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Li, Lu, Qiyao Wang, Hui Zhang, Minjun Yang, Mazhar I. Khan und Xiaohui Zhou. „Sensor histidine kinase is a β-lactam receptor and induces resistance to β-lactam antibiotics“. Proceedings of the National Academy of Sciences 113, Nr. 6 (01.02.2016): 1648–53. http://dx.doi.org/10.1073/pnas.1520300113.
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β-Lactams disrupt bacterial cell wall synthesis, and these agents are the most widely used antibiotics. One of the principle mechanisms by which bacteria resist the action of β-lactams is by producing β-lactamases, enzymes that degrade β-lactams. In Gram-negative bacteria, production of β-lactamases is often induced in response to the antibiotic-associated damage to the cell wall. Here, we have identified a previously unidentified mechanism that governs β-lactamase production. In the Gram-negative enteric pathogenVibrio parahaemolyticus, we found a histidine kinase/response regulator pair (VbrK/VbrR) that controls expression of a β-lactamase. Mutants lacking either VbrK or VbrR do not produce the β-lactamase and are no longer resistant to β-lactam antibiotics. Notably, VbrK autophosphorylation is activated by β-lactam antibiotics, but not by other lactams. However, single amino acid substitutions in the putative periplasmic binding pocket of VbrK leads its phosphorylation in response to both β-lactam and other lactams, suggesting that this kinase is a β-lactam receptor that can directly detect β-lactam antibiotics instead of detecting the damage to cell wall resulting from β-lactams. In strong support of this idea, we found that purified periplasmic sensor domain of VbrK binds penicillin, and that such binding is critical for VbrK autophosphorylation and β-lactamase production. Direct recognition of β-lactam antibiotics by a histidine kinase receptor may represent an evolutionarily favorable mechanism to defend against β-lactam antibiotics.
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Medina, Marjorie B., Dana J. Poole und M. Ranae Anderson. „A Screening Method for β-Lactams in Tissues Hydrolyzed with Penicillinase I and Lactamase II“. Journal of AOAC INTERNATIONAL 81, Nr. 5 (01.09.1998): 963–72. http://dx.doi.org/10.1093/jaoac/81.5.963.
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Abstract Antibiotic residues above tolerance levels are not allowed in foods derived from farm animals. Microbial inhibition assays are used to screen antibiotics in U.S. regulatory laboratories. We developed a screening approach to classify β-lactams through selective hydrolysis of the β-lactam ring with Penase™ or lactamase II, thereby inactivating the β- lactam activity. Optimum conditions for hydrolysis of β-lactams with Penase and lactamase II were determined. p-Lactams were detected by a microbial inhibition assay and with enzyme-linked immunosorbent assays before and after hydrolysis. β- Lactams (10-100 ppb) were spiked in kidney extracts and hydrolyzed. Results indicate a pattern that tentatively classified the β-lactams into 3 subgroups. Desfuroyl-ceftiofur-cysteine, a major metabolite of ceftiofur, was clearly detected. Penicillin G, ampicillin, amoxicillin, and cloxacillin were distinguishable from cephapirin, ceftiofur metabolite, and high levels of hetacillin. Liver and kidney tissue samples were analyzed with the combined enzyme hydrolysis and screening assays, which tentatively identified the residues. This approach can speed up screening analysis of β-lactam residues prior to identification and quantitation by chromatographic analysis, thus enhancing positive identification of residues to provide a safer food supply
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Alves, Américo J. S., Nuno G. Alves, Cátia C. Caratão, Margarida I. M. Esteves, Diana Fontinha, Inês Bártolo, Maria I. L. Soares et al. „Spiro-Lactams as Novel Antimicrobial Agents“. Current Topics in Medicinal Chemistry 20, Nr. 2 (19.02.2020): 140–52. http://dx.doi.org/10.2174/1568026619666191105110049.
