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1.
The effect of weakly coordinating anions, , as axial ligands on the formation and coordination chemistry of verdoheme analogues have been examined. Two new five-coordinate and stable iron(II) verdoheme analogues, [OEOPFeIIX], where OEOP is the monoanion of octaethyloxoporphyrin and X = AsF6 and SbF6, have been isolated. The compounds have been characterized by different spectroscopic methods as well as elemental analysis. 1H NMR spectroscopy and magnetic moment measurements show that the [OEOPFeIIX] are paramagnetic and iron is five-coordinate. Exposure of dichloromethane solutions of [OEOPFeIIX] (X = AsF6 (2), SbF6 (3)) to dioxygen result in their transformation into the μ-oxo bridged compounds, [(OEOPFe)2O](X)2 (X = AsF6 (4), SbF6 (5)). The structures of 4 and 5 have been determined by X-ray diffraction analysis, both are structurally similar with a P21/c space group in the monoclinic crystal system.  相似文献   

2.
RNA modifications are being recognized as an essential factor in gene expression regulation. They play essential roles in germ line development, differentiation and disease. In eukaryotic mRNAs, N6-adenosine methylation (m6A) is the most prevalent internal chemical modification identified to date. The m6A pathway involves factors called writers, readers and erasers. m6A thus offers an interesting concept of dynamic reversible modification with implications in fine-tuning the cellular metabolism. In mammals, FTO and ALKBH5 have been initially identified as m6A erasers. Recently, FTO m6A specificity has been debated as new reports identify FTO targeting N6,2′-O-dimethyladenosine (m6Am). The two adenosine demethylases have diverse roles in the metabolism of mRNAs and their activity is involved in key processes, such as embryogenesis, disease or infection. In this article, we review the current knowledge of their function and mechanisms and discuss the existing contradictions in the field. This article is part of a Special Issue entitled: mRNA modifications in gene expression control edited by Dr. Soller Matthias and Dr. Fray Rupert.  相似文献   

3.
An efficient synthesis of a series of 6-chloro-3-substituted-[1,2,4]triazolo[4,3-b]pyridazines is described via intramolecular oxidative cyclization of various 6-chloropyridazin-3-yl hydrazones with iodobenzene diacetate. The structures of the newly synthesized compounds were assigned on the basis of elemental analysis, IR, NMR (1H and 13C) and mass spectral data. All the thirty three compounds 3a-q and 4b-q synthesized in the present study were evaluated for their in vitro cytotoxic activities against two Acute Lymphoblastic Leukemia (ALL) cell lines named, SB-ALL and NALM-6, and a human breast adenocarcinoma cell lines (MCF-7). The results revealed that triazoles 4 exhibit better cytotoxicity than their hydrazone precursors 3. Among triazoles, compounds 4f, 4j and 4q exhibited potent cytotoxic activity against SB-ALL and NALM-6 with IC50 values in the range of ∼1.64–5.66 μM and ∼1.14–3.7 μM, respectively, compared with doxorubicin (IC50 = 0.167 μM, SB-ALL). Compounds 4f, 4j and 4q were subjected to apoptosis assay after 48 h treatment and these compounds induced apoptosis of NALM-6 cells via caspase 3/7 activation. Results revealed that compound 4q represents potential promising lead.  相似文献   

4.
Three new compounds (13) and 20 known compounds were isolated from the rhizomes and roots of Sophora tonkinensis, and all the isolates were tested for their inhibitory activity against IL-6 production in HMC-1 cells stimulated by PMA plus ionophore, A23187. Of the tested compounds, compounds 1, 5, 9, and 21 were found to potently inhibit IL-6 production with IC50 values of 1.62, 0.73, 3.01, and 4.02 μM, respectively.  相似文献   

5.
A.M. El-Badry 《BBA》1974,333(2):366-377
Hexosediphosphatase (d-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) has been isolated, purified, and crystallized, from previously isolated spinach chloroplasts. The effects of various anions, cations, and sulfhydryl compounds were tested, and activation by Mg2+, glycine, HCO3?, and sulfhydryl compounds is described. The purified enzyme is very specific for fructose 1,6-diphosphate and does not attack sedoheptulose-1,7-bisphosphate. The s20 value of the enzyme was 7.7, from which the molecular weight of the enzyme was estimated as 140 000.  相似文献   

