共查询到20条相似文献，搜索用时 15 毫秒
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Florent Darriet Jean‐Marie Desjobert Jean Costa Alain Muselli 《Phytochemical analysis : PCA》2009,20(4):279-292
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Diane R. Lester Linda M.
ster Martin Svenda Inger Andersson 《Acta Crystallographica. Section D, Structural Biology》2004,60(9):1618-1621
Cephamycins are broad‐spectrum β‐lactam antibiotics that show resistance to certain forms of β‐lactamases. They differ from cephalosporins by the presence of a methoxyl group at the C‐7α position. The gene products of cmcI and cmcJ are believed to control 7α‐methoxylation of cephalosporins through successive steps of hydroxylation and methylation. Here, the expression, purification, crystallization and initial data‐collection statistics of the 236‐amino‐acid protein product of cmcI from Streptomyces clavuligerus is reported. The crystals belong to space group P21, with unit‐cell parameters a = 93.6, b = 182.6, c = 103.2 Å, β = 91.05°. Diffraction data were collected to 2.5 Å. 相似文献
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Ismail Yener Mustafa Abdullah Yilmaz Ozge Tokul Olmez Mehmet Akdeniz Fetullah Tekin Nesrin Hasimi Mehmet Huseyin Alkan Mehmet Ozturk Abdulselam Ertas 《化学与生物多样性》2020,17(3)
Representatives of the Achillea genus are widely used as foods or nutraceuticals. Considering the increasing demand for herbal dietary supplements with health promoting effects, the objective of this research was to evaluate the chemical composition and biological activities of the essential oils obtained from sixteen Achillea species (A. biebersteinii, A. wilhelmsii subsp. wilhelmsii, A. aleppica subsp. zederbaueri, A. vermicularis, A. monocephala, A. nobilis, A. goniocephala, A. sintenisii, A. coarctata, A. kotschyi subsp. kotschyi, A. millefolium subsp. millefolium, A. lycaonica, A. spinulifolia, A. teretifolia, A. setacea, and A. schischkinii). Anticholinesterase, antiurease, antityrosinase enzymes inhibition, antioxidant, antimicrobial, toxic and cytotoxic activities of obtained essential oils were investigated. DPPH activities were found to be very low in all studied samples, while ABTS and CUPRAC antioxidant activities were found to be moderate. In addition, all samples were found to have moderate anticholinesterase and antimicrobial effects. It has been determined that the studied species have low cytotoxicity and high toxicity. Besides, chemical composition of the essential oils were determined by GC/MS and the results were chemometrically analyzed. The chemometric analyses of Achillea species collected from nine different regions were accomplished by principal component analysis (PCA) and hierarchical cluster analysis (HCA) techniques. According to the PCA analysis, A. nobilis subsp. neilreichii was found to be different from all studied species in terms of essential oil composition. The major components found in these species were piperitone, camphor, α‐terpinene, eucalyptol, artemisia ketone, endo‐borneol, β‐eudesmol and verbenol. The fact that camphor was toxic and found in majority of the studied species stands out as a remarkable result. 相似文献
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Larry R. Masterson Marcus A. Etienne Fernando Porcelli George Barany Robert P. Hammer Gianluigi Veglia 《Peptide Science》2007,88(5):746-753
The use of α,α‐disubstituted amino acids represents a valuable strategy to exercise conformational control in peptides. Incorporation of the nonstereogenic α‐aminoisobutyryl‐glycyl (Aib‐Gly) dipeptidyl sequence into i + 1 and i + 2 positions of an acyclic peptide sequence, originally designed and investigated by Gellman and coworkers, [H‐Arg‐Tyr‐Val‐Glu‐Val‐Yyy‐Xxx‐Orn‐Lys‐Ile‐Leu‐Gln‐NH2] nucleates a stable [2:4] left‐handed type I′ β‐turn in water. NMR spectra show that this newly designed β‐hairpin does not aggregate in water up to a concentration of ∼1 mM, and that its backbone conformation is superimposable on corresponding hairpins containing the D Pro‐Gly (literature) and Aib‐D Ala (this work) sequences. The Aib‐Gly turn‐inducer sequence eliminates complications because of cis–trans isomerization of Zzz‐Pro bonds, and constitutes an attractive alternative to the proteogenic Asn‐Gly and nonproteogenic D Pro‐Gly motifs previously suggested as turn‐inducer sequences. These design principles could be exploited to prepare water‐soluble β‐hairpin peptides with robust structures and novel function. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 746–753, 2007. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com 相似文献
