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Wendel L. Nelson - One of the best experts on this subject based on the ideXlab platform.
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Electrophilic opioid ligands. Oxygen tethered alpha-methylene-gamma-lactone, acrylate, isothiocyanate, and epoxide derivatives of 6 beta-naltrexol.
Journal of medicinal chemistry, 1992Co-Authors: William E. Dasher, Peter Klein, Wendel L. NelsonAbstract:O6-Ether derivatives of 6 beta-naltrexol in which the ether substituent includes various electrophilic groups have been synthesized in an effort to examine structure-activity requirements at the 6 beta-substituent for receptor affinity and irreversibility of binding in opioid receptor preparations. A series of tethered 6 beta-ethers having terminal epoxides, alpha-methylene-gamma-lactones, and an isothiocyanate group were prepared. The stereochemistry of the alpha-methylene-gamma-lactones was established by convergent synthesis of their reduction products from epoxides of known absolute stereochemistry. In general, the tested compounds showed comparable affinity and selectivity for the receptor subtypes. All were found with high affinity for mu-sites. The terminal epoxide ether diastereomers 8 and 9 were not bound irreversibly in the assay for total opioid receptors. The alpha-methylene-gamma-lactone diastereomers 10 and 11, and their O14-acetyl precursors 20 and 21, respectively, varied in their irreversible effects, but where noted these effects were mu-site selective. Methacrylate ether 7 and isothiocyanate ether 12 were bound irreversibly at both mu- and delta-sites.
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Electrophilic .gamma.-lactone .kappa.-opioid receptor probes. Analogs of 2'-hydroxy-2-(tetrahydrofurfuryl)-5,9-dimethyl-6,7-benzomorphan diastereomers
Journal of medicinal chemistry, 1991Co-Authors: Peter Klein, Wendel L. NelsonAbstract:Benzomorphans with an electrophilic group in the nitrogen substituent were prepared as potentially irreversible ligands for the kappa-opioid receptor. These were synthesized from products of the reaction of normetazocine with the enantiomers of 5-(iodomethyl)-gamma-butyrolactone (11). alpha-Methylene gamma-lactones 5 and 7 and endocyclic alpha,beta-unsaturated gamma-lactones 8 and 9 were prepared from the corresponding saturated gamma-lactones 13 and 23 possessing the "active" (1R,5R,9R)-benzomorphan stereochemistry. Only gamma-lactones 8, 9, 13, and 23, lacking the exocyclic methylene group, retain significant affinities for opioid receptor binding sites when compared with the reference compounds (2"S)-3 and (2"R)-3. As observed with these references compounds, greater binding affinity is also seen with gamma-lactone diastereomers having the 2"S stereochemistry in the nitrogen substituent. Although the gamma-lactones do not bind irreversibly in opioid receptor preparations, they do show kappa-receptor selectivities comparable to those observed for the reference compounds.
Jacek Bardowski - One of the best experts on this subject based on the ideXlab platform.
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Alternative lactose catabolic pathway in Lactococcus lactis IL1403
Applied and Environmental Microbiology, 2005Co-Authors: Tamara Aleksandrzak-piekarczyk, Pierre Renault, Jacek BardowskiAbstract:In this study, we present a glimpse of the diversity of Lactococcus lactis subsp. lactis IL1403 beta-galactosidase phenotype-negative mutants isolated by negative selection on solid media containing cellobiose or lactose and X-Gal (5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside), and we identify several genes essential for lactose assimilation. Among these are ccpA (encoding catabolite control protein A), bglS (encoding phospho-beta-glucosidase), and several genes from the Leloir pathway gene cluster encoding proteins presumably essential for lactose metabolism. The functions of these genes were demonstrated by their disruption and testing of the growth of resultant mutants in lactose-containing media. By examining the ccpA and bglS mutants for phospho-beta-galactosidase activity, we showed that expression of bglS is not under strong control of CcpA. Moreover, this analysis revealed that although BglS is homologous to a putative phospho-beta-glucosidase, it also exhibits phospho-beta-galactosidase activity and is the major enzyme in L. lactis IL1403 involved in lactose hydrolysis.
