PSYCHE CPMG-HSQMBC: An NMR Spectroscopic Method for Precise and Simple Measurement of Long-Range Heteronuclear Coupling Constants

• Published in: Chemistry : a European journal 2015-09, Vol.21 (40), p.13939-13942
• Main Authors: Timari, István, Szilagyi, László, Kover, Katalin E
• Format: Article
• Language: English
• Subjects: Broadband; broadband homonuclear decoupling; Carbohydrates; Chemistry; Constants; Couplings; HSQMBC; Joining; long-range heteronuclear coupling; Maxima; NMR; NMR spectroscopy; Nuclear magnetic resonance; Rangefinding; Spectroscopy; Splitting
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201502641

Among the NMR spectroscopic parameters, long‐range heteronuclear coupling constants convey invaluable information on torsion angles relevant to glycosidic linkages of carbohydrates. A broadband homonuclear decoupled PSYCHE CPMG–HSQMBC method for the precise and direct measurement of multiple‐bond heteronuclear couplings is presented. The PSYCHE scheme built into the pulse sequence efficiently eliminates unwanted proton–proton splittings from the heteronuclear multiplets so that the desired heteronuclear couplings can be determined simply by measuring frequency differences between peak maxima of pure antiphase doublets. Moreover, PSYCHE CPMG–HSQMBC can provide significant improvement in sensitivity as compared to an earlier Zangger–Sterk‐based method. Applications of the proposed pulse sequence are demonstrated for the extraction of nJ(1H,77Se) and nJ(1H,13C) values, respectively, in carbohydrates; further extensions can be envisioned in any J‐based structural and conformational studies. A PSYCHE sequence incorporated in the CPMG–HSQMBC NMR experiment for broadband homonuclear decoupling efficiently removes undesired proton–proton splittings from heteronuclear multiplets. This method allows long‐range heteronuclear couplings of interest to be determined simply by measuring frequency differences between maxima of pure antiphase doublets.