Analysis and characterization of heparin impurities

This review discusses recent developments in analytical methods available for the sensitive separation, detection and structural characterization of heparin contaminants. The adulteration of raw heparin with oversulfated chondroitin sulfate (OSCS) in 2007–2008 spawned a global crisis resulting in extensive revisions to the pharmacopeia monographs on heparin and prompting the FDA to recommend the development of additional physicochemical methods for the analysis of heparin purity. The analytical chemistry community quickly responded to this challenge, developing a wide variety of innovative approaches, several of which are reported in this special issue. This review provides an overview of methods of heparin isolation and digestion, discusses known heparin contaminants, including OSCS, and summarizes recent publications on heparin impurity analysis using sensors, near-IR, Raman, and NMR spectroscopy, as well as electrophoretic and chromatographic separations

Publisher Correction:Network inference from glycoproteomics data reveals new reactions in the IgG glycosylation pathway

Correction to: Nature Communications (2017) 8:1231. doi:10.1038/s41467-017-01525-

On the path to glycan conformer identification: Gas-phase study of the anomers of methyl glycosides of N-acetyl-d-glucosamine and N-acetyl-d-galactosamine

The methyl glycosides of N-acetyl-d-glucosamine (d-GlcNAc) and N-acetyl-d-galactosamine (d-GalNAc) have been used as model glycan analogs to study the effects of lithium cation binding on glycan structure in gas-phase experiments. Infrared multiple photon dissociation (IRMPD) spectra for the two Li+-complexed anomers of methyl-d-GlcNAc revealed a difference of 10 cm−1 between their respective carbonyl stretching band positions. A corresponding 11 cm−1 shift was observed for the two Li+-complexed anomers of methyl-d-GalNAc. Theoretical calculations indicate that the position of the methyl group (α and β, or axial and equatorial, respectively) on carbon 1 of the sugar and its close proximity to the carbonyl of the acetamido group on carbon 2 cause the average orientation of the carbonyl to change in order to minimize steric hindrance. This change in orientation is postulated to be the cause of the observed CO stretching band shift. The calculations also predict competitive binding of the lithium cation between two or more regions of d-GlcNAc and d-GalNAc. This is primarily due to differences in the spatial arrangement and orientation of lone pairs of electrons among the isomers, and stereochemical differences in hydrogen bonding. From an application point of view, differences in the infrared spectra of lithium adducts of acetamido sugars establish the value of variable-wavelength IRMPD as an alternative to fragmentation patterns in discriminating between these isomers

On the path to glycan conformer identification: Gas-phase study of the anomers of methyl glycosides of n-acetyl-d-glucosamine and n-acetyl-d-galactosamine

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Molecular cloning and expression of cDNA encoding the rat UDP-N-Acetylglucosamine:-6-D Mannoside ?-1,2-N-Acetylglucosaminyltransferase II

UDP-N-acetyl-D-glucosamine:alpha-6-D-mannoside beta-1,2-N-acetylglucosaminyltransferase II (EC 2.4.1.143) (GnT II) is a Golgi resident enzyme that catalyzes an essential step in the biosynthetic pathway leading from high mannose to complex N-linked oligosaccharides. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the enzyme purified from rat liver revealed a polypeptide of 42 kDa. Amino acid sequences were obtained from the N terminus and a tryptic peptide. Overlapping cDNA clones coding for the full-length rat GnT II were obtained. The complete nucleotide sequence revealed a 1326-base pair open reading frame that codes for a polypeptide of 442 amino acids, including a presumptive N-terminal membrane-anchoring domain. The region of cDNA coding for the C-terminal 389 amino acids of rat GnT II was linked in frame to a cDNA segment encoding the cleavable signal sequence of the human interleukin-2 receptor and transiently expressed in COS-7 cells. A 77-fold enhancement of GnT II activity over a control carrying the GnT II cDNA out-of-frame was detected in the culture medium at 72 h after transfection. 1H-NMR spectroscopy confirmed that the oligosaccharide synthesized in vitro by the recombinant enzyme was the product of GnT II activity. These data verify the identity of the cloned GnT II cDNA and demonstrate that the C-terminal region of the protein includes the catalytic domai