ARTSY-J: Convenient and precise measurement of 3JHNH? couplings in medium-size proteins from TROSY-HSQC spectra
Publication date: Available online 3 May 2016
Source:Journal of Magnetic Resonance
Author(s): Julien Roche, Jinfa Ying, Yang Shen, Dennis A. Torchia, Ad Bax
A new and convenient method, named ARTSY-J, is introduced that permits extraction of the 3 J HNH? couplings in proteins from the relative intensities in a pair of 15N-1H TROSY-HSQC spectra. The pulse scheme includes 3 J HNH? dephasing of the narrower TROSY 1HN-{15N} doublet component during a delay, integrated into the regular two-dimensional TROSY-HSQC pulse scheme, and compares the obtained intensity with a reference spectrum where 3 J HNH? dephasing is suppressed. The effect of passive 1H? spin flips downscales the apparent 3 J HNH? coupling by a uniform factor that depends approximately linearly on both the duration of the 3 J HNH? dephasing delay and the 1H-1H cross relaxation rate. Using such a correction factor, which accounts for the effects of both inhomogeneity of the radiofrequency field and 1H? spin flips, agreement between prior and newly measured values for the small model protein GB3 is better than 0.3 Hz. Measurement for the HIV protease homodimer (22 kDa) yields 3 J HNH? values that agree to better than 0.7 Hz with predictions made on the basis of a previously parameterized Karplus equation. Although for Gly residues the two individual 3 J HNH? couplings cannot be extracted from a single set of ARTSY-J spectra, the measurement provides valuable ? angle information.
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