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Biomedical subjects

L Dorland

Publications and source records attributed to L Dorland.

At least 91 records · Page 5Linked to original sources
PubMed1984

Chemical behaviour of cytidine 5'-monophospho-N-acetyl-beta-D-neuraminic acid under neutral and alkaline conditions.

The chemical behaviour of CMP-N-acetylneuraminic acid under neutral and different alkaline conditions has been investigated. The products formed were isolated by ion-exchange chromatography and gel filtration and analysed by colorimetric methods, thin-layer chromatography, combined gas-liquid chromatography/mass spectrometry and/or 360-MHz 1H-NMR spectroscopy. A maximum stability of CMP-N-acetylneuraminic acid was observed at pH8-11. In the tested pH range of 6-13, CMP and N-acetylneuraminic acid were formed in variable amounts as decomposition products. 2-Deoxy-2,3-dehydro-N-acetylneuraminic acid was produced at pH greater than 7; the amount of this substance increased with increasing pH. In anhydrous triethylamine its yield was 50%. A new neuraminic acid derivative, N-acetyl-beta-D-neuraminic acid 2-phosphate, could be isolated from the mixture of alkaline decomposition products of CMP-N-acetylneuraminic acid. The yield of this compound was maximum 22% in anhydrous triethylamine. Because 2-deoxy-2,3-dehydro-N-acetylneuraminic acid was formed under simulated physiological conditions, it is assumed that this compound, which occurs in tissues and fluids of man and animals, is derived from CMP-N-acetylneuraminic acid non-enzymically also under conditions in vivo.

Chemical Phenomena↗
PubMed1984

Identification of methyl-branched chain dicarboxylic acids in amniotic fluid and urine in propionic and methylmalonic acidemia.

3-Methyladipic, 4-methylpimelic, 4-methylsuberic, pimelic, and azeleic acids were identified by gas chromatography-mass spectrometry in the amniotic fluid of fetuses with propionic acidemia. These compounds were virtually undetectable in normal amniotic fluid. Concentrations much higher than those of the amniotic fluid were found in the urine of neonatal infants with propionic acidemia and methylmalonic acidemia. It appears that the accumulation of these compounds is a consequence of the accumulation of propionyl-CoA. Evidence was obtained for the presence of other methyl-branched chain dicarboxylic acids. 4-Methylpimelic acid and 4-methylsuberic acid have not previously been identified in human physiological fluids.

Amniotic Fluid↗
PubMed1983

Structure determination of the carbohydrate chains of rat alpha-fetoprotein.

By affinity chromatography on concanavalin A (ConA) linked to Sepharose, S-carboxymethylated rat alpha-fetoprotein could be separated into two molecular variants: a ConA-reactive and a ConA-nonreactive fraction. The carbohydrate chains were quantitatively released from the protein by hydrazinolysis. Based on methylation analysis and high-resolution 1H-NMR spectroscopy of the re-N-acetylated hydrazinolysates, the carbohydrate structures of the two ConA-molecular variants of alpha-fetoprotein were established. The ConA-reactive species contains two N-glycosidic carbohydrate units per molecule, both having the following structure: (formula; see text) The ConA-nonreactive species possesses also two N-glycosidically linked oligosaccharide chains per molecule; each of these has the following structure: (formula; see text)

Animals↗
PubMed1983

Isovalerylglucuronide, a new urinary metabolite in isovaleric acidemia. Identification problems due to rearrangement reactions.

Isovaleryl-beta-D-glucuronide, a new metabolite in the urine of patients with isovaleric acidemia, is described. Its gas chromatographic and mass spectrometric parameters are presented. In alkaline solution this glucuronide exhibited intramolecular rearrangements, resulting in isomers bearing the acyl moiety on C-2, C-3 and C-4. The isomers showed similar mass spectra but different positions on the gas chromatogram. In the index patient isovalerylglucuronide was a main metabolite, but the excretion was a transient phenomenon. Only traces of isovalerylglucuronide could also be detected in the urine of three other patients with isovaleric acidemia. The significance of this metabolite for the detoxication of isovalerate in isovaleric acidemia is discussed.

