A solid-state deuterium NMR study of localized mobility at the C9pG10 step in the DNA dodecamer
[d(CGCGAATTCGCG)]2 is described. In contrast to the results of earlier deuterium NMR studies of furanose
ring and backbone dynamics within the d(AATT) moiety, the furanose ring and helix backbone of dC9 display
large amplitudes of motion on the 0.1 ms time scale at hydration levels characteristic of the B form structure.
Solid-state deuterium NMR line shape data obtained from labeled dC9 DNA are interpreted using a composite
motion model, in which the DNA oligomer is treated as rotating as a whole about the helix axis, while the
base, furanose ring, and phosphodiester backbone execute localized motions. Consistent with past solid-state
NMR studies, the amplitude and rate of the uniform rotation of the dC9-labeled oligomer are found to be
sensitive to hydration level. Amplitudes of localized reorientational motions of C−D bonds in the furanose
ring and backbone of dC9 are found to be larger than the librational amplitudes for the C−D bonds in the base
of dC9, indicating that the pyrimidine base sugar does not move as a rigid entity and intersects a locally
flexible region of the phosphodiester backbone. At hydration levels corresponding to 10−12 waters per
nucleotide, Zeeman relaxation times for the furanose ring and backbone deuterons of dC9 in B form DNA
equal 0.025 and 0.03 ms, respectively, and are the shortest relaxation times observed thus far for any deuteron
in the DNA dodecamer at comparable hydration levels. The results of this solid-state NMR study suggest the
existence of a significant dynamic component of sequence-specific recognition in this system.
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