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Transverse 1H cross relaxation in 1H-15N correlated 1H CPMG experiments
R Ishima1, J M Louis, D A Torchia
1Molecular Structural Biology Unit, National Institute of Dental and Craniofacial Research, Bethesda, Maryland, 20892-4326, USA.
Abstract:
Transverse 1H cross relaxation was observed in Carr-Purcell-Meiboom-Gill (CPMG) experiments by recording 15N-1H correlated spectra of amides in HIV protease that was perdeuterated at nonexchangeable sites. Perdeuteration suppresses 1H-1H J coupling and improves spectral resolution and sensitivity. Measurements of cross-peak intensities, arising from cross relaxation, were made as a function of (i) Deltaf, the frequency difference between the spins, and (ii) tauCPMG, one-half of the duration between CPMG pi pulses. Cross peaks were observed when tauCPMG was less than 1/(2Deltaf), in agreement with theoretical calculations.