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Introduction: Structural modulation of previously identified lead spiro-β-lactams with antimicrobial activity was carried out. Objective: The main objective of this work was to synthesize and evaluate the biological activity of novel spiro-lactams based on previously identified lead compounds with antimicrobial activity. Methods: The target chiral spiro-γ-lactams were synthesized through 1,3-dipolar cycloaddition reaction of a diazo-γ-lactam with electron-deficient dipolarophiles. In vitro activity against HIV and Plasmodium of a wide range of spiro-β-lactams and spiro-γ-lactams was evaluated. Among these compounds, one derivative with good anti-HIV activity and two with promising antiplasmodial activity (IC50 < 3.5 µM) were identified. Results: A novel synthetic route to chiral spiro-γ-lactams has been established. The studied β- and γ- lactams were not cytotoxic, and three compounds with promising antimicrobial activity were identified, whose structural modulation may lead to new and more potent drugs. Conclusion: The designed structural modulation of biologically active spiro-β-lactams involved the replacement of the four-membered β-lactam ring by a five-membered γ-lactam ring. Although conformational and superimposition computational studies revealed no significant differences between β- and γ- lactam pharmacophoric features, the studied structural modulation did not lead to compounds with a similar biological profile. The observed results suggest that the β-lactamic core is a requirement for the activity against both HIV and Plasmodium.
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Li, Xian-Zhi, Li Zhang, Ramakrishnan Srikumar und Keith Poole. „β-Lactamase Inhibitors Are Substrates for the Multidrug Efflux Pumps of Pseudomonas aeruginosa“. Antimicrobial Agents and Chemotherapy 42, Nr. 2 (01.02.1998): 399–403. http://dx.doi.org/10.1128/aac.42.2.399.
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ABSTRACT The MexAB-OprM multidrug efflux system exports a number of antimicrobial compounds, including β-lactams. In an attempt to define more fully the range of antimicrobial compounds exported by this system, and, in particular, to determine whether β-lactamase inhibitors were also accommodated by the MexAB-OprM pump, the influence of pump status (its presence or absence) on the intrinsic antibacterial activities of these compounds and on their abilities to enhance β-lactam susceptibility in intact cells was assessed. MIC determinations clearly demonstrated that all three compounds tested, clavulanate, cloxacillin, and BRL42715, were accommodated by the pump. Moreover, by using β-lactams which were readily hydrolyzed by thePseudomonas aeruginosa class C chromosomal β-lactamase, it was demonstrated that elimination of themexAB-oprM-encoded efflux system greatly enhanced the abilities of cloxacillin and BRL42715 (but not clavulanate) to increase β-lactam susceptibility. With β-lactams which were poorly hydrolyzed, however, the inhibitors failed to enhance β-lactam susceptibility in MexAB-OprM+ strains, although BRL42715 did enhance β-lactam susceptibility in MexAB-OprM−strains, suggesting that even with poorly hydrolyzed β-lactams this inhibitor was effective when it was not subjected to efflux. MexEF-OprN-overexpressing strains, but not MexCD-OprJ-overexpressing strains, also facilitated resistance to β-lactamase inhibitors, indicating that these compounds are also substrates for the MexEF-OprN pump. These data indicate that an ability to inactivate MexAB-OprM (and like efflux systems in other bacteria) will markedly enhance the efficacies of β-lactam–β-lactamase inhibitor combinations in treating bacterial infections.
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Brilhante, R. S. N., L. G. A. Valente, M. F. G. Rocha, T. J. P. G. Bandeira, R. A. Cordeiro, R. A. C. Lima, J. J. G. Leite et al. „Sesquiterpene Farnesol Contributes to Increased Susceptibility to β-Lactams in Strains of Burkholderia pseudomallei“. Antimicrobial Agents and Chemotherapy 56, Nr. 4 (30.01.2012): 2198–200. http://dx.doi.org/10.1128/aac.05885-11.
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ABSTRACTThis study aimed to evaluate thein vitrocombination of farnesol and β-lactams againstBurkholderia pseudomallei. A total of 12 β-lactamase-positive strains were tested according to CLSI standards. All strains were inhibited by farnesol, with MICs ranging from 75 to 150 μM. The combination of this compound with β-lactams resulted in statistically significant β-lactam MIC reduction (P≤ 0.05). This study provides new perspectives for the use of farnesol combined with β-lactam antibiotics against strains ofB. pseudomallei.
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Sekiguchi, Jun-ichiro, Koji Morita, Tomoe Kitao, Noboru Watanabe, Mitsuhiro Okazaki, Tohru Miyoshi-Akiyama, Masato Kanamori und Teruo Kirikae. „KHM-1, a Novel Plasmid-Mediated Metallo-β-Lactamase from a Citrobacter freundii Clinical Isolate“. Antimicrobial Agents and Chemotherapy 52, Nr. 11 (02.09.2008): 4194–97. http://dx.doi.org/10.1128/aac.01337-07.
