Aqueous solutions of inclusion complexes of host cyclomaltohexa- and cyclomaltohepta-ose (cyclohexa- and cyclohepta-amylose) with guest phenols p-substituted with Br, Cl, CN, NO2, CH3, CHO, and COOH have been studied by 1H- and 13C-n.m.r. spectroscopy. The stability of the complexes depends on the guests, the cycloamyloses, and the ionisation states of the host hydroxyl groups. The 1H data for the host protons in the complexes show that the guests are more deeply inserted into the cavity of cyclomaltoheptaose than into that of cyclomaltohexaose. 相似文献
Proton-decoupled 13C-n.m.r. spectra were determined for D2O solutions of several wall teichoic acids containing glycosylated ribitol 1,5-diphosphate residues and for their dephosphorylated repeating-units. Assignments were made by correlating the chemical shift values observed with those reported for isolated constituents, allowing for perturbations of the latter resonances because of the presence of O-glycosyl or phosphodiester bonds. Anomeric configurations of hexopyranosyl residues and their position of substitution on ribitol were indicated from the distinctive chemical shifts of the carbons concerned. Three-bond 13C31P couplings (6–8 Hz) were observed, and two-bond 13C31P couplings were indicated by broadened signals. The lack of resolution for the latter resonances is probably due to the heterogeneous nature of the polymers. 相似文献
The structures in aqueous solution of all major contributing forms of D-altro-heptulose 1,7-diphosphate, and D-glycero-D-altro and D-glycero-D-ido-octulose 1,8-diphosphates have been established by 13C-n.m.r. spectroscopy. Assignments to individual carbon atoms were made with the aid of isotopically enriched analogues and by comparison with related sugars. 相似文献
The pH dependence of the labeled-carbon resonances of reductively [13C] methylated compounds tri-l-Ser, glyco-octapeptide AM, asialoglyco-octapeptide AM, glyco-octapeptide AN, asialoglyco-octapeptide AN, and a glycopentapeptide was investigated. The results are discussed relative to those previously observed for reductively [13C]methylated, intact glycophorins AM and AN, and in terms of the mode of display of the MN blood-group specificities by these related glycoproteins. The results indicated that the α-d-NeuAc groups appear to affect the pH-titration results of glyco-octapeptides AM and AN. Moreover, comparison of the pH-titration results for reductively [13C]methylated glyco-octapeptide AM and reductively [13C]methylated asialoglyco-octapeptide AM with those of a reductively [13C]methylated glycopentapeptide and reductively [13C]methylated tri-l-Ser indicated that the other carbohydrate residues present (α-d-GalNAc and β-d-Gal) may also affect the pH-titration results. The reductive-methylation modification appears to affect the chemical shifts of the carbohydrate and peptide carbon atoms of the glycopentapeptide minimally. 相似文献
The conformations of d-glucono-1,5-lactone (1) and d-mannono-1,5-lactone (2) in solution were investigated by 1H- and 13C-n.m.r. spectroscopy. Conformational equilibria for 1 and 2 were found to lie strongly in favor of the 4H3(d),gg and B2,5(d),gg conformations, respectively. 相似文献
The polysaccharide antigen produced by Eubacterium saburreum, strain O2, is composed of (1 leads to 6)-linked beta-D-glycero-D-galacto-heptopyranosyl residues, all of which are substituted with 6-deoxy-alpha-D-altro-heptofuranosyl groups at O-3. 相似文献
1H- and 13C-n.m.r. spectra for 16 synthetic methyl manno-oligosaccharides were recorded, and the signals for the anomeric protons and anomeric carbon atoms in branched manno-pentaosides and -hexaosides were assigned, based on the data for methyl manno-biosides and -triosides. These n.m.r. data identified the branching pattern of high-mannose types of glycans of glycopeptides with those of unambiguously synthesized manno-oligosaccharides, and confirmed the structures proposed for such glycans. 相似文献
Several disagreements in the 13C n.m.r. assignments of the methine carbons of D-fructose exist in the literature. In order to settle these inconsistencies, we examined the 13C n.m.r. spectrum of 3-O-methyl-D-fructose. By following the methyl induced shift in this spectrum, as compared to the parent sugar, we identified the alkylated C-3 resonance of all four tautomeric forms of D-fructose. This information, together with our previous identification of the C-5 resonances of the α- and β-forms of D-fructofuranose 6-phosphate, allow the unambiguous identification of all methine carbons of D-fructose in its 13C n.m.r. spectrum. The tautomeric composition of 3-O-methyl-D-fructose at 16.5°, in aqueous solution, was found to be as follows: α-pyranose 18%, β-pyranose 37%, α-furanose 11% and β-furanose 34%. 相似文献
