The Synthesis and Herbicidal Evaluation of Fluorine-Containing Phenoxyacetoxyalkylphosphonate Derivatives

To investigate the influence of a fluorine moiety on the biological activity of phenoxyacetoxyalkylphosphonates, a series of fluorine-containing phenoxyacetoxyalkylphosphonates were synthesized and screened for herbicidal activity in a greenhouse. The majority of the title compounds showed better preemergence activity than postemergence activity against the test plants, especially on monocotyledon. Compound 5l exhibited notable activity. Results showed that by introducing a fluorine moiety to the parent structure of phenoxyacetoxyalkylphosphonates, a series of new compounds with satisfactory herbicidal activity could be synthesized. A reasonable combination of a fluorine moiety and other substituents on the benzene ring had a great influence on the herbicidal activity.     

Activation and stabilization of enzymes entrapped into reversed micelles

Observations of the activity of two hydrolyzing enzymes—protease and α-amylase—entrapped inside the reversed micelles formed by surfactants in hexane, benzene, and cyclohexane are reported. The surfactants chosen for this study are: Tween 80, a nonionic surfactant, Cetyl pyridinium chloride, a cationic surfactant, and two anionic surfactants, sodium lauryl sulfate and Aerosol OT. Tween 80 enhances the activity of both protease and α-amylase. Sodium lauryl sulfate and Aerosol OT, which are ionic surfactants, enhance the activity of protease, but inhibit the activity of α-amylase. Cetyl pyridinium chloride, however, enhances the activity of α-amylase, but inhibits the activity of protease. Enhanced activity is generally severalfold greater in comparison to the activity observed in the usual aqueous system in the absence of reversed micelles. It has also been observed that the enhanced activity of the enzymes entrapped inside the reversed micelles remains preserved for a much longer period of time in comparison to the activity in the usual aqueous systems. These observations, which support the view that with proper choice of surfactant and the organic solvent, reversed micelles act like a microreactor that provides a favorable aqueous microenvironment for enzyme activity, have biotechnological overtones.     

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.     

Design of multitarget activity landscapes that capture hierarchical activity cliff distributions

An activity landscape model of a compound data set can be rationalized as a graphical representation that integrates molecular similarity and potency relationships. Activity landscape representations of different design are utilized to aid in the analysis of structure-activity relationships and the selection of informative compounds. Activity landscape models reported thus far focus on a single target (i.e., a single biological activity) or at most two targets, giving rise to selectivity landscapes. For compounds active against more than two targets, landscapes representing multitarget activities are difficult to conceptualize and have not yet been reported. Herein, we present a first activity landscape design that integrates compound potency relationships across multiple targets in a formally consistent manner. These multitarget activity landscapes are based on a general activity cliff classification scheme and are visualized in graph representations, where activity cliffs are represented as edges. Furthermore, the contributions of individual compounds to structure-activity relationship discontinuity across multiple targets are monitored. The methodology has been applied to derive multitarget activity landscapes for compound data sets active against different target families. The resulting landscapes identify single-, dual-, and triple-target activity cliffs and reveal the presence of hierarchical cliff distributions. From these multitarget activity landscapes, compounds forming complex activity cliffs can be readily selected.     

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.     

Hydrogenation of olefins by π-arene ruthenium complexes : A role of π-arene ligand in catalytic activity

The divalent ruthenium complexes bearing benzene, mesitylene triphenylbenzene as a π-ligand were prepared and their catalytic activity for olefin hydrogenation was examined. They showed activity in the presence of a small amount of base. Particularly, the complex with triphenylbenzene was found to have extremely high activity. Discussion here is on a role of a π-arene ligand in the activity.     

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.     

Towards the understanding of the activity of G9a inhibitors: an activity landscape and molecular modeling approach

In this work, we analyze the structure–activity relationships (SAR) of epigenetic inhibitors (lysine mimetics) against lysine methyltransferase (G9a or EHMT2) using a combined activity landscape, molecular docking and molecular dynamics approach. The study was based on a set of 251 G9a inhibitors with reported experimental activity. The activity landscape analysis rapidly led to the identification of activity cliffs, scaffolds hops and other active an inactive molecules with distinct SAR. Structure-based analysis of activity cliffs, scaffold hops and other selected active and inactive G9a inhibitors by means of docking followed by molecular dynamics simulations led to the identification of interactions with key residues involved in activity against G9a, for instance with ASP 1083, LEU 1086, ASP 1088, TYR 1154 and PHE 1158. The outcome of this work is expected to further advance the development of G9a inhibitors.

     

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.     

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.     

