Interresidue carbonyl-carbonyl polarization transfer experiments in uniformly 13C,15N-labeled peptides and proteins

In this work, we demonstrate that Homonuclear Rotary Resonance Recoupling (HORROR) can be used to reintroduce carbonyl-carbonyl interresidue dipolar interactions and to achieve efficient polarization transfer between carbonyl atoms in uniformly C-13,N-15-labeled peptides and proteins We show that the HORROR condition is anisotropically broadened and overall shifted to higher radio frequency intensities because of the CSA effects These effects are analyzed theoretically using Average Hamiltonian Theory At spinning frequencies used in this study, 22 kHz, this broadening is experimentally found to be oil the order of a kilohertz at a proton field of 600 MHz To match HORROR condition over all powder orientations, variable amplitude radio frequency (RF) fields are required, and efficient direct transfers oil the order of 20-30% can be straightforwardly established Two- and three-dimensional chemical shift correlation experiments establishing long-range interresidue connectivities (e.g, (N[1]-CO[1 - 2])) are demonstrated oil the model peptide N-acetyl-valilne-leucine, and on the third immunoglobulin binding domain of protein G. Possible future developments are discussed (C) 2009 Elsevier Inc All rights reserved