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ABSTRACT A novel gene, bla KHM-1, encoding a metallo-β-lactamase, KHM-1, was cloned from a clinical isolate of Citrobacter freundii resistant to most β-lactam antibiotics. Escherichia coli expressing bla KHM-1 was resistant to all broad-spectrum β-lactams except for monobactams and showed reduced susceptibility to carbapenems. Recombinant KHM-1 exhibited EDTA-inhibitable hydrolytic activity against most β-lactams, with an overall preference for cephalosporins.
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Glen, Karl A., und Iain L. Lamont. „β-lactam Resistance in Pseudomonas aeruginosa: Current Status, Future Prospects“. Pathogens 10, Nr. 12 (18.12.2021): 1638. http://dx.doi.org/10.3390/pathogens10121638.
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Pseudomonas aeruginosa is a major opportunistic pathogen, causing a wide range of acute and chronic infections. β-lactam antibiotics including penicillins, carbapenems, monobactams, and cephalosporins play a key role in the treatment of P. aeruginosa infections. However, a significant number of isolates of these bacteria are resistant to β-lactams, complicating treatment of infections and leading to worse outcomes for patients. In this review, we summarize studies demonstrating the health and economic impacts associated with β-lactam-resistant P. aeruginosa. We then describe how β-lactams bind to and inhibit P. aeruginosa penicillin-binding proteins that are required for synthesis and remodelling of peptidoglycan. Resistance to β-lactams is multifactorial and can involve changes to a key target protein, penicillin-binding protein 3, that is essential for cell division; reduced uptake or increased efflux of β-lactams; degradation of β-lactam antibiotics by increased expression or altered substrate specificity of an AmpC β-lactamase, or by the acquisition of β-lactamases through horizontal gene transfer; and changes to biofilm formation and metabolism. The current understanding of these mechanisms is discussed. Lastly, important knowledge gaps are identified, and possible strategies for enhancing the effectiveness of β-lactam antibiotics in treating P. aeruginosa infections are considered.
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Li, Fu, Li Wan, Tongyang Xiao, Haican Liu, Yi Jiang, Xiuqin Zhao, Ruibai Wang und Kanglin Wan. „In Vitro Activity of β-Lactams in Combination with β-Lactamase Inhibitors against Mycobacterium tuberculosis Clinical Isolates“. BioMed Research International 2018 (02.07.2018): 1–8. http://dx.doi.org/10.1155/2018/3579832.
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Objectives. Evaluating the activity of nineteen β-lactams in combination with different β-lactamase inhibitors to determine the most potent combination against Mycobacterium tuberculosis (MTB) in vitro. Methods. Drug activity was examined by drug susceptibility test with 122 clinical isolates from China. Mutations of blaC and drug targets ldtMt1, ldtMt2, dacB2, and crfA were analyzed by nucleotide sequencing. Results. Tebipenem (TBM) in combination with clavulanate (CLA) exhibited the highest anti-TB activity. The MIC of β-lactam antibiotics was reduced most evidently in the presence of CLA, compared to avibactam (AVI) and sulbactam (SUB). Eight polymorphism sites were identified in blaC, which were not associated with β-lactams resistance. Interestingly, one strain carrying G514A mutation in blaC was highly susceptible to β-lactams regardless of the presence of inhibitors. The transpeptidase encoding genes, ldtMt1, ldtMt2, and dacB2, harboured three mutations, two mutations, and one mutation, respectively, but no correlation was found between these mutations and drug resistance. Conclusion. The activity of β-lactams against MTB and different synergetic effect of β-lactamase inhibitors were indicated. TBM/CLA exhibited the most activity and has a great prospect in developing novel anti-TB regimen; however, further clinical research is warranted. Moreover, the resistance to the β-lactam antibiotics might not be conferred by single target mutation in MTB and requires further studies.
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Mukhopadhyay, S., und P. Chakrabarti. „Altered permeability and beta-lactam resistance in a mutant of Mycobacterium smegmatis.“ Antimicrobial Agents and Chemotherapy 41, Nr. 8 (August 1997): 1721–24. http://dx.doi.org/10.1128/aac.41.8.1721.
