Presentation Title

Effect of size and charge on amide proton solvent exchange in glycosaminoglycans

Start Date

November 2016

End Date

November 2016

Location

MSE 103

Type of Presentation

Oral Talk

Abstract

Interactions between glycosaminoglycans (GAG’s) and proteins mediate diverse physiological processes. Binding to GAG’s can immobilize proteins at their sites of production and in the extracellular matrix, regulate enzyme activity, influence the binding of ligands to their receptors, and protect proteins against degradation. The varied biological activities of GAG’s are in part determined by their sequence and local structure of regions within the biopolymer chain. As a part of a larger research project characterizing the effects of GAG structure on the exchange rates of amide protons, this work focuses on measurements with oligosaccharides of native hyaluronic acid (HA) and HA modified by chemical oversulfation. Preparation of the HA oligosaccharides involves the enzymatic depolymerization of the intact HA polysaccharide, followed by size-exclusion chromatography to separate the digest into size-uniform fractions. Preparation of the oversulfated size-uniform HA oligosaccharides involves chemical reaction with a sulfur trioxide pyridine complex. Resultant size-uniform HA and oversulfated HA oligosaccharides are characterized by NMR and mass spectrometry. The oligosaccharides are then subjected to kinetics experiments to measure the rate of exchange of the amide protons with water as a function of temperature. Chemical shift and line shape analysis of the 1H NMR spectra allow calculation and quantitative comparison of the temperature coefficients and energy barriers for amide proton exchange. 1H NMR has been previously used to determine exchange rates of labile protons in sulfamate and hydroxyl groups for several GAG’s and has revealed the presence of stable solution-state intramolecular hydrogen bonds in the synthetic heparin drug Fondaparinux. In Fondaparinux these hydrogen bonds pre-organize the secondary structure of this synthetic heparin to facilitate protein recognition. Therefore, the effect of the size and degree of sulfation of HA oligosaccharides on the amide proton exchange rates has potential to provide important new insights into the structure of these oligosaccharides in aqueous solutions.

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Nov 12th, 10:45 AM Nov 12th, 11:00 AM

Effect of size and charge on amide proton solvent exchange in glycosaminoglycans

MSE 103

Interactions between glycosaminoglycans (GAG’s) and proteins mediate diverse physiological processes. Binding to GAG’s can immobilize proteins at their sites of production and in the extracellular matrix, regulate enzyme activity, influence the binding of ligands to their receptors, and protect proteins against degradation. The varied biological activities of GAG’s are in part determined by their sequence and local structure of regions within the biopolymer chain. As a part of a larger research project characterizing the effects of GAG structure on the exchange rates of amide protons, this work focuses on measurements with oligosaccharides of native hyaluronic acid (HA) and HA modified by chemical oversulfation. Preparation of the HA oligosaccharides involves the enzymatic depolymerization of the intact HA polysaccharide, followed by size-exclusion chromatography to separate the digest into size-uniform fractions. Preparation of the oversulfated size-uniform HA oligosaccharides involves chemical reaction with a sulfur trioxide pyridine complex. Resultant size-uniform HA and oversulfated HA oligosaccharides are characterized by NMR and mass spectrometry. The oligosaccharides are then subjected to kinetics experiments to measure the rate of exchange of the amide protons with water as a function of temperature. Chemical shift and line shape analysis of the 1H NMR spectra allow calculation and quantitative comparison of the temperature coefficients and energy barriers for amide proton exchange. 1H NMR has been previously used to determine exchange rates of labile protons in sulfamate and hydroxyl groups for several GAG’s and has revealed the presence of stable solution-state intramolecular hydrogen bonds in the synthetic heparin drug Fondaparinux. In Fondaparinux these hydrogen bonds pre-organize the secondary structure of this synthetic heparin to facilitate protein recognition. Therefore, the effect of the size and degree of sulfation of HA oligosaccharides on the amide proton exchange rates has potential to provide important new insights into the structure of these oligosaccharides in aqueous solutions.