Static disorder and librational motions of the purine bases in films of oriented Li-DNA.
Solid-state 2H nuclear magnetic resonance line shapes have been obtained from folded films of oriented Li-DNA molecules with the purine bases selectively labeled with deuterium at the 8-position. From line shape simulations, the static base tilts as well as the anisotropic motional amplitudes were determined as a function of hydration level and temperature. It was found that the average tilt angle of the bases is close to 0 degrees and at a hydration of ten water molecules per nucleotide the distribution width of tilt angles about this average cannot be larger than 9 degrees (standard deviation). A slightly increased distribution width is observed at low hydration levels. The motional amplitudes are hydration dependent, with the tilting motion ranging from 4 degrees for the driest, up to 15 degrees for the wettest sample, and slightly larger amplitudes are observed for the twisting motion. The amplitude of the twisting motion is unaffected by a temperature decrease down to -60 degrees C, in contrast to the tilting motion that is suppressed at low temperatures.
Brandes
R
R
Department of Chemistry, University of California-San Diego, La Jolla 92093.
Vold
R R
RR
Kearns
D R
DR
Rupprecht
A
A
D000818:Animals; D004247:DNA; D008094:Lithium; D009682:Magnetic Resonance Spectroscopy; D009038:Motion; D009690:Nucleic Acid Conformation; D011687:Purines; D013696:Temperature
D011687:Purines; D004247:DNA; D008094:Lithium