Structural determination of the polysaccharide antigens of Neisseria meningitidis serogroups Y, W-135, and BO

1976 ◽  
Vol 54 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Apurba K. Bhattacharjee ◽  
Harold J. Jennings ◽  
C. Paul Kenny ◽  
Adèle Martin ◽  
Ian C. P. Smith
Keyword(s):  
Sialic Acid ◽  
Acetyl Derivative ◽  
Major Product ◽  
Hydroxyl Group ◽  
Nmr Studies ◽  
Acetylneuraminic Acid ◽  
Nmr Data ◽  
Polysaccharide Antigens ◽  
C Nmr

The purified high molecular weight serogoup Y meningococcal polysaccharide contains equimolar proportions of D-glucose and N-acetylneuraminic acid and is partially O-acetylated. Carbon-13 nuclear magnetic resonance (NMR) studies, together with other chemical data, have indicated that the polysaccharide is linked only at C-6 of the D-glucose and C-4 of the sialic acid residues, all the linkages being in the α-configuration. The 13C NMR data also indicated that the Y polysaccharide is composed of an alternating sequence of these two different residues, and this was confirmed by its autohydrolysis where the major product was 4-O-α-D-glucopyranosyl-β-D-N-acetylneuraminic acid. The W-135 polysaccharide differs from that of Y only in the absence of O-acetylation and in the configuration of one hydroxyl group of the disaccharide repeating unit. In this case autohydrolysis yielded 4-O-α-D-galactopyranosyl-β-D-N-acetylneuraminic acid as the major product. Structural evidence indicates that the BO and Y polysaccharides are identical.Methanolysis of the Y polysaccharide yielded in addition to the methyl glycosides of glucose and sialic acid, a 9-O-acetyl derivative of the latter. This derivative was formed during the re-N-acetylation process and its formation was mainly due to the presence of sodium ions in the original polysaccharide.

scholarly journals Structural Investigations of C-Nitrosobenzenes. Part 3.1 Solid-state and Solution 13C NMR Studies, and Crystal Structure of E-(4-CIC6H4NO)2

1999 ◽  
Vol 23 (3) ◽  
pp. 202-203
Author(s):  
Daniel A. Fletcher ◽  
Brian G. Gowenlock ◽  
Keith G. Orrell ◽  
David C. Apperley ◽  
Michael B. Hursthouse ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
13C Nmr ◽  
Nmr Studies ◽  
Structural Investigations ◽  
Nmr Data ◽  
C Nmr

Solid-state and solution 13C NMR data for the monomers and dimers of 3- and 4-substituted nitrosobenzenes, and the crystal structure of E-(4-CIC6H4NO)2 are reported.

scholarly journals Characterization of Cerebral Glutamine Uptake from Blood in the Mouse Brain: Implications for Metabolic Modeling of 13C NMR Data

2014 ◽  
Vol 34 (10) ◽  
pp. 1666-1672 ◽  
Author(s):  
Puneet Bagga ◽  
Kevin L Behar ◽  
Graeme F Mason ◽  
Henk M De Feyter ◽  
Douglas L Rothman ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Metabolic Model ◽  
Synthesis Rate ◽  
Nmr Studies ◽  
Nmr Data ◽  
Glutamine Synthesis ◽  
Time Courses ◽  
Glutamine Uptake ◽  
C Nmr

13C Nuclear Magnetic Resonance (NMR) studies of rodent and human brain using [1-13C]/[1,6-13C2]glucose as labeled substrate have consistently found a lower enrichment (~25% to 30%) of glutamine-C4 compared with glutamate-C4 at isotopic steady state. The source of this isotope dilution has not been established experimentally but may potentially arise either from blood/brain exchange of glutamine or from metabolism of unlabeled substrates in astrocytes, where glutamine synthesis occurs. In this study, the contribution of the former was evaluated ex vivo using 1H-[13C]-NMR spectroscopy together with intravenous infusion of [U-13C5]glutamine for 3, 15, 30, and 60 minutes in mice. 13C labeling of brain glutamine was found to be saturated at plasma glutamine levels > 1.0 mmol/L. Fitting a blood–astrocyte–neuron metabolic model to the 13C enrichment time courses of glutamate and glutamine yielded the value of glutamine influx, VGln(in), 0.036 ± 0.002 μmol/g per minute for plasma glutamine of 1.8 mmol/L. For physiologic plasma glutamine level (~0.6 mmol/L), VGln(in) would be ~0.010 μmol/g per minute, which corresponds to ~6% of the glutamine synthesis rate and rises to ~11% for saturating blood glutamine concentrations. Thus, glutamine influx from blood contributes at most ~20% to the dilution of astroglial glutamine-C4 consistently seen in metabolic studies using [1-13C]glucose.

