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Temperature dependencies of amide 1 H‐ and 15 N‐chemical shifts in hyaluronan oligosaccharides
Author(s) -
Blundell Charles D.,
Almond Andrew
Publication year - 2007
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1969
Subject(s) - chemistry , amide , intramolecular force , chemical shift , glucuronic acid , proton , hydrogen bond , atmospheric temperature range , polysaccharide , stereochemistry , molecule , crystallography , organic chemistry , physics , quantum mechanics , meteorology
Temperature coefficients (Δδ/ΔT) of amide chemical shifts of N ‐acetylglucosamine residues have been measured in a range of oligosaccharides of the important vertebrate polysaccharide hyaluronan. Odd‐ and even‐numbered oligosaccharides with glucuronic acid, Δ‐4,5‐unsaturated glucuronic acid and N ‐acetylglucosamine at the termini were investigated. All amide proton temperature coefficients were only slightly less negative (−6.9 to − 9.1 ppb/ °C) than those of amide protons in free exchange with water (≈− 11 ppb/ °C), indicating an absence of persistent intramolecular hydrogen bonds. With the exception of amide groups in reducing‐terminal N ‐acetylglucosamine rings, all amide proton environments have the same temperature coefficient (−6.9 ppb/ °C), irrespective of differences in amide group chemical shifts and 3 J HH coupling constants, i.e. they do not sense subtle differences in orientation of the amide group. Amide nitrogen temperature coefficients report the same phenomena but with greater sensitivity. These data provide a set of reference values for temperature coefficients measured in other carbohydrates with acetamido sugars. Copyright © 2007 John Wiley & Sons, Ltd.