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

Youlin Xia, Glen Legge, Kyu Yeon Jun, Yulan Qi, Hunjoong Lee, Xiaolian Gao

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34 Scopus citations


The IP-COSY experiment presented in this paper gives an in-phase spectral presentation in both the F1 and F2 dimensions by a combined use of a constant evolution time (CT) in t1 and a symmetrical refocusing period before t2. 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. 3J(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.

Original languageEnglish (US)
Pages (from-to)372-379
Number of pages8
JournalMagnetic Resonance in Chemistry
Issue number5
StatePublished - May 2005
Externally publishedYes


  • COSY
  • NMR
  • Oligonucleotides
  • Sensitivity enhancement


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