Ricky L Ulrich - One of the best experts on this subject based on the ideXlab platform.
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quorum quenching enzymatic disruption of n acylhomoserine lactone mediated bacterial communication in burkholderia thailandensis
Applied and Environmental Microbiology, 2004Co-Authors: Ricky L UlrichAbstract:Many species of gram-negative bacteria communicate by synthesizing, secreting, and responding to Nacylhomoserine lactones (AHLs), a mechanism termed quorum sensing. Several investigations have characterized numerous AHL-degrading enzymes (AiiA lactonases) encoded by environmental isolates of Bacillus spp. The Burkholderia thailandensis quorum system is comprised of at least three AHL synthases (AHSs) and five transcriptional regulators belonging to the LuxIR class of proteins. Expression of the Bacillus anthracis (Ames strain) AiiA lactonase in B. thailandensis completely abolished the accumulation of N-decanoylhomoserine lactone (C10-HSL) and N-octanoylhomoserine lactone (C8-HSL), reduced N-hexanoylhomoserine lactone (C6HSL) levels, altered both swarming and twitching motility, caused a significant increase in generation time, and affected carbon metabolism. In contrast, heterologous expression of the Bacillus cereus strain A24 AiiA lactonase in B. thailandensis reduced the concentrations of C6-HSL, C8-HSL, and C10-HSL to nondetectable levels; altered both swarming and twitching motility; and caused fluctuations in carbon utilization. Individual disruption of the B. thailandensis AHSs, specifically disruption of the btaI1 and btaI3 genes, which encode the proteins that direct the synthesis of C8-HSL and C6-HSL, respectively, caused the hyper-beta-hemolysis of sheep erythrocytes on blood agar plates. In contrast, AHL cleavage in B. thailandensis by the Bacillus AiiA lactonases failed to enhance beta-hemolytic activity. The results of this study demonstrate that heterologous expression of Bacillus sp. AiiA lactonases in B. thailandensis reduced AHL accumulation, affected both swarming and twitching motility, increased generation time, altered substrate utilization, and prevented the betahemolysis of sheep erythrocytes.
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mutational analysis and biochemical characterization of the burkholderia thailandensis dw503 quorum sensing network
Journal of Bacteriology, 2004Co-Authors: Ricky L Ulrich, Harry B Hines, N Parthasarathy, Jeffrey A JeddelohAbstract:Numerous gram-negative bacteria communicate and regulate gene expression through a cell density-responsive mechanism termed quorum sensing (QS), which involves the synthesis and perception of diffusible N-acyl-homoserine lactones (AHL). In this study we genetically and physiologically characterized the Burkholderia thailandensis DW503 QS network. In silico analysis of the B. thailandensis genome revealed the presence of at least three AHL synthases (AHS) and five transcriptional regulators belonging to the LuxIR family of proteins. Mass spectrometry demonstrated that wild-type B. thailandensis synthesizes N-hexanoyl-homoserine lactone (C6-HSL), N-octanoyl-homoserine lactone (C8-HSL), and N-decanoyl-homoserine lactone (C10-HSL). Mutation of the btaI1 (luxI) AHS gene prevented accumulation of C8-HSL in culture supernatants, enhanced beta-hemolysis of sheep erythrocytes, increased lipase production, and altered colony morphology on swarming and twitching motility plates. Disruption of the btaI3 (luxI) AHS prevented biosynthesis of C6-HSL and increased lipase production and beta-hemolysis, whereas mutagenesis of the btaI2 (luxI) allele eliminated C10-HSL accumulation and reduced lipase production. Complementation of the btaI1 and btaI3 mutants fully restored the synthesis of C8-HSL and C6-HSL to parental levels. In contrast, mutagenesis of the btaR1, btaR3, btaR4, and btaR5 (luxR) transcriptional regulators had no effect on AHL accumulation, enhanced lipase production, and resulted in extensive beta-hemolysis on sheep blood agar plates. Furthermore, interruption of the btaI1, btaR1, and btaR3 genes altered colony morphology on twitching and swarming motility plates and induced pigmentation. Additionally, phenotypic microarray analysis indicated that QS in B. thailandensis both positively and negatively affects the metabolism of numerous substrates, including citric acid, formic acid, glucose 6-phosphate, capric acid, γ-hydroxybutyric acid, and d-arabinose. These results demonstrate that mutagenesis of the B. thailandensis QS system affects various cellular processes, including lipase production, swarming and twitching motility, beta-hemolysis of sheep erythrocytes, and carbon metabolism and/or transport.