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Beta-lactam resistance in mycobacteria results from an interplay between the following: (i) beta-lactamase production, (ii) affinity of the penicillin-binding proteins (PBPs) for the drugs, and (iii) permeation of the drugs. A laboratory mutant of Mycobacterium smegmatis was studied in order to evaluate the roles of these factors in beta-lactam resistance. Mutant M13 was between 7- and 78-fold more resistant than the wild type to cephaloridine, cefoxitin, cefazolin, cefamandole, and cephalothin. Increased beta-lactamase activity toward these antibiotics was not observed in the mutant. The PBP profiles of the wild type and M13 were comparable. However, the affinities of PBP 1 for the beta-lactams tested were lower for the mutant than for the wild type. The permeation of the drugs measured in intact cells was lower for M13 than for the parent strain. The liposome swelling technique, which could be used for cephaloridine, also supported this view. Reduced permeation was not restricted to the beta-lactams alone. Glycine uptake was also lower in M13. Taken together, the results suggest that decreased affinities of PBP 1 for beta-lactams, combined with the decreased permeability of the cell wall of the mutant, lead to the development of high-level acquired beta-lactam resistance.
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Yin, Jianhua, Yiyang Sun, Yinting Mao, Miao Jin und Haichun Gao. „PBP1a/LpoA but Not PBP1b/LpoB Are Involved in Regulation of the Major β-Lactamase GeneblaAin Shewanella oneidensis“. Antimicrobial Agents and Chemotherapy 59, Nr. 6 (30.03.2015): 3357–64. http://dx.doi.org/10.1128/aac.04669-14.
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ABSTRACTβ-Lactamase production is one of the most important strategies for Gram-negative bacteria to combat β-lactam antibiotics. Studies of the regulation of β-lactamase expression have largely been focused on the class C β-lactamase AmpC, whose induction by β-lactams requires LysR-type regulator AmpR and permease AmpG-dependent peptidoglycan recycling intermediates. InShewanella, which is ubiquitous in aquatic environments and is a reservoir for antibiotic resistance, production of the class D β-lactamase BlaA confers bacteria with natural resistance to many β-lactams. Expression of theblaAgene in the genus representativeShewanella oneidensisis distinct from the AmpC paradigm because of the lack of an AmpR homologue and the presence of an additional AmpG-independent regulatory pathway. In this study, using transposon mutagenesis, we identify proteins that are involved inblaAregulation. Inactivation ofmrcAandlpoA, which encode penicillin binding protein 1a (PBP1a) and its lipoprotein cofactor, LpoA, respectively, drastically enhancesblaAexpression in the absence of β-lactams. Although PBP1b and its cognate, LpoB, also exist inS. oneidensis, their roles inblaAinduction are dispensable. We further show that themrcA-mediatedblaAexpression is independent of AmpG.
Betou, Marie. „Semipinacol rearrangement of cis-fused β-lactam diols into bicyclic lactams“. Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4348/.
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The 6-azabicyclo[3.2.1]octane ring system is found in a wide variety of biologically active natural and non-natural products. The aim of this project is to prepare the 7,8-diketo-6-azabicyclo[3.2.1]octane structure via a semipinacol rearrangement of ring-fused β -lactams. Chapter 1 introduces the pinacol and semipinacol rearrangement, including the use of cyclic sulfites and phosphoranes, and ring expansion of β -lactams. Previous work in the Grainger group for the synthesis of lactams via tandem radical cyclisation-dithiocarbamate group transfer is also discussed. Chapter 2 describes the methodology developed for the semipinacol rearrangement of β-lactams. Access to suitable precursors for the semipinacol rearrangement is achieved through a sequence of 4-exo trig radical cyclisation, base-mediated dithiocarbamate group elimination and dihydroxylation. Formation of the 7,8-diketo-6-azabicyclo[3.2.1]octane ring system occurs through semipinacol rearrangement of the corresponding cyclic sulfites and phosphoranes. In Chapter 3, the scope and limitations of the methodology are explored. Different substituents on the nitrogen of the β-lactam, groups on the cyclohexane moiety (methyl and oxygenation) and ring sizes are investigated. An original approach to the total synthesis of peduncularine is described in Chapter 4. Synthesis of a suitably functionalised β-lactam and attempts to further transform it into the desired 7,8-diketo-6- azabicyclo[3.2.1]oct-3-ene structure are reported. Work towards the total synthesis of calyciphylline D, calyciphylline F and caldaphnidine M is described in chapter 5. Reductive amination and stereoselective reduction of piperitone are investigated. Use of a model system for the addition of nucleophiles onto thiolactams is also described.
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Warren, H. A. „New routes to sugar lactams, lactim ethers and cyclic amidines“. Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639351.
