Motional Properties of Two Vicinally Disubstituted Trisaccharides As Studied by Multiple-Field Carbon-13 NMR Relaxation

Abstract

Multiple-field carbon-13 NMR relaxation measurements have been performed on the two vicinally disubstituted trisaccharides -D- (2). Trisaccharide 1 has trans disubstitution of the terminal -glucosyl residues, while trisaccharide 2 has cis disubstitution. Carbon-13 T 1 and T 2 relaxation and NOE measurements were performed outside the extreme-narrowing regime at three temperatures 283, 303, and 323 K and four magnetic field strengths 6.3, 9.4, 11.7, and 14.1 T. The obtained relaxation rates and NOE factors, averaged for each sugar residue, were fitted to overall and internal correlation times and order parameters using the Lipari-Szabo "model-free" formalism. The 2,3-disubstituted O-methyl glycoside showed fairly high-order parameters, S 2 ≈ 0.9, for both trisaccharides at all three temperatures, while the terminal glucosyl residues of 1 and 2 showed lower and slightly temperature-dependent order parameters, S 2 ≈ 0.8. In 1, the terminal residues were found to have similar motional properties and an internal correlation time of ∼60 ps could be obtained from a simultaneous three-parameter fit at 303 K. Similar results were obtained for trisaccharide 2. This study shows that the branch-point residue displays more restricted mobility than the terminal residues in both trisaccharides and that internal motions can be detected for small oligosaccharides using NMR relaxation measurements and the Lipari-Szabo model-free formalism.

Comparison of the conformation and dynamics of a polysaccharide and of its isolated heptasaccharide repeating unit on the basis of nuclear Overhauser effect, long-range C-C and C-H coupling constants, and NMR relaxation data

“…Our observation that τ eff for the polysaccharide is only slightly larger than that for the heptasaccharide argues that these segments must be of the order of 3–10 residues, a value consistent with estimates of persistence lengths for some other polysaccharides 40. While these conclusions might not be universally applicable to all polysaccharides, the relaxation data reported here for the J22 heptasaccharide does not differ greatly from those reported for some other complex oligosaccharides 38, 41, 42…”

A Conformational Study of the Trisaccharideβ-D-Glcp-(1→2)[β-D-Glcp-(1→3)]α-D-Glcp-OMe by NMR NOESY and TROESY Experiments, Computer Simulations, and X-Ray Crystal Structure Analysis

“…[24] Despite the slower tumbling rate it is reasonable to assume that the solute molecule behaves in a similar way as in water since the solvent mixture contains 70 molar % water and carbohydrates are hydrated in solution. [25,26] The D 2 O/[D 6 ]DMSO mixture was recently used in studies of the 13 C NMR relaxation [27] and 1 H, 13 C long-range coupling constant [28] of the trisaccharide. The experimental cross-relaxation rates are reported in Table 1.…”

“…For the intraresidue interaction H1g ± H2g, an overall correlation time t M 0.89 ns, a generalized order parameter S 2 0.84, and an internal correlation time t e 18 ps were used, taken from the fits of 13 C NMR data of the g residue reported in Table 3 of the 13 C work. [27] From the NOE measurements interproton distances of 2.51 and 2.52 were obtained at 500 and 600 MHz, respectively. The TROE measurements resulted in shorter distances, 2.37 and 2.35 , respectively, at the two different magnetic fields.…”

A conformational study of the vicinally branched trisaccharide ?-D-Glcp-(1 ? 2)[?-D-Glcp-(1 ? 3)]?-D-Manp-OMe by nuclear Overhauser effect spectroscopy (NOESY) and transverse rotating-frame Overhauser effect spectroscopy (TROESY) experiments: Comparison to Monte Carlo and Langevin dynamics simulations

“…51 The cryo-solvent is more viscous than water, which slows down the molecular reorientation, i.e., the global correlation time M , and makes it possible to separate a local correlation time e , if present, from the global one. Although the cryo-solvent brought the molecule out of the extreme narrowing regime, it did not bring it into the spin diffusion limit.…”

“…56 Since the dynamics of trisaccharide 1 has been determined in the cryo-solvent ( Table 3 in Ref. 51), we used this information and the cross-relaxation rates obtained in this work together with Eqs. (1), (3), and (5) to calculate proton-proton distances.…”