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41.
Although there are a number of existing assays for monitoring the activity of both isopenicillin N synthase (IPNS) and deacetoxycephalosporin C synthase (DAOCS), none have demonstrated the qualities required for screening a mutant library. Hence, enzyme-linked immunosorbent assays (ELISAs) for IPNS and DAOCS were developed based on the detection of the catalytic turnover products isopenicillin N and cephalexin/phenylacetyl-7-aminodeacetoxycephalosporanic acid (G-7-ADCA), respectively. These assays are relatively fast compared to existing assays, such as the hole-plate bioassay, and are amenable with high-throughput screening. Both the IPNS and DAOCS-ELISAs were optimised for use with crude protein extracts rather than purified protein, thereby eliminating any additional time required for purification. The ELISA developed for the detection of cephalexin had an IC50 value of 154 ± 9 ng mL−1 and LOD of 7.2 ± 2.2 ng mL−1 under conditions required for the assay. Good recoveries and correlation was observed for spiked samples when the concentration of crude protein was kept below 1 mg mL−1. The DAOCS-ELISA was found to have increased sensitivity compared to the hole-plate bioassay (10.3 μg mL−1). The IPNS-ELISA did not significantly increase the sensitivity (approximately 5 μg mL−1) compared to that of the hole-plate bioassay (16 μg mL−1) for isopenicillin N. The minimum amount of crude protein extract required for producing detectable amounts of product for both assays was below 0.5% of the maximum amount of protein that the assay could contain without any effect on the ELISA. This suggests that when screening a mutant library, mutants producing low amounts of the product could still be detected using these assays. 相似文献
42.
Echigo S Hara N Carderon GJ Duque C Fujimoto Y 《Chemical & pharmaceutical bulletin》2006,54(10):1473-1477
The C-24 configuration of (22E,24xi)-24-isopropenyl-22-dehydrocholesterol (1), which was recently isolated from the Colombian Caribbean sponge, Topsentia ophiraphidites, was investigated. Synthesis of the stereodefined (24R)- and (24S)-(22E)-24-isopropenyl-22-dehydrocholesterols (1a, 1b) followed by (1)H- and (13)C-NMR data comparison of these sterols established the (24R)-configuration of 1. In addition, (24R)- and (24S)-24-isopropenylcholesterols (2a and 2b) were also synthesized and their NMR data are provided. The C-24 configurations of the samples of 24-isopropenylcholesterol reported previously are discussed. 相似文献
43.
Venke Kristoffersen Marte Jenssen Heba Raid Jawad Johan Isaksson Espen H. Hansen Teppo Rm Kine
. Hansen Jeanette Hammer Andersen 《Molecules (Basel, Switzerland)》2021,26(17)
The Lacinutrix genus was discovered in 2005 and includes 12 Gram-negative bacterial species. To the best of our knowledge, the secondary metabolite production potential of this genus has not been explored before, and examination of Lacinutrix species may reveal novel chemistry. As part of a screening project of Arctic marine bacteria, the Lacinutrix sp. strain M09B143 was cultivated, extracted, fractionated and tested for antibacterial and cytotoxic activities. One fraction had antibacterial activity and was subjected to mass spectrometry analysis, which revealed two compounds with elemental composition that did not match any known compounds in databases. This resulted in the identification and isolation of two novel isobranched lyso-ornithine lipids, whose structures were elucidated by mass spectrometry and NMR spectroscopy. Lyso-ornithine lipids consist of a 3-hydroxy fatty acid linked to the alpha amino group of an ornithine amino acid through an amide bond. The fatty acid chains were determined to be iso-C15:0 (1) and iso-C16:0 (2). Compound 1 was active against the Gram-positive S. agalactiae, while 2 showed cytotoxic activity against A2058 human melanoma cells. 相似文献
44.