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Chapter 1 introduces the biological importance of glycosidase inhibitors. The biosynthesis of N-linked glycoproteins is briefly described and the mode of action of glycosidase enzymes is discussed. Some naturally occurring amino-sugar glycosidase inhibitors are detailed. In addition certain sugar lactones, lactams and cyclic amidines which have also been shown to inhibit glycosidase enzymes are reviewed. Chapter 2 introduces the syntheses of various polyhydroxylated piperidine and pyrrolidine alkaloids and sugar lactams. In addition the formation of cyclic sugar amidines and their derivatives is discussed. Chapter 3 involves the syntheses of four novel sugar lactams. The syntheses of 4-amino-4-deoxy-D-allonolactam and 4-amino-4-deoxy-D-talonolactam via novel routes developed by the author are dealt with in detail. The preparations of the corresponding D- and L-ribono compounds by a shortening of the carbon chain are also described. Chapter 4 introduces the syntheses of the novel D-allono-, D-talono- and D-ribono- amidines from the corresponding lactam derivatives. Chapter 4 also reports on literature preparations of sugar tetrazoles and their inhibitory properties towards glycosidase enzymes. Also included is the synthesis of the novel D-talonotetrazole.
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Guignard, Guillaume Michel Pablo. „Open-chain building blocks from chiral lactams. Enantioselective synthesis of macrocyclic nitrogen-containing natural products“. Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/396650.
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1. (R)-Phenylglycinol-derived oxazolopiperidone lactams can be converted to enantiopure open-chain amino ester scaffolds by alkaline hydrolysis of the N-Boc 2-piperidones resulting from the reductive cleavage of the oxazolidine ring.
2. Lithium amidotrihydroborate (LiNH2BH3) reduction of diversely substituted (R)-phenylglycinol-derived oxazolopiperidone lactams brought about the reductive opening of both the oxazolidine and lactam rings, providing general access to structurally diverse enantiopure amino diols A bearing a variety of substitution patterns, substituents (alkyl, benzyl, aryl, protected hydroxy), and stereochemistries.
3. Reductive removal of the phenylethanol moiety present in the amino diols prepared by the above procedure, followed by treatment of the resulting primary amines with (Boc)2O provides a general synthetic entry to enantiopure N-Boc 5-aminopentanols bearing substitutents at the 2-, 3-, 4-, 2,2-, 2,3-, 2,4-, and 3,4- positions.
4. The oxidative removal of the phenylglycinol moiety of amino diols A (previously O-silylated) using the I2/aq NH3 system constitutes an excellent procedure for the straightforward preparation of enantiopure substituted 5-hydroxypentanenitrile derivatives.
5. The m-CPBA-promoted oxidative removal of the phenylglycinol moiety of amino diols A (previously O-silylated) constitutes an excellent procedure for the straightforward preparation of enantiopure substituted 5-hydroxypentanoic acid derivatives.
6. As both enantiomers of phenylglycinol are commercially available, both enantiomers of a target 5-aminopentanol, 5-hydroxypentanoic acid, and 5-hydroxypentanenitrile are accessible through the above methodology.
7. The synthetic value of the open-chain amino diols A has been demonstrated with their use as key scaffolds for the enantioselective synthesis of the Haliclona alkaloids haliclorensin C (first total synthesis), haliclorensin (total), halitulin (formal), and isohaliclorensin (formal).
8. The synthetic value of the open-chain amino diols 5-hydroxypentanoic acids, and 5-hydroxypentanenitriles prepared from (S)-phenylglycinol-derived lactams has been demonstrated with their use as key scaffolds for the synthesis of the natural macrolactam fluvirucinin B1.
9. The approach we have developed significantly expands the potential of phenylglycinol-derived d-lactams, which have been converted for the first time to enantiopure open-chain building blocks.
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Sheppard, L. N. „Synthesis of B-lactams“. Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354855.
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McKenna, Jeffrey M. „Asymmetric synthesis of #beta#-lactams“. Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240681.
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Goh, Kee Chuan. „The biosynthesis of β-lactams“. Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:24b6b29d-87cc-48f2-bd1b-bb64c663604f.