As a prelude to studies using bovine N-acetylglucosaminide-β-(1→4)-galactosyltransferase to label membrane-surface glycoproteins with isotopically enriched d-galactose, the structural specificity of the enzymic reaction with water-soluble, hen ovalbumin has been examined. The enzyme-catalyzed transfer of d-galactose from UDP-d-galactose requires a (nonreducing) terminal 2-acetamido-2-deoxy-d-glucosyl group and exhibits selectivity towards saccharide chains containing d-mannose. This study considers the structural specificity of the enzyme with regard to the anomeric linkage between 2-acetamido-2-deoxy-d-glucose and d-mannose in the carbohydrate chains of hen ovalbumin. Uniformly 13C-enriched d-galactose was enzymically attached to the ovalbumin carbohydrate chain (which exhibits microheterogeneity in its structure), the protein was hydrolyzed, and separate glycopeptide fractions were chromatographically isolated. The 13C-n.m.r. spectra (60.5 MHz) of the fractions revealed two peaks for the anomeric carbon atom of d-galactose. The two peaks, at 104.20 and 104.39 p.p.m., were ascribed to d-galactosyl groups attached to 2-acetamido-2-deoxy-d-glucose respectively linked β-(1→4) and β-(1→2), to d-mannose in the glycopeptide chains. Quantifying of the spectral data revealed no specificity of d-galactosyltransferase towards the linkage from the terminal 2-acetamido-2-deoxy-d-glucosyl group to the penultimate d-mannosyl residue. 相似文献
The structure of the capsular polysaccharide of Type XIX Streptococcus pneumoniae (S-XIX) has been elucidated by 1H- and 13C-n.m.r. spectroscopy. Mild hydrolysis of S-XIX with acid yielded a major oligosaccharide, the repeating unit of S-XIX, which was shown to be O-2-acetamido-2-deoxy-β-d-mannopyranosyl-(1→4)-O-α-d-glucopyranosyl-(1→2)-l-rhamnose 4′′-phosphate. Phosphoric acid forms a diester linkage in the S-XIX molecule, which explains the instability of S-XIX towards acid or alkali. The phosphodiester linkages in S-XIX join HO-1 of α-l-rhamnose and HO-4 of the 2-acetamido-2-deoxy-d-mannopyranosyl residue in the next repeating-unit. Treatment of S-XIX with alkali or alkaline-NaBH4 produced the repeating units in a lower yield. The proposed structure of S-XIX is 相似文献
The hyperfine-shifted proton nuclear magnetic resonance (NMR) spectra of the low-spin complexes of human adult methemoglobin were found to be much altered by the addition of inositol hexaphosphate (IHP). The stoichiometry and pH-dependence of IHP binding, and the spin equilibrium of azide methemoglobin are parallel to those of high-spin human methemoglobin and of carp methemoglobin, both of which are proposed to be switched from the R to T states with IHP. The present NMR results show that IHP affects the structure of human methemoglobin regardless of the spin state of the heme iron, suggesting that there is no correspondence between quaternary structure and the spin state of ferric heme iron. 相似文献
Poly(A) molecules containing on average 25, 45 and 90 nucleotide residues are all eluted from DEAE-Sephadex in the presence of 7 M urea by approximately the same NaCl concentration which is higher than that required to elute 4 S and 5 S RNA. The same poly(A) molecules have electrophoretic mobilities on 12% polyacrylamide gels which are proportional to the logarithm of the number of nucleotide residues they contain but not to the number found in 4 S and 5 S RNA, even after denaturation of the RNA and performing electrophoresis in the presence of 2.2 M formaldehyde. As a result, many reported estimates of poly(A) size derived from such techniques are probably too large and need re-evaluation. Corrections are suggested for the use of 4 S and 5 S RNA as molecular weight markers for electrophoresis on 12% polyacrylamide gels. 相似文献
