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1.
Byung Yun Yang James S.S. Gray Rex Montgomery 《International journal of biological macromolecules》1994,16(6):306-312
Many strains of Erwinia chrysanthemi, which are Gram-negative bacterial phytopathogens, produce copious amounts of extracellular polysaccharides. The extracellular polysaccharide from E. chrysanthemi pv. zeae strain SR 260, a phytopathogen of corn, is a branched-chain glucomannorhamnan of proven structure (Gray et al., Carbohydr. Res. 1993, 245, 271–287). The extracellular polysaccharide from E. chrysanthemi Ech6 is different, containing no rhamnose or mannose. It is composed of
-fucose,
-galactose,
-glucose and
-glucuronic acid in the ratio 2:2:1:1. The structure of the polysaccharide is as follows: 相似文献
2.
Klaus W. Neumann Jun-ichi Tamura Tomoya Ogawa 《Bioorganic & medicinal chemistry》1995,3(12):1637-1650
The glycopeptides 1 and 2 ), carrying the core structure of serine-linked cell-surface proteoglycans were synthesized in a stereocontrolled manner. The carbohydrate key imidate xylosyl donors 3 and glycotetraosyl donors 4 and 5, as well as a tetrapeptide glycosyl acceptor 6, were coupled in the crucial glycosylation step. In these reactions, the application of either trimethylsilyl trifluoromethanesulfonate (TMSOTf) or borontrifluoride etherate (BF3-Et2O) as catalysts proved to be highly efficient. The serine linked glycopeptides 34, 36 and 37 thus obtained yielded target compounds 1 and 2 on complete deprotection. 相似文献
3.
Tammo von Schrenck Knut Müller Christian Schulze Silvia Mirau Andreas Raedler Heiner Greten 《Peptides》1993,14(6):1309-1315
It has been reported that certain N-carboxyacyl analogues of CCK-8 and of CCK-7 with a substituted Gly in position 3 or 4 of the peptide possess higher potencies at stimulating pancreatic enzyme secretion than at stimulating gallbladder contraction, suggesting that these analogues are able to differentiate subtypes of CCKA receptors. However, no studies examined directly the interaction of these peptides with the CCK receptors in both tissues. In the present study, CCK-8 and various N-carboxyacyl analogues of CCK-7 and of CCK-8 were prepared by solid phase synthesis using Fmoc chemistry and were purified by HPLC; molecular weight and sufficient sulfation were determined by mass spectrometry. [125I]Bolton-Hunter(BH)-CCK-8 binding to sections of the guinea pig pancreas and gallbladder was determined under identical conditions; amylase release from pancreatic acini and contraction of gallbladder muscle strips were measured in vitro. Each peptide stimulated amylase release (EC50): ). The same relative potencies were found for stimulation of gallbladder contraction, and for the inhibition of [125I]BH-CCK-8 binding to pancreas and gallbladder sections. These data demonstrate that the CCKA receptors in the pancreas and on gallbladder smooth muscle possess similar affinities for the various N-carboxyacyl analogues of CCK-7 and CCK-8 with a substituted Gly and provide further evidence that the CCKA receptors in gallbladder and pancreas cannot be distinguished pharmacologically. 相似文献
4.
Methyl , a 3-O hexyl analogue of the octaosyl component of fungal lipooligosaccharide HS-142-1, was stereo- and regioselectively synthesized as a potent antagonist for the tetrameric atrial natriuretic peptide (ANP) receptors. 相似文献
5.
A convenient synthesis for enantiomeric pure
, (or
and
(or
has been described. Starting from myo-inositol, penta-O-acetyl-myo-inositol was made in five steps. Then enantiomeric purification was done by a diastereomeric salts separation method, and the purity of each enantiomer was spectroscopically measured (19F-NMR). The phosphodiester was made via phosphoramidites. The enantiomeric products (>99% optical purity) of all compounds were easily obtained in large quantities (5–10 g). Synthetic phosphatidylinositol analogues of precisely defined structure and configuration are interesting tools for studying signal transduction mechanism and cell activity modulation. 相似文献
6.
