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101.
Chemical investigation of the diethyl ether extract from the liverwort Corsinia coriandrina resulted in the isolation of a new 2-arylbenzofuran compound called corsifuran A. The structure was identified by spectroscopic techniques and confirmed by synthesis. Two minor constituents of similar structure, and two related stilbenoids and a bibenzyl were identified by comparison of the mass spectra and GC retention indices with authentic samples. Due to the similarity in substitution patterns a stilbenoid origin of the corsifurans is proposed. 相似文献
102.
The essential oils and extracts of Mylia taylorii and M. nuda were investigated by gas chromatography, mass spectrometry, NMR spectroscopy and chemical correlations. Beside several known compounds 13 new constituents including three new carbon skeletons could be identified. Four hydrocarbons with a molecular formula of C15H22 (m/z 202) were identified as myli-4(15)-ene (1), aromadendra-1(10),4(15)-diene (19), aromadendra-4,10(14)-diene (20) and aromadendra-4,9-diene (21). Three oxaspiro-compounds were identified as 7-epi-bourbon-3-en-5,11-oxide (22), guai-3,10(14)-dien-5,11-oxide (23) and guai-3,9-dien-5,11-oxide (24). The absolute configuration of myli-4(15)-en-3-one (5) could be established by chemical correlation. Together with α-taylorione (7) the corresponding 6,11-seco-compound taylopyran (25) with a new carbon skeleton was identified which serves as a precursor to taylocyclane (26) and taylofuran (27). Taynudol (28) contains a new carbon skeleton with a cyclobutenyl structure. 相似文献
103.
104.
Repair of hydrolytic DNA deamination damage in thermophilic bacteria: cloning and characterization of a Vsr endonuclease homolog from Bacillus stearothermophilus 总被引:1,自引:1,他引:0 下载免费PDF全文
Hydrolytic deamination of 5-methyl cytosine in double stranded DNA results in formation of a T/G mismatch that—if left unrepaired—leads to a C→T transition mutation in half of the progeny. In addition to several mismatch-specific glycosylases that have been found in both pro- and eukaryotes to channel this lesion into base excision repair by removing the T from the mismatch, Vsr endonuclease from Escherichia coli has been described which initiates repair by an endonucleolytic strand incision 5′ to the mismatched T. We have isolated a gene coding for a homolog of E.coli Vsr endonuclease from the thermophilic bacterium Bacillus stearothermophilus H3 (Vsr.Bst) using a method that allows PCR amplification with degenerated primers of gene segments which code for only one highly conserved amino acid region. Vsr.Bst was produced heterologously in E.coli and purified to apparent homogeneity. Vsr.Bst specifically incises heteroduplex DNA with a preference for T/G mismatches. The selectivity of Vsr.Bst for the sequence context of the T/G mismatch appears less pronounced than for Vsr.Eco. 相似文献
105.
Hickman HD Luis AD Bardet W Buchli R Battson CL Shearer MH Jackson KW Kennedy RC Hildebrand WH 《Journal of immunology (Baltimore, Md. : 1950)》2003,171(1):22-26
Class I MHC molecules bind intracellular peptides for presentation to cytotoxic T lymphocytes. Identification of peptides presented by class I molecules during infection is therefore a priority for detecting and targeting intracellular pathogens. To understand which host-encoded peptides distinguish HIV-infected cells, we have developed a mass spectrometric approach to characterize HLA-B*0702 peptides unique to or up-regulated on infected T cells. In this study, we identify 15 host proteins that are differentially presented on infected human T cells. Peptides with increased expression on HIV-infected cells were derived from multiple categories of cellular proteins including RNA binding proteins and cell cycle regulatory proteins. Therefore, comprehensive analysis of the B*0702 peptide repertoire demonstrates that marked differences in host protein presentation occur after HIV infection. 相似文献
106.
Molecular phylogeny of living xenarthrans and the impact of character and taxon sampling on the placental tree rooting 总被引:14,自引:0,他引:14
Delsuc F Scally M Madsen O Stanhope MJ de Jong WW Catzeflis FM Springer MS Douzery EJ 《Molecular biology and evolution》2002,19(10):1656-1671
Extant xenarthrans (armadillos, anteaters and sloths) are among the most derived placental mammals ever evolved. South America was the cradle of their evolutionary history. During the Tertiary, xenarthrans experienced an extraordinary radiation, whereas South America remained isolated from other continents. The 13 living genera are relics of this earlier diversification and represent one of the four major clades of placental mammals. Sequences of the three independent protein-coding nuclear markers alpha2B adrenergic receptor (ADRA2B), breast cancer susceptibility (BRCA1), and von Willebrand Factor (VWF) were determined for 12 of the 13 living xenarthran genera. Comparative evolutionary dynamics of these nuclear exons using a likelihood framework revealed contrasting patterns of molecular evolution. All codon positions of BRCA1 were shown to evolve in a strikingly similar manner, and third codon positions appeared less saturated within placentals than those of ADRA2B and VWF. Maximum likelihood and Bayesian phylogenetic analyses of a 47 placental taxa data set rooted by three marsupial outgroups resolved the phylogeny of Xenarthra with some evidence for two radiation events in armadillos and provided a strongly supported picture of placental interordinal relationships. This topology was fully compatible with recent studies, dividing placentals into the Southern Hemisphere clades Afrotheria and Xenarthra and a monophyletic Northern Hemisphere clade (Boreoeutheria) composed of Laurasiatheria and Euarchontoglires. Partitioned likelihood statistical tests of the position of the root, under different character partition schemes, identified three almost equally likely hypotheses for early placental divergences: a basal Afrotheria, an Afrotheria + Xenarthra clade, or a basal Xenarthra (Epitheria hypothesis). We took advantage of the extensive sampling realized within Xenarthra to assess its impact on the location of the root on the placental tree. By resampling taxa within Xenarthra, the conservative Shimodaira-Hasegawa likelihood-based test of alternative topologies was shown to be sensitive to both character and taxon sampling. 相似文献
107.
