Solution structure of a LewisX analogue by off-resonance 1H NMR spectroscopy without use of an internal distance reference |
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Authors: | P Berthault N Birlirakis G Rubinstenn P Sinaÿ H Desvaux |
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Institution: | (1) Molecular Chemistry Service, NMR Laboratory, C.E.A/C.E., Saclay, F-91191 Gif-sur-Yvette Cédex, France;(2) Department of Chemistry, Ecole Normale Supérieure, 24 Rue Lhomond, F-75231 Paris Cédex 05, France;(3) National High Magnetic Field Laboratory, Center for Interdisciplinary Magnetic Resonance, 1800 East Paul Dirac Drive, 32310 Tallahassee, FL, USA |
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Abstract: | Summary A recent 1H NMR method has been applied to the determination of the solution structure and internal dynamics of a synthetic mixed C/O trisaccharide related to sialyl Lewisx. Varying the rf field offset in ROESY-type experiments enabled the measurement of longitudinal and transverse dipolar cross-relaxation rates with high accuracy. Assuming that for each proton pair the motion could be represented by a single exponential autocorrelation function, it was possible to derive geometrical parameters (r) and dynamic parameters cp. With this assumption, 224 cross-relaxation rates have been transformed into 30 interproton distance constraints and 30 dipolar correlation times. The distance constraints have been used in a simulated-annealing procedure. This trisaccharide exhibits a structure close to the O-glycosidic analogue, but its flexibility seems highly reduced. On the basis of the determined structure and dynamics, it is shown that no conformational exchange occurs, the molecule existing in the form of a unique family in aqueous solution. In order to assess the quality of the resulting structures and to validate this new experimental procedure of distance extraction, we finally compare these solution structures to the ones obtained using three different sets of distances deduced from three choices of internal reference. It appears that this procedure allows the determination of the most precise and accurate solution.Abbreviations COSY
correlation spectroscopy
- NOE
nuclear Overhauser enhancement
- NOESY
nuclear Overhauser enhancement spectroscopy; rmsd, root-mean-square deviation
- ROESY
rotating frame Overhauser enhancement spectroscopy
- SLex
sialyl Lewisx
- TOCSY
total correlation spectroscopy |
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Keywords: | Lewisx Off-resonance ROESY Solution structure Internal dynamics |
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