IP-COSY, a totally in-phase and sensitive COSY experiment

Abstract

The IP-COSY experiment presented in this paper gives an in-phase spectral presentation in both the F(1) and F(2) dimensions by a combined use of a constant evolution time (CT) in t(1) and a symmetrical refocusing period before t(2). Compared with DQF-COSY and CT-COSY, IP-COSY further alleviates the effect of signal reduction due to a small ratio p (= J/linewidth), showing (1) improved lineshape and cross-peak definition and (2) especially enhancement in signals of the peaks of small active J coupling constant and the peaks of broader linewidth. A new strategy was adopted to eliminate or reduce effectively artifactual peaks by adding a 0.1-0.2 ms variation to the time delays of the CT period used for each scan of the FID in IP-COSY and CT-COSY. (3)J(H,H) coupling constants of larger than 4 Hz in the fingerprint region of peptides can be directly derived from the separation of doublets. IP-COSY cross peaks are stronger than those in DQF-COSY by 4-20-fold for tested peptides and oligonucleotides (MW < 8 kDa) with acquisition and processing parameters used in the work, and they are easier to identify than those in CT-COSY. The overall improvement in IP-COSY should make the detection/autodetection of the COSY cross peaks and the measurements of the various coupling constants more easily achieved, providing valuable information for the structure elucidation of peptides/small proteins and oligonucleotides.

Spectroscopic Characterization of Successive Phosphorylation of the Tissue Factor Cytoplasmic Region

“…The IP-COSY [25] experiments were acquired at 600 and 800 MHz Bruker Spectrometers at 285 K with water suppression achieved by Excitation Sculpting [26]. Homonuclear 1 H/ 1 H TOCSY spectra were acquired with a 70 ms mixing time, whereas both the 1 H/ 1 H NOESY and ROESY spectra were acquired with mixing times of 100 and 300 ms, respectively.…”

In vivo comprehensive multiphase NMR

“…azteca . The in‐phase COSY experiment was introduced in 2005 by Xia et al and gives considerable sensitivity enhancements especially in complex samples with fast relaxation as is the case in vivo. In Figure , it is concatenated with W5‐WATERGATE water suppression, this version of the sequence is available from the authors of this manuscript on request.…”

Decoupling Two‐Dimensional NMR Spectroscopy in Both Dimensions: Pure Shift NOESY and COSY

“…[1][2][3][4][5][6][7][8][9][10] Recently, it has been shown that applying covariance processing to a TOCSY dataset decoupled in one dimension gives a fully decoupled 2D spectrum. If the multiplet structure caused by spinspin coupling is suppressed, spectral resolution can be greatly increased, and the process of assignment correspondingly simplified.…”

“…[1][2][3][4][5][6][7][8][9][10] Recently, it has been shown that applying covariance processing to a TOCSY dataset decoupled in one dimension gives a fully decoupled 2D spectrum. [8][9][10] All such methods trade sensitivity for resolution, to a greater or lesser extent. [12][13][14] The considerably increased resolution in, and simplicity of, fully decoupled 2D spectra makes them particularly attractive for automated structure elucidation.…”