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Olivier Hennebert Sonia Chalbot Severine Alran Robert Morfin 《The Journal of steroid biochemistry and molecular biology》2007,104(3-5):326
Dehydroepiandrosterone (DHEA) is 7α-hydroxylated by the cytochome P450 7B1 (CYP7B1) in the human brain and liver. This produces 7α-hydroxy-DHEA that is a substrate for 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) which exists in the same tissues and carries out the inter-conversion of 7α- and 7β-hydroxy-DHEA through a 7-oxo-intermediary. Since the role of 11β-HSD1 is to transform the inactive cortisone into active cortisol, its competitive inhibition by 7α-hydroxy-DHEA may support the paradigm of native anti-glucocorticoid arising from DHEA. Therefore, our objective was to use human tissues to assess the presences of both CYP7B1 and 11β-HSD1. Human skin was selected then and used to test its ability to produce 7α-hydroxy-DHEA, and to test the interference of 7α- and 7β-hydroxy-DHEA and 7-oxo-DHEA with the 11β-HSD1-mediated oxidoreduction of cortisol and cortisone. Immuno-histochemical studies showed the presence of both CYP7B1 and 11β-HSD1 in the liver, skin and tonsils. DHEA was readily 7α-hydroxylated when incubated using skin slices. A S9 fraction of dermal homogenates containing the 11β-HSD1 carried out the oxidoreduction of cortisol and cortisone. Inhibition of the cortisol oxidation by 7α-hydroxy-DHEA and 7β-hydroxy-DHEA was competitive with a Ki at 1.85 ± 0.495 and 0.255 ± 0.005 μM, respectively. Inhibition of cortisone reduction by 7-oxo-DHEA was of a mixed type with a Ki at 1.13 ± 0.15 μM. These findings may support the previously proposed native anti-glucocorticoid paradigm and suggest that the 7α-hydroxy-DHEA production is a key for the fine tuning of glucocorticoid levels in tissues. 相似文献
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Göran Karlsson Cecilia Persson Maxim Mayzel Mattias Hedenström Lars Backman 《Proteins》2016,84(4):461-466
Cell motility is dependent on a dynamic meshwork of actin filaments that is remodelled continuously. A large number of associated proteins that are severs, cross‐links, or caps the filament ends have been identified and the actin cross‐linker α‐actinin has been implied in several important cellular processes. In Entamoeba histolytica, the etiological agent of human amoebiasis, α‐actinin is believed to be required for infection. To better understand the role of α‐actinin in the infectious process we have determined the solution structure of the C‐terminal calmodulin‐like domain using NMR. The final structure ensemble of the apo form shows two lobes, that both resemble other pairs of calcium‐binding EF‐hand motifs, connected with a mobile linker. Proteins 2016; 84:461–466. © 2016 Wiley Periodicals, Inc. 相似文献
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贵州老鹰茶（红果黄肉楠）挥发油成分研究 总被引：4，自引：0，他引：4
利用常压水蒸气蒸馏提取贵州老鹰茶（Actinoaphne cupularis(Hembsl.)Gamble)的挥发油,挥发油得率0．21％,用气相色谱－质谱联用仪进行定性分析。结合计算机检索技术,对挥发油的化学成分进行分离鉴定,NIST化合物谱库检索,应用气相色谱峰面积归一化法测定各成分的相对含量。从Actinodaplme cupularis挥发油中检出138种成分,鉴定出66种成分,占挥发油组成的47．83％,主要成分是异丁子香烯（I*socaryophillene),含量8＝28％;其次是大根香叶烯B（Germacrene,1,2,3,4,4a,5,6,8a-octahydro-7-methyl-4-methylene-1-(1-methylethyl)-(1.α.,4a.α.,8a.α.)-),含量6．57％,其挥发油成分主要是萜类。 相似文献
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A 34‐residue α/β peptide [IG(28–61)], derived from the C‐terminal part of the B3 domain of the immunoglobulin binding protein G from Streptoccocus, was studied using CD and NMR spectroscopy at various temperatures and by differential scanning calorimetry. It was found that the C‐terminal part (a 16‐residue‐long fragment) of this peptide, which corresponds to the sequence of the β‐hairpin in the native structure, forms structure similar to the β‐hairpin only at T = 313 K, and the structure is stabilized by non‐native long‐range hydrophobic interactions (Val47–Val59). On the other hand, the N‐terminal part of IG(28–61), which corresponds to the middle α‐helix in the native structure, is unstructured at low temperature (283 K) and forms an α‐helix‐like structure at 305 K, and only one helical turn is observed at 313 K. At all temperatures at which NMR experiments were performed (283, 305, and 313 K), we do not observe any long‐range connectivities which would have supported packing between the C‐terminal (β‐hairpin) and the N‐terminal (α‐helix) parts of the sequence. Such interactions are absent, in contrast to the folding pathway of the B domain of protein G, proposed recently by Kmiecik and Kolinski (Biophys J 2008, 94, 726–736), based on Monte‐Carlo dynamics studies. Alternative folding mechanisms are proposed and discussed. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 469–480, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com 相似文献
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Tomas Erban Michaela Erbanova Marta Nesvorna Jan Hubert 《Archives of insect biochemistry and physiology》2009,71(3):139-158
The adaptation of nine species of mites that infest stored products for starch utilization was tested by (1) enzymatic analysis using feces and whole mite extracts, (2) biotests, and (3) inhibition experiments. Acarus siro, Aleuroglyphus ovatus, and Tyroborus lini were associated with the starch‐type substrates and maltose, with higher enzymatic activities observed in whole mite extracts. Lepidoglyphus destructor was associated with the same substrates but had higher activities in feces. Dermatophagoides farinae, Chortoglyphus arcuatus, and Caloglyphus redickorzevi were associated with sucrose. Tyrophagus putrescentiae and Carpoglyphus lactis had low or intermediate enzymatic activity on the tested substrates. Biotests on starch additive diets showed accelerated growth of species associated with the starch‐type substrates. The inhibitor acarbose suppressed starch hydrolysis and growth of the mites. We suggest that the species with higher starch hydrolytic activity in feces were more tolerant to acarbose, and α‐amylase and α‐glucosidase of synanthropic mites are suitable targets for inhibitor‐based strategies of mite control. © 2009 Wiley Periodicals, Inc. 相似文献
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Jinyoung Son Misun Kim Ilo Jou Kyoung Chan Park Hee Young Kang 《Pigment cell & melanoma research》2014,27(2):201-208
Inflammatory cytokines are closely related to pigmentary changes. In this study, the effects of IFN‐γ on melanogenesis were investigated. IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis in B16 melanoma cells and normal human melanocytes. MITF mRNA and protein expressions were significantly inhibited in response to IFN‐γ. IFN‐γ inhibited CREB binding to the MITF promoter but did not affect CREB phosphorylation. Instead, IFN‐γ inhibited the association of CBP and CREB through the increased association between CREB binding protein (CBP) and STAT1. These findings suggest that IFN‐γ inhibits both basal and α‐MSH‐induced melanogenesis by inhibiting MITF expression. The inhibitory action of IFN‐γ in α‐MSH‐induced melanogenesis is likely to be associated with the sequestration of CBP via the association between CBP and STAT1. These data suggest that IFN‐γ plays a role in controlling inflammation‐ or UV‐induced pigmentary changes. 相似文献
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Helmut Spreitzer Iris Piringer Andrea Pichler Wolfgang Holzer Jana Ruzicka Michael Widhalm 《Chirality》1999,11(2):133-138
Several stereoisomeric, monocyclic analogs of (−)‐β‐vetivone (1), one of the main constituents of vetiver oil, were studied to examine if the olfactory properties of (−)‐β‐vetivone (1) could be reproduced from these structurally simpler, synthetically accessible compounds. The effects of diastereomeric and enantiomeric structural differences on the odor of the partial vetivone structure were studied. A chiral phenyl sulfoximine was used for separation of the racemic mixtures. Detailed nuclear magnetic resonance (NMR)‐spectroscopic studies (1H, 13C) were used to determine relative configurations whereas absolute configurations were determined by circular dichroism (CD) methods. Chirality 11:133–138, 1999. © 1999 Wiley‐Liss, Inc. 相似文献
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Helmut Spreitzer Iris Piringer Andrea Pichler Wolfgang Holzer Petra Schreder Michael Widhalm 《Chirality》1999,11(1):14-20
Several, stereoisomeric, monocyclic analogs of (−)‐β‐vetivone (1), one of the main constituents of vetiver oil, were studied to determine whether the olfactory properties of (−)‐β‐vetivone (1) could be reproduced from these structurally simpler, synthetically accessible compounds. The effects of diastereomeric and enantiomeric structural differences on the odor of the partial vetivone structure were determined. A chiral phenyl sulfoximine was used for separation of the racemic mixtures. Detailed nuclear magnetic resonance (NMR) spectroscopic studies (1H, 13C) were used to determine relative configurations while absolute configurations were determined by circular dichroism (CD) methods. Chirality 11:14–20, 1999. © 1999 Wiley‐Liss, Inc. 相似文献
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A conformational analysis of peptides having dipropylglycine (Dpg) or 1‐aminocycloheptanecarboxylic acid (Ac7c) within l ‐leucine (Leu) residues was conducted in solution and in a crystal state. Dpg and Ac7c had similar structures with acyclic and cyclic side chains, respectively. FTIR, 1H NMR, and CD spectra measurements revealed that the preferred conformations of Dpg‐ and Ac7c‐containing l ‐Leu peptides in solution were similar; both had a right‐handed (P) 310‐helix. The Dpg‐containing octapeptide adopted a right‐handed (P) α‐helix in the crystal state. Dpg and Ac7c homopeptides had planar and helical structures as their preferred conformations, respectively; however, Dpg‐ and Ac7c‐containing l ‐Leu peptides adopted similar structures in solution. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 210–218, 2016. 相似文献
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Nobuo Okazaki Maki Kumei Miho Manzoku Seiki Kuramitsu Mikako Shirouzu Akeo Shinkai Shigeyuki Yokoyama 《Acta Crystallographica. Section F, Structural Biology Communications》2007,63(3):173-177
TTHA0281 is a hypothetical protein from Thermus thermophilus HB8 that belongs to an uncharacterized protein family, UPF0150, in the Pfam database and to COG1598 in the National Center for Biotechnology Information Database of Clusters of Orthologous Groups. The X‐ray crystal structure of the protein was determined by a multiple‐wavelength anomalous dispersion technique and was refined at 1.9 Å resolution to a final R factor of 18.5%. The TTHA0281 monomer adopts an α‐β‐β‐β‐α fold and forms a homotetramer. Based on the properties and functions of structural homologues of the TTHA0281 monomer, the TTHA0281 protein is speculated to be involved in RNA metabolism, including RNA binding and cleavage. 相似文献
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Jia Wang Dan McElheny Yanwen Fu Guangyu Li Joohyun Kim Zhe Zhou Ling Wu Timothy A. Keiderling Robert P. Hammer 《Peptide Science》2009,92(5):452-464
Cα,α‐disubstituted amino acids (ααAAs) are widely used to conformationally constrain peptides. A series of pentapeptides containing dipropylglycine (Dpg) at alternating positions and their α‐amino acid counterpart L ‐norvaline (Nva) analogues were synthesized to fully investigate the impact of Dpg on peptide backbone structure in aqueous solution. CD, VCD, and NMR spectral analysis suggest that Dpg containing peptides adopt more ordered structures relative to their Nva containing analogues. The central residues (Ala, Thr, Tyr, Val) and the charged side‐chains of Glu and Lys play important roles in the degree of peptide folding. Hydrophobic and branched residues (Val, Tyr) at the central position of the peptide produce greater folding as judged by CD and NMR. Variation of the chemical shift with temperature (Δδ/ΔT NH) of Ac‐Glu‐Dpg‐Tyr‐Dpg‐Lys‐NH2 suggests a series of i → i + 3 hydrogen bonds between the N‐terminal acetyl carbonyl and the Tyr3 NH, and the Glu1 carbonyl and the Dpg4 NH. The solution conformation of Ac‐Glu‐Dpg‐Tyr‐Dpg‐Lys‐NH2 calculated from NMR‐derived constraints shows a 310‐helical structure (two repetitive type‐III β‐turns) at residues 1‐4, which is supported by 2D NMR, CD, and VCD spectra. Analysis of NMR‐derived models of these peptides suggest that there is a strong hydrophobic interaction of the pro‐S propyl side chain of Dpg2 and the Tyr3 side‐chain that may be a strong stabilizing force of the peptide folding in water. © 2009 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 92: 452–464, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com 相似文献
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The NMR and molecular dynamics methods are used to study the conformations of a hexapeptide, GRGDTP, which has been shown to be accessible to various types of cell‐adhesion based cellular behaviors such as cell‐to‐matrix interactions, cell differentiation, immunogenicity development, gene expression, angiogenesis, metastasis, sex determination and gamete fusion. 1H‐NMR results indicate the existence of weak 5→2 hydrogen bonded β‐turn type‐III. Molecular simulation studies using a mixed protocol of distance geometry, constrained minimization, restrained molecular dynamics followed by energy minimization resulted additional conformations that include about 64% of population of inverse γ‐turn (HB, 3→1) and about 35% population of γ‐turn (HB, 4→2). The inter‐proton distances observed in γ‐and inverse γ‐turns are also consistent with the NMR constraints. The variable internal hydrogen bonding due to γ‐turns initiated at Gly 1 and Arg 2 , and its tendency to inter‐convert between γ‐and inverse γ‐turn conformations imply that the peptide is flexible in nature. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 460–471, 2013. 相似文献