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1.
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. 相似文献
2.
H Koga N Mori H Yamada Y Nishimura K Tokuda K Kato T Imoto 《Chemical & pharmaceutical bulletin》1992,40(4):965-970
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. 相似文献
3.
4.
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. 相似文献
5.
Whole cells ofBrevibacterium flavum having high fumarase activity were immobilized using K-carrageenan. The reason for the high stability of fumarase activity
of immobilized cells was investigated.
One of main reasons for stabilizing fumarase activity by immobilization using K-carrageenan against organic solvents such
as ethanol and acetone was the lower concentration of these solvents in the carrageenan gel compared with that in outer bulk
solution. The stabilization of fumarase activity in the immobilized cells against protein-denaturing reagents was found to
be related to rheological properties of K-carrageenan gel. Another reason for stabilizing fumarase activity by immobilization
with K-carrageenan was to protect the cells from lysis.
When immobilized cells were freeze-thawed, their fumarase activity increased and operation stability decreased. Therefore,
one reason for the high decay of fumarase activity caused by the freeze-thawing may be a change in the pore size of the K-carrageenan
gel.
Fumarase activity and the operational stability of immobilized cells was found to depend on gelling conditions. Therefore,
the steric structure of the K-carrageenan gel may be related to the decay of fumarase activity. 相似文献
6.
Water Activity Dependence of Lipases in Non-aqueous Biocatalysis 总被引:1,自引:0,他引:1
Xiaole Xia Chen Wang Bo Yang Yong-Hua Wang Xiaoning Wang 《Applied biochemistry and biotechnology》2009,159(3):759-767
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. 相似文献
7.
Dimova D Wawer M Wassermann AM Bajorath J 《Journal of chemical information and modeling》2011,51(2):258-266
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. 相似文献
8.
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. 相似文献
9.
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. 相似文献
10.
11.
Ting Chen Ping Shen Yanjun Li Hongwu He 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):2135-2145
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. 相似文献
12.
The development of rocket enzyme activity electrophoresis for the detection and quantification of various proteinases, lipases and pectinases is presented. Rocket enzyme activity electrophoresis is more sensitive than the radial diffusion assay and often enables distinction between qualitatively different enzymes present in the same samples, whereas the radial diffusion assay only provides information on the overall enzyme activity. However, calibration and optimization of the enzyme activity electrophoretic assay have to be performed for each new enzyme-substrate system to be analyzed. Some of the common pitfalls in the development of new enzyme activity electrophoretic assays are presented. Enzyme activity electrophoresis can be applied in combination with other electrophoretic assays. Particularly the combination of enzyme activity electrophoresis with various immunoelectrophoretic methods can provide detailed information on the enzymes studies. 相似文献
13.
FAN Lin-Lin PENG Shu-Hui WEN Cheng-Rong HE Ming-Xiang WEI Xue-Qi WU Chun-Hua YAO Min-Na FENG Rui PANG Jie 《结构化学》2012,31(4):605-613
Biological activity of konjac glucomannan is closely related to its structure,in particular to its high-level structure.Researches on the activity mechanism of konjac glucomannan are significant for revealing the mysteries of participation in life activity.In this paper,analysis of the effects of konjac glucomannan configuration and various factors on its structure and activity was conducted,mechanism of biological activity of konjac glucomannan was explored,and the hot research topic of konjac glucomannan was given. 相似文献
14.
15.
Free ribonuclease (RNase)-inhibitor activities in both ventral and dorsal prostates had their highest peaks in 4-week-old rats and smallest peaks in around 7-week-old animals. Total RNase activity in the ventral prostate decreased overall with age, while that in the dorsal prostate increased. No significant amount of free RNase activity was found in either prostate. Weight, protein content, and free RNase-inhibitor activity in both prostates decreased after castration and increased after administration of testosterone to castrated rats. Total RNase activity in the ventral prostate was increased by castration and decreased by testosterone administration. In the dorsal prostate, total RNase activity had two peaks, 7 d after castration and 2 d after testosterone administration. A large amount of free RNase activity was found in the ventral prostate 7 d after castration and this activity was decreased by testosterone administration. In the dorsal prostate, free RNase activity was not detected after castration and testosterone administration. These results suggest that changes in the level of RNase-inhibitor in both prostates are involved in the regulation of their RNA content through the control of free RNase activity. 相似文献
16.
17.
4,5-二氢-1,3,4-噻二唑-5-酮-2-甲氨基取代氰基丙烯酸酯类化合物的 合成及生物活性研究 总被引:1,自引:0,他引:1
采用氰基丙烯酸酯与5-甲氧基-1,3,4-噻二唑-2-甲氨在乙醇中加热回流的方法合成了一系列4,5-二氢-1,3,4-噻二唑-5-酮-2-甲氨基取代的氰基丙烯酸酯类化合物. 目标化合物结构均经1H NMR, IR和元素分析确证. 生物活性测试结果表明: 部分化合物对双子叶杂草显示出较好的除草活性及良好的选择性, 化合物6j在1.5 kg/ha的剂量下对油菜的茎叶处理抑制率达到100%; 部分化合物还表现出了一定的杀菌和植物生长调节活性. 构效关系研究发现氰基丙烯酸酯3-位取代基的体积对除草活性影响较大, 3-位为异丙基时活性最高. 相似文献
18.
Francesco Malatesta 《Journal of Solid State Electrochemistry》2011,15(10):2169-2171
A. Ferse and H.O. Müller have recently presented a mathematical method aimed at subdividing the activity coefficients of electrolytes
into functions of individual ionic species; these functions are suggested to be the ionic activity coefficients. By examining
the method, it is possible to verify that the peculiar mathematical structure of the functions in question really guarantees
a unique result, unlike the usual subdivisions of electrolyte activity coefficients, which admit infinite possibilities for
the ionic activity coefficients. But the subsequent step of the reasoning, i.e., that these functions have to be the activity
coefficients of the ionic species, is an illation. And indeed, another kind of subdivision in individual functions can be
exemplified, whose mathematical structure also guarantees results that are unique and perfectly compatible with all theoretical
properties of the ionic activity coefficients. It is concluded that it is impossible to rely on mathematical method to pull
the activity coefficients of ions out of the mean activity coefficients of the electrolytes. And hence, the individual functions
for the ionic species determined by Ferse and Müller do not represent the ionic activity coefficients and do not have any
particular utility. 相似文献
19.
Age dependent increase of elastase type protease activity in mouse skin. Effect of UV-irradiation 总被引:1,自引:0,他引:1
Labat-Robert J Fourtanier A Boyer-Lafargue B Robert L 《Journal of photochemistry and photobiology. B, Biology》2000,57(2-3):113-118
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. 相似文献
20.
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 总被引:17,自引:0,他引:17
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: 相似文献