Filtering methods for selection of singlet and doublet signals in NMR spectra of DNA oligomers.

The base proton (purine H8 and pyrimidine H6) resonances are key signals for the assignment of the proton resonances of DNA oligomers. They are classified into two groups, i.e., cytosine H6 signals, observed as doublets, and the other base proton signals, observed as singlets. Here we propose some experiments for distinguishing the cytosine H6 signals from the other base proton signals. Moreover, the ability of signal selection and the sensitivity as to signal detection were compared for all experiments, and the optimum conditions for spectral measurements were surveyed. Some of the experiments were employed as the NOESY detection pulse. Previously proposed experiments, such as HOENOE and HAL, were also used in the comparison.