13C-N.m.r. spectra have been recorded for previously reported, comb-like derivatives of amylose produced by orthoester and Helferich condensation of D-glucose to amylose. As known from monomeric studies, the Helferich condensation conditions (the presence of mercury salts) favor α-D-glucosylation, and orthoester condensation conditions favor β-D-glycosylation. It was anticipated that, for these polymer condensations, the Helferich and orthoester condensations would also favor α- or β-D-glycosylation, respectively. The 13C-n.m.r. spectra of representative products of the Helferich and orthoester condensations confirmed the presence of 4,6-di-O-substituted α-D-glucopyranosyl residues, and also the degree of polymer linearity derived from independent, analytical data. However, these spectra indicate extensive, if not exclusive, β-D-glycosylation for both the helferich and the orthoester conditions. These results were obtained by using the product from an enzymically synthesized, strictly linear amylose in the Helferich condensation reaction. 相似文献
β-Lactamase (EC 3.5.2.6: penicillin amido-β-lactam hydrolase) I from B. cereus is inactivated by treatment with phenylglyoxal. Inactivation depends on the pH and the presence of bicarbonate in a manner which suggests that it is due to the modification of arginyl residues. Total inactivation correlates with the loss of 8 arginines per β-lactamase, and a competitive inhibitor provides full protection from inactivation and protects ca. 2 arginines from modification. 相似文献
The 3-carboxamido-13C resonance of NADP+ in its complex with dihydrofolate reductase and folate has been studied as a function of pH. At low pH a single resonance is observed, while at high pH two resonances are observed, neither of which has the same chemical shift as that seen at low pH. The rates of interconversion between the three states of the complex represented by these resonances are < 19 s?1 at 11°C. 相似文献
Haemophilus influenzae type b capsular polysaccharide [repeating unit, →3)-β- d-Ribf-(1 → 1)- d-Ribol-5-(PO 2H→] was partially hydrolyzed with HCl to give oligosaccharides that were isolated by size-exclusion chromatography, and then characterized by 31P- and 13C-n.m.r.-spectral and chemical methods, in order to determine the end-group composition and, hence, the number-average chain-length がL. The ratio (~17:8) of monophosphate end-groups to d-ribofuranose end-groups revealed the relative rates of hydrolysis of the phosphoric diester linkage and the glycosidic linkage in the repeating-unit structure. Cleavage of the phosphoric diester linkage was ~92% regioselective, as indicated by the ~ 12:1 ratio of d-ribofuranose monophosphate end-groups to d-ribitol monophosphate end-groups. The n.m.r. spectra of the oligosaccharide repeating-unit provided evidence for partial stereomutation (~3–8%) that involved rearrangement of the d-ribofuranose phosphoric diester linkage and anomerization at C-1 of d-ribofuranose. Variously sized oligosaccharides (がL = 4, 7, and 12) that had d-ribofuranose end-groups reacted with bovine serum albumin that had an average of ~9 adipyl hydrazide functionalities, to give, within experimental error, quantitative yields of the corresponding, hydrazone-linked, oligosaccharide-protein conjugates. 相似文献
Using periodate oxidation, methylation analysis, the characterization of oligosaccharides obtained by partial acid hydrolysis, p.m.r. spectroscopy, and analytical ultracentrifugation, the structure of the (mildly alkali-treated) Klebsiella serotype 11 capsular polysaccharide has been elucidated. The tetrasaccharide repeating-unit comprises the sequence ?3)-β-D-Glcp-(1?3)-β-D-GlcUAp-(1?3)-α-D-Galp-(1→ with a 4,6-O-(1-car?yethylidene)-α-D-galactosyl residue linked to O-4 of the glucuronic acid residue. The structural basis for some serological cross-reactions of the Klebsiella K11 antigen is discussed, and it is shown that rabbit antisera against the Klebsiella K11 test-strain predominantly contain K agglutinins specific for branch-terminal 4,6-O-(1-car?yethylidene)-D-galactose. 相似文献
The purified polysaccharide isolated from the cambium layer of a young bael (Aegle marmelos) tree contains galactose, arabinose, rhamnose, xylose, and glucose in the molar ratios of 10.0:9.8:1.4:1.9:1. Methylation analysis and Smith degradation studies established the linkages of the different monosaccharide residues. The anomeric configurations of the various sugar units were determined by oxidation of the acetylated polysaccharide with chromium(VI) trioxide. The oligosaccharides isolated from the polysaccharide by graded hydrolysis were characterized. The structural significance of these results is discussed. 相似文献