6.
Robert H. White 《Chirality》1996,8(4):332-340
The configuration at the C-9 of methanopterin (MPT) has been determined by comparing the circular dichroism (CD) spectra of MPT and its hydrolytic fragment, 1-[4-[[1-(2-amino-7-methyl-4-hydroxy-6-pteridinyl)-ethyl]amino]phenyl]-1-deoxy-D -ribitol (HP-1), with the CD spectra of a series of model compounds of known stereochemistry. These compounds included (S)-6-[1-(4-carboxymethylanilino)ethyl]pterin, (S-6(1-hydroxyethyl)-7-methylpterin, (S-6-(1-hydroxyethyl)pterin, (R)-6-(1-phenoxyethyl)pterin, D (+)-neopterin, and L -biopterin. From this comparison it was concluded that MPT has the R configuration at C-9 and is thus configurationally related to D (+)-neopterin, which has the S configuration at C-1. From previous work establishing the relative stereochemistry at C-6, C-7, and C-9 of N5-N10-methenyl-5,6,7,8-tetrahydromethanopterin (N5-N10-methenyl-H4MPT) as R, S, and R, respectively, it is clear that the remaining asymmetric carbons at C-6 and C-7 of H4MPT have the S and S configuration, respectively. Comparison of these latter two positions to the equivalent carbons in 5,6,7,8-tetrahydrofolate (H4folate) show that the steps involved in the biological reduction of MPT to H4MPT occur with the same stereochemical outcome as those involved in the biological reduction of folate to H4folate. © 1996 Wiley-Liss, Inc.  相似文献   

7.
Two extended metal atom chain (EMAC) compounds having a symmetrical Co36+ metal chain encapsulated by two N,N′-bis[(6′-pyrid-2″-yl)aminopyrid-2′yl]-bismethyl-2,6-diaminopyridinate (mpeptea) ligands have been prepared in good yield, and they have been structurally characterized by X-ray crystallography, magnetic and electrochemical measurements and spectroscopic techniques. For the EMAC [Co3(mpeptea)2]Cl2 two solvates have been crystallized. Anion exchange has also allowed isolation of [Co3(mpeptea)2](BPh4)2. In these three species the Co36+ units are cocooned within two polypyridine ligands having nine nitrogen atoms although only seven of these coordinate to the metal centers. The cations [Co3(mpeptea)2]2+ are similar and have Co ··· Co separations of ca. 2.3 Å at 213 K. These distances are consistent with partial bond formation between Co atoms. Electrochemical measurements show a unique one-electron oxidation process that differs from that in open chain species which show two reversible oxidation processes. At 300 K, the χT value is 7.32 emu K mol−1 but this value drops to 1.47 emu K mol−1 as the temperature is lowered to 2 K. The X-band EPR spectra for Co3(mpeptea)22+ show g values of 2.3 at room temperature. The magnetic behavior is quite different from that in compounds with open Co36+ units. A discussion is provided.  相似文献   

8.
The reactivity of Mo(PMe3)6 towards 6-membered heterocyclic aromatic nitrogen compounds, namely pyridine, pyrazine, pyrimidine and triazine, has been investigated as part of an effort to define the coordination chemistry of molybdenum relevant to hydrodenitrogenation. For example, Mo(PMe3)6 reacts with pyridine to yield initially (η2-N,C-pyridyl)Mo(PMe3)4H, an uncommon example of an η2-pyridyl-hydride complex. The formation of (η2-N,C-pyridyl)Mo(PMe3)4H is reversible and treatment with PMe3 regenerates Mo(PMe3)6 and pyridine. At elevated temperatures, (η2-N,C-pyridyl)Mo(PMe3)4H dissociates PMe3 and converts to the η6-pyridine complex (η6-pyridine)Mo(PMe3)3. Pyrazine, pyrimidine and 1,3,5-triazine likewise react with Mo(PMe3)6 to yield (η2-N,C-pyrazinyl)Mo(PMe3)4H, (η2-N,C-pyrimidinyl)Mo(PMe3)4H and (η2-N,C-triazinyl)Mo(PMe3)4H, respectively. At elevated temperatures (η2-N,C-pyrazinyl)Mo(PMe3)4H and (η2-N,C-pyrimidinyl)Mo(PMe3)4H dissociate PMe3 and convert to (η6-pyrazine)Mo(PMe3)3 and (η6-pyrimidine)Mo(PMe3)3 in which the heterocycle coordinates to molybdenum in an unprecedented η6-manner.  相似文献   

