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

Three types of experiments for measuring J(CH) 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 propel-ties; finally, the HSQC-TOCSY-IPAP experiment is introduced, a sequence derived front previously published alpha and beta 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. (C) 2007 Elsevier Inc. All rights reserved.