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21.
Butler Michael J. Aphale Jayant S. DiZonno Michele A. Krygsman Phyllis Walczyk Eva Malek Lawrence T. 《Journal of industrial microbiology & biotechnology》1994,13(1):24-29
Summary We have investigated the aminopeptidase activities present inStreptomyces lividans strains. The majority of these activities proved to be intracellular with multiple active species. Two aminopeptidase P genes were identified to be responsible for the ability to hydrolyze amino terminal peptide bonds adjacent to proline residues. Two other broad spectrum aminopeptidases were found to display homology at both the DNA and protein levels. One showed significant homology to PepN proteins, particularly around the putative zinc-binding residues which are important for catalysis. The second broad spectrum activity was not analyzed in detail but showed a different spectrum of substrate specificity to that of PepN. 相似文献
22.
The temporal changes in extracellular enzyme activities in freshwater microbial biofilms were examined in two contrasting
river sites in North Wales over a 12 month period. Sites were a first order, unshaded oligotrophic upland stream (Nant Waen)
and a fourth order, mildly eutrophic river with riparian tree cover (River Clywedog). When algal populations were low, biofilms
of the more eutrophic site supported greater enzyme activities and higher population densities than the oligotrophic site.
Composition, concentration and origin of substrates available to the respective biofilm communities influenced extracellular
processing patterns. Reduction in algal populations depressed total and extracellular activities in biofilms from the first
order site, suggesting that biofilm communities here were maintained by in situ primary production. Biofilms from Nant Waen were often found to contain higher extracellular activities per cell than the
more eutrophic River Clywedog biofilms, which might represent the enhanced ability of an oligotrophic biofilm to accumulate
extracellular enzymes. In contrast, light and darkgrown River Clywedog biofilms were not enzymatically distinct, inferring
a less important role for biofilm phototrophs. Some evidence was found for increased reliance on allochthonous substrates
in the River Clywedog for biofilm maintenance. 相似文献
23.
自然保护区对维护生物多样性,改善生态环境质量具有重要作用。然而,我国自然保护区生态环境质量变化及其对自然因素与人类活动的响应规律还不清晰,理解这些规律对我国的生态文明建设以及生物多样性的保护具有重要意义。基于2001—2019年中国历史高分辨率生态环境质量数据CHEQ数据集以及自然因素,利用Theil-Sen Median趋势分析、Mann-Kendall检验以及多元回归残差分析等方法,探究了2001—2019年中国自然保护区的生态环境质量时空变化特征及其对自然因素与人类活动驱动因素的响应。结果表明:(1)我国自然保护区的CHEQ指数呈现多阶段波动变化,总体呈小幅度下降趋势,平均趋势率为-0.54×10-3/a;在空间上,中国自然保护区CHEQ变化趋势值呈“南高北低,东高西低”的分布格局;(2)自然因素与人类活动的共同作用是我国自然保护区生态环境质量恶化的主要原因,且恶化区域主要分布在自然保护区的实验区和缓冲区。其中自然因素对我国自然保护区生态环境质量变化的影响在-3×10-3/a—0/a之间,人类活动的影响在-1×10-3 相似文献
24.
In our previous work, two dopamine derivatives with benzothiazole fragment were isolated and identified from Polyrhachis dives (P. dives). Based on their characteristic structure, we used them as lead compound to carry out structural optimization and subsequent fungicidal evaluation. Here 20 dopamine derivatives with benzothiazole fragment were designed and synthesized by a facile method, and their structures were characterized by 1H-NMR, 13CNMR and HMRS. In bioassays, most of the title compounds possess potential fungicidal activities against Altenaia alternala (A. alternala) and Botrytis cinerea (B. cinerea). Especially, (E)-N-(2-(benzo[d]thiazol-6-yl)ethyl)-3-(p-tolyl)acrylamide and (E)-N-(2-(benzo[d]thiazol-6-yl)ethyl)-3-(4-(trifluoromethyl)phenyl)acrylamide displayed 29.3 mg/L and 10.7 mg/L EC50 value against A. alternala, respectively, which possessed equivalent fungicidal activities level to hymexazol. 相似文献
25.
