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1.
Sequence analysis of the biosynthetic gene cluster for the enediyne antitumor antibiotic C-1027 from Streptomyces globisporus has previously suggested that the sgcA1 gene encodes a alpha-d-glucopyranosyl-1-phosphate thymidylyltransferase (Glc-1-P-TT) catalyzing the first step in the biosynthesis of the 4-deoxy-4-(dimethylamino)-5,5-dimethyl-d-ribopyranose moiety by activating alpha-d-glucopyranosyl-1-phosphate (Glc-1-P) into deoxythymidine diphosphate-alpha-d-glucose (dTDP-Glc). Here we report the overexpression of sgcA1 in E. coli, purification of the overproduced SgcA1 to homogenetity, biochemical and kinetic characterization of the purified SgcA1 as a Glc-1-P-TT, and yield improvement for C-1027 production by overexpression of sgcA1 and its flanking gene in S. globisporus. These findings provide biochemical evidence supporting the genetics-based hypothesis for C-1027 biosynthesis, set the stage for further investigation of the deoxysugar biosynthetic pathway, and demonstrate the utility of sugar biosynthesis genes in natural product yield improvement via combinatorial biosynthesis methods. In contrast to the homotetrameric quaternary structure known for Glc-1-P-TT enzymes from primary metabolic pathways, Glc-1-P-TT enzymes such as SgcA1 from secondary metabolic pathways are monomeric in solution. Sequence differences between the two subclasses of Glc-1-P-TT enzymes were noted. The monomeric structural feature of the latter enzymes could be exploited in engineering Glc-1-P-TT enzymes with broad substrate specificity for structural diversity via the glycorandomization strategy.  相似文献
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The structure of the title compound, (+)-7S-hydroxyxestospongin A was solved by single-crystal X-ray diffraction analysis and the absolute stereochemistry obtained by analysis of the derived R and S Mosher's esters. The absolute configuration of xestospongin D was determined for the first time by analysis of anomalous scattering from the X-ray crystal diffraction data set. Xestospongins A, C, and D, araguspongine C, and demethylxestospongin B exhibited modest antifungal activity (MIC 30-100 g/mL) against various fluconazole-resistant Candida spp., but 7S-hydroxyxestospongin A was inactive.  相似文献
4.
Bleomycin (BLM) biosynthesis has been studied as a model for hybrid peptide-polyketide natural product biosynthesis. Cloning, sequencing, and biochemical characterization of the blm biosynthetic gene cluster from Streptomyces verticillus ATCC15003 revealed that (1) the BLM hybrid peptide-polyketide aglycon is assembled by the BLM megasynthetase that consists of both nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) modules; (2) BlmIX/BlmVIII/BlmVII constitute a natural hybrid NRPS/PKS/NRPS system, serving as a model for both hybrid NRPS/PKS and PKS/NRPS systems; (3) the catalytic sites appear to be conserved in both hybrid NRPS/PKS and nonhybrid NRPS or PKS systems, with the exception of the KS domains in the hybrid NRPS/PKS systems that are unique; (4) specific interpolypeptide linkers may play a critical role in intermodular communication to facilitate the transfer of the growing intermediates between the interacting NRPS and/or PKS modules; (5) post-translational modification of the BLM megasynthetase has been accomplished by a single PPTase with broad carrier protein specificity; and (6) BlmIV/BlmIII-templated assembly of the BLM bithiazole moiety requires intriguing protein juxtaposition and modular recognition. These results lay the foundation to investigate the molecular basis for intermodular communication between NRPS and PKS in hybrid peptide-polyketide natural product biosynthesis and set the stage for engineering novel BLM analogues by genetic manipulation of genes governing BLM biosynthesis.  相似文献
5.
Elloramycin A (1) belongs to a small family of naphthacenequinones characterized by a unique highly hydroxylated cyclohexenone moiety. A cosmid clone 16F4, harboring genes for the production of 1 from Streptomyces olivaceus Tü2353, has been previously isolated. DNA sequence analysis of a 3.2-kb fragment from 16F4 revealed four open reading frames--the elmGHIJ genes. Heterologous expressions of the elmGHI genes in either Escherichia coli or Streptomyces lividans, followed by biochemical characterizations of the ElmGHI proteins, established ElmG as tetracenomycin B2 oxygenase, ElmH as tetracenomycin F1 monooxygenase, and ElmI as tetracenomycin F2 cyclase. These results provide direct biochemical evidence for the hypothesis that the biosynthesis of 1 in S. olivaceus parallels that of tetracenomycin C (2) in Streptomyces glaucescens and support the notion that the biosynthesis of the highly hydroxylated cyclohexenone moiety in other polyketides most likely follows the same paradigm as the tetracenomycin B2 or A2 oxygenase.  相似文献
6.
The structure of oceanapiside, an antifungal alpha, omega-bis-aminohydroxylipid glycoside from the temperate marine sponge Oceanapia sp., was elucidated by a combination of 2D NMR, chemical degradation/correlation, and MALDI MS-MS spectrometry. Oceanapiside exhibits antifungal activity against Candida glabrata at 10 micrograms/mL (MIC).  相似文献
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An examination of an organic extract of the cyanobacterium Lyngbya majuscula, collected from Wasini Island off the southern Kenyan coast, led to the isolation of the known cyclic depsipeptide antanapeptin A (1), recently isolated from a Madagascan collection of L. majuscula, and a new bioactive cyclic depsipeptide, homodolastatin 16 (2). The structures of these two compounds were determined from NMR and mass spectrometry data. Homodolastatin 16, a higher homologue of the potential anticancer agent dolastatin 16, exhibited moderate activity against oesophageal and cervical cancer cell lines.  相似文献
8.
The alpha-glucosidase inhibitor 1,4-dideoxy-1,4-imino-D-arabinitol (1) was isolated from two marine sponges collected in Western Australia and shown by LC-MS to be responsible for the alpha-glycosidase inhibitory activity in different sponge extracts collected over a wide geographic area. The configuration of 1 was determined by application of Marfey's method. The two most inhibitory extracts contained only 1, while the less inhibitory extracts contained 1,4-dideoxy-1,4-imino-D-xylitol (2) or the putative diastereomeric imino pentitols 3 and 4. The least active or inactive extracts showed no detectable imino pentitols. While both 1 and 2 are known from plants, this is the first report on the isolation and detection of 1 and 2 in marine invertebrates.  相似文献
9.
Investigations of the marine sponge Prianos osiros, collected in Pohnpei, gave a new cytotoxic acetylenic carotenoid, (3R,3'R,5S)-3,3',5,19'-tetrahydroxy-7',8'-didehydro-gamma,epsilon-carotene-8-one. The absolute configuration of this carotenoid was solved by interpretation of IR, MS, and 2D NMR spectra and application of the modified Mosher's method. Compound 1 is cytotoxic toward cultured human colon tumor cells, HCT 116 (IC(50) 4.38 microg/mL).  相似文献
10.
The novel antifungal compound majusculoic acid was isolated from a cyanobacterial mat microbial community. The structure of majusculoic acid was solved by interpretation of mass spectrometric and NMR data and conversion to the corresponding methyl ester. Majusculoic acid exhibits antifungal activity against Candida albicans ATCC 14503 (MIC 8 microM).  相似文献
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