Internal dynamics of hydroxymethyl rotation from CH2 cross-correlated dipolar relaxation in methyl-beta-D-glucopyranoside.

Conventional relaxation parameters (T1(-1), T2(-1), and NOE), obtained at different temperatures and magnetic fields, are reported for the hydroxymethyl (C6) carbon in methyl-beta-D-glucopyranoside in a D2O/DMSO cryosolvent. These data are interpreted with the Lipari-Szabo model. In addition, two-field measurements of longitudinal and spin-locked relaxation rates related to the cross-correlated carbon-proton dipole-dipole interactions for the same carbon are reported. The complete data set consisting the conventional and cross-correlated relaxation parameters is interpreted using a new "hybrid" approach, in which the Lipari-Szabo model for the auto-correlated spectral densities is combined with the two-site jump model for the cross-correlated spectral densities, with the global correlation time as a common parameter. The two-site jump rates thus obtained are in reasonable agreement with the ultrasonic relaxation measurements, and have reasonable temperature dependence.