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This thesis reports the work done on two research projects which were carried out independently of each other but converge on the central theme of β-lactam biosynthesis. Chapter 1 provides an overview of biosynthesis in secondary metabolism, with special emphasis on current knowledge about the β-lactams. The first project, covered from Chapters 2 to 5, was part of our group's continuing effort to understand the structure and mechanism of Ring Expandase-Hydroxylase (REXH), an enzyme involved in the biosynthesis of cephalosporin C in Cephalosporium acremonium. REXH is a bifunctional enzyme, converting penicillin N to DAOC and thence to DAC. [diagram omitted from transcription] Chapter 3 discusses the investigation of purification protocols for native REXH and soluble recombinant REXH, as well as an improved refolding method for recombinant REXH expressed as inclusion bodies. Chapter 4 describes two new alternative substrates for REXH, viz. carba-DAOC and DAC, whilst the y-lactam analogue of penicillin N was not found to be a substrate for REXH. Chapter 5 summarises some structural investigations of REXH employing methods such as electrospray mass spectrometry, selective proteolysis and inhibition kinetics. [diagram omitted from transcription] The second project, covered from Chapters 6 to 9, represents the first biosynthetic studies on valclavam, an antifungal produced by Streptomyces antibioticus. Valclavam belongs to the family of clavams which includes clavulanic acid as its most well studied member. [diagram omitted from transcription] Chapter 7 details the development of methods for the bioassay, fermentation and isolation of valclavam. It also describes the isolation of a stable degradation fragment of valclavam which led to the revision of the structures of valclavam and Tü 1718B (another metabolite from the same organism). Chapter 8 gives an account of the whole-cell feeding experiments which strongly suggest that the primary metabolic precursors for valclavam are L-valine, L-arginine, L-methionine and glycerol. Chapter 9 reports the discovery of two enzymic activities, belonging to those of clavaminic acid synthase and proclavaminic acid amidino hydrolase, which are likely to be involved in the biosynthesis of valclavam. Together, the results of Chapters 8 and 9 point to an extensive overlap between the clavulanic acid pathway in Streptomyces clavuligerus and the valclavam pathway in Streptomyces antibioticus.
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Welchman, Elizabeth Victoria. „The chemistry of β lactams“. Thesis, University of Sunderland, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247775.
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Walker, Matthew David. „Diastereoselective reactions of atropisomeric lactams“. Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247569.
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Pérez, Bosch Maria. „Addicions conjugades a lactames bicícliques derivades del fenilglicinol: síntesi enantioselectiva de piperidines 3,4- i 3,4,5-substituïdes“. Doctoral thesis, Universitat de Barcelona, 2002. http://hdl.handle.net/10803/673099.
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La adición conjugada de cianocupratos de orden inferior a las lactamas insaturadas derivadas del fenilglilcinol transcurre con buenos rendimientos y elevada selectividad facial. En aquellas que poseen un sustituyente etilo en posición contigua al carbono electrófilo del doble enlace proporciona estereoselectivamente productos con una relación cis entre el sustituyente carbonado introducido y el grupo etilo. Estos resultados pueden justificarse considerando que la conformación del anillo de piperidina se halla condicionada por la configuración de un estereocentro, independientemente de la presencia de un sustituyente etilo, y que el ataque del cianocuprato tiene lugar bajo control estereoeléctrónico proporcionando el producto de control cinético debido a la irreversibilidad de la reacción.
Por otro lado, la adición de aniones estabilizados a una lactama insaturada que posee un sustituyente etilo contiguo al carbono electrófilo del doble proporciona compuestos que guardan una relación trans entre el sustituyente carbonado introducido en la adición y el grupo etilo. La estereoselectividad observada es atribuible a la reversibilidad de la reacción de adición conjugada de aniones estabilizados, lo que conduce al compuesto termodinámicamente más estable.
La utilidad sintética de las anteriores reacciones de adición conjugada se ha puesto de manifiesto con la síntesis enantioselectiva de diversas piperidinas cis- y trans-3,4-disustituidas.
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Ogliaruso, Michael A., und James F. Wolfe, Hrsg. Synthesis of Lactones and Lactams (1993). Chichester, UK: John Wiley & Sons, Inc., 1993. http://dx.doi.org/10.1002/9780470772522.
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Bhalla, Aman, Shamsher S. Bari und Jitender Bhalla. „Synthesis of Diverse β-Lactams: Role of Appended Hetero Moiety on Its Activity“. In Beta-Lactams, 1–39. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_1.
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Sowinska, Marta, Maja Morawiak, Zofia Urbanczyk-Lipkowska und Jolanta Solecka. „Nanochemistry in Drug Design“. In Beta-Lactams, 311–34. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_10.