9.
DFT calculations with full geometry optimizations have been carried out on a series of real and hypothetical compounds of the CpM(C6NH7) and (CO)3M(C6NH7) (M = transition-metal) type. A rationalization of the bonding in all the known compounds and in hypothetical complexes is provided. Depending on the electron count and the nature of the metal, the azepine ligand can bind to the metal through the η1, η2, η4, η6, or η7 coordination mode.  相似文献   

10.
Two anodic isoenzymes of glucose-6-phosphate dehydrogenase (G6PDH) were isolated from tobacco suspension culture WR-132, utilizing fractional ammonium sulfate precipitation and DEAE-cellulose chromatography. The pH optimum was 9.0 for isoenzyme G6PDH I and 8.0–8.3 for G6PDH IV. Isoenzyme G6PDH I exhibited Michaelis-Menten kinetics for both substrates, G6P and NADP+, with Km's of 0.22 mM and 0.06 mM, respectively. G6PDH IV exhibited Michaelis-Menten kinetics for G6P with a Km of 0.31 mM. The NADP+ double reciprocal plot showed an abrupt transition between two linear sections. This transition corresponds to an abrupt increase in the apparent Km and Vmax values with increasing NADP+, denoting negative cooperativity. The two Km's for high and low NADP+ concentrations were 0.06 mM and 0.015 mM, respectively. MWs of the isoenzymes as determined by SDS disc gel electrophoresis were 85 000–91 000 for G6PDH I and 54 000–59 000 for G6PDH IV. Gel filtration chromatography on Sephadex G-150 showed MW's of 91 000 for G6PDH I and 115 000 for G6PDH IV. A probable dimeric structure for IV is suggested, with two NADP+ binding sites.  相似文献   

11.
The 6-phospho-β-glucosidase BglA-2 (EC 3.2.1.86) from glycoside hydrolase family 1 (GH-1) catalyzes the hydrolysis of β-1,4-linked cellobiose 6-phosphate (cellobiose-6′P) to yield glucose and glucose 6-phosphate. Both reaction products are further metabolized by the energy-generating glycolytic pathway. Here, we present the first crystal structures of the apo and complex forms of BglA-2 with thiocellobiose-6′P (a non-metabolizable analog of cellobiose-6′P) at 2.0 and 2.4 Å resolution, respectively. Similar to other GH-1 enzymes, the overall structure of BglA-2 from Streptococcus pneumoniae adopts a typical (β/α)8 TIM-barrel, with the active site located at the center of the convex surface of the β-barrel. Structural analyses, in combination with enzymatic data obtained from site-directed mutant proteins, suggest that three aromatic residues, Tyr126, Tyr303, and Trp338, at subsite +1 of BglA-2 determine substrate specificity with respect to 1,4-linked 6-phospho-β-glucosides. Moreover, three additional residues, Ser424, Lys430, and Tyr432 of BglA-2, were found to play important roles in the hydrolytic selectivity toward phosphorylated rather than non-phosphorylated compounds. Comparative structural analysis suggests that a tryptophan versus a methionine/alanine residue at subsite −1 may contribute to the catalytic and substrate selectivity with respect to structurally similar 6-phospho-β-galactosidases and 6-phospho-β-glucosidases assigned to the GH-1 family.  相似文献   

12.
Three new compounds, 17β-cevanin-6-oxo-5α,20β-diol yibeinine (1), 2-(tetrahydro-5-(2-hydroxyphenyl)-2H-pyran-3-yl) phenol (2), 1,3-O-diferuloyl-2-methoxypropane diol (3), as well as four known compounds (47), have been isolated from the ethanol extract of dried bulbs of Fritillaria pallidiflora Schrenk. All structures were determined based on their spectroscopic data (1D and 2D NMR (including 1H NMR, 13C NMR, 1H-1H COSY, HMBC, HSQC, HSQC-TOCSY, and NOESY experiments), and MS). Biological evaluation showed that compounds 14 inhibited the production of nitric oxide (NO) in LPS-stimulated RAW 264.7 cells with IC50 values of 18.0, 38.7, 29.5, and 47.1 μM, respectively. These results indicated that compound 1 has potential anti-inflammatory activity.  相似文献   

