Assignment of the deoxyribofuranoside protons in DNA oligomers by the application of relayed coherence transfer two-dimensional nuclear magnetic resonance spectroscopy

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Abstract
Assignment of the deoxyribofuranose protons in short DNA oligomers by techniques such as homonuclear shift-correlated (COSY) 2-D nmr becomes difficult when there are overlapping diagonal signals. To solve this problem we have applied the method of relayed coherence transfer 2-D nmr to generate cross-peaks between protons such as 1′ and 3′, 3′ and 5′ and 5″ which are not coupled but belong to the same spin system. Plotting cross-sections through the diagonal peaks of the 3′ protons produced completely resolved spectra of the deoxyribofuranoside protons for each nucleotide. Chemical shifts were assigned by comparing each cross-section with the one-dimensional spectrum. A new phase-cycling procedure for the transmitter and receiver was determined and allowed data acquisition with suppression of p-type peaks. This technique is illustrated by the spectra of deoxycytidine and the deoxytriribonucleotide, dCpTpGp.