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排序方式: 共有106条查询结果,搜索用时 15 毫秒
1.
Summary Polyclonal antibodies were produced against the highly purified enzymes L-hydantoinase, hydantoin-racemase and L-N-carbamoylamino acid amidohydrolase of Arthrobacter aurescens DSM 3747. In order to exploit these antibodies for basic research (molecular biology) or bioengineering (process development), the serological properties had to be characterized. Both, the hydantoinase- and carbamoylase-antibodies were observed to be monofunctional, whereas the hydantoin-racemase-antibody was found to be additionally specific against the L-hydantoinase. Monospecificity was realized after affinity chromatography. Investigations on serological crossreactions with several linear- and cyclic amidases (e.g. hydantoinases) as well as hydantoin-racemases are demonstrated in this paper.Deticated to Prof. Dr. Klaus Mosbach on the occation of his 60th birthday. 相似文献
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Yi Wang Juli Carrillo Evan Siemann Gregory S. Wheeler Lin Zhu Xue Gu Jianqing Ding 《Annals of botany》2013,112(4):751-756
Background and Aims
Invasive plants can be released from specialist herbivores and encounter novel generalists in their introduced ranges, leading to variation in defence among native and invasive populations. However, few studies have examined how constitutive and induced indirect defences change during plant invasion, especially during the juvenile stage.Methods
Constitutive extrafloral nectar (EFN) production of native and invasive populations of juvenile tallow tree (Triadica sebifera) were compared, and leaf clipping, and damage by a native specialist (Noctuid) and two native generalist caterpillars (Noctuid and Limacodid) were used to examine inducible EFN production.Key results
Plants from introduced populations had more leaves producing constitutive EFN than did native populations, but the content of soluble solids of EFN did not differ. Herbivores induced EFN production more than simulated herbivory. The specialist (Noctuid) induced more EFN than either generalist for native populations. The content of soluble solids in EFN was higher (2·1 times), with the specialist vs. the generalists causing the stronger response for native populations, but the specialist response was always comparable with the generalist responses for invasive populations.Conclusions
These results suggest that constitutive and induced indirect defences are retained in juvenile plants of invasive populations even during plant establishment, perhaps due to generalist herbivory in the introduced range. However, responses specific to a specialist herbivore may be reduced in the introduced range where specialists are absent. This decreased defence may benefit specialist insects that are introduced for classical biological control of invasive plants. 相似文献4.
Zhang Hao Wang Jin-Yan Chen Yi-Juan Siemann Evan Ji Xiang-Yun Jiang Jie-Xian Wan Nian-Feng 《BioControl》2022,67(1):1-13
BioControl - The effects of plant volatiles on parasitoids are important with regards to the tri-trophic interactions among host plants, insect herbivores, and their natural enemies. However, the... 相似文献
5.
Thiols as classical and slow-binding inhibitors of IMP-1 and other binuclear metallo-beta-lactamases
The inhibitory effect of a variety of thiol compounds on the function of binuclear metallo-beta-lactamases, with a particular focus on IMP-1 from Pseudomonas aeruginosa, has been investigated. Thiol inhibitors, depending on their structural features, fall into two categories, one in which inhibition at neutral pH was instantaneous and the other in which inhibition was time-dependent. While mercaptans with anionic substituents in the vicinity of their SH groups exhibited the former type of inhibition, neutral thiols appear to induce a slow, time-dependent isomerization of the initially formed EI complex to a tighter EI complex. Kinetic parameters describing the latter process were obtained by fitting progress curves of substrate hydrolysis using standard and numerical procedures. The failure of charged thiols to exhibit slow binding is suggested to be due to a rapid isomerization of the initial EI complex. Slow binding in the case of neutral thiols was observed only below pH 8. Studies on the pH dependence of catalysis by IMP-1 revealed that (i) enzyme inactivation at low pH is a slow process with presumably two groups with a pK(a) of approximately 5.2 in the protein being responsible for the loss of activity, (ii) inhibition by thiols is independent of pH between pH 5 and 9, and (iii) an apparent enhancement of the catalytic activity of IMP-1 by thiols occurs at pH <5. The last mentioned phenomenon is explained by a model in which mercaptans retard the proton-dependent isomerization of the enzyme. Studies on the thiol-mediated inhibition of the binuclear forms of Bacteroides fragilis (CcrA) and Bacillus cereus (BcII strain 5/B/6) metallo-beta-lactamase have revealed that while CcrA was instantaneously albeit moderately inhibited by mercaptans, BcII mimicked IMP-1 in its interaction with thiols. These differences are proposed to be due partly to the structural divergence of these proteins in the vicinity of Zn2. 相似文献
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Oelschlaeger P Lange S Schmitt J Siemann M Reuss M Schmid RD 《Applied microbiology and biotechnology》2003,61(2):123-132
7.
