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S F Wheeler

Publications and source records attributed to S F Wheeler.

9 recordsLinked to original sources
PubMed2001

Extension of the in-gel release method for structural analysis of neutral and sialylated N-linked glycans to the analysis of sulfated glycans: application to the glycans from bovine thyroid-stimulating hormone.

This paper reports an extension of the in-gel technique for releasing N-linked glycans from glycoproteins for analysis by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry reported by B. Küster, S. F. Wheeler, A. P. Hunter, R. A. Dwek, and D. J. Harvey (1997, Anal. Biochem. 250, 82-101) to allow it to be used for sulfated glycans. The method was used to identify N-linked glycans from bovine thyroid-stimulating hormone. Following glycan release, either in gel or in solution, the glycans were fractionated directly with a porous graphatized carbon column. The sulfated glycans were examined by MALDI mass spectrometry in negative ion mode with d-arabinosazone as the matrix and both neutral and acidic glycans were examined in positive ion mode from 2,5-dihydroxybenzoic acid. Negative ion post-source decay spectra were also obtained. Twenty-two neutral and fifteen sulfated N-linked glycans were identified and it was shown that negligible loss of sulfate groups occurred even though these groups are often readily lost during MALDI analysis. The glycans were mainly sulfated hybrid and biantennary complex structures. Negative ion post-source decay and positive ion collision-induced fragmentation spectra were obtained.

Amidohydrolases↗
PubMed2000

Negative ion mass spectrometry of sialylated carbohydrates: discrimination of N-acetylneuraminic acid linkages by MALDI-TOF and ESI-TOF mass spectrometry.

Negative ion MALDI and electrospray fragmentation spectra were recorded from 12 sialylated carbohydrates ranging from trisaccharides to biantennary N-linked glycans. D-Arabinosazone was found to be the most satisfactory MALDI matrix for these compounds. Fragmentation mechanisms were investigated with the aid of several synthesized analogues of the sugars labeled with 13C and 2H. The substitution position of the sialic acid (alpha2-->3 or alpha2-->6) was found to have a dramatic effect on the overall fragmentation pattern of these compounds, and several features of the spectra were identified that allowed the substitution pattern to be determined. In particular, the appearance of an ion at m/z 306 appeared to be diagnostic of the presence of an alpha2-->6-linked sialic acid. Selection and further fragmentation of the in-source (conevoltage) fragment ion corresponding to the trisaccharide Neu5Acalpha2-->3(or 6)Galbeta1-->4GlcNAc from larger, N-linked glycans, ionized by electrospray, gave fragmentation patterns identical to those of the reference trisaccharides, thus providing a method for confirming the sialic acid linkage.

Carbohydrate Sequence↗
PubMed1999

Glycosylation differences between the normal and pathogenic prion protein isoforms.

Prion protein consists of an ensemble of glycosylated variants or glycoforms. The enzymes that direct oligosaccharide processing, and hence control the glycan profile for any given glycoprotein, are often exquisitely sensitive to other events taking place within the cell in which the glycoprotein is expressed. Alterations in the populations of sugars attached to proteins can reflect changes caused, for example, by developmental processes or by disease. Here we report that normal (PrP(C)) and pathogenic (PrP(Sc)) prion proteins (PrP) from Syrian hamsters contain the same set of at least 52 bi-, tri-, and tetraantennary N-linked oligosaccharides, although the relative proportions of individual glycans differ. This conservation of structure suggests that the conversion of PrP(C) into PrP(Sc) is not confined to a subset of PrPs that contain specific sugars. Compared with PrP(C), PrP(Sc) contains decreased levels of glycans with bisecting GlcNAc residues and increased levels of tri- and tetraantennary sugars. This change is consistent with a decrease in the activity of N-acetylglucosaminyltransferase III (GnTIII) toward PrP(C) in cells where PrP(Sc) is formed and argues that, in at least some cells forming PrP(Sc), the glycosylation machinery has been perturbed. The reduction in GnTIII activity is intriguing both with respect to the pathogenesis of the prion disease and the replication pathway for prions.

Animals↗
PubMed1998

Structural determination of N-linked carbohydrates by matrix-assisted laser desorption/ionization-mass spectrometry following enzymatic release within sodium dodecyl sulphate-polyacrylamide electrophoresis gels: application to species-specific glycosylation of alpha1-acid glycoprotein.

This paper describes a sensitive method for analysis of N-linked carbohydrates released enzymatically from within the gel following separation of glycoproteins (50-100 pmols) by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The separated bands containing the glycoproteins were cut from the gel, destained, reduced and alkylated. N-linked glycans were then released by in-gel incubation with peptide N-glycosidase-F (PNGase-F) and extracted with water and acetonitrile. Sialic acid-containing glycans were converted into methyl esters by reaction with methyl iodide, salts and reagents were removed by passage through a mixed-bed column of ion-exchange resins and the glycans were examined by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry. Structural determination of the released glycans was performed by exoglycosidase digestion. Following glycan release and extraction, the protein could be digested within the gel with trypsin, and the masses of the tryptic peptides could be compared with those generated from a sequence database for protein identification. The method is applied to the analysis of N-linked glycans from alpha1-acid glycoprotein from man, cow, sheep and dog. Major species-specific differences in glycosylation were found. Thus, although all four species used N-acetyl-neuraminic acid, only cow and sheep additionally used N-glycolyl-neuraminic acid. Biantennary glycans were the predominant carbohydrates in cow, sheep and dog but man produced more triantennary glycans and a substantial amount of tetraantennary sugars. Fucosylation was only found in glycans from man and cow and both cow and sheep glycans were found to have beta1-3- and well as beta1-4-linked galactose residues in the antennae.