Weber W Marty RR Keller B Rimann M Kramer BP Fussenegger M 《Biotechnology and bioengineering》2002,80(6):691-705
The novel macrolide-inducible and -repressible mammalian gene regulation systems (E.REX) have been cloned into a variety of sophisticated expression configurations including (1) multi-purpose expression vectors, (2) pTRIDENT-based artificial operons, (3) dual-regulated expression strategies for independent control of two different transgenes, (4) autoregulated vectors for one-step installation of adjustable multigene expression, and (5) oncoretroviral and lentiviral plasmids for transduction of macrolide-, streptogramin- and tetracycline-dependent transactivators and production of cell lines supporting independent control of three different transgenes. This vector portfolio represents a construction kit-like toolbox for efficient installation of adjustable gene expression responsive to clinically licensed antibiotics and enables the design of multiregulated multigene metabolic engineering strategies required for biopharmaceutical manufacturing, gene therapy, and tissue engineering. 相似文献
108.
Lange UE Backfisch G Delzer J Geneste H Graef C Hornberger W Kling A Lauterbach A Subkowski T Zechel C 《Bioorganic & medicinal chemistry letters》2002,12(10):1379-1382
Solid-phase synthesis and SAR of integrin alpha(V)beta3-receptor antagonists containing a urea moiety as non-basic guanidine mimetic are described. The most potent compounds exhibited IC(50) values towards alpha(V)beta3 in the nanomolar range and high selectivity versus related integrins like alpha(IIb)beta3. For selected examples efficacy in functional cellular assays is demonstrated. 相似文献
109.
Cholesteryl ester flux from HDL to VLDL-1 is preferentially enhanced in type IIB hyperlipidemia in the postprandial state 总被引:2,自引:0,他引:2
Guerin M Egger P Soudant C Le Goff W van Tol A Dupuis R Chapman MJ 《Journal of lipid research》2002,43(10):1652-1660
Postprandial triglyceride-rich lipoproteins (TRL) exert proatherogenic effects at the arterial wall, including lipid deposition. Following consumption of a mixed meal (1200 kcal), plasma-mediated cellular free cholesterol (FC) efflux, lecithin:cholesterol acyltransferase (LCAT), and cholesteryl ester transfer protein (CETP) activities were determined in subjects (n = 12) displaying type IIB hyperlipidemia and compared with those in a normolipidemic control group (n = 14). The relative capacity of plasma to induce FC efflux from Fu5AH cells via the SR-BI receptor was significantly increased 4 h postprandially (+23%; P < 0.005) in the type IIB group, whereas it remained unchanged for postprandial plasma from normolipidemic subjects. LCAT activity was significantly elevated 2 h postprandially in both the IIB and control groups, (+46% and +36%, respectively; P < 0.005 vs. respective baseline value). In type IIB subjects, total cholesteryl ester (CE) mass transfer from HDL to total TRL [chylomicrons (CMs) + VLDL-1 + VLDL-2 + IDL] increased progressively from 15 +/- 2 micro g CE/h/ml at baseline to 28 +/- 2 micro g CE transferred/h/ml (+87%; P = 0.0004) at 4 h postprandially. CE transfer to CMs and VLDL-1 was preferentially stimulated (2.6-fold and 2.3-fold respectively) at 4 h in IIB subjects and occurred concomitantly with elevation in mass and particle number of both CMs (2.3-fold) and VLDL-1 (1.3-fold). Furthermore, in type IIB subjects, CETP-mediated total CE flux over the 8 h postprandial period from HDL to potentially atherogenic TRL was significantly enhanced, and notably to VLDL-1 (32-fold elevation; P < 0.005), relative to control subjects. Such CE transfer flux was reflected in a significant postprandial increase in CE-TG ratio in both CMs and VLDL-1 in type IIB plasmas. In conclusion, HDL-CE is preferentially targeted to VLDL-1 via the action of CETP during alimentary lipemia, thereby favoring formation and accumulation of atherogenic CE-rich remnant particles. 相似文献
110.
Many lakes around the world are contaminated with bird schistosome cercariae, which penetrate into human skin, causing an itching dermatitis called "swimmers' itch." Bathers could be forewarned from exposure to the larvae and ecological examinations could be performed, when a sensitive method to detect the parasites in aquatic systems, where lots of organisms hinder microscopic examinations, would be available. For this purpose we cloned, sequenced, and analyzed a 396 bp tandem repeated DNA sequence from Trichobilharzia ocellata (ToSau3A), and employed it for developing molecular detection assays. It hybridized with less than 100 pg DNA from different Trichobilharzia species (T. ocellata, Trichobilharzia franki, and Trichobilharzia regenti), but not with 10 ng DNA from other related or sympatric trematodes. A PCR assay, amplifying this sequence with the same specificity, detected 100 fg T. ocellata DNA, 1 cercaria in 0.5 g plankton, and 2 cercariae in 0.5 g host snail tissues. 相似文献