HCCCH experiment for through-bond correlation of thymine resonances in C-13-labeled DNA oligonucleotides

Application of heteronuclear magnetic resonance pulse methods to C-13\,N-15 -labeled nucleic acids is important for the accurate structure determinatio n of larger RNA and DNA oligonucleotides and protein-nucleic acid complexes . These methods have been applied primarily to RNA, due to the availability of labeled samples. The two major differences between DNA and RNA are at t he C2' of the ribose and deoxyribose and the additional methyl group on thy mine versus uracil. We have enzymatically synthesized a C-13,N-15-labeled 3 2 base DNA oligonucleotide that folds to form an intramolecular tripler. We present two- and three-dimensional versions of a new HCCCH-TOCSY experimen t that provides intraresidue correlation between the thymine H6 and methyl resonances via the intervening carbons (H6-C6-C5-Cme-Hme). (C) 1999 Academi c Press.