title: Observation of individual transitions in magnetically equivalent spin systems.
abstract: Individual transitions of magnetically equivalent spin systems such as methyl groups residing on isotropically tumbling molecules in solution usually cannot be observed as multiplet-split NMR lines. We propose a pair of NMR experiments, 2D [13C,1Halphaalpha]Methyl and [13C,1Hbetabeta]Methyl HSQC, to overcome this limitation and enable direct and selective observation of individual 1H transitions in 13C-labeled methyl spin systems. Immediate applications include quantitative measurements of 1H-1H residual dipolar couplings (RDC) and cross-correlated relaxation between 1H chemical shift anisotropy and 1H-1H dipole-dipole interactions. The use of the experiments for the measurement of RDCs is demonstrated with two proteins, one weakly aligned by means of Pf1 phages and the other using a naturally present paramagnetic heme group.
authors.affiliation: Laboratory of Physical Chemistry, Swiss Federal Institute of Technology, ETH Hönggerberg, CH-8093 Zürich, Switzerland. kopeko@phys.chem.ethz.ch
authors.forename: Konstantin
authors.initials: K
authors.lastname: Pervushin
authors.forename: Beat
authors.initials: B
authors.lastname: Vögeli
mesh_terms: D001059:Apoproteins / Q000737:chemistry; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D025561:Bacteriophage Pf1 / Q000737:chemistry; D029968:Escherichia coli Proteins; D006418:Heme / Q000737:chemistry*; D006420:Hemeproteins / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*
chemical_list: D001059:Apoproteins; D001425:Bacterial Outer Membrane Proteins; C115384:CcmE protein, E coli; D029968:Escherichia coli Proteins; D006420:Hemeproteins; D006418:Heme