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排序方式: 共有308条查询结果,搜索用时 19 毫秒
1.
Rushton Parker 《BMJ (Clinical research ed.)》1888,1(1422):690-691
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The free radical (II) produced by one-electron reduction of adriamycin (I) exists in aqueous solution at pH 7.0 in equilibrium with the parent and the two-electron reduced form (III). Over some hundreds of milliseconds deglycosylation takes place yielding an aglycone (IV) which subsequently rearranges to form a more stable aglycone. 7-deoxyadriamycinone (V). The changes in the optical absorption spectrum accompanying these processes are reported. The rate constant for III + IV is 1.1 s-1 and for IV + V is 1.5 × 10--2 s.-1. At pH 4.0 the two electron reduced form of adriamycin exists predominantly in a different tautomeric form (VII). It is suggested that this deglycosylates via a free radical mechanism involving the acidic form of the semiquinone free radical (VI) 相似文献
3.
Interaction of elicitor-induced DNA-binding proteins with elicitor response elements in the promoters of parsley PR1 genes. 总被引:29,自引:0,他引:29 下载免费PDF全文
P J Rushton J T Torres M Parniske P Wernert K Hahlbrock I E Somssich 《The EMBO journal》1996,15(20):5690-5700
PR1 is a pathogenesis-related protein encoded in the parsley genome by a family of three genes (PR1-1, PR1-2 and PR1-3). Loss- and gain-of-function experiments in a transient expression system demonstrated the presence of two fungal elicitor responsive elements in each of the PR1-1 and PR1-2 promoters. These elements, W1, W2 and W3, contain the sequence (T)TGAC(C) and mutations that disrupt this sequence abolish function. Gel shift experiments demonstrated that W1, W2 and W3 are bound specifically by similar nuclear proteins. Three cDNA clones encoding sequence-specific DNA-binding proteins were isolated by South-Western screening and these proteins, designated WRKY1, 2 and 3, also bind specifically to W1, W2 and W3. WRKY1, 2 and 3 are members of the family of sequence-specific DNA-binding proteins, which we call the WRKY family. Treatment of parsley cells with the specific oligopeptide elicitor Pep25 induced a transient and extremely rapid increase in mRNA levels of WRKY1 and 3. WRKY2 mRNA levels in contrast showed a concomitant transient decrease. These rapid changes in WRKY mRNA levels in response to a defined signal molecule suggest that WRKY1, 2 and 3 play a key role in a signal transduction pathway that leads from elicitor perception to PR1 gene activation. 相似文献
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Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
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Summary The hypothesis that faeces recycling in isopods evolved as an adaption to facilitate maintenance of an adequate copper balance in terrestrial environments is examined. Experimental observations on the consumption, absorption and growth rates of Porcellio scaber fed Betula pendula leaf litter varying in copper content and extent of microbial decay are reported. Preventing the isopods from reingesting their faeces caused a reduction in the growth rates of experimental animals fed their natural low copper diet but also of those fed copper enriched diets. When the availability of copper in the primary food was increased consumption of the litter decreased and growth rates were significantly reduced. These results suggest that copper is not normally a critically limiting nutrient for terrestrial isopods.When the primary diet was supplemented with shredded carrot, faeces deprivation did not cause a decrease in growth rates. These experimental animals gained weight significantly faster than controls fed decaying leaf litter alone.Faeces formed a significantly greater proportion of the diet when the animals were fed freshly fallen rather than decayed litter.We conclude a) that enhanced microbial activity in the faeces increases their nutrient status in such a way that some coprophagy is necessary in order to optimize overall nutrient uptake, and b) that theability to vary the extent to which faeces are recycled in response to differences in food quality is important in that it introduces greater flexibility into the feeding strategies of these generalist macro-decomposers. 相似文献
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O'Donnell AG Young IM Rushton SP Shirley MD Crawford JW 《Nature reviews. Microbiology》2007,5(9):689-699
The introduction of new approaches for characterizing microbial communities and imaging soil environments has benefited soil microbiology by providing new ways of detecting and locating microorganisms. Consequently, soil microbiology is poised to progress from simply cataloguing microbial complexity to becoming a systems science. A systems approach will enable the structures of microbial communities to be characterized and will inform how microbial communities affect soil function. Systems approaches require accurate analyses of the spatio-temporal properties of the different microenvironments present in soil. In this Review we advocate the need for the convergence of the experimental and theoretical approaches that are used to characterize and model the development of microbial communities in soils. 相似文献