Chemoenzymatic synthesis of ring 18O-labeled sialic acid

2008 ◽  
Vol 86 (11) ◽  
pp. 1005-1009 ◽  
Author(s):  
Deepani Indurugalla ◽  
Andrew J Bennet
Keyword(s):  
Sialic Acid ◽  
Functional Group ◽  
Chemoenzymatic Synthesis ◽  
Hydroxyl Group ◽  
Synthetic Route ◽  
Acetylneuraminic Acid ◽  
O 18 ◽  
Sialic Acid Aldolase

Methyl 4,6-O-benzylidene-α-D-glucopyranoside was converted into methyl 2-azido-2-deoxy-4,6-O-benzylidene-α-D-altropyranoside via a synthetic route that incorporated two inversions of configuration. Activation of the C-3 hydroxyl group as a triflate ester followed by an SN2 reaction with O-18 labeled benzoate gave, after standard functional group manipulations, 2-acetamido-2-deoxy-D-(3-18O)mannose. Coupling of the labeled N-acetyl-mannosamine with pyruvate was catalyzed by sialic acid aldolase to give ring-oxygen-labeled sialic acid in an overall yield of 11.4% over 10 steps.Key words: N-acetylneuraminic acid, sialic acid oxygen-18, chemoenzymatic.

scholarly journals The First Liquid-Chromatographic Separation of the (R)- and (S)-Enantiomers of a Chiral Silanol, Silane and Germane

1995 ◽  
Vol 50 (4) ◽  
pp. 568-572 ◽  
Author(s):  
Reinhold Tacke ◽  
Dirk Reichel ◽  
Kurt Günther ◽  
Stefan Merget
Keyword(s):  
Chiral Stationary Phase ◽  
Enantiomeric Purity ◽  
Nmr Studies ◽  
Enantiomerically Pure ◽  
Chemically Modified ◽  
Liquid Chromatographic Separation ◽  
Racemic Mixtures ◽  
Liquid Chromatographic ◽  
C Nmr

The racemic mixtures of the muscarinic antagonists cyclohexyl(phenyl)(2-pyrrolidinoethyl)silanol (sila-procyclidine, rac-1), cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)-silane (rac-2) and cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)germane (rac-3) were resolved by analytical liquid chromatography (HPLC) using chemically modified cellulose (1) or amylose (2, 3) as the chiral stationary phase. This chromatographic method was used for the quantitative determination of enantiomeric purity of the (R)- and (S)-enantiomers of 1 - 3 , which were obtained by preparative resolution with chiral auxiliary agents. Furthermore, the enantiomeric purity of these samples was established by 13C NMR studies using chiral shift reagents. According to these studies, the resolved antipodes of 1 - 3 (obtained by preparative resolution) were almost enantiomerically pure [HPLC: ≥ 98.2% ee ((R )-3) to 99.4% ee ((R)-1, (S)-1); NMR: ≥ 97% ee].

Modes of Xanthine Complexation to Dirhodium Tetrakis[(R)-α-methoxy-α- (trifluoromethyl)-phenylacetate] in Solution and in the Solid State

2001 ◽  
Vol 56 (3) ◽  
pp. 319-324 ◽  
Author(s):  
Sven Rockitt ◽  
Rudolf Wartchow ◽  
Helmut Duddeck ◽  
Anna Drabczynska ◽  
Katarzyna Kiec-Kononowicz
Keyword(s):  
Solid State ◽  
Diffraction Analysis ◽  
Carbonyl Group ◽  
Enantiomeric Excess ◽  
Carbonyl Groups ◽  
X Ray Diffraction ◽  
Nmr Studies ◽  
X Ray ◽  
C Nmr

Abstract It is show n by IR and NMR studies that the xanthines 1-5 prefer a side-on com plexation to the chiral dirhodium tetrakis[(R)-α-methoxy-α-(trifluoromethyl)phenylacetatel (Rh*) in solution whereas carbonyl groups are involved in the solid state. For 6, at least the carbonyl group C-6 contributes to complexation in solution as well. A lternating strands of 6 and Rh* exist in the solid state as revealed by X-ray diffraction analysis described in detail. The determination of enantiomeric excess of the chiral xanthine 6 can easily be accomplished by the “dirhodium method ” (1H and 13C NMR in the presence of Rh*).