Gurijala V. Reddy Rakesh K. Jain Robert D. Locke Khushi L. Matta 《Carbohydrate research》1996,280(2):261-276
Stereoselective syntheses of 3-O-SO3Na-β-Gal-(1 → 4)-β-GlcNAc-(1 → 3)-β-Gal-(1 → 4)-GlcNAc-β-OBn (15) and 3-O-SO3Na-β-Gal-(1 → 3)-β-GlcNAc-(1 → 3)-β-Gal-(1 → 3)-β-GlcNAc-(1 → 3)-β-Gal-(1 → 4)-Glc-β-OBn (25) were accomplished through the use of two novel glycosyl donors, namely, ethyl (8) and ethyl (18). 相似文献
7.
S. O. Aisien F. I. Opute S. N. Ali B. A. Obiamiwe 《International journal for parasitology》1986,16(6):655-657
& Obiamiwe B. A. 1986. Lipid composition of adult Foleyella agamae. International Journal for Parasitology 16: 655–657. The lipid and fatty acid composition of the filarial parasite Foleyella agamae were investigated. Total lipids accounted for 7.05% of the parasite fresh weight. Neutral lipids comprised 56.34% of the total and polar lipids 43.66%. The major lipid classes detected include sterol esters, cholesterol, phosphatidyl choline and phosphatidyl ethanolamine. Fatty acids varying in chain length from 10 carbon atoms through 20 carbon atoms were identified in the total lipid extract. The 18 carbon fatty acids formed the predominant components. The 20 carbon fatty acids were confined to the polar lipds. 相似文献
8.
A model which predicts the filtrate flux and the pressure drop over the length of a cross-flow hollow-fibre microfilter is presented. Data from a series of 128 experimental runs were fitted using a multi-variable, non-linear regression program. Average errors of less than 10% were found. The final equations of average flux and pressure drop were: 相似文献
9.
The structure of the O-antigen chain of the lipopolysaccharide (LPS) of Rhizobium trifolii 4s has been determined by a combination of chemical and spectroscopic methods. The glycosyl components were found to be
-rhamnose, N-acetyl-
-glucosamine, and N-acetyl-
-mannosamine in 3:1:1 molar proportion, as determined by gas chromatography and gas chromatography-mass spectrometry of alditol acetate and persilylated (R)-2-hydroxybutyl glycoside derivatives. The linkage positions and configurations of the glycosyl residues were obtained by 1D and 2D NMR spectroscopy. The polymer has a pentasaccharide repeating-unit containing rhammose and N-acetylglucosamine in the main chain and N-acetylmannosamine as the sole-side chain component. This latter residue is linked to a main-chain rhamnose residue. This result was suggested by NMR spectroscopy and confirmed by periodate oxidation. The sequence was deduced by 1D and 2D NMR NOE experiments and by partial hydrolysis studies. The repeating unit of the polysaccharide is shown. This constitutes the first complete structure of an O-antigenic chain of the lipopolysaccharide of any strain of Rhizobium trifolii. 相似文献
10.
Anders Johansson Gran Widmalm Per-Erik Jansson Stephen G. Wilkinson 《Carbohydrate research》1995,270(2):191-199
The structure of the acidic polysaccharide from Serratia marcescens serogroup O1 has been investigated. NMR spectroscopy together with sugar and methylation analysis have been used as well as a uronic acid degradation. The polysaccharide consists of pentasaccharide repeating units having the following structure.
The polysaccharide also contains one equivalent of O-acetyl groups per repeating unit present on, inter alia, a hydroxymethyl group. 相似文献
11.
Light-induced changes of absorbance were measured in Fraction 1 particles prepared from spinach chloroplasts according to a method developed by 6 that employs breakage of chloroplasts in the French pressure cell and centrifugation of the resulting fragments on a sucrose density gradient. Absorbance changes were measured in the presence of ascorbate and 2,3,5,6-tetramethyl-1,4-phenylenediamine as an electron donating system. In addition to the oxidation of P700 and cytochrome f, that was investigated in our previous study11, three other light-induced absorbance changes were observed; reduction of cytochrome b with a peak at 562 nm, the so-called 515-nm change showing an absorbance increase at 515 nm and a decrease at 480 nm, and a broad band of unknown absorbance increase covering wave-lengths from 490 to 570 nm. Uncouplers such as carbonylcyanide-m-chlorophenylhydrazone and gramicidin D inhibited the 515-nm change under continuous light and accelerated the dark decay of flash-light-induced change. The other broad absorbance change was insensitive to these inhibitors. 相似文献
12.
Masahiko Maekawa Megumu Munakata Takayoshi Kuroda-Sowa Koji Hachiya 《Inorganica chimica acta》1995,230(1-2):249-252
A novel hexanickel(II) complex [Ni6(NCCHCH2CH2CHCN)6] (2) with 1,4-dicyanobutane-1,4-diyl (L) which was produced by the metal-induced dimerization of acrylonitrile (AN) has been isolated and the structure has been determined crystallographically. Complex 2 is triclinic, space group . Each nickel atom is coordinated by two carbon atoms of L and two nitrogen atoms of the cyano group of two other L, providing a square-plenar geometry. The six nickel atoms are bridged by the cyano group and carbon atom to form the slightly distorted octahedral Ni6 core. 相似文献
13.
Effect of preillumination wavelength on the deactivation of oxidized forms of the Photosystem II electron donor
Deactivation was studied using chlorella cells or spinach chloroplasts after an illumination of different wavelengths (light I = 710 nm, light II = 650 or 480 nm). The measurements concerned mainly the third oxidized state S3 of the System II electron donor, according to the scheme proposed by
, (Photochem. Photobiol., 11 (1970)457). The time course of deactivation was followed during the dark after each preillumination. Different results were obtained with algae in state 1 or state 2 as defined by , (Biochim. Biophys. Acta, 189 (1969) 366). In state 1 the deactivation of S3 is faster after light 11 than after light 1; in state 2, except at the beginning of the decay, the deactivation of S3 is almost the same after the two kinds of preillumination. With chloroplasts the deactivation is slower, but always faster after light II than after light I, no transition between state 1 and state 2 was observed. The results are discussed with reference to the possible reducing substrates of the reaction. 相似文献14.
N-Troc-protected (Troc = 2,2,2-trichloroethoxycarbonyl) glucosamine and galactosamine glycosyl donors (1-O-acetyl sugar, bromo sugar, and thioglycoside) were compared with the corresponding N-Phth-protected derivatives in glycosylations of 2-(trimethylsilyl)ethanol, 2-bromoethanol, methyl 3-mercaptopropionate, N-Fmoc-protected serine, and 2-(trimethylsilyl)ethyl . The N-Troc-protected donors gave pure β-glycosides in somewhat higher yields than the N-Phth-protected counterparts. The N-Troc protecting group can be removed by reduction with zinc, which allows selective N-deprotection in oligosaccharides containing both N-Troc and N-Phth groups. 相似文献
15.
Isocyanide-substituted Re alkyl complexes cis-p-XC6H4CH2Re(CO)4(CN-p-tolyl) (X = Cl, OMe) were prepared from the PdO-catalyzed reaction of p-XC6H4CH2Re(CO)5 (X = Cl, OMe) with p-tolyl isocyanide. On heating in toluene these complexes undergo isocyanide insertion into the Re---C bond to afford iminoacyl complexes which further react to orthometallate the p-tolyl ring. An X-ray crystal structure determination on (CO)4 (3a) revealed that C19H13ClO4NRe crystallizes in the monoclinic space group P21/c with 4 formulas per unit cell. Unit cell parameters are a = 9.799 (1), B = 15.252 (2), C = 13.569 (2) Å and β = 110.788 (8)°. The structure shows Re---C bond distances indicative of substantial carbenoid character. 相似文献
16.
Rudolf Christian Gerhard Schulz Frank M. Unger
Paul Messner
Zaruhi Kü pcü Uwe B. Sleytr 《Carbohydrate research》1986,150(1):265-272The structure of a glycan from the surface-layer glycoprotein of Bacillus stearothermophilus strain NRS 2004/3a has been studied by 1H- and 13C-n.m.r. spectroscopy. The results indicate the glycan to be a polymer of the trisaccharide repeating-unit 相似文献
17.
2,3-BUTANEDIONE INACTIVATES THE [H]NITRENDIPINE BINDING SITES, WHEREAS DIETHYLPYROCARBONATE DOES NOT
BARBARA COSTA LAURA GIUSTI CLAUDIA MARTINI ANTONIO LUCACCHINI 《Neurochemistry international》1996,29(6):623-627
The modification of [3H]nitrendipine binding sites in rabbit brain membranes with 2,3-butanedione and diethylpyrocarbonate was investigated. 2,3-Butanedione, an arginine-specific reagent, causes a dose- and time-dependent decrease in the number of [3H]nitrendipine binding sites without altering its dissociation constant. Scatchard analysis of the binding data shows that 50 mM 2,3-butanedione decreases the binding capacity of [3H]nitrendipine from a control value of 71 ± 6 fmol/mg of protein to 40 ± 3 fmol/mg of protein. Complete and selective protection against inactivation is provided by nifedipine. No decrease of [3H]nitrendipine binding occurs when membranes are pretreated with selective histidine reagent diethylpyrocarbonate. The results indicate that arginine but not histidine residue in -type calcium channel domain is critical for [3H]nitrendipine binding. Copyright © 1996 Elsevier Science Ltd 相似文献
18.
A metal ion-based method for the screening of nitrilases 总被引:1,自引:0,他引:1
Daniel R. Yazbeck Paulo J. Durao Zhiyi Xie Junhua Tao 《Journal of Molecular Catalysis .B, Enzymatic》2006,39(1-4):156-159
In this paper we describe a colorimetric method for the screening of nitrilases. When a buffered solution of CoCl2 is added to a nitrilase-catalyzed hydrolysis reaction, the ammonia product forms a complex with the cobalt ion resulting in a color change from light pink to yellow, which can readily be quantified using a spectrophotometer at 375 nm. This method has been demonstrated for both wild-type and evolved nitrilases.
相似文献
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19.
Akbar Ali Ansari Lennart Kenne Bengt Lindberg
Bj
rn Gustafsson Tord Holme 《Carbohydrate research》1986,150(1):213-219The O-antigen from Vibrio cholerae O:21 has been investigated, using n.m.r. spectroscopy, methylation analysis, and Smith degradation as the main methods. It is concluded that the O-antigen is composed of tetrasaccharide repeating-units having the following structure (in which Hep =
-glycero-
-manno-heptose). 相似文献
20.
M. Akhtar P. Lee-Robichaud M. E. Akhtar J. N. Wright 《The Journal of steroid biochemistry and molecular biology》1997,61(3-6):127-132
Experimental findings from a number of laboratories have converged to show that the conversion of androgens into oestrogen, catalysed by aromatase, involves three distinct reactions which occur at a single active site. That each one of these reactions belongs to a different generic type was revealed by chemical consideration, together with our 18O-experiments. In particular, these findings high-lighted the fact that the third reaction in the sequence occurs by a novel process for which a number of plausible mechanisms have been considered. The scrutiny of these mechanisms has involved either studies on aromatase itself, or on related enzymes which catalyse the aromatase type of cleavage reaction as generalized in equation 1: The acyl-carbon cleavage reaction of equation 1 is catalysed by sterol 14-demethylases, accounts for several side-chain fission products formed by CYP17 (17-hydroxylase-17,20-lyase), and constitutes a weak property of certain drug metabolizing P450s, when given aliphatic aldehydes as substrates. From cumulative studies on these enzymes, consensus is beginning to emerge that the acyl-carbon fission may be promoted by the FeIII---OOH intermediate, formed during the catalytic cycles of P450s. The precedent for the direct involvement of the FeIII---OOH species in the reaction of equation 1 is influencing our thinking regarding the mechanism of the conventional hydroxylation reaction. The status of knowledge surrounding the current debate on these issues will be reviewed. 相似文献