Xiong Zhang Ming-You Peng En-Ming Feng Qing-Dan Li Lu Chen Hu-Cheng Yang Bing Guo Hong Liang Ying-Tong Di Lei Tang Ying Yan 《化学与生物多样性》2023,20(10):e202301061
Three previously undescribed diterpenoids, helioscopnoids A–C, and eight known compounds were isolated from the whole plants of Euphorbia helioscopia. Their structures were established by extensive analysis of spectra and data comparison with previous literatures. Among them, compound 4 was identified as 24,24-dimethoxy-25,26,27-trinoreuphan-3β-ol with revised configurations of C-13, C-14, and C-17 (13R*, 14R*, 17R*). Cytotoxicity assays revealed that all compounds exhibited varying levels of cytotoxicity against H1975 cells, with compound 9 displaying the most potent activity, as indicated by cell viability rates of 18.13 % and 20.76 % at concentrations of 20 μM and 5 μM, respectively. This study expands the understanding of E. helioscopia terpenoids’ structural diversity and biological activities, contributing to the exploration of potential therapeutic applications. 相似文献
26.
Land use induced changes of organic carbon storage in soils of China 总被引:29,自引:0,他引:29
Using the data compiled from China's second national soil survey and an improved method of soil carbon bulk density, we have estimated the changes of soil organic carbon due to land use, and compared the spatial distribution and storage of soil organic carbon (SOC) in cultivated soils and noncultivated soils in China. The results reveal that ~ 57% of the cultivated soil subgroups ( ~ 31% of the total soil surface) have experienced a significant carbon loss, ranging from 40% to 10% relative to their noncultivated counterparts. The most significant carbon loss is observed for the non‐irrigated soils (dry farmland) within a semiarid/semihumid belt from northeastern to southwestern China, with the maximum loss occurring in northeast China. On the contrary, SOC has increased in the paddy and irrigated soils in northwest China. No significant change is observed for forest soils in southern China, grassland and desert soils in northwest China, as well as irrigated soils in eastern China. The SOC storage and density under noncultivated conditions in China are estimated to ~ 77.4 Pg (1015 g) and ~ 8.8 kg C m?2, respectively, compared to a SOC storage of ~ 70.3 Pg and an average SOC density of ~ 8.0 kg C m?2 under the present‐day conditions. This suggests a loss of ~ 7.1 Pg SOC and a decrease of ~ 0.8 kg C m?2 SOC density due to increasing human activities, in which the loss in organic horizons has contributed to ~ 77%. This total loss of SOC in China induced by land use represents ~ 9.5% of the world's SOC decrease. This amount is equivalent to ~ 3.5 ppmv of the atmospheric CO2 increase. Since ~ 78% of the currently cultivated soils in China have been degraded to a low/medium productivities and are responsible for most of the SOC loss, an improved land management, such as the development of irrigated and paddy land uses, would have a considerable potential in restoring the SOC storage. Assuming a restoration of ~ 50% of the lost SOC during the next 20–50 years, the soils in China would absorb ~ 3.5 Pg of carbon from the atmosphere. 相似文献
27.
Marie-France Dietsch 《Vegetation History and Archaeobotany》1996,5(1-2):89-97
Recent rescue excavations at Bercy (Paris), a site on the alluvial plain of the Seine valley, yielded plant remains which
are associated with the recent occupation phase dating from the middle Neolithic II (Chasséen), when a village was established
on the former channel of the river Seine. Various contexts (the channel, the flat lower part of the bank, and several archaeological
features) have been studied and 84 taxa have been identified. Cultivated plants are represented by Triticum aestivum/durum, T. dicoccum, T. monococcum and Hordeum vulgare. Among the wild plants with potentially edible fruits or seeds, only very few satisfy the various criteria for association
with human activities: Corylus avellana, Vitis sylvestris, Cornus sanguinea, Quercus sp. and Prunus spinosa of which carbonized fruits were also present, were found in archaeological features and were very abundant. Though not found
in archaeological features, we consider that Crataegus monogyna (carbonized and well represented) and Rubus spp. (especially abundant) were not deposited there naturally and had also been intentionally collected. Finally, it is suggested
that the allochthonous (varied) origin of these taxa is the reason why there are no concentrations of their fruits in the
channel. The exploitation of wild seeds and fruits appears to have been very selective. All other wild taxa can be attributed
to natural deposition. 相似文献
28.