Diehloro(η5 -cyclopentadienyl)chrom-Dimer / Dichloro(η5-cyclopentadienyl)chromium Dimer

1983 ◽  
Vol 38 (11) ◽  
pp. 1406-1411 ◽  
Author(s):  
Frank H. Köhler ◽  
Ren de Cao ◽  
Klaus Ackermann ◽  
Josef Sedlmair
Keyword(s):  
Temperature Dependent ◽  
Nmr Studies ◽  
Magnetic Exchange ◽  
Chlorine Atoms ◽  
X Ray ◽  
Nmr Data ◽  
Metal Metal ◽  
C Nmr

Reaction of chromocene with chloroform yields [Cp2Cr]+[CpCrCl3]- (2) which is trans­formed to trans-[CpCrCl2]2 (3 a) on heating and to a mixture of cis/trans-[CpCrCl2]2 (3 b/a) on standing in chloroform. 2 and 3a/b have been characterized by paramagnetic 1H and 13C NMR yielding the first spectra of the chromocenium cation and the halfsandwich type [CpCrX2L]n-. For comparison, CpCrCl2(pyridine) (4) has been studied; the NMR data of 4 and [CpCrC3]- indicate that both are electronically similar. An X-ray analysis shows one isomer of 3 to be the trans-compound. Its chromium and bridging chlorine atoms consti­tute a square with a metal-metal distance of 336.2 pm. Magnetic exchange is established for 3 a by temperature dependent NMR studies. The X-ray results suggest superexchange to be the dominating mechanism.

Improved Automated Determination of Bound N-Acetylneuraminic Acid in Serum

1973 ◽  
Vol 19 (11) ◽  
pp. 1285-1287 ◽  
Author(s):  
Lucile Gerbaut ◽  
Elisabeth Rey ◽  
Christian Lombart
Keyword(s):  
Sialic Acid ◽  
Organic Solvent ◽  
Thiobarbituric Acid ◽  
Acetylneuraminic Acid ◽  
Automated Determination ◽  
Entire Procedure ◽  
Acid Determination

Abstract The method in which thiobarbituric acid is used for sialic acid determination was adapted to a fully automated procedure, in which the chromogen need not be extracted with an organic solvent. The entire procedure, including hydrolysis, requires 35 min and 25 µl of serum for one analysis, but 30 samples can be analyzed per hour. The procedure, slightly modified, can be used to measure as little as 10 mg of bound sialic acid per liter.

Evaluation of 1,10-Phenanthroline as a Reagent for Sialic Acid Determinations

1974 ◽  
Vol 20 (3) ◽  
pp. 387-388 ◽  
Author(s):  
S L Snyder ◽  
N S Mathewson ◽  
P Z Sobocinski
Keyword(s):  
Sialic Acid ◽  
Complex Formation ◽  
Sialic Acids ◽  
Previous Investigator ◽  
Acetylneuraminic Acid ◽  
Specific Reagent

Abstract Use of o-phenanthroline as a reagent for determination of sialic acids was proposed by a previous investigator. This method was based on an increase in absorbance at 307 nm that occurred when solutions of o-phenanthroline and various sialic acids were mixed. It was postulated that the increased absorbance was a result of formation of specific complexes. Using N-acetylneuraminic acid, we found no evidence for complex formation. Our results indicate that the observations of the previous investigator resulted from shifts in the pH of the medium rather than from formation of specific complexes. Therefore o-phenanthroline is not a specific reagent for sialic acids and its use is not recommended.

Formation of a trimeric chloroguaiacol quinone in the preparation of tetrachloroguaiacol and crystal structure of its tetramethoxy derivative

1986 ◽  
Vol 64 (5) ◽  
pp. 950-954
Author(s):  
Nick Burlinson ◽  
Steven J. Rettig ◽  
James Trotter ◽  
Bruce McKague
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Conformational Isomerism ◽  
Nmr Studies ◽  
Full Matrix ◽  
X Ray ◽  
Expected Values ◽  
Intermolecular Distances ◽  
C Nmr

A by-product formed in the preparation of tetrachloroguaiacol is shown to be a trimeric quinone. Derivatization of the quinone to a crystalline tetramethoxy derivative allowed X-ray determination of its crystal structure as 3,6-dichloro-4,5-dimethoxy-1,2-bis(2′-methoxy-3′,4′,5′,6′-tetrachlorophenoxy)benzene, 4. Rarely observed long range JCH coupling between ring carbons and methoxyl hydrogens as well as conformational isomerism were observed in 1H and 13C nmr studies of 4. Crystals of 4 are triclinic, a = 12.562 (1), b = 12.708(1), c = 9.223(1) Å, α = 96.93(1), β = 97.478(7), γ = 101.285(8)°, Z = 2, space group[Formula: see text]. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.056 and Rw = 0.056 for 2946 reflections with I ≥ 1.5σ(I). The molecule contains a central six-membered dichloro-tetraoxo substituted aromatic ring, linked via oxygen bridges to two identical tetrachloro-dioxo substituted rings; intramolecular steric overcrowding causes significant deviations from a symmetrical conformation. Bond lengths, angles, and intermolecular distances are generally close to expected values.

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