具有植物激素活性的Schiff碱化合物的研究(Ⅲ)——噻二唑类Schiff碱的合成及其生物活性

含杂环的Schiff碱类化合物具有很高的植物生长激素的活性[1],近十几年来受到化学家的重视.前文[2]已报道了三唑类Schiff碱的合成及其生物活性.已发现含噻二唑环的化合物具有高的生物活性,1,3,4-噻二唑的衍生物可以作为杀菌剂、除草剂和植物生长调节剂[3～6],连有巯基(-SH)的噻二唑的席夫碱目前还未见报道.我们将2-氨基-5-巯基-1,3,4-噻二唑与芳醛或杂环醛作用,合成了12个新的Schiff碱化合物,发现其中一些化合物具有明显的植物激素活性,合成的反应式为:     

4-烷氧/苄氧基苯基四唑和1,3,4-噁二唑类化合物的合成及除草活性

以4-氰基苯酚为起始原料,在4-烷氧基/苄氧基苯甲脒结构基础上,设计合成了5个4-烷氧基/苄氧基苯基四唑及17个新型2-取代-5-(4-烷氧基/苄氧基)苯基噁二唑类化合物,通过元素分析、1H NMR和MS对所合成的新化合物进行了结构表征.初步除草活性测试结果表明,部分化合物对双子叶油菜和单子叶稗草表现出较好的生长抑制活性.     

Modification and structure-activity relationship of a small molecule HIV-1 inhibitor targeting the viral envelope glycoprotein gp120

This paper describes selected modification and structure-activity relationship of the small molecule HIV-1 inhibitor, 4-benzoyl-1-[(4-methoxy-1H-pyrrolo[2,3-b]pyridin-3-yl)oxoacetyl]-2-(R)-methylpiperazine (BMS-378806). The results revealed: i) that both the presence and configuration (R vs. S) of the 3-methyl group on the piperazine moiety are important for the antiviral activity, with the 3-(R)-methyl derivatives showing the highest activity; ii) that the electronegativity of the C-4 substituent on the indole or azaindole ring seems to be important for the activity, with a small, electron-donating group such as a fluoro or a methoxy group showing enhanced activity, while a nitro group diminishes the activity; iii) that the N-1 position of the indole ring is not eligible for modification without losing activity; and iv) that bulky groups around the C-4 position of the indole or azaindole ring diminish the activity, probably due to steric hindrance in the binding. We found that a synthetic bivalent compound with two BMS-378806 moieties being tethered by a spacer demonstrated about 5-fold enhanced activity in an nM range against HIV-1 infection than the corresponding monomeric inhibitor. But the polyacrylamide-based polyvalent compounds did not show inhibitory activity at up to 200 nM.     

pH对增强生物除磷系统酶活性的影响

通过比较不同pH值下增强生物除磷系统中关键酶活性的变化规律, 研究了酶活性与聚磷菌污泥产率系数及可溶性正磷酸盐(SOP)的关系. 结果表明, 在pH=6.4-7.6范围内, 脱氢酶、腺苷酸激酶和聚磷酸盐激酶的活性随着pH的增加而线性增加, 酸性磷酸酶和碱性磷酸酶的活性不受pH的影响. 聚磷菌的产率系数与脱氢酶活性、厌氧释磷速率与腺苷酸激酶活性、好氧吸磷速率与聚磷酸盐激酶活性分别呈线性关系. 表明较高的pH有利于聚磷菌的生长和提高聚磷菌的活性, 从而提高了除磷效率.     

Numerical values of individual activity coefficients of single-ion species in concentrated aqueous electrolyte solutions and the attempt of a qualitative interpretation on a model of electrostatic interaction

Individual activity coefficients of single-ion species can be achieved by the factorizing of a new concentration function for the mean activity coefficient to the required power applying a purely mathematical method. These single-ion activity coefficients, calculated in this manner, are listed for some aqueous strong electrolytes. The reasons for the magnitude and variation of the activity coefficients as a function of the concentration are, without a doubt, of complex nature. Activity coefficients have their meaning as practical values. In relation to the analytical concentration, the individual activity coefficients represent the macroscopic effectiveness of the single-ion species in solution an easy manner. However, with increasing deviations from Debye–Hückel conditions of an infinitely diluted electrolyte solution, a physically correct interpretation of the macroscopically visible activity coefficient is becoming more and more difficult, if not impossible to find. On the basis of a model of electrostatic interaction, an attempt has been made to create a qualitative interpretation of the individual ion activity coefficients in concentrated aqueous electrolyte solutions which were calculated applying the purely mathematical method by Ferse.     

Defining and measuring biological activity: applying the principles of metrology

A definition of biological activity is proposed that is superficially analogous to the equation relating the thermodynamic activity of a solute to its concentration via an activity coefficient. The biological activity of a molecular entity is defined as A=cf, where A is the activity, c the amount-of-substance concentration, and f is a parameter designated as “inherent activity.” Units and dimensions are determined by the type of activity, catalytic (katal) or binding (mol⁻¹ L). The measurand is described by a chemical equation that identifies the entity for which an activity is being monitored. This definition of biological activity has the advantage of separating the chemical characterization of the entity in terms of structure and amount from the assessment of biological activity. Ideally, a homogeneous entity is used for the measurement of f. In instances where impure materials are used or the chemical equation defining the activity is unknown, the evaluated parameter should be designated as f′ to denote its empirical nature. Any measurement of f or f′ should be qualified with an appropriate estimate of measurement uncertainty.     