A series of platinum(II) complexes with the formulas Pt(diimine)(pip(2)NCNH(2))(L)(2+) [pip(2)NCNH(2)(+) = 2,6-bis(piperidiniummethyl)phenyl cation; L = Cl, Br, I, NCS, OCN, and NO(2); diimine = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO(2)phen), and 5,5'-ditrifluoromethyl-2,2'-bipyridine (dtfmbpy)] were prepared by the treatment of Pt(pip(2)NCN)Cl with a silver(I) salt followed by the addition of the diimine and halide/pseudohalide under acidic conditions. Crystallographic data as well as (1)H NMR spectra establish that the metal center is bonded to a bidentate phenanthroline and a monodentate halide/pseudohalide. The pip(2)NCNH(2)(+) ligand with protonated piperidyl groups is monodentate and bonded to the platinum through the phenyl ring. Structural and spectroscopic data indicate that the halide/pseudohalide group (L(-)) and the metal center in Pt(phen)(pip(2)NCNH(2))(L)(2+) behave as Br?nsted bases, forming intramolecular NH···L/NH···Pt interactions involving the piperidinium groups. A close examination of the 10 structures reported here reveals linear correlations between N-H···Pt/L angles and H···Pt/L distances. In most cases, the N-H bond is directed toward the Pt-L bond, thereby giving the appearance that the proton bridges the Pt and L groups. In contrast to observations for Pt(tpy)(pip(2)NCN)(+) (tpy = 2,2';6',2"-terpyridine), the electrochemical oxidation of deprotonated adducts, Pt(diimine)(L)(pip(2)NCN), is chemically and electrochemically irreversible. 相似文献
45.
A. A. A. Emara Jeanette A. Krause Bauer A. Galal 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(5):515-517
The title compound crystallizes as the monohydrate, [Co(SeO3)(NH3)4]NO3·H2O. The crystallographic mirror symmetry coincides with the molecular symmetry; the mirror plane passes through the cation, anion and water molecule. The CoN4O2 octahedron is distorted, with the selenito group acting as a bidentate ligand through two bridging O atoms to the cobalt. The coordinated Se—O distance is 1.742 (2) Å, whereas the uncoordinated Se—O distance is 1.646 (3) Å. A three‐dimensional hydrogen‐bonded network exists between [Co(SeO3)(NH3)4]NO3 and the water molecule. The nitrate anion and water molecule form open pores in the structure when hydrogen bonded to two neighboring [Co(SeO3)(NH3)4]+ cations. Selenium participates in two types of relatively close intermolecular interactions with neighboring charged species (Se?N1 and Se?O3), but does not participate in an interaction with a neighboring O2 atom, the nearest contact distance being 4.638 (3) Å. 相似文献
46.
Michael J. Goldcamp Jeanette A. Krause Bauer Michael J. Baldwin 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e602-e603
Tris[2‐(benzoylamino)ethyl]amine [alternatively, N,N′,N′′‐(nitrilotriethyl)tribenzamide], C27H30N4O3, adopts a folded structure, forming a symmetrical cavity with an average depth of 7.3 Å and width ranging from 4.1–4.4 Å. The folded structure is a result of one intramolecular N—H?O hydrogen bond. A linear chain motif along the c axis best describes the extended intermolecular N—H?O hydrogen bonding. 相似文献
47.
48.
Component structure in the evolution of random hypergraphs 总被引:1,自引:0,他引:1
The component structure of the most general random hypergraphs, with edges of differen sizes, is analyzed. We show that, as
this is the case for random graphs, there is a “double jump” in the probable and almost sure size of the greatest component
of hypergraphs, when the average vertex degree passes the value 1. 相似文献
49.
Anders Holmbom Jeanette Silfver Nils Svanstedt Niklas Wellander 《Applications of Mathematics》2006,51(3):247-262
A general concept of two-scale convergence is introduced and two-scale compactness theorems are stated and proved for some
classes of sequences of bounded functions in L
2(Ω) involving no periodicity assumptions. Further, the relation to the classical notion of compensated compactness and the
recent concepts of two-scale compensated compactness and unfolding is discussed and a defect measure for two-scale convergence
is introduced. 相似文献
50.
E. Jacquemin Latour Yvon Wurtz Marty R. Brunner S. Cotton C. Weigelt A. Gautier V. Griessmayer Skalweit K. Portele und E. Mach 《Fresenius' Journal of Analytical Chemistry》1880,19(1):225-229
Ohne Zusammenfassung 相似文献