A complete set of novel 2D correlation NMR experiments based on heteronuclear J-cross polarization

A suite of multiple-purpose sensitivity-enhanced 2D correlation NMR experiments based on heteronuclear J-cross polarization (HCP) techniques are introduced for isotropic liquid samples. Several pulse sequences using an adaptable heteronuclear TOCