Multiple‐field carbon‐13 NMR relaxation investigation on melezitose

Abstract

Multiple-field carbon-13 relaxation data are reported for melezitose, a trisaccharide consisting of two a-linked glucose residues attached at positions 2 and 3 to a p-linked fructofuranose residue. Values for TI and NOE were measured at 4.7, 9.4, 11.8 and 14.1 T and transverse relaxation rates at 4.7 and 9.4 T. The measurements were camed out by means of standard techniques and by polarization transfer (INEPT) enhanced methods. The relaxation data were interpreted with the Lipariszabo 'model-free' approach. It was found that the relaxation data of the ring carbons can be described by the use of the truncated form of the Liplvcszabo equation. The global correlation time and order parameter .for melizitose were calculated at two temperatures. For the exocyclic CH, carbons, fits to obtain a local correlation time are reported. For three out of the four exocyciic carbons, a fast correlation time is obtained and their order parameter is lower than that for the ring carbons. The fructose C-1 exocyclic carbon does not seem to display the same local motions as the other CHI groups, and a higher order parameter is obtained indicating hindered local motion of that CH, group.

NMR relaxation interference effects and internal dynamics in γ-cyclodextrin

“…In earlier work on carbohydrates from our laboratory, we have commonly used the Lipari-Szabo model free approach [32,33] for analyzing the data for both the CH and CH 2 groups [25,38,39]. The spectral density function is obtained by considering two types of motions, a rapid local motion and a slower global motion.…”

Dipole–Dipole Coupling Constant for a Directly Bonded CH Pair—A Carbon-13 Relaxation Study

“…In this approach, the exact value of the DCC is again of minor importance: a possible missetting leads only to changes in the generalized order parameter, a quantity whose relative values within a molecule or in a series of related molecules are usually more interesting than the absolute ones. For example, in a series of papers on oligosaccharides from one of our laboratories (27)(28)(29)(30)(31)(32)(33), we have consistently used the r CH = 109.8 pm. The issue of the accurate carbon-proton DCCs has attracted renewed interest in the past few years.…”

“…Moreover, it is safe to assume that there are no large-amplitude internal motions and that the harmonic force field for small-amplitude vibrations is known. We studied HMTA in the cryosolvent that we have often used in our oligosaccharide work (27)(28)(29)(30)(31)(32). Using this solvent and working at a low temperature, to take the system out of extreme narrowing, we derive the DCC and the rotational correlation time from variable-field measurements of carbon-13 T 1 , T 2 , and NOE.…”

Multiple field carbon-13 NMR relaxation of calix[4]arene in solution

“…The Lipari-Szabo spectral densities contain one more term, which is explicitly dependent on a correlation time of the local motions, but this term can often be neglected in relatively rigid systems 12,15 (e.g. when S 2 ½ 0.8).…”