Methods for Measurement of Intermolecular NOEs by Multinuclear NMR Spectroscopy: Application to a Bacteriophage λ N-Peptide/boxB RNA Complex

Abstract

New pulse schemes for recording intermolecular NOEs in a molecular complex consisting of 15N,13C labeled and unlabeled components are presented. The pulse sequences select for magnetization transferred from protons on the unlabeled component to proximal protons of the labeled molecule. Filtering (suppression of signal from 13C labeled molecules) is accomplished using adiabatic 13C inversion pulses which are swept at a rate which is tuned according to the one-bond 1H−13C scalar coupling vs carbon chemical shift profile of the labeled molecule in the complex. Significantly improved spectra are obtained relative to data recorded with other purging schemes. Improvements are demonstrated in experiments where intermolecular NOEs between labeled RNA-unlabeled peptide and labeled protein−unlabeled peptide are recorded. A discussion of structural information obtained for a complex of the amino-terminal arginine rich domain of the N protein from bacteriophage λ and boxB RNA using the new methodology is presented.