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

✍ Scribed by Youlin Xia; Glen Legge; Kyu-Yeon Jun; Yulan Qi; Hunjoong Lee; Xiaolian Gao

• Book ID: 102951197
• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 581 KB
• Volume: 43
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1558

✦ Synopsis

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.