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Palomo, Claudio, und Mikel Oiarbide. „Asymmetric Synthesis of β-Lactams via the Ketene-Imine Cycloaddition“. In Beta-Lactams, 335–72. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_11.
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Bhattacharya, Prabuddha, Sansa Dutta, Koushik Chandra und Amit Basak. „The Never-Ending Story of β-Lactams: Use as Molecular Scaffolds and Building Blocks“. In Beta-Lactams, 373–419. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_12.
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Bari, Shamsher S., Aman Bhalla und Jitender Bhalla. „Role of Transition Metal Reagents in β-Lactam Synthesis: New Paradigms“. In Beta-Lactams, 41–71. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_2.
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Klimczak, Urszula, Bartłomiej Furman und Bartosz Zambroń. „4-Vinyloxyazetidin-2-one, a Novel Substrate for β-Lactam Synthesis“. In Beta-Lactams, 73–104. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_3.
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Tidwell, Thomas T. „β-Lactams from Ketene-Imine Cycloadditions: An Update“. In Beta-Lactams, 105–28. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_4.
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Delpiccolo, Carina M. L., Maitena Martinez-Amezaga und Ernesto G. Mata. „Recent Approaches Toward the Generation of Molecular Diversity Based on β-Lactam Structures“. In Beta-Lactams, 129–62. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_5.
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Alcaide, Benito, Pedro Almendros und Cristina Aragoncillo. „Synthesis of Five-Membered Heterocycles Through β-Lactam Ring-Expansion Reaction“. In Beta-Lactams, 163–218. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_6.
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Konferenzberichte zum Thema "Lactams":
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McLoughlin, Eavan, Niamh O'Boyle und Mary Meegan. „Stories from Staudinger: Synthesis of chiral beta-lactams“. In 5th International Electronic Conference on Medicinal Chemistry. Basel, Switzerland: MDPI, 2019. http://dx.doi.org/10.3390/ecmc2019-06402.
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Kupka, Teobald, Piotr Lodowski, Maria Jaworska und Jan O. Dzięgielewski. „Semi empirical PM3 and spectroscopic studies on β-lactams“. In The first European conference on computational chemistry (E.C.C.C.1). AIP, 1995. http://dx.doi.org/10.1063/1.47686.
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Espadinha, Margarida, Jorge Dourado, Rocio Lajarin-Cuesta, Clara Herrera- Arozamena, Lídia Gonçalves, João Lopes, María Rodríguez-Franco, Daniel J. V. A. dos Santos, Cristobal de los Rios und Maria M. M. Santos. „Bicyclic lactams as potential inhibitors of the NMDA receptor“. In 4th International Electronic Conference on Medicinal Chemistry. Basel, Switzerland: MDPI, 2018. http://dx.doi.org/10.3390/ecmc-4-05631.
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McLoughlin, Eavan, und Niamh O'Boyle. „Enantiomeric β-Lactams for the Treatment of Breast Cancer“. In 6th International Electronic Conference on Medicinal Chemistry. Basel, Switzerland: MDPI, 2020. http://dx.doi.org/10.3390/ecmc2020-07507.
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Couture, Axel, Pierre Grandclaudon, Stéphane Lebrun und Gwenaëlle Liberge. „Convenient synthesis of functionalized α-methylenebutano-4-lactams or lactones“. In The 15th International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2011. http://dx.doi.org/10.3390/ecsoc-15-00570.
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Rezali, Nurul Syafiqah. „The Syntheses Of Fused Cyclic 5/6-Membered Ring Lactams Via Enamine Hydrogenation“. In 8th International Conference on Multidisciplinary Research 2019. European Publisher, 2020. http://dx.doi.org/10.15405/epsbs.2020.03.03.87.
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Khalifa, Abdulrhman Y., Mahmood Sh Magtoof und Husam M. Kredy. „Synthesis, spectral characterization, antioxidant and anticancer evaluation of 1, 2, 3-trisubstituted-γ-lactams“. In PROCEEDING OF THE 1ST INTERNATIONAL CONFERENCE ON ADVANCED RESEARCH IN PURE AND APPLIED SCIENCE (ICARPAS2021): Third Annual Conference of Al-Muthanna University/College of Science. AIP Publishing, 2022. http://dx.doi.org/10.1063/5.0093789.
