A Pure-Phase Homonuclear J-Modulated HMQC Experiment with Tilted Cross-Peak Patterns for an Accurate Determination of Homonuclear Coupling Constants

✍ Scribed by Wiktor Koźmiński

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 90 KB
• Volume: 141
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1999.1888

✦ Synopsis

A new HMQC-based experiment is presented which allows for an efficient determination of accurate homonuclear coupling-constant values. Pure absorption lineshapes with tilted cross-peak patterns are obtained by a combination of the active-couplingpattern tilting (ACT) scheme with J-scaling. Characteristic features include separate heteronuclear echo and antiecho acquisition with a BIRD y pulse positioned before or after the t 1 period, respectively, to refocus I-spin homonuclear coupling evolution. Additionally, due to the incorporation of J-scaling the relative spacing of the S-spin chemical-shift differences and I-spin homonuclear coupling splittings in the F 1 domain is largely under experimental control. The most important advantage of the proposed method is that the I-spin homonuclear coupling evolution occurs simultaneously with the evolution of the heteronuclear zero and double-quantum coherences, which exhibit a slower transverse relaxation than I-spin single-quantum coherences. The effectiveness of the new sequence is demonstrated by a determination of the 3 J HN,H␣ couplings in a peptide sample. Additionally, the broadband property of the new sequence is verified with a sucrose sample.