ISSN:
1573-5001
Keywords:
A ⋅ (G ⋅ G ⋅ G ⋅ G) ⋅ A hexad
;
G ⋅ C ⋅ G ⋅ C tetrad
;
G ⋅ G ⋅ G ⋅ G tetrad
;
HNN-COSY
;
2hJNN
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Several structural motifs found in nucleic acids involve N-H ... N hydrogen bonds in which the donor hydrogens are broadened to extinction due to chemical or conformational exchange. In such situations, it is impossible to use the well-established HNN-COSY or soft HNN-COSY experiments, which report the presence of the hydrogen bond directly on the donor proton(s). We present a pulse sequence, H(CN)N(H), for alleviating this problem in hydrogen bonds of the type NdH ... Na-CH, in which the donor Nd nitrogen is correlated with the corresponding non-exchangeable C-H proton associated with the acceptor Na nitrogen. In this way, missing NdH ... Na correlations in an HNN-COSY spectrum may be recovered from CH-Nd correlations in the H(CN)N(H) spectrum. By correlating a different set of nuclei relative to the HNN-COSY class of experiments, the H(CN)N(H) experiment also serves to remove ambiguities associated with degeneracies in HNN-COSY spectra. The technique is demonstrated on d(GGAGGAG)4,a quadruplex containing a novel A ⋅ (G ⋅ G ⋅ G ⋅ G) ⋅ A hexad and on d(GGGCAGGT)4, containing a G ⋅ C ⋅ G ⋅ C tetrad, in which missing NH2 ... N7 correlations are retrieved via H8-(N2,N6) correlations in the H(CN)N(H) spectrum.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1008357304708
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