13.
Six new compounds, including a new compound with an unusual 2, 4, 6-cycloheptatrien ketone skeleton (1), two new diphenylpropanoid ethers (2, 3), a new protostane-type triterpenoid (4), two new norsesquiterpene (5a, 5b), and two new natural products (6, 7), together with eleven known compounds (818) were isolated from the aqueous extract of Alismatis Rhizoma (AR). Their structures were elucidated by a combination of 1D and 2D NMR (1H and 13C NMR, COSY, HSQC, HMBC, and NOESY), HRESIMS spectroscopic data, experimental and calculated electronic circular dichroism (ECD) spectra. Some of the compounds were evaluated for their inhibitory effects on nitric oxide (NO) production in LPS-induced RAW 264.7 cells. Two protostane-type triterpenoids, compounds 4 and 17, exhibited potent inhibitory activities with the IC50 values of 39.3 and 63.9 μM compared with indomethacin. In the meanwhile, their anti-inflammatory effects were also confirmed by acute inflammation model induced by CuSO4 in zebrafish.  相似文献   

14.
《Carbohydrate research》1999,315(1-2):98-105
Syntheses of five ‘direct linked’ C-disaccharides 8a–e were reported. The (Et3SiH/BF3·Et2O) reduction of pyranulose glycoside 1 yielded (6S)- and (6R)-6-(2,3,5-tri-O-benzoyl-β-d-ribofuranosyl)pyran-3(2H,6H)-one (2a and 2b) in a ratio of ca. 2:1 and in 88% combined yield. The absolute stereochemistry of each was determined from its CD spectrum. The reduction of 2a with NaBH4 in methanol afforded two allylic alcohols 6a and 6b in 14 and 73% yield, respectively. The reduction of 2b with NaBH4 afforded 6c and 6d in 30 and 56% yield, respectively. Cis hydroxylation of the double bond in compounds 6a–d with osmium tetroxide gave 7a–e. The stereoisomers 7a–e were separated and their configuration was established by 1H NMR spectroscopy. Debenzoylation of compounds 7a–e with aqueous sodium carbonate produced deprotected C-disaccharides 8a–e.  相似文献   

15.
A series of 24 novel heterocyclic compounds—functionalized at position 4 with aldehyde (5a5f), carboxylic acid (6a6f), nitrile (7a7f) and oxime (8a8f) functional groups—bearing 6-aminosulfonybenzothiazole moiety at position 1 of pyrazole has been synthesized and investigated for the inhibition of four isoforms of the α-class carbonic anhydrases (CAs, EC 4.2.1.1), comprising hCAs I and II (cytosolic, ubiquitous isozymes) and hCAs IX and XII (transmembrane, tumor associated isozymes). Against the human isozyme hCA I, compounds 6a6f showed medium-weak inhibitory potential with Ki values in the range of 157–690 nM with 6a showing better potential than the standard drug acetazolamide (AZA). Against hCA II, all the compounds showed excellent to moderate inhibition with Ki values of compounds 5a, 5d, 5f, 6a6f, 8d and 8f lower than 12 nM (Ki of AZA). Against hCA IX, all the compounds showed moderate inhibition with the exception of 6e which showed nearly 9 fold a better profile compared to AZA, whereas against hCA XII, four compounds 6e, 7a, 7b and 7d showed Ki in the same order as that of AZA. Carboxylic acid 6e was found to be an excellent inhibitor of both hCA IX and XII, with Ki values of 2.8 nM and 5.5 nM, respectively.  相似文献   

16.
Some new Schiff bases (H1-H7) have been synthesized by the condensation of 2-aminophenol, 2-amino-4-nitrophenol, 2-amino-4-methylphenol, 2-amino benzimidazole with thiophene-2-carboxaldehyde and pyrrole-2-carboxaldehyde. The structures of newly synthesized compounds were characterized by elemental analysis, FT-IR, 1 H NMR, UV–VIS, and single crystal X-ray crystallography. The in vitro antibacterial activity of the synthesized compounds has been tested against Salmonella typhi, Bacillus coagulans, Bacillus pumills, Escherichia coli, Bacillus circulans, Pseudomonas, Clostridium and Klebsilla pneumonia by disk diffusion method. The quantitative antimicrobial activity of the test compounds was evaluated using Resazurin based Microtiter Dilution Assay. Ampicillin was used as standard antibiotics. Schiff bases individually exhibited varying degrees of inhibitory effects on the growth of the tested bacterial species. The antioxidant activity of the synthesized compounds was determined by the 1,1-diphenyl-2-picrylhydrazyl(DPPH) method. IC50 value of synthesized Schiff bases were calculated and compared with standard BHA.  相似文献   

