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Magn Reson Chem. 2010 Jan;48(1):20-4. doi: 10.1002/mrc.2532.

Simultaneous measurement of N-H and Calpha-Halpha coupling constants in proteins.

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Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.


We present a pulse sequence for the simultaneous measurement of N-H and Calpha-Halpha couplings in double-labeled proteins from 2D spectra. The proposed sequence, a modification of the HN(CO)CA experiment, combines the J-modulation method and the IPAP scheme. The couplings can be readily retrieved from a series of 2D (15)N-(1)H correlation spectra, differing in the time point at which a (1)H 180 degrees pulse is applied. This induces an intensity modulation of the (15)N-(1)H correlation peaks with the Calpha-Halpha coupling. The Calpha-Halpha coupling is then obtained by fitting the observed intensities to the modulation equation. The N-H coupling is measured in each member of the set from peak-to-peak separations in the IPAP subspectra. The pulse sequence is experimentally verified with a sample of (15)N/(13)C-enriched ubiquitin.

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