A new way to measure small proton-carbon coupling constants

About this Journal“IPAP–HSQMBC: Measurement of long-range heteronuclear coupling constants from spin-state selective multiplets”, by Sergi Gil, Juan Félix Espinosa and Teodor ParellaJournal of Magnetic Resonance, 207, 312-321 (2010). DOI: 10.1016/j.jmr.2010.09.017

A new NMR approach is proposed for the measurement of long-range heteronuclear coupling constants (nJXH,n > 1) in natural abundance molecules. Two complementary in-phase (IP) and anti-phase (AP) data are separately recorded from a modified HSQMBC experiment and then added/subtracted to provide spin-state-selective α/β–HSQMBC spectra. The magnitude of nJXH can be directly determined by simple analysis of the relative displacement between α– and β-cross-peaks. The robustness of this IPAP–HSQMBC experiment is evaluated experimentally and by simulation using a variety of different conditions. Important aspects such as signal intensity dependence and presence of unwanted cross-talk effects are discussed and examples on the measurement of small proton–carbon (nJCH) and proton–nitrogen (nJNH) coupling constants are provided.

The combination of 1D slices from the 1H–15N 2D IPAP–HSQMBC experiment allows the precise measurement of long-range proton-nitrogen coupling constants.

Bruker Pulse Program: ipap_hsqmbc 

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