Measurement of homonuclear proton couplings based on cross-peak nulling in CT-COSY.
A method in which 1H-1H scalar and dipolar couplings are obtained from the cross-peak nulling condition in a series of constant-time (CT) COSY spectra, as a function of the duration of the CT period, is described. The method is best suited for measurement of 1H-1H couplings in the range 5-20 Hz. It is shown, however, that results can be sensitive to cross-correlated relaxation effects. Also, artifactual resonances, resulting from strong coupling, can be quite pronounced in CT-COSY spectra, even when /J(AB)/(deltaA-deltaB)/<0.1. The experiments are demonstrated for the DNA dodecamer d(CGCGAATTCGCG)2, both in isotropic solution and in a liquid crystalline phase.
Wu
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Z
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Bax
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D003196:Computer Graphics; D004247:DNA / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011522:Protons; D012815:Signal Processing, Computer-Assisted
D011522:Protons; D004247:DNA