17.
Four new caged xanthones (14) and two known compounds (5, 6) were isolated from the roots of Cratoxylum cochinchinense, a polyphenol rich plant, collected in China. The structures of the isolated compounds (16) were characterized by obtaining their detailed spectroscopic data. In particular, compounds 1 and 6 were fully identified by X-ray crystallographic data. The isolated compounds (16) were evaluated against protein tyrosine phosphatase 1B (PTP1B), which plays an important role in diabetes, obesity, and cancer. Among these compounds, 3, 4, and 6 displayed significant inhibition with IC50 values of 76.3, 43.2, and 6.6 µM, respectively. A detailed kinetic study was conducted by determining Km, Vmax, and the ratio of Kik and Kiv, which revealed that all the compounds behaved as competitive inhibitors.  相似文献   

18.
A new flavone derivative, 7-hydroxy-3,5-dimethoxy-6,8-dimethylflavone (1) and a new eudesmane derivative, eudesmane-4β,7α-diol (2), have been isolated from the aerial part of Lawsonia inermis, together with ten known compounds (312). The structures of two new compounds were determined through spectroscopic and MS analyses. All compounds were evaluated for their inhibitory effects on Nitric Oxide production in LPS-stimulated RAW264.7 cells and compounds 3, 4, 6, 7, 9, and 10 showed inhibition with IC50 values of 8.11, 2.32, 1.87, 7.72, 2.18, and 6.34 μg/mL, respectively.  相似文献   

19.
The gem-dialkyl effect has been investigated in the reactions of cyclotriphosphazene, N3P3Cl61, with various 2,2′-derivatives of 1,3-propandiol, CXY(CH2OH)2, in either THF or DCM to form spiro (6-membered) and ansa (8-membered ring) derivatives. The reactions were made with a number of symmetrically-substituted (X = Y, methyl, ethyl, n-butyl and a malonate ester) and unsymmetrically-substituted (X ≠ Y, methyl/H, phenyl/H, methyl/n-propyl, ethyl/n-butyl and Br/NO2) 1,3-propandiols. The products were analysed by 1H and 31P NMR spectroscopy and some of the spiro and ansa derivatives were also characterized by X-ray crystallography. Reactions of 1 with unsymmetrically-substituted 1,3-propandiols results in the formation of two structural isomers of ansa-substituted compounds, both isomers (endo and exo) have been structurally-characterized by X-ray crystallography for the ethyl/n-butyl derivative. It is found that the regioselectivity of the reaction is changed when the base is changed. The relative proportions of spiro and ansa compounds formed under different reaction conditions were quantified by 31P NMR measurements of the reaction mixtures. The results were rationalised mainly in terms of the electronic effect of the substituents, whereas the steric effect has a secondary role in the formation of both spiro and ansa compounds.  相似文献   

20.
Solvothermal reactions in methanol of nickel acetate tetrahydrate, Ni(OAc)2 · 4H2O, with benzonitrile derivatives NC(C6H4)X, where X is one of the electron withdrawing substituents -CN, -NO2, or -CF3, located at the m- or p-positions relative to -CN, yield complexes of the general formula Ni{HNC(R)-NC(R)-NH}2. More specifically, 3-nitrobenzonitrile, 4-nitrobenzonitrile, 1,3-dicyanobenzene, 1,4-dicyanobenzene, and ααα-trifluoro-p-toluonitrile are found to react with Ni(OAc)2 · 4H2O to yield Ni{HNC(R)-NC(R)-NH}2, where R = 3-(NO2)C6H4, 4-(NO2)C6H4, 3-(CN)C6H4, 4-(CN)C6H4, or 4-(CF3)C6H4, respectively. Analogous reactions of nitriles lacking electron withdrawing groups do not occur under similar conditions. Solid-state structures have been determined for the complexes with p-NO2, p-CN, and p-CF3 substituents on the phenyl rings. In addition, we describe density functional theory (DFT) and natural bonding orbital theory (NBO) studies on a simplified analog of these compounds, aimed at understanding their molecular bonding. It is shown that the new compounds for which solid-state structures have been determined are model examples of coordination compounds containing robust ω-bonds.  相似文献   

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