CARB 64 |
| Protein amino groups react with reducing sugars such as D-glucose in vivo to form Schiff bases, which subsequently rearrange to produce stable, covalently bound Amadori adducts. These adducts degrade to form advanced glycation end-products (AGEs). Glycation reactions are promoted in diabetic patients due to elevated glucose concentrations, and many of the physiological complications caused by this disease are mediated by the effects of glycation on protein structure and function. To gain more insight into the chemistry of non-enzymatic glycation, 13C NMR studies were conducted on a model protein, RNase A, which was reacted in vitro with a group of 13C-labeled aldoses: D-[2-13C]glucose, 6-O-methyl-D-[2-13C]glucose, 3-O-methyl-[2-13C]glucose, D-[2-13C]ribose, D-[2-13C]xylose, 5-O-methyl-D-[2-13C]xylose, 3-deoxy-D-[2-13C]glucose, and 2-deoxy-[1-13C]ribose. These aldoses were selected to probe the glycation reaction pathway by either inhibiting/preventing enediol formation, affecting the equilibrium distribution of cyclic and acyclic forms of the Amadori intermediate, or promoting Schiff base formation without subsequent Amadori rearrangement. 13C-Labeling at C2 allowed selective detection of the aldose C2 carbon above background, thus permitting the monitoring of Amadori formation and its chemical fate. Time-lapse 13C{1H} NMR spectra of glycated RNase were collected over 1-2 months at 20 oC or 36 oC to follow the formation of labeled intermediates and end products and measure their rates of appearance or disappearance. Results show that aldose structure significantly influenced the course of the reaction. Labeled carbon signals were observed clustered near 210, 180, 130, 100, and 80 ppm, with signal intensities in these regions varying considerably with aldose reactant. In some cases, only Amadori signals were detected (~100 ppm), whereas in others, signals were observed in all five regions over time, with 13C label eventually accumulating at 130 ppm. |
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General Posters
6:00 PM-8:00 PM, Tuesday, March 27, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Carbohydrate Chemistry |