Amino Acid Metabolism, Inborn Errors↗
PubMed1983

Characterization of the B-chain of human plasma alpha 2HS-glycoprotein. The complete amino acid sequence and primary structure of its heteroglycan.

alpha 2HS-Glycoprotein, a normal human plasma protein, was recently shown to consist of two polypeptide chains. In the present study, we have separated these two chains from one another and have elucidated the complete primary structure of the B-chain. Employing automated Edman degradation, the polypeptide moiety of this chain was shown to consist of 27 amino acid residues with an unequal distribution of the neutral and charged amino acid residues. The first 20 residues are uncharged, whereas the carboxyl-terminal heptapeptide contains all charged residues. Utilizing 500-MHz 1H-NMR spectroscopy, the carbohydrate unit proved to be a trisaccharide consisting of sialic acid, galactose, and N-acetylgalactosamine O-glycosidically linked to serine (residue 6). The structure of the B-chain was found to be as follows. (formula; see text) Thus, the molecular weight of the B-chain is 3386. Evaluation of the polypeptide chain by the procedure of Chou and Fasman (Chou, P.Y., and Fasman, G.D. (1979) Adv. Enzymol. 47, 45-148) predicts that the B-chain has two beta-turns. Thereby, the carbohydrate unit which is linked to the Ser residue located in the first beta-turn appears to be directed away from the protein. The second beta-turn probably includes the Cys residue which links the B- to the A-chain. In agreement with the CD analysis, the B-chain lacks beta-conformation but possesses a short alpha-helical region.

Amino Acid Sequence↗
PubMed1983

Primary structure of a novel N-glycosidic carbohydrate unit, derived from hen ovomucoid. A 500-MHz 1H-NMR study.

The N-glycosidic carbohydrate chains of hen beta-ovomucoid were released from the protein by hydrazinolysis, and separated by HPLC. Primary structural analysis of 3 major fractions was conducted by applying 500-MHz 1H-NMR spectroscopy in combination with methylation analysis. One of the fractions investigated appeared to consist of an intersected penta-antennary structure extended with one Gal residue. The location of the latter in a certain branch could be established unambiguously by NMR. This structure is a novel member of the family of N-glycosidic carbohydrates of glycoproteins.

Animals↗
PubMed1982

A novel type of carbohydrate structure present in hen ovomucoid.

Hen ovomucoid is characterized by a high degree of microheterogeneity of its carbohydrate moieties, as was recently demonstrated by hydrazinolysis in combination with high performance liquid chromatography (Paz Parente, J., Strecker, G., Leroy, Y., Montreuil, J., and Fournet, B. (1982) J. Chromatogr., in press). This approach resulted in 17 oligosaccharide-alditol fractions; the major one could be purified to homogeneity. Primary structural analysis of this fraction was carried out by methylation analysis, partial acid hydrolysis, and 500-MHz 1H NMR spectroscopy. Combination of these techniques enabled the unambiguous determination of a novel type of asparagine-bound carbohydrate chain: (formula, see text).

Animals↗
PubMed1982

Newcastle disease virus contains a linkage-specific glycoprotein sialidase. Application to the localization of sialic acid residues in N-linked oligosaccharides of alpha 1-acid glycoprotein.

