title: Sensitivity improvement and new acquisition scheme of heteronuclear active-coupling-pattern-tilting spectroscopy.
abstract: A simplified phase-cycling scheme for heteronuclear active-coupling-pattern tilting (ACT) spectroscopy is presented. It is demonstrated that the theoretically expected twofold sensitivity gain over earlier implementations can be experimentally realized. A further intensity increase by a factor of 2 is obtained with standard sensitivity-enhancement pulse-sequence elements. The HSQC-HECADE sequence presented is designed for an accurate determination of heteronuclear one-bond and, with subsequent I-spin isotropic mixing, long-range coupling constants. As an exemplary application, the determination of the (3)J(N,Hbeta) coupling constants in a peptide at natural isotope abundance is demonstrated. Additionally, a new polarization-transfer step for the long-range HSQC-HECADE experiment is proposed which avoids a fixed delay tuned to a specific coupling-constant value. Thus, the long-range correlation experiment does not require prior knowledge of the coupling constants to be measured and yields more uniform cross-peak intensity for a broad range of active coupling constants.
authors.affiliation: Department of Chemistry, Warsaw University, ul. Pasteura 1, Warsaw, 02-093, Poland.
authors.forename: W
authors.initials: W
authors.lastname: Kozmiński
authors.forename: D
authors.initials: D
authors.lastname: Nanz
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000379:methods*