期刊
JOURNAL OF MAGNETIC RESONANCE
卷 142, 期 2, 页码 294-299出版社
ACADEMIC PRESS INC
DOI: 10.1006/jmre.1999.1939
关键词
J-couplings; active-coupling-pattern tilting; ACT; accordion spectroscopy; HSQC; sensitivity enhancement
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,H beta) 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. (C) 2000 Academic Press.
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