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排序方式: 共有347条查询结果,搜索用时 15 毫秒
341.
Brachmann AO Joyce SA Jenke-Kodama H Schwär G Clarke DJ Bode HB 《Chembiochem : a European journal of chemical biology》2007,8(14):1721-1728
Type II polyketide synthases are involved in the biosynthesis of numerous clinically relevant secondary metabolites with potent antibiotic or anticancer activity. Until recently the only known producers of type II PKSs were members of the Gram-positive actimomycetes, well-known producers of secondary metabolites in general. Here we present the second example of a type II PKS from Gram-negative bacteria. We have identified the biosynthesis gene cluster responsible for the production of anthraquinones (AQs) from the entomopathogenic bacterium Photorhabdus luminescens. This is the first example of AQ production in Gram-negative bacteria, and their heptaketide origin was confirmed by feeding experiments. Deletion of a cyclase/aromatase involved in AQ biosynthesis resulted in accumulation of mutactin and dehydromutactin, which have been described as shunt products of typical octaketide compounds from streptomycetes, and a pathway for AQ formation from octaketide intermediates is discussed. 相似文献
342.
This paper describes an analytical method for estimation of the economical feasibility of a project for wind energy utilization in Jordan. The method is applied to a windfarm and is based on the wind speed distribution at the site considered and on the financial parameters for the complete plant and its running costs. For this method, equations were derived to calculate the cost of a kWh generated by wind turbines with different characteristics as a function of the capital investment per kW installed capacity. The method was applied to the sites at which Royal Scientific Society performs wind speed measurements, and the results indicate that some of these sites are well suited for cost efficient generation of electricity by wind energy. The results also show that a wind tribine which is designed to have a relatively low rated speed has a wider range of economical operation than a wind turbine with a higher rated speed for the sites investigated assuming that the maximum rated power for all for the wind turbines is held constant. 相似文献
343.
Distler U Hülsewig M Souady J Dreisewerd K Haier J Senninger N Friedrich AW Karch H Hillenkamp F Berkenkamp S Peter-Katalinić J Müthing J 《Analytical chemistry》2008,80(6):1835-1846
Glycosphingolipids (GSLs), composed of a hydrophilic carbohydrate chain and a lipophilic ceramide anchor, play pivotal roles in countless biological processes, including the development of cancer. As part of the investigation of the vertebrate glycome, GSL analysis is undergoing rapid expansion owing to the application of modern mass spectrometry. Here we introduce direct coupling of IR-MALDI-o-TOF mass spectrometry with the TLC overlay binding assay for the structural characterization of GSLs. We matched three complementary methods including (i) TLC separation of GSLs, (ii) their detection with oligosaccharide-specific proteins, and (iii) in situ MS analysis of protein-detected GSLs. The high specificity and sensitivity is demonstrated by use of antibodies, bacterial toxins, and a plant lectin. The procedure works on a nanogram scale, and detection limits of less than 1 ng at its best of immunostained GSLs were obtained. Furthermore, only crude lipid extracts of biological sources are required for TLC-IR-MALDI-MS, omitting any laborious GSL downstream purification procedures. This strategy was successfully applied to the identification of cancer-associated GSLs in human hepatocellular and pancreatic tumors. Thus, the in situ TLC-IR-MALDI-MS of immunolabeled GSLs opens new doors by delivering specific structural information of trace quantities of GSLs with only a limited investment in sample preparation. 相似文献
344.
The Uppsala University 5 MV Pelletron tandem accelerator has been used to study (14)C-labeled biological samples utilizing accelerator mass spectrometry (AMS) technology. We have adapted a sample preparation method for small biological samples down to a few tens of micrograms of carbon, involving among others, miniaturizing of the graphitization reactor. Standard AMS requires about 1 mg of carbon with a limit of quantitation of about 10 amol. Results are presented for a range of small sample sizes with concentrations down to below 1 pM of a pharmaceutical substance in human blood. It is shown that (14)C-labeled molecular markers can be routinely measured from the femtomole range down to a few hundred zeptomole (10 (-21) mol), without the use of any additional separation methods. 相似文献
345.
346.
Anna Proschak Patrice Lubuta Peter Grün Dr. Frank Löhr Dr. Gottfried Wilharm Veronique De Berardinis Prof. Dr. Helge B. Bode 《Chembiochem : a European journal of chemical biology》2013,14(5):633-638
Novel chatechol/hydroxamate siderophores (named “fimsbactins”) were identified in Acinetobacter baumannii ATCC 17978 and Acinetobacter baylyi ADP1. The major compound, fimsbactin A, was isolated from low‐iron cultures of A. baylyi ADP1, and its chemical structure was elucidated by mass spectrometry, and detailed 1H, 13C and 15N NMR spectroscopy. From inverse feeding experiments following HPLC‐MS analysis, the structures of five additional derivatives were elucidated. The gene cluster encoding the fimsbactin synthetase (fbs) was identified in both genomes, and mutants in fbs genes in A. baylyi were analyzed, thus allowing prediction of the fimsbactin biosynthesis pathway. 相似文献
347.
Bode HB Ring MW Schwär G Altmeyer MO Kegler C Jose IR Singer M Müller R 《Chembiochem : a European journal of chemical biology》2009,10(1):128-140
Isovaleryl-CoA (IV-CoA) is usually derived from the degradation of leucine by using the Bkd (branched-chain keto acid dehydrogenase) complex. We have previously identified an alternative pathway for IV-CoA formation in myxobacteria that branches from the well-known mevalonate-dependent isoprenoid biosynthesis pathway. We identified 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (MvaS) to be involved in this pathway in Myxococcus xanthus, which is induced in mutants with impaired leucine degradation (e.g., bkd(-)) or during myxobacterial fruiting-body formation. Here, we show that the proteins required for leucine degradation are also involved in the alternative IV-CoA biosynthesis pathway through the efficient catalysis of the reverse reactions. Moreover, we conducted a global gene-expression experiment and compared vegetative wild-type cells with bkd mutants, and identified a five-gene operon that is highly up-regulated in bkd mutants and contains mvaS and other genes that are directly involved in the alternative pathway. Based on our experiments, we assigned roles to the genes required for the formation of IV-CoA from HMG-CoA. Additionally, several genes involved in outer-membrane biosynthesis and a plethora of genes encoding regulatory proteins were decreased in expression levels in the bkd(-) mutant; this explains the complex phenotype of bkd mutants including a lack of adhesion in developmental submerse culture. 相似文献