Measurement of the helix opening rate in Z-DNA by 1H nuclear magnetic resonance relaxation spectroscopy.
The exchange rate of the hydrogen-bonded guanine imino protons N(1) in the high-salt form of Poly(dG-dC) was measured by following the non-selective inversion-recovery of their 1H NMR signal at 360 MHz, in the temperature range between 77 degrees C and 90 degrees C. In a 4.5M NaCl solution, Poly(dG-dC) is believed to adapt the left-handed Z-conformation, and the results reported here represent the first quantitative measurements of this rate process for Z-DNA by Nuclear Magnetic Resonance, complementing previous measurements made by tritium exchange at 0 degrees C (Ramstein, J. and Leng, M. (1980) Nature 288, 413-414). The results confirm that this process is much slower in the Z-form, compared to the B-structure, and that this difference in rates results mainly from a large decrease in the entropy of activation for Z-DNA.
D004247:DNA; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D009690:Nucleic Acid Conformation; D011066:Poly C; D011068:Poly G; D013696:Temperature
D011068:Poly G; C008961:poly G-poly C; D011066:Poly C; D004247:DNA