ANTIOXIDANT DEFENSE OF THE CABBAGE LOOPER, Trichoplusia ni: ENZYMATIC RESPONSES TO THE SUPEROXIDE-GENERATING FLAVONOID, QUERCETIN, and PHOTODYNAMIC FURANOCOUMARIN, XANTHOTOXIN

Abstract— Superoxide dismutase (SOD) activity was induced by ca 2-fold (to5–6 U) when Trichoplusia ni midfifth-instar larvae were exposed to two toxic oxygen species generating plant pro-oxidants, quercetin (a flavonoid) and xanthotoxin (8-methoxypsoralen; a photoactive furanocoumarin). Very high catalase (CAT) activity ( ca 300 U) of this insect was not affected by 8-methoxypsoralen, but was slightly decreased by quercetin. No Se-dependent glutathione peroxidase (GPOX) activity was observed, but high glutathione transferase (GST) peroxidase activity (over 50 U) in this insect was slightly induced by 8-methoxypsoralen (8-MOP), and was partially inhibited by quercetin, 8-Methoxypsoralen induced the activity of glutathione reductase (GR), but quercetin partially inhibited the activity of this enzyme. An increase in SOD activity appears to be the main response of this insect to dietary exposure to pro-oxidant compounds. High CAT activity guarantees the destruction of large cellular increases in H₂O₂, a product of rapid dismutation of superoxide from induced activity of SOD. Moreover, GST with its peroxidase activity apparently substitutes for GPOX, forming a GST/GR enzyme pair as a primary line of defense against deleterious organic hydroperoxides. These studies clearly point out the key role for an insect's antioxidant enzymatic countermeasures against defensive pro-oxidant compounds produced by plants.     

Age dependent increase of elastase type protease activity in mouse skin. Effect of UV-irradiation

The effect of chronological aging and photoaging (UV-radiation) on elastase-type enzyme activity of hairless mouse skin was studied. Aging resulted in the increase of elastase type endopeptidase activity extractable from mouse skins. Both chronic UVA and UVB radiation resulted in a significant increase of elastase type activity. PBS extracted only small part of the elastase activity, UV-A produced an increase of about 90-120% according to the type of irradiation (xenon or UV-A SUN) and UV-B produced a 72% increase. Extraction by Triton X-100 suggested that most of the activity is bound to cells and fibrous structures. EDTA inhibited 80-90% of the elastase activity in chronologically aged skin extracts and also the activity induced by UVA radiation suggesting that metallo-elastase(s) are involved. About 30% of the UVB induced activity could only be inhibited by EDTA and about 50% by PMSF suggesting that irradiation by UVB increased more serine endopeptidase activity but also MMP-activity. Chronic UVA radiation produced an increase of skin elastase activity equivalent to that observed after 24 months of aging in non-irradiated animals (approximately 100 weeks) corresponding to approximately 90% of total life span of these mice. The total increase produced by UVB was less, but the strong increase of a serine elastase, presumably from PMN-s, appear to produce a much more pronounced biological activity as shown by the presence of fibronectin degradation products in skin extracts. Such degradation products were shown to exert harmful effects on tissues. These results may well have biological significance and distinguish chronological aging and photoaging.     

新型5-脂肪基-1,2,4-三唑曼尼希碱的合成及生物活性

设计并合成了22个具有长脂肪链取代的新型三唑曼尼希碱,研究了其植物生长调节活性、除草活性和对细胞周期分裂蛋白25B(CDC25B)抑制活性,结果发现,多数目标分子表现出优良的促进细胞生长素活性和除草活性,表明该类分子有望成为优良的新型农药;对CDC25B抑制活性筛选发现一种曼尼希碱具有优良的CDC25B抑制活性,其IC₅₀值低于阳性参照物正钒酸钠,有望成为肿瘤治疗的药物先导物。     

Assessment of Xylanase Activity in Dry Storage as a Potential Method of Reducing Feedstock Cost

Enzymatic preprocessing of lignocellulosic biomass in dry storage systems has the potential to improve feedstock characteristics and lower ethanol production costs. To assess the potential for endoxylanase activity at low water contents, endoxylanase activity was tested using a refined wheat arabinoxylan substrate and three commercial endoxylanases over the water activity range 0.21–1.0, corresponding to water contents of 5% to >60% (dry basis). Homogeneously mixed dry samples were prepared at a fixed enzyme to substrate ratio and incubated in chambers at a variety of fixed water activities. Replicates were sacrificed periodically, and endoxylanase activity was quantified as an increase in reducing sugar relative to desiccant-stored controls. Endoxylanase activity was observed at water activities over 0.91 in all enzyme preparations in less than 4 days and at a water activity of 0.59 in less than 1 week in two preparations. Endoxylanase activity after storage was confirmed for selected desiccant-stored controls by incubation at 100% relative humidity. Water content to water activity relationships were determined for three lignocellulosic substrates, and results indicate that two endoxylanase preparations retained limited activity as low as 7% to 13% water content (dry basis), which is well within the range of water contents representative of dry biomass storage. Future work will examine the effects of endoxylanase activity toward substrates such as corn stover, wheat straw, and switchgrass in low water content environments.