Deoxyribonucleic acid dynamics from phosphorus-31 nuclear magnetic resonance

Abstract
31P NMR of native high MW [calf thymus] DNA shows that the phosphodiester backbone undergoes reorientation, with a rotational correlation time of about 2 .times. 10-6 s at 30.degree. C. This rate is consistent with the flexibility of the polymer and does not require the presence of internal phosphate motions. The line width of the P resonance of DNA is due to incompletely averaged 31P-1H dipolar couplings and 31P chemical shift anisotropy relaxation; high-power proton decoupling and magnetic field dependence experiments separate the 2 effects and allow the use of the line width for determination of the rotational correlation time. The line width is dependent on temperature, and an activation energy of 5-8 kcal/mol is calculated for the motion of DNA.