Untitled

Abstract

The ratios of cross peak intensities in a selective constant-time NOESY experiment, recorded with and without 31P decoupling, yield values for the sum of the H3'-P scalar and dipolar couplings. The selective refocusing of H3' resonances in this experiment results in excellent resolution and sensitivity, even in the liquid crystalline phase where the 1H spectrum is broadened by unresolved homonuclear dipolar couplings. The vicinal H3'-P scalar and dipolar couplings in the DNA oligomer d(CGCGAATTCGCG)2 were measured in both isotropic solution, and in a liquid crystalline phase. Isotropic values are in good agreement with values reported previously. Dipolar couplings are in excellent agreement with the NMR structure for this dodecamer, and to a somewhat lesser extent with the X-ray structures.

Determination of 3J(1H3′31P) couplings in a DNA oligomer with enhanced sensitivity employing a constant‐time TOCSY difference experiment

“…2(a). The scheme is derived from the CT-NOESY experiment [9] via replacing the longitudinal (NOE) mixing period by a TOCSY spin-lock. The TOCSY coherence transfer serves to achieve dispersion of the J-coupling information away from the diagonal in the homonuclear 2D proton spectrum.…”

“…As for the CT-NOESY experiment [9] shown in Fig. 2(b), the initial part of the sequence (up to the TOCSY spinlock) with application of all 31 P 180…”

“…[8,9,1] To compare the CT-TOCSY with the CT-NOESY sequence, both were tested on a DNA octamer d(GCACGTGC) 2 sample, dissolved in buffered D 2 O (see Materials and Methods Section). Figure 3 displays the H1 -H3 cross-peak region of CT-TOCSY.…”

“…[6] In quantitative J-correlation techniques [7] such as CT-COSY, [8] CT-NOESY [9] and the TOCSY experiments described below, 3 J( 1 H3 -31 P) is calculated from the amplitude difference of selected signals between experiments with and without decoupling of phosphorous. Further heteronuclear experiments for 13 C-labeled oligomers have been developed, such as CT-HMQC techniques, which permit the additional determination of 3 J(C4 -31 P) [10] or 3 J( 1 H5 /H5 -31 P).…”

“…Compared with its predecessor, CT-NOESY, [9] the proposed pulse scheme offers largely improved sensitivity. [9] for the determination 3 J( 1 H3 -31 P); The experiments are performed in an interleaved fashion, alternating between a J-attenuated experiment, where all three 31 P pulses are executed and a reference experiments, where the first and third 31 P pulses (represented by empty rectangles) are omitted. The phase cycles are as follows: CT-TOCSY:…”