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Prickett, Michelle, Joanne Cullina, Anna Lam und Manu Jain. „The Effects Of Single Agent Therapy With ²-lactams For Severe Cystic Fibrosis Exacerbations During Pregnancy“. In American Thoracic Society 2010 International Conference, May 14-19, 2010 • New Orleans. American Thoracic Society, 2010. http://dx.doi.org/10.1164/ajrccm-conference.2010.181.1_meetingabstracts.a1815.
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Pereira, Ulisses A., Luiz C. A. Barbosa, Célia R. A. Maltha, Antônio Jacinto Demuner und Andréa de L. Pimenta. „Synthesis of lactones and lactams analogues to rubrolides as inhibitors of Enterococcus faecalis biofilm formation“. In 15th Brazilian Meeting on Organic Synthesis. São Paulo: Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-15bmos-bmos2013_2013814154045.
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Gámez-Montaño, Rocío, Pedro A. Cano und Alejandro Islas-Jácome. „Synthesis of spiro-cyclohexendienone-gamma-lactams via free-radicals and study of thermal regioselective spirocyclization“. In The 21st International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2017. http://dx.doi.org/10.3390/ecsoc-21-04779.
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Berichte der Organisationen zum Thema "Lactams":
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Chiu, Chia-Yu, und Amara Sarwal. Impact of area under the curve-based vancomycin dosing combination with anti-pseudomonal beta-lactam antibiotics: a systematic review and meta-analysis. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, Dezember 2022. http://dx.doi.org/10.37766/inplasy2022.12.0025.
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Annotation:
Review question / Objective: Did AUC-based vancomycin dosing reduce acute kidney injury than trough-based dosing when combined with anti-pseudomonal beta-lactam antibiotic? Condition being studied: Patients received Vancomycin combined with anti-pseudomonal beta-lactam antibiotics and monitor with either trough-base dosing or AUC-based dosing vancomycin. Information sources: All study types except case reports, case series, and conference abstracts were considered. PubMed, Embase, Cochrane Library, and ClinicalTrials.gov were searched from inception to November2022.
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Mosher, Jennifer J., Meghan M. Drake, Susan L. Carroll, Zamin K. Yang, Christopher W. Schadt, Stephen D. Brown, Mircea Podar et al. Microbial Community Dynamics of Lactate Enriched Hanford Groundwaters. Office of Scientific and Technical Information (OSTI), Mai 2010. http://dx.doi.org/10.2172/986244.
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Meyer, Birte, und David Stahl. Syntrophic Degradation of Lactate in Methanogenic Co-cultures. Office of Scientific and Technical Information (OSTI), Mai 2010. http://dx.doi.org/10.2172/986317.
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Ma, Lianjia. Multichannel Simultaneous Determination of Activities of Lactate Dehydrogenase. Office of Scientific and Technical Information (OSTI), September 2000. http://dx.doi.org/10.2172/764689.
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Piper, Robert C. Parasite Lactate Dehydrogenase for Diagnosis of Plasmodium Falciparum. Phase II. Fort Belvoir, VA: Defense Technical Information Center, April 1997. http://dx.doi.org/10.21236/adb230017.
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Kim, Yuan, Edward M. Steadham, Steven M. Lonergan und Elisabeth J. Huff-Lonergan. Antioxidant Capacity of Calcium Lactate on m-Calpain Activity In Vitro. Ames (Iowa): Iowa State University, Januar 2009. http://dx.doi.org/10.31274/ans_air-180814-1237.
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Reeves, John T. Beta-Adrenergic Blockade and Lactate Metabolism during Exercise at High Altitude. Fort Belvoir, VA: Defense Technical Information Center, Januar 1993. http://dx.doi.org/10.21236/ada263544.
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Dou, Q. P. Synthetic Beta-Lactam Antibiotics as a Selective Breast Cancer Cell Apoptosis Inducer: Significance in Breast Cancer Prevention and Treatment. Fort Belvoir, VA: Defense Technical Information Center, März 2007. http://dx.doi.org/10.21236/ada572620.
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Li, Fenglei. Automated High Throughput Protein Crystallization Screening at Nanoliter Scale and Protein Structural Study on Lactate Dehydrogenase. Office of Scientific and Technical Information (OSTI), August 2006. http://dx.doi.org/10.2172/892735.
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Qian, Chengliang. Structurally Integrated Photoluminescence-Based Lactate Sensor Using Organic Light Emitting Devices (OLEDs) as the Light Source. Office of Scientific and Technical Information (OSTI), Januar 2006. http://dx.doi.org/10.2172/892736.
