title: X-filtering for a range of coupling constants: application to the detection of intermolecular NOEs.
abstract: A new method for heteronuclear X-filtering is presented, which relies on repetitive applications of 90 degrees (1H)-tau(1/41J(HC))-180 degrees (1H,13C)-tau(1/41J(HC))-90 degrees (1H,13C)-PFG building blocks employing gradient-mediated suppression of magnetization built up for directly heteronuclear coupled protons. Thereby, a range of heteronuclear coupling constants can be suppressed by varying the delays of scalar coupling evolution both within and between individual transients. To achieve efficient destruction of 13C-coupled protons in macromolecular systems, the scalar coupling evolution delays were optimized using simulated annealing by including transverse relaxation effects. With a combination of regular hard pulses, delays and pulsed field gradients only, this method yields sufficient X-filtering to allow the observation of intermolecular nuclear overhauser effects in a molecular complex consisting of a 13C, 15N double-labeled, and an unlabeled protein. This is achieved by exciting magnetization of 12C- and 14N-bound protons and detecting 13C-bound 1H magnetization in a 3D 13C-filtered, 13C-edited NOESY-HSQC experiment. The method is tested on the 18 kDa homodimeric bacterial antidote ParD.
authors.affiliation: Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Heinrichstrasse 28, A-8010 Graz, Austria. klaus.zangger@kfunigraz.ac.at
authors.forename: Klaus
authors.initials: K
authors.lastname: Zangger
authors.forename: Monika
authors.initials: M
authors.lastname: Oberer
authors.forename: Walter
authors.initials: W
authors.lastname: Keller
authors.forename: Heinz
authors.initials: H
authors.lastname: Sterk
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry*; D005583:Fourier Analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009584:Nitrogen / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D011506:Proteins; D009584:Nitrogen