and the chemical structures of derivatives of dihydropyrazine (DHPs) has been investigated. The addition of Cu(2+) enhanced the activity remarkably. The introduction of a methyl or phenyl group onto the DHP ring or a cyclohexyl group fused onto the DHP ring also increased the activity. These properties indicated that the activity was due to the facility of electron release from the DHP ring, followed by radical generation. The determination of ionization potential and electrostatic potential values, and bond dissociation energy via semi-empirical MO calculations suggested strongly that the activity is induced by a DHP ring structure that contains a configuration suitable for hyperconjugation.     

Antibacterial activity of long-chain fatty alcohols against Staphylococcus aureus

The antibacterial activity against Staphylococcus aureus of long-chain fatty alcohols was investigated, with a focus on normal alcohols. The antibacterial activity varied with the length of the aliphatic carbon chain and not with the water/octanol partition coefficient. 1-Nonanol, 1-decanol and 1-undecanol had bactericidal activity and membrane-damaging activity. 1-Dodecanol and 1-tridecanol had the highest antibacterial activity among the long-chain fatty alcohols tested, but had no membrane-damaging activity. Consequently, it appears that not only the antibacterial activity but also the mode of action of long-chain fatty alcohols might be determined by the length of the aliphatic carbon chain.     

Antimicrobial and antioxidant activities of essential oils of Satureja thymbra growing wild in Libya

The composition of essential oil isolated from Satureja thymbra, growing wild in Libya, was analyzed by GC and GC-MS. The essential oil was characterized by γ-terpinene (39.23%), thymol (25.16%), p-cymene (7.17%) and carvacrol (4.18%) as the major constituents. Antioxidant activity was analyzed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. It possessed strong antioxidant activity (IC50 = 0.0967 mg/mL). The essential oil was also screened for its antimicrobial activity against eight bacterial and eight fungal species, showing excellent antimicrobial activity against the microorganisms used, in particular against the fungi. The oil of S. thymbra showed bacteriostatic activity at 0.001-0.1 mg/mL and was bactericidal at 0.002-0.2 mg/mL; fungistatic effects at 0.001-0.025 mg/mL and fungicidal effects at 0.001-0.1 mg/mL. The main constituents thymol, carvacrol and γ-terpinene also showed strong antimicrobial activity. The commercial fungicide bifonazole showed much lower antifungal activity than the tested oil.     

电解煤浆制氢阳极的制备及电催化活性研究

将钛片进行预处理, 用处理后的钛片作为电极基体, 然后用循环伏安法在钛基体上沉积制备了Pt/Ti, Pt-Ru/Ti, Pt-Ir/Ti, Pt-Ru-Ir/Ti催化电极, 通过扫描电镜(SEM)、X射线衍射(XRD)、电子能谱(EDS)以及等离子发射光谱(ICP)等方法对所制备电极进行了表征, 包括电极表面形貌、组分的沉积状态、催化层成分组成以及电极寿命等; 在煤浆电解过程中, 采用两电极体系, 对所制备电极的电催化活性进行了测试. 结果表明: 所制备的电极催化活性都高于同面积的铂片电极, 含有Ru, Ir的二元催化电极的活性好于镀铂催化电极. 在一定范围内, 随着Ru元素比例增大, 电极活性增强, 而Ir元素含量过大, 电极活性反而稍微降低, 所以Pt-Ir(1∶0.5)/Ti, Pt-Ru(1∶5)/Ti两电极的催化活性相对较好. 本文所制备的三元催化电极的催化活性低于二元催化电极. Pt-Ru/Ti电极催化活性最好, 相同条件下具有最大的电解电流, H₂的电解效率可达95%以上.     

导致旋光性根本原因的探讨

旋光性是由结构决定的，手性是一种抽象概念，抽象概念不能决定旋光性，旋光性具有明确的方向性，它必然是由具有明确方向性的结构特征所决定。螺旋结构是具有明确方向性的结构，它是实体不是抽象概念，它与旋光方向和旋光度大小可以联系在一起，螺旋结构才是导致旋光性的根本原因。     

TBP在水相中活度系数的探讨

本文对TBP-C6H6、TBP-CCl4、TBP-CHCl3及TBP-C6H5Cl四体系作了蒸汽压法测量.对TBP-C6H5Cl体系作了^3^2P标记法测量,其它三体系^3^2P标记法数据取自文献.分析了二种测量的结果.所得的稀释剂的活度系数应该基本一致.     

短裸甲藻毒素(Brevetoxins)的电子结构与构效关系研究

对短裸甲藻毒素衍生物进行了电子结构研究和构象分析,确定了它们的活性部位,探讨了作用方式,讨论了它们的结构-活性关系及受体的相互作用,解释了衍生物之间活性差异的原因。研究结果表明,分子骨架中段环上的烯键,A环及R烯键对活性有重要影响,分子骨架的折曲程度对活性也有较大影响。     

纳米TiO_2薄膜的制备及性能表征

采用溶胶-凝胶法制备了以玻璃为基底具有高光催化活性,表面均匀、透明、无裂纹的纳米TiO2薄膜.研究了反应物配比对薄膜表面形貌、透光率和光催化活性的影响,确定了最佳反应物配比.采用扣除背景干扰的方法,利用甲基橙的降解率对TiO2薄膜的光催化性能进行了评价,对其透光率、光催化活性以及物相形貌进行了表征.结果表明,在最佳反应物配比条件下,所制备的TiO2薄膜表面光滑平整,粒径为纳米级且分布均匀,具有80%高透光率和99%高光催化活性.     

Inhibitory analysis of the effect of polycyclic aromatic hydrocarbons on the activity of chitinase by means of liquid chromatography-mass spectrometry of chitin oligosaccharides

The analytical method of determining enzyme activity by liquid chromatography-mass spectrometry (LC/MS) was developed and applied for investigation of the effect of polycyclic aromatic hydrocarbons (PAHs) on the enzyme activity of chitinase. The measurement of chitinase activity by LC/MS is useful in order to use the nonderivatized substrate, which can show in vivo chitinase activity. Substrate consumption and product formation were monitored in order to determine chitinase activity. It was shown that, for the first time, in vitro addition of PAHs inhibited the activity of chitinase in a noncompetitive manner. The IC₅₀ value of benzo[a]pyrene was 1.4 μM, and PAHs containing four or more aromatic rings showed the same or higher inhibitory effect, whereas PAHs with a lower number of aromatic rings showed lower inhibition of the chitinase activity than benzo[a]pyrene.