Magdalena J. Rossowska Parvaneh Ghanel Tetsuo Nakamoto 《Biological trace element research》1995,50(3):229-236
The purpose of this study was to determine the relationship between concentrations of Zn and Cu and the activities of superoxide
dismutase and glutathione peroxidase in the heart and liver of young rat pups whose dams were fed a diet supplemented with
caffeine and/or Zn. Four groups of dams with their newborn pups were fed one of the following diets for 22 d: 20% protein
basal diet; the basal diet supplemented with caffeine (2 mg/100 body wt); the basal diet supplemented with Zn (300 mg/kg diet);
or the basal diet supplemented with caffeine plus Zn. The Cu levels in the livers of the pups were decreased by maternal intake
of the caffeine and Zn diet. The maternal intake of the caffeine diet increased Mn-superoxide dismutase (MnSOD) activity and
Cu, Zn-superoxide dismutase (CUZnSOD) in the heart of the pups. On the other hand, the activity of Cu,ZnSOD was significantly
reduced in the liver of pups whose dams consumed a caffeine, Zn, or caffeine plus Zn diet. Cu, ZnSOD activity in the liver
of the pups seems to be correlated with Cu levels in the tissue. Selenium-dependent glutathione peroxidase (GSH-Px) activities
in the heart and liver showed no difference among the groups. The effect of dietary caffeine and/or Zn on the activity of
antioxidant enzymes in the heart and liver were different in young rats. The activities of these enzymes in the heart were
lower than in the liver of 22-d-old rats. Our experiments indicate that the heart has limited defenses against the toxic effects
of peroxides when compared to the liver. 相似文献
29.
Chyi-Liang Chen Li-Kwan Chang Yu-Sun Chang Shih-Tung Liu Johannes Scheng-Ming Tschen 《Molecular & general genetics : MGG》1995,248(2):121-125
A total of 20Bacillus subtilis F29-3 mutants defective in fengycin biosynthesis was obtained by Tn917 mutagenesis. Cloning and mapping results showed that the transposon in these mutants was inserted in eleven different locations on the chromosome. We were able to use the chromosomal sequence adjacent to the transposon as a probe to screen for cosmid clones containing the fengycin biosynthesis genes. One of the clones obtained, pFC660, was 46 kb long. Eight transposon insertion sites were mapped within this plasmid. Among the eleven different mutants analyzed, four mutants had Tn917 inserted in regions which encoded peptide sequences similar to part of gramicidin S synthetase, surfactin synthetase, and tyrocidine synthetase. Our results suggest that fengycin is synthesized nonribosomally by the multienzyme thiotemplate mechanism. 相似文献
30.
革胡子鲇上颌须离体标本味觉反应的测定 总被引:1,自引:0,他引:1
本实验采用革胡子鲇离体上颌须-传入神经标本,记录传入神经电活动,测定了须部味蕾对动物组织浸提液、氨基酸、酸盐化合物等多种化学刺激的反应。发现某些物质有较强的刺激作用。另外,机械刺激也引起较强的反应。分析传入神经单纤维的记录结果,可将化学刺激引起的味觉反应分为3种单元类型:(1)对精氨酸特别敏感;(2)对柠檬酸和氯化胺有较强的反应;(3)对多种刺激都有一定的反应。实验表明,革胡子鲇的须部味蕾可能是一 相似文献