Guolin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Two diterpenes and three diterpene glucosides from Phlogacanthus curviflorus.
Journal of natural products, 2005Co-Authors: Xiao-hong Yuan, Xiu-yun Zhang, Min Zhou, Guolin ZhangAbstract:Two new diterpene lactones, phlogacantholides B (1) and C (2), and three new diterpene lactone glucosides, phlogacanthosides A (3), B (4), and C (5), together with lupeol, beta-sitosterol, betulin, P-daucosterol, (+)syringaresinol, and (+)-syringaresinol-4-O-beta-D-glucopyranoside, were isolated from the roots of Phlogacanthus curviflorus. Their structures were elucidated by chemical and spectroscopic evidence. The structure, including the relative configuration of phlogacantholide B (1), was confirmed by X-ray crystallographic analysis of its diacetate (6).
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phytoecdysteroids and glycoceramides from eriophyton wallchii
Steroids, 2004Co-Authors: Yinggang Luo, Guolin ZhangAbstract:Two new compounds, 28-epi-cyasterone and eriophytonoide, along with I I known compounds, cyasterone, ajuforrestins A and 13, 20-hydroxyecdysone, polypodin 13, ajugalactone, 8-O-acetylharpagid, apigenin, N-[2hydroxy-(nonadecanoyl-tricosanoyl)1-4-hydroxy-trans-8-sphingenine, beta-sitosterol, and daucosterol, were isolated from the aqueous ethanolic extract of the whole herb of Eriophyton wallchii Benth. The structures of 28-epi-cyasterone and eriophytonoide were elucidated as (22R,24S,25S,28S)-5beta-stigmast-7-en-26-oic acid, 2beta,3beta,14,20,22,28-hexahydroxy-6-oxo-gamma-lactone, and 1-O-beta-D-glucopyranosyl -(2S,3S,4R,8E)-2- [(2R)-2-hydroxyhexadecanoylamino]-1,3,4-octadecanetriol-8-ene, respectively, on the basis of spectral and chemical evidence. (C) 2004 Elsevier Inc. All rights reserved.
Tamara Aleksandrzak-piekarczyk - One of the best experts on this subject based on the ideXlab platform.
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Alternative lactose catabolic pathway in Lactococcus lactis IL1403
Applied and Environmental Microbiology, 2005Co-Authors: Tamara Aleksandrzak-piekarczyk, Pierre Renault, Jacek BardowskiAbstract:In this study, we present a glimpse of the diversity of Lactococcus lactis subsp. lactis IL1403 beta-galactosidase phenotype-negative mutants isolated by negative selection on solid media containing cellobiose or lactose and X-Gal (5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside), and we identify several genes essential for lactose assimilation. Among these are ccpA (encoding catabolite control protein A), bglS (encoding phospho-beta-glucosidase), and several genes from the Leloir pathway gene cluster encoding proteins presumably essential for lactose metabolism. The functions of these genes were demonstrated by their disruption and testing of the growth of resultant mutants in lactose-containing media. By examining the ccpA and bglS mutants for phospho-beta-galactosidase activity, we showed that expression of bglS is not under strong control of CcpA. Moreover, this analysis revealed that although BglS is homologous to a putative phospho-beta-glucosidase, it also exhibits phospho-beta-galactosidase activity and is the major enzyme in L. lactis IL1403 involved in lactose hydrolysis.