A SOLID-STATE DEUTERIUM NMR-STUDY OF FURANOSE RING DYNAMICS IN [D(CGCGAATTCGCG)]2

Solid-state deuterium NMR spectroscopy has been used to characterize the dynamics of the furanose rings of A5 and A6 (and by symmetry A17 and A18) in the self-complementary DNA dodecamer duplex (d(CGCGAATTCGCG)]2, which contains the EcoRI binding site. 2'-Deoxyadenosine, deuterated at the 2“ position by direct chemical methods, was incorporated into the A5 and A6 sites of the dodecamer by using the solid-phase phosphite triester method. 2H NMR line shape studies of monomeric 2'-deoxyadenosine-2“-d1 yielded a QCCeff of 172 kHz. Assuming a QCCstatic of 178 kHz, as derived from NQR studies of tetradeuteriofuran, and a static asymmetry parameter of zero, this line shape may be simulated by assuming a two-site libration of the furanose ring with an amplitude of ±9°. Relaxation studies of the selectively deuterated DNA dodecamer indicate that at high levels of hydration, the T1 of the 2“ deuterons varies in constant proportion to the T1 of the base deuterons, implying that the dynamics of the furanose rings and the bases may be coupled. Simulation of 2H NMR line shapes over a hydration range varying from W = 0 to W = 28 (mol H2O/mol nucleotide) shows a small decrease in QCCeff from 172 to 146 kHz, which precludes the occurrence of large amplitude (≫20°) dynamics in these furanose rings over this hydration range. Line shape perturbations produced by intermediate regime motions may be simulated by using models of restricted reorientation about the helix axis, increasing in rate and amplitude at higher hydration levels. DNA samples equilibrated at 92% relative humidity produce line shapes consistent with the formation of a liquid crystal phase. © 1990, American Chemical Society. All rights reserved.