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Transient hydrogen bonding in uniformly 13 C, 15 N‐Labeled Carbohydrates in Water
Author(s) -
Norris Scott E.,
Landström Jens,
Weintraub Andrej,
Bull Thomas E.,
Widmalm Göran,
Freedberg Darón I.
Publication year - 2012
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.21710
Subject(s) - chemistry , hydrogen bond , amide , residue (chemistry) , crystallography , hydrogen , carbon 13 nmr , resonance (particle physics) , polysaccharide , molecular dynamics , stereochemistry , computational chemistry , molecule , organic chemistry , physics , particle physics
We report NMR studies of transient hydrogen bonding in a polysaccharide (PS) dissolved in water without cosolvent at ambient temperature. The PS portion of the Escherichia coli O142 lipopolysaccharide is comprised of repeating pentasaccharide units of GalNAc (N‐acetyl galactosamine), GlcNAc (N‐acetyl glucosamine), and rhamnose in a 3:1:1 ratio, respectively. A 105‐ns molecular dynamics (MD) simulation on one pentasaccharide repeat unit predicts transient inter‐residue hydrogen bonds from the GalNAc NH groups in the PS. To investigate these predictions experimentally, the PS was uniformly 13 C, 15 N enriched and the NH, carbonyl, C2, C4, and methyl resonances of the GalNAc and GlcNAc residues assigned using through‐bond triple‐resonance NMR experiments. Temperature dependence of amide NH chemical shifts and one‐bond NH J couplings support that NH groups on two of the GalNAc residues are donors in transient hydrogen bonds. The remaining GalNAc and GlcNAc NHs do not appear to be donors from either temperature‐dependent chemical shifts or one‐bond NH J couplings. These results substantiate the presence of weak or partial hydrogen bonds in carbohydrates, and that MD simulations of repeating units in PSs provide insight into overall PS structure and dynamics. Published 2011 Wiley Periodicals, Inc. Biopolymers 97: 145–154, 2012.