Amidohydrolases↗
PubMed1997

Sequencing of N-linked oligosaccharides directly from protein gels: in-gel deglycosylation followed by matrix-assisted laser desorption/ionization mass spectrometry and normal-phase high-performance liquid chromatography.

A generally applicable, rapid, and sensitive method for profiling and sequencing of glycoprotein-associated N-linked oligosaccharides from protein gels was developed. The method employed sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for protein separation and purification and in-gel deglycosylation using PNGase F for glycan release. Profiles of the neutral glycans from bovine ribonuclease B, chicken ovalbumin, and human immunoglobulin G (IgG), as well as sialic acid-containing sugars (following esterification of the acidic groups) of bovine fetuin and bovine alpha1-acid glycoprotein, were obtained by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) and by normal-phase high-performance liquid chromatography following fluorescent labeling. Oligosaccharides were sequenced using specific exoglycosidases, and digestion products were analyzed by MALDI MS. Between 50 and 100 pmol (1.5 to 15 microg) of glycoprotein applied to the gel was sufficient to characterize its oligosaccharide contents. The identity of all glycoproteins investigated could be confirmed after deglycosylation by in-gel trypsin treatment followed by MALDI MS mass mapping and matching the measured molecular weights to a sequence database. The technique was used for the characterization of the glycan moieties of human immunodeficiency virus recombinant gp120 (Chinese hamster ovary cells) and to monitor changes in the glycosylation of this glycoprotein when produced in the presence of a glucosidase I inhibitor. Furthermore, since heavy and light chains of IgG became separated by SDS-PAGE, it could be established that most glycans were associated with the heavy chains.

1-Deoxynojirimycin↗
PubMed1997

Molecular weight measurements of low molecular weight heparins by gel permeation chromatography.

The molecular weight profiles of low molecular weight heparin samples have been measured by high-performance gel permeation chromatography using as calibrant the heparinase-degraded material (90/686) now established as the 1st International Reference Preparation (IRP) Low Molecular Weight Heparin for Molecular Weight Calibration Use of the calibrant as a broad molecular weight standard is described and a calibration table provided based on data collected over several years in one laboratory. In order to confirm the assignment of degree of polymerisation to resolved oligosaccharide peaks in the calibrant, molecular weights of oligosaccharides fractionated from the 1st IRP were independently determined by fast atom bombardment mass spectrometry (FAB MS). The molecular weight distributions of commercial low molecular weight heparins have been characterized. Measurements of molecular weight parameters of heparin molecular weight standards from several sources provide comparisons between the molecular weight scales of this and other studies.

Calibration↗
PubMed1994

Drying from phosphate-buffered solutions can result in the phosphorylation of primary and secondary alcohol groups of saccharides, hydroxylated amino acids, proteins, and glycoproteins.

Drying (e.g., freeze-drying) aqueous phosphate-buffered solutions of organic compounds containing primary and/or secondary alcohol groups promotes esterification, producing orthophosphate esters. The reaction is accelerated by heat and by pH values < 7 and is affected by residual moisture content. The same preparations as solutions, similarly treated, produced little or no phosphorylated materials. The promotion of esterification in the dry state can, in part, be rationalized in terms of a mass-action effect because of the resulting low-water activity in dried preparations. When metaphosphates are used, esterification proceeds at a greatly increased rate and to a greater extent. Because of the relatively facile interconversion of phosphorus oxyacid salts, it is possible that a "metaphosphate species" may be responsible for the esterification reaction in all cases. We conclude that care should be exercised when hydroxylated organic compounds are dried from phosphate buffers so as to avoid the formation of phosphorylated artifacts.

Amino Acids↗
PubMed1993

Substance abuse during pregnancy.

Use and abuse of both licit and illicit drugs is common. Although certain variables can appropriately serve as markers for increased risk, the possibility of substance abuse should be considered in all pregnant women. Alcohol is the leading identified cause of teratogenesis by drugs or environmental agents; most other drugs of abuse do not increase the risk of congenital malformations on a large scale. Substance abuse can produce significant degrees of toxicity in both pregnant women and their offspring. Screening and counseling of pregnant women concerning past and present use of tobacco, alcohol, and illicit drugs should be routine. Prenatal care must include increased surveillance for drug-related complications; coordinated, comprehensive, family-oriented drug treatment; and social services. Rehabilitation and support efforts should continue after delivery and address issues that lead to and maintain patterns of abuse. The drug-exposed neonate must be anticipated and evaluated with a knowledge of the maternal drug abuse history and specific drug risks, including neonatal abstinence syndrome. Continuing care of the child should address the increased risk of developmental and behavioral problems from both prenatal exposures and continuing socioenvironmental barriers.

Adolescent↗