Analyses, extensions and comparison of three experimental schemes for measuring (nJCHÂ +Â DCH)-couplings at natural abundance

Three types of experiments for measuring nJCH heteronuclear long-range coupling constants are examined and extended with state-of-the-art pulse sequence building-blocks: The use of a HMBC with corresponding reference-HSQC for accurate coupling determination is combined with the constant time technique and the conversion of antiphase magnetization into ZQ/DQ-coherences; CPMG-based LR-CAHSQC and BIRDr,X-HSQMBC experiments are examined in detail with respect to their coherence transfer properties; finally, the HSQC-TOCSY-IPAP experiment is introduced, a sequence derived from previously published α and β selective HSQC-TOCSYs using a different spin state selection technique and a recently developed ZQ-suppression method. The experiments are characterized with their advantages and disadvantages and compared using strychnine and menthol as standard molecules.