Conformational states of cellobiose and maltose in solution: A comparison of calculated and experimental data

NMR and conformational study of branched oligosaccharides containing 2,3-disubstituted residues of α-L-rhamnose

“…It was shown that the energy of nonbonded interactions for the disaccharide units of trisaccharides was best calculated using the Scott and Scheraga function (9), and interactions of the nonbonded carbohydrate residues, using the Momany et al (10) or Zhurkin et al (1 1) potentials, suggested for the calculation of molecular packing in crystals. As was shown (12), the potentials in the calculations of the conformations of oligosaccharides in aqueous solution are those of "medium force". The parametrization of other minor components of the energy is also dealt with in ref.…”

Influence of solvent on the magnitude of the anomeric effect

“…In contrast, Tvaroska and Kozar (21) have presented a theoretical study of the hydration of the acetal segment in glycosides and concluded that hydration does not operate against the anomeric and exo-anomeric effects. Also, as already mentioned, Lipkind et al (18) concluded, on the basis of a theoretical conformational analysis of disaccharide derivatives in aqueous solution, that the exo-anomeric effect and intramolecular hydrogen bonding are of no significance. We disagree.…”

“…For example, Lipkind, Verovsky, and Kochetkov (18) recently published on the conformational states of cellulose, lactose, and maltose, and state, in the absence of acceptable experimental support, that the exo-anomeric effect does "not play a significant role under the conditions of an aqueous medium." In fact, as will be demonstrated below, the exo-anomeric effect appears to be not only of major importance but even of special importance in aqueous solution.…”

Conformational properties of glucose-based disaccharides investigated using molecular dynamics simulations with local elevation umbrella sampling

“…marginally populated (up to 1.3% at most) for the D-glucpyranose disaccharides in aqueous solution at 300 K and 1 bar. Experimentally, population estimates ranging from a fraction of a percent up to 92 13% have been proposed for these metastable states in disaccharide derivatives and trisaccharides (J-coupling 92,106 or/ and NOE-based 93,212,213 mixed NMR/MD approaches 210,211 ). Note that some of these estimates have subsequently been questioned.…”

“…For simplicity, however, the eight reducing disaccharides are only simulated in their b-anomeric form at the reducing end, which accounts for about 60% of the total anomeric population. 82,83 All of these disaccharides have been subjected to previous investigations, both experimentally by X-ray crystallography, 2,84-90 NMR spectroscopy, 83,[91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106] or circular dichroism 92,107 (CD), as well as theoretically by quantum mechanics [108][109][110][111][112][113][114][115][116] (QM), molecular mechanics 117-125 (MM), or MD simulation. 58,59,95,[101][102][103][104] The 11 + 2 new simulations with LEUS sampling enhancement (all disaccharides with LEUS applied to / and w, plus I and G with LEUS applied to /, w, andx) are analyzed in terms of (i) calculated free-energy maps G(/, w), as well as Gð/; w;xÞ for the (1?6)-linked disaccharides, in the subspace of the glycosidic dihedral angles; (ii) relative free energies of the identified conformational states (free-energy basins); (iii) interconversion barriers between these states (and transition timescales estimated using the TST approximation 75 ); (iv) occurrences of intramolecular H-bonds in these states; (v) estimates for the single molecule configurational entropies (QH analysis plus correction terms 69,<...>…”