11 research outputs found
Multi-Site N-glycan mapping study 1: Capillary electrophoresis â laser induced fluorescence
An international team that included 20 independent laboratories from biopharmaceutical companies, universities, analytical contract laboratories and national authorities in the United States, Europe and Asia was formed to evaluate the reproducibility of sample preparation and analysis of N-glycans using capillary electrophoresis of 8-aminopyrene-1,3,6-trisulfonic acid (APTS)-labeled glycans with laser induced fluorescence (CE-LIF) detection (16 sites) and ultra highperformance
liquid chromatography (UHPLC, 12 sites; results to be reported in a subsequent publication). All participants used the same lot of chemicals, samples, reagents, and columns/capillaries to run their assays. Migration time, peak area and peak area percent values were determined for all peaks with >0.1% peak area. Our results demonstrated low variability and high reproducibility, both, within any given site as well across all sites, which indicates that a standard N-glycan analysis platform appropriate for general use (clone selection, process development, lot release, etc.) within the industry can be established
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Identification, Characterization, and Quantification of Dicarbonyl Adducts in the Plasma Proteome in Type-2 Diabetes
Glyco-oxidation is linked to the pathophysiology of diabetes and diabetic complications. The process of glyco-oxidation generates reactive dicarbonyls, which form adducts on arginine residues in distributions throughout the proteome that are site-specific depending on the protein microenvironment. Dicarbonyl adducts are thus markers for glyco-oxidative stress. Various approaches using mass spectrometry permits the identification, localization, and quantification of these dicarbonyl adducts. Using MG as a model dicarbonyl, a shotgun proteomics approach identified the sites for modification of major plasma proteins. Thirty five sites on seven abundant plasma proteins were found, and investigation into the microenvironment surrounding the target arginine sites revealed a neighboring charged residue motif where adjacent residues were either negatively or positively charged. One of the sites identified was R257 in HSA, which is located in the important drug binding site I. We validated drug site I as a target for MG modification by the adaptation of two assays to monitor the effect of MG modification. MG significantly decreases the rate of hydrolysis of PGE2 in drug site I, and induces the displacement of prodan from drug site I. Molecular modeling of warfarin docking at drug site I with the MG-modified R257 resulted in significantly decreased binding and change in binding orientation. The oxidation products of susceptible residues methionine, tryptophan, and cysteine were evaluated using MRM of oxidized HSA peptides. Oxidation of methionine gave the M+16 single oxidized product, and M329 in HSA was the most responsive site. Oxidation of the sole W214 tryptophan produced the W+32 double oxidation product, and oxidation of C34 produced the C+48 triple oxidation product. MG, 3DG, and glucosone were evaluated for propensity to modify 12 HSA sites based on MRM of dicarbonyl modified HSA. Dicarbonyl modification was independent of arginine solvent accessibility. In a clinical study using nephropathy as an endpoint, sites of oxidation and modification of HSA by MG, 3DG, and glucosone were quantified by MRM. The most important variable among diabetic subjects was metformin use, and subjects taking metformin had significantly reduced markers for glyco-oxidation. These findings may be useful in the development of new diabetes therapies that aim to ameliorate glyco-oxidative stress