Proton Nuclear Magnetic Resonance Investigations and Ring Current Calculations of Guanine N-1 and Thymine N-3 Hydrogen-Bonded Protons in Double-Helical Deoxyribonucleotides in Aqueous Solution

摘要

Methods are outlined for assigning the guanine-N1H and thymine-N3H protons to particular base pairs in the proton nuclear magnetic resonance spectra of double-stranded oligodeoxyribonucleotides of known sequence in aqueous solution. Ring current calculations have been used to evaluate the upfield shifts of the guanine-N1H and thymine-N3H protons from the pyrimidine and purine rings of nearest-neighbor base pairs in DNA B-type double-helical structures. Chemical shifts of 13.6 ± 0.1 ppm and 14.6 ± 0.2 ppm are assigned to the guanine-N1H proton of an isolated G·C base pair and the thymine-N3H proton of an isolated A·T base pair, respectively.