Sensitivity Improvement and New Acquisition Scheme of Heteronuclear Active-Coupling-Pattern-Tilting Spectroscopy

✍ Scribed by Wiktor Koźmiński; Daniel Nanz

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 105 KB
• Volume: 142
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1999.1939

✦ Synopsis

A simplified phase-cycling scheme for heteronuclear activecoupling-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␤ 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 longrange 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.