NMR Detection of Hydrogen Bonds

Most of the early methods for assigning isotopically labeled nucleic acids were developed using RNA samples, since 13C and 15N isotopes can be incorporated in RNA more easily than in DNA. While most of the magnetization transfer pathways in RNA and DNA are the same, the latter contains thymine rather than uracil. To remove the ambiguity of intra- and inter-residue H6-CH3 peak assignment in thymine, the HCCCH through-bond method was proposed [51] as a more sensitive alternative to NOE or ROE. 

The pulse sequences used for the resonance assignments are not discussed in this chapter. For further details the interested reader is referred to the paper of Ref. [2] and references therein. 

The detection of scalar couplings is not only a theoretically interesting direct proof of the covalent character of the hydrogen bonds. It is also of great value in studies of struc- 

The hydrogen bond length in Watson-Crick base pairs can be characterized using the recently developed method of measuring the cross-correlated relaxation [61] between H chemical shift anisotropy and dipole-dipole coupling of H and its hydrogen bond donor 

Using the two measured cross-correlated relaxation rates, an apparent hydrogen bond length can be determined. Data for the 15N3-1H3...15N1 hydrogen bond in A-T base pairs of Antennapedia homeodomain DNA complex with a correlation time of 20 ns has been presented. 

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