ABSTRACT Because a diversity of resources should support a diversity of consumers, most models predict that increasing plant diversity increases animal diversity. We report results of a direct experimental test of the dependence of animal diversity on plant diversity. We sampled arthropods in a well-replicated grassland experiment in which plant species richness and plant functional richness were directly manipulated. In simple regressions, both the number of species planted ([Formula: see text] transformed) and the number of functional groups planted significantly increased arthropod species richness but not arthropod abundance. However, the number of species planted was the only significant predictor of arthropod species richness when both predictor variables were included in ANOVAs or a MANOVA. Although highly significant, arthropod species richness regressions had low [Formula: see text] values, high intercepts (24 arthropod species in monocultures), and shallow slopes. Analyses of relations among plants and arthropod trophic groups indicated that herbivore diversity was influenced by plant, parasite, and predator diversity. Furthermore, herbivore diversity was more strongly correlated with parasite and predator diversity than with plant diversity. Together with regression results, this suggests that, although increasing plant diversity significantly increased arthropod diversity, local herbivore diversity is also maintained by, and in turn maintains, a diversity of parasites and predators. 相似文献
8.
Current status of antisense DNA methods in behavioral studies 总被引:4,自引:0,他引:4
The antisense DNA method has been used successfully to block the expression
of specific genes in vivo in neuronal systems. An increasing number of
studies in the last few years have shown that antisense DNA administered
directly into the brain can modify various kinds of behaviors. These
findings strongly suggest that the antisense DNA method can be used as a
powerful tool to study causal relationships between molecular processes in
the brain and behavior. In this article we review the current status of the
antisense method in behavioral studies and discuss its potentials and
problems by focusing on the following four aspects; (i) optimal application
paradigms of antisense DNA methods in behavioral studies; (ii) efficiencies
of different administration methods of antisense DNA used in behavioral
studies; (iii) determination of specificity of behavioral effects of
antisense DNA; and (iv) discrepancies between antisense DNA effects on
behaviors and those on protein levels of the targeted gene.
相似文献
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Negative plant-soil feedbacks may limit persistence of an invasive tree due to rapid accumulation of soil pathogens 总被引:1,自引:0,他引:1
Nijjer S Rogers WE Siemann E 《Proceedings. Biological sciences / The Royal Society》2007,274(1625):2621-2627
Soil organisms influence plant species coexistence and invasion potential. Plant-soil feedbacks occur when plants change soil community composition such that interactions with that soil community in turn may positively or negatively affect the performance of conspecifics. Theories predict and studies show that invasions may be promoted by stronger negative soil feedbacks for native compared with exotic species. We present a counter-example of a successful invader with strong negative soil feedbacks apparently caused by host-specific, pathogenic soil fungi. Using a feedback experiment in pots, we investigated whether the relative strength of plant-soil feedbacks experienced by a non-native woody invader, Sapium sebiferum, differed from several native tree species by examining their performance in soils collected near conspecifics ('home soils') or heterospecifics ('away soils') in the introduced range. Sapium seedlings, but no native seedlings, had lower survival and biomass in its home soils compared with soils of other species (negative feedback'). To investigate biotic agents potentially responsible for the observed negative feedbacks, we conducted two additional experiments designed to eliminate different soil taxa ('rescue experiments'). We found that soil sterilization (pot experiment ) or soil fungicide applications (pot and field experiments) restored Sapium performance in home soil thereby eliminating the negative feedbacks we observed in the original experiment. Such negative feedbacks apparently mediated by soil fungi could have important effects on persistence of this invader by limiting Sapium seedling success in Sapium dominated forests (home soils) though their weak effects in heterospecific (away) soils suggest a weak role in limiting initial establishment. 相似文献