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Titolo:
Molecular dynamics and NMR study of the alpha(1 -> 4) and alpha(1 -> 6) glycosidic linkages: Maltose and isomaltose
Autore:
Best, RB; Jackson, GE; Naidoo, KJ;
Indirizzi:
Univ Cape Town, Dept Chem, ZA-7701 Rondebosch, South Africa Univ Cape Town Rondebosch South Africa ZA-7701 Rondebosch, South Africa
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 20, volume: 105, anno: 2001,
pagine: 4742 - 4751
SICI:
1520-6106(20010524)105:20<4742:MDANSO>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEAR-MAGNETIC-RESONANCE; MODEL-FREE APPROACH; RELATE 2 SETS; AQUEOUS-SOLUTION; CONFORMATIONAL-ANALYSIS; HYDROXYMETHYL GROUPS; LIQUID WATER; CRYSTAL-STRUCTURE; INTERNAL MOTIONS; STARCH GRANULES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
56
Recensione:
Indirizzi per estratti:
Indirizzo: Naidoo, KJ Univ Cape Town, Dept Chem, ZA-7701 Rondebosch, South Africa Univ Cape Town Rondebosch South Africa ZA-7701 , South Africa
Citazione:
R.B. Best et al., "Molecular dynamics and NMR study of the alpha(1 -> 4) and alpha(1 -> 6) glycosidic linkages: Maltose and isomaltose", J PHYS CH B, 105(20), 2001, pp. 4742-4751

Abstract

We report the results of molecular dynamics (MD) simulations compared withNMR relaxation experiments for maltose and isomaltose. The (Phi,Psi) adiabatic map for maltose shows a single principal energy well, while the (Phi,Psi,Omega) map of isomaltose reveals multiple low energy minima separated bysignificant barriers (9 kcal/mol) in some cases. The greater accessible conformational space of the alpha (1 -->6) linkage appears to make it more flexible as compared with the alpha (1 -->4) linkage, especially in the presence of water. Correlation times for glycosidic dihedral angle fluctuations are significantly shorter in the case of isomaltose. While the generalized order parameters calculated from the simulations do not show a large difference in the spatial restriction of the motion, they are nonetheless generally lower for isomaltose. The time scales of the overall rotational motion (tau (M)) and the local molecular motion (tau (e)) are similar for both maltose and isomaltose. This makes reliable estimates of order parameters from experimental relaxation data (using the model-free formalism) unfeasible. We were, however, able to show that T-1 relaxation times calculated from theMD data agree well with the experimental values. As a further measure of solution flexibility, three-dimensional water distributions were calculated about each disaccharide. These demonstrate that the more rigid maltose solute causes the water to adopt a more localized structure about it. Because of its extended structure, isomaltose appears to make a greater number of hydrogen bonds to water.

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Documento generato il 09/04/20 alle ore 00:11:44