PMC:2728246 / 66656-67858 JSONTXT

{"project":"2_test","denotations":[{"id":"19652920-16939274-56191019","span":{"begin":1010,"end":1014},"obj":"16939274"},{"id":"19652920-12862493-56191020","span":{"begin":1139,"end":1143},"obj":"12862493"}],"text":"We have used RDCs to detect methyl group motion faster than ms with special focus on the supra-τc window (ns to μs) in ubiquitin. A very wide range of motional amplitudes exist in side chains depending on solvent exposure, residue type and distance to the backbone. Considerable additional dynamics slower than the correlation time τc has been detected. On average, the amplitude of motion expressed in terms of order parameters associated with the supra-τc window contributes as much mobility as the ps-ns motion of the methyl groups measured from relaxation data. The RDC-based order parameters covering motion up to ms and the relaxation derived order parameter show a correlation coefficient of r = 0.72, suggesting that a fair portion of the additional mobility in the supra-τc region can be interpreted mostly as a “broadening” of the amplitude of motion. Amplitude-wise, we find a good match with the order parameters derived from solid-state measurements of CH dipolar couplings (Lorieau and McDermott 2006) and an even better match with those derived from a combined J-coupling and residual dipolar coupling approach (Chou et al. 2003) and supplemented with the fast motions from the backbone."}