Newcastle disease virus sialidase was found to exhibit strict specificity for hydrolysis of the NeuAc alpha 2 leads to 3Gal linkage contained in glycoprotein oligosaccharides both N-linked to asparagine and O-linked to threonine or serine under conditions that left oligosaccharides containing the NeuAc alpha 2 leads to 2 leads to 6Gal and NeuAc alpha 2 leads to 6GallNAc linkages intact. This was determined, in part, by examining the viral sialidase for its ability to hydrolyze glycoprotein oligosaccharides derivatized with purified sialyltransferases to contain the [14C]NeuAc alpha 2 leads to 3Gal, [14C]NeuAc alpha 2 leads to 6GalNAc, and [14C]NeuAc alpha 2 leads to 6Gal linkages. The viral sialidase was also tested for hydrolysis of the NeuAc alpha 2 leads to 3Gal and NeuAc alpha 2 leads to 6Gal linkages on the N-linked oligosaccharides of alpha 1-acid glycoprotein. Selective hydrolysis of the NeuAc alpha 2 leads to 3Gal linkage was shown by periodate oxidation and by 500-MHz 1H-NMR spectroscopy of native and sialidase-treated glycopeptides. The NMR spectra, together with composition data, further indicated that the NeuAc alpha 2 leads to 3Gal and NeuAc alpha 2 leads to 6Gal linkages were localized to specific branches of the major tri- and tetraantennary oligosaccharides of alpha 1-acid glycoprotein. The results indicate that the Newcastle disease virus sialidase can initiate the selective degradation of N-linked oligosaccharide branches containing the NeuAc alpha 2 leads to 3Gal linkage.

Carbohydrate Conformation↗
PubMed1982

Structural studies of 4-O-acetyl-alpha-N-acetylneuraminyl-(2 goes to 3)-lactose, the main oligosaccharide in echidna milk.

The main oligosaccharide (50%) in the milk of the Australian echidna (Tachyglossus aculeatus) has been identified unequivocally as 4-O-acetyl-alpha-N-acetylneuraminyl-(2 goes to 3)-lactose. The 4-O-acetyl substituent of the sialic acid residue was characterized by g.l.c.-m.s. of the isolated (after mild, acid hydrolysis) and trimethyl-silylated/esterified sialic acid, and by m.s. (after derivatisation) and 500-MHz, 1H-n.m.r. spectroscopy of the intact oligosaccharide. Information about the glycosidic bonds was obtained by methylation analysis and 500-MHz, 1H-n.m.r. spectroscopy. This animals species is the third one known to produce 4-O-acetylated sialic acid.

Animals↗
PubMed1982

The structures of six urinary oligosaccharides that are characteristic for a patient with Morquio syndrome type B.

Morquio syndrome type B is an inherited, lysosomal storage disease characterised by a marked deficiency in acid beta-D-galactosidase, while the 2-acetamido-2-deoxy-beta-D-galactose 6-sulphate sulphatase activity is normal. Urinary oligosaccharides were studied in order to evaluate the effect of the diminished beta-D-galactosidase activity on the catabolism of glycoconjugates and to compare their structure with those excreted by patients with GM1-gangliosidosis. The following oligosaccharides were isolated: beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)-beta-D-Manp-(1 leads to 4)-D-GlcpNac(1), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)-[alpha-D-Manp-(1 leads to 3)]-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (2a), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-[alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (2b), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-[beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (3), beta-D-Galp-(1 leads to 4)-beta-D-Glcp-NAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-(beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-[beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 6)]-alpha-D-Manp-(1 leads to 6))-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (4), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-[beta-D-GlcpNAc-(1 leads to 4)]-[beta-D-Glap-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-D-Glcp-NAc (5). Significant differences between Morquio syndrome type B and GM1- gangliosidosis have been observed, with regard to the excretion rate and the specific structures of urinary oligosaccharides. Compounds 2a, 2b, and 5 are novel members of the series of oligosaccharides isolated from the urine of patients with inherited lysosomal storage diseases.

Carbohydrate Conformation↗
PubMed1982

Primary structure of the glycans from human lactotransferrin.

The polypeptide chain of human lactotransferrin possesses two glycoslyation sites to which glycans are linked through an N-(beta-aspartyl)-N-acetylglucosaminylamine bond and which are structurally heterogenous. After chymotryptic or pronase digestions, glycopeptides with five different glycan structures could be isolated. For three of them, the structure has been determined by the application of methanolysis, methylation analysis, hydrazinolysis/nitrous deamination, enzymatic cleavage and 1H-NMR spectroscopy at 360 MHz: Glycopeptides A and B: NeuAc(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-3)[NeuAc(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-6)]Man(beta 1-4)GlcNAc(beta-1-4)[Fuc(alpha 1-6)]GlcNAc(beta 1-)Asn; Glycopeptide C: NeuAc(alpha 2-6)(Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-3)(Gal(beta 1-4)[Fuc(alpha 1-3)]GlcNAc(beta 1-2)Man(alpha 1-6))Man(beta 1-4)GlcNAc(beta 1-4)[Fuc(alpha 1-6)]GlcNAc(beta 1-)Asn. Glycopeptide D: NeuAc(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-3)[Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-6)]Man(beta 1-4)Glc-NAc(beta 1-4)[Fuc(alpha 1-6)]GlcNAc(beta 1-)Asn. Two other glycopeptides were obtained in very low amount and possess more complex structures.

Chemical Phenomena↗
PubMed1982

High-resolution 1H-NMR spectroscopy of free and glycosidically linked O-acetylated sialic acids.

A number of naturally occurring and synthetic, partially O-acetylated derivatives of N-acetylneuraminic and N-glycoloylneuraminic acids have been investigated by 360-MHz 1H-NMR spectroscopy. O-Acetylation causes strong downfield shifts for the resonances of neighbouring sugar-skeleton protons. The chemical shifts of these resonances, together with their characteristic multiplet shapes, can be used for localisation of the position of O-acetyl substituents in the molecule. The number of such substituents in the molecule can be inferred from the number of acetyl-methyl singlets, which also have characteristic resonance positions. This method for determination of the number and position of O-acetyl substituents in sialic acid residues is very powerful for structural analysis of underivatized carbohydrate chains derived from glycoconjugates. This is demonstrated for the oligosaccharide N-acetyl-4-O-acetylneuraminosyl-(alpha 2 leads to 3)-lactose isolated from echidna milk.

Acetylation↗
PubMed1982

Primary structure of the N-glycosidically linked sialoglycans of secretory immunoglobulins A from human milk.

The alkali-stable sialoglycopeptides of secretory immunoglobulins A from human milk have been separated from the alkali-labile glycopeptides by gel filtration and from the asialoglycopeptides by ion-exchange chromatography. The structures of five of them have been determined on the basis of the results obtained by methylation analysis, mass spectrometry and 360 MHz 1H-NMR spectroscopy. For glycopeptide B, the following structure has been found: (formula; see text) The other glycopeptides can be considered as extensions of this structure. The following extensions to Gal-6' are proposed: NeuAc(alpha 2-6) (glycopeptide A), Gal(beta 1-3) (glycopeptide D) and Fuc(alpha 1-6) (glycopeptide E). Furthermore, in glycopeptide C a fucose residue in (alpha 1-3) linkage to GlcNAc-5' could be traced.

Alkalies↗
PubMed1982

A 500-MHz proton-magnetic-resonance study of several fragments of the carbohydrate-protein linkage region commonly occurring in proteoglycans.

The proton-magnetic-resonance spectra of three partial structures of the carbohydrate-protein linkage region that frequently occurs in proteoglycans, namely, beta-D-Galp-(1 leads to 3)-beta-D-Galp-(1 leads to 4)-beta-D-Xylp-(1 leads to O)-L-Ser, were recorded in 2H2O at 500 MHz; they could be completely interpreted, both for the glyco-serines and for the corresponding glyco-xylitols. The chemical shifts and the coupling constants were refined by computer simulation of the spectra. The change in the chemical shift of H-4 of a D-galactopyranosyl residue upon substitution at C-3 by a beta-D-galactopyranosyl group is proposed to be characteristic for this particular attachment, making H-4 of galactose a structural-reporter group. The three constituting monosaccharides adopt the 4C1 (D) ring conformation. The terminal galactopyranosyl group and the internal galactopyranosyl residue differ as to the population of rotamers around the C-5/C-6 axis. Concomitantly, the flexibility of their glycosidic linkages is distinct.

Carbohydrates↗