title: Mixed-time parallel evolution in multiple quantum NMR experiments: sensitivity and resolution enhancement in heteronuclear NMR.
abstract: A new strategy is demonstrated that simultaneously enhances sensitivity and resolution in three- or higher-dimensional heteronuclear multiple quantum NMR experiments. The approach, referred to as mixed-time parallel evolution (MT-PARE), utilizes evolution of chemical shifts of the spins participating in the multiple quantum coherence in parallel, thereby reducing signal losses relative to sequential evolution. The signal in a given PARE dimension, t1, is of a non-decaying constant-time nature for a duration that depends on the length of t2, and vice versa, prior to the onset of conventional exponential decay. Line shape simulations for the 1H-15N PARE indicate that this strategy significantly enhances both sensitivity and resolution in the indirect (1)H dimension, and that the unusual signal decay profile results in acceptable line shapes. Incorporation of the MT-PARE approach into a 3D HMQC-NOESY experiment for measurement of HN-HN NOEs in KcsA in SDS micelles at 50 degrees C was found to increase the experimental sensitivity by a factor of 1.7+/-0.3 with a concomitant resolution increase in the indirectly detected 1H dimension. The method is also demonstrated for a situation in which homonuclear 13C-13C decoupling is required while measuring weak H3'-2'OH NOEs in an RNA oligomer.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Jinfa
authors.initials: J
authors.lastname: Ying
authors.forename: Jordan H
authors.initials: JH
authors.lastname: Chill
authors.forename: John M
authors.initials: JM
authors.lastname: Louis
authors.forename: Ad
authors.initials: A
authors.lastname: Bax
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D021621:Imaging, Three-Dimensional; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008823:Micelles; D009690:Nucleic Acid Conformation; D015221:Potassium Channels / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011522:Protons; D012313:RNA / Q000737:chemistry; D012680:Sensitivity and Specificity; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D048170:Streptomyces lividans / Q000378:metabolism; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D008823:Micelles; D015221:Potassium Channels; D011522:Protons; C107790:prokaryotic potassium channel; D012967:Sodium Dodecyl Sulfate; D012313:RNA