TY - JOUR
T1 - Noncovalent Interactions in the Gas-Phase Conformers of Anionic Iduronate (methyl 2-O-sulfo-alpha-L-iduronate)
T2 - Variation of Subconformer versus Ring Conformer Energetics for a Prototypical Anionic Monosaccharide Studied Using Computational Methods
AU - Taylor, Christopher J.
AU - Nix, Michael G. D.
AU - Dessent, Caroline E. H.
PY - 2010/10/28
Y1 - 2010/10/28
N2 - The conformational preferences of the prototypical anionic monosaccharide (methyl 2-O-sulfo-alpha-L-iduronate) have been studied at various computational levels to investigate the energetic variation of 17 subconfoemers associated with the C-4(1), S-2(0), S-5(1), and C-1(4) ring conformers. These calculations include the first fully optimized MP2 calculations that have been performed for an anionic sugar system, and therefore allow an assessment of the performance of a group of DFT functionals (B3LYP, PW9113W91, and M05-2X) for treating the noncovalent dispersion and anomeric effects that are present in this system. We find that the recently developed M05-2X functional of Truhlar and co-workers [Y. Zhao, N. E. Schultz, D. G. Truhlar, J. Chem. Theory Comput., 2006, 2, 364] reproduces the MP2 results most closely, thus indicating that it may well be suitable for computational studies of larger ionic saccharides. Most importantly, the results presented indicate that it is crucial to consider the subconformers (which correspond to rearrangements of the sugar-ring side-chains) of the main ring-conformers in order to obtain a reliable overview of the potential energy surface of such systems. We find that the lowest isolated (gas-phase) conformer corresponds to a C-4(l) chair conformer, which displays a pair of strong C(3)-OH center dot center dot center dot SO3- and OMe center dot center dot center dot SO3- electrostatic hydrogen-bonding interactions, coupled with a looser C(4) OH center dot center dot center dot SO3- interaction. Overall, the relative energies of the subconformers appear to be straightforwardly related to the number of hydrogen-bonding interactions that each conformer displays among its pendant functional groups.
AB - The conformational preferences of the prototypical anionic monosaccharide (methyl 2-O-sulfo-alpha-L-iduronate) have been studied at various computational levels to investigate the energetic variation of 17 subconfoemers associated with the C-4(1), S-2(0), S-5(1), and C-1(4) ring conformers. These calculations include the first fully optimized MP2 calculations that have been performed for an anionic sugar system, and therefore allow an assessment of the performance of a group of DFT functionals (B3LYP, PW9113W91, and M05-2X) for treating the noncovalent dispersion and anomeric effects that are present in this system. We find that the recently developed M05-2X functional of Truhlar and co-workers [Y. Zhao, N. E. Schultz, D. G. Truhlar, J. Chem. Theory Comput., 2006, 2, 364] reproduces the MP2 results most closely, thus indicating that it may well be suitable for computational studies of larger ionic saccharides. Most importantly, the results presented indicate that it is crucial to consider the subconformers (which correspond to rearrangements of the sugar-ring side-chains) of the main ring-conformers in order to obtain a reliable overview of the potential energy surface of such systems. We find that the lowest isolated (gas-phase) conformer corresponds to a C-4(l) chair conformer, which displays a pair of strong C(3)-OH center dot center dot center dot SO3- and OMe center dot center dot center dot SO3- electrostatic hydrogen-bonding interactions, coupled with a looser C(4) OH center dot center dot center dot SO3- interaction. Overall, the relative energies of the subconformers appear to be straightforwardly related to the number of hydrogen-bonding interactions that each conformer displays among its pendant functional groups.
KW - DENSITY-FUNCTIONAL THEORY
KW - HEPARAN-SULFATE OLIGOSACCHARIDES
KW - BASIS-SET LIMIT
KW - VAN-DER-WAALS
KW - MASS-SPECTROMETRY
KW - INTERACTION ENERGIES
KW - ADENOSINE 5'-TRIPHOSPHATE
KW - CONFORMATIONAL CHOICE
KW - EXCESS CHARGE
KW - BINDING-SITE
UR - http://www.scopus.com/inward/record.url?scp=77958486249&partnerID=8YFLogxK
U2 - 10.1021/jp102657t
DO - 10.1021/jp102657t
M3 - Article
SN - 1089-5639
VL - 114
SP - 11153
EP - 11160
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 42
ER -