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A Conformational Study of the Trisaccharide β ‐ D ‐Glc p ‐(1→2)[ β ‐ D ‐Glc p ‐(1→3)] α ‐ D ‐Glc p ‐OMe by NMR NOESY and TROESY Experiments, Computer Simulations, and X‐Ray Crystal Structure Analysis
Author(s) -
Rundlöf Torgny,
Eriksson Lars,
Widmalm Göran
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010417)7:8<1750::aid-chem17500>3.0.co;2-x
Subject(s) - trisaccharide , chemistry , proton , two dimensional nuclear magnetic resonance spectroscopy , nuclear overhauser effect , crystallography , molecular dynamics , relaxation (psychology) , glycosidic bond , proton nmr , population , crystal structure , single crystal , molecular physics , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , stereochemistry , computational chemistry , physics , nuclear physics , psychology , social psychology , biochemistry , enzyme , demography , sociology
Proton–proton cross‐relaxation rates have been measured for the trisaccharide β ‐ D ‐Glc p ‐(1→2)[ β ‐ D ‐Glc p ‐(1→3)] α ‐ D ‐Glc p ‐OMe in D 2 O as well as in D 2 O/[D 6 ]DMSO 7:3 solution at 30 °C by means of one‐dimensional NMR pulsed field gradient 1 H, 1 H NOESY and TROESY experiments. Interatomic distances for the trisaccharide in D 2 O were calculated from the cross‐relaxation rates for two intraresidue and three interglycosidic proton pairs, using the isolated spin‐pair approximation. In the solvent mixture one intraresidue and three interglycosidic distances were derived without the use of a specific molecular model. In this case the distances were calculated from the cross‐relaxation rates in combination with “model‐free” motional parameters previously derived from 13 C relaxation measurements. The proton–proton distances for interglycosidic pairs were compared with those averaged from Metropolis Monte Carlo and Langevin Dynamics simulations with the HSEA, PARM 22, and CHEAT 95 force fields. The crystal structure of the trisaccharide was solved by analysis of X‐ray data. Interresidue proton pairs from the crystal structure and those observed by NMR experiments were similar. However, the corresponding proton–proton distances generated by computer simulations were longer. For the (1→2) linkage the glycosidic torsion angles of the crystal structure were found in a region of conformational space populated by all three force fields, whereas for the (1→3) linkage they occupied a region of low population density, as seen from the simulations.