Evidence for slow motion in proteins by multiple refocusing of heteronuclear nitrogen/proton multiple quantum coherences in NMR.
A novel NMR method characterizes slow motions in proteins by multiple refocusing of double- and zero-quantum coherences of amide protons and nitrogen-15 nuclei. If both nuclei experience changes in their isotropic chemical shifts because of internal motions on slow time scales (mus - ms), this leads to a difference in the relaxation rates of double- and zero-quantum coherences. This is due to CSM/CSM (chemical shift modulation) cross-correlation effects that are related to the well-known chemical exchange contribution Rex to the decay rate R2 = 1/T2 of nitrogen-15 nuclei. The CSM/CSM contributions can be distinguished from other mechanisms through their dependence on the repetition rate of a Carr-Purcell-Meiboom-Gill (CPMG) multiple refocusing sequence. In ubiquitin, motional processes can be identified that could hitherto not be observed by conventional CPMG nitrogen-15 NMR.
Dittmer
Jens
J
Institut de chimie moléculaire et biologique, Ecole polytechnique fédérale de Lausanne, 1015 Lausanne, Switzerland.
Bodenhausen
Geoffrey
G
D016880:Anisotropy; D003903:Deuterium; D007532:Isoleucine / Q000737:chemistry; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D013816:Thermodynamics; D025801:Ubiquitin / Q000737:chemistry
D009587:Nitrogen Isotopes; D011506:Proteins; D011522:Protons; D025801:Ubiquitin; D007532:Isoleucine; D003903:Deuterium