N-Acetylated amino sugars: the dependence of NMR 3J(HNH2)-couplings on conformation, dynamics and solvent

Mobli, Mehdi and Almond, Andrew (2007) N-Acetylated amino sugars: the dependence of NMR 3J(HNH2)-couplings on conformation, dynamics and solvent. Organic and biomolecular chemistry, 5 14: 2243-2251. doi:10.1039/b705761j


Author Mobli, Mehdi
Almond, Andrew
Title N-Acetylated amino sugars: the dependence of NMR 3J(HNH2)-couplings on conformation, dynamics and solvent
Formatted title
N-Acetylated amino sugars: the dependence of NMR 3J(HNH2)-couplings on conformation, dynamics and solvent
Journal name Organic and biomolecular chemistry   Check publisher's open access policy
ISSN 1477-0520
1477-0539
Publication date 2007-01-01
Sub-type Article (original research)
DOI 10.1039/b705761j
Open Access Status Not Open Access
Volume 5
Issue 14
Start page 2243
End page 2251
Total pages 9
Place of publication Cambridge, United Kingdom
Publisher Royal Society of Chemistry
Language eng
Formatted abstract
N-Acetylated amino sugars are essential components of living organisms, but their dynamic conformational properties are poorly understood due to a lack of suitable experimental methodologies. Nuclear magnetic resonance (NMR) is ideally suited to these conformational studies, but accurate equations relating the conformation of key substituents (e.g., the acetamido group) to NMR observables are unavailable. To address this, density functional theory (DFT) methods have been used to calculate vicinal coupling constants in N-acetylated amino sugars and derive empirical Karplus equations for 3J(HNH2) of N-acetyl-D-glucosamine (GlcNAc) and N-acetyl-D-galactosamine (GalNAc). The fitted Karplus parameters were found to be similar to those previously derived for peptide amide groups, but are consistently larger in magnitude. Local intramolecular interactions had a small effect on the calculated J-couplings and comparison with experimental data suggested that DFT slightly overestimated them. An implicit solvation model consistently lowered the magnitude of the calculated values, improving the agreement with the experimental data. However, an explicit solvent model, while having a small effect, worsened the agreement with experimental data. The largest contributor to experimentally-determined 3J(HNH2)-couplings is proposed to be librations of the amide group, which are well approximated by a Gaussian distribution about a mean dihedral angle. Exemplifying the usefulness of our derived Karplus equations, the libration of the amide group could be estimated in amino sugars from experimental data. The dynamical spread of the acetamido group in free -GlcNAc, -GlcNAc and -GalNAc was estimated to be 32°, 42° and 20°, with corresponding mean dihedral angles of 160°, 180° and 146°, respectively.

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Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
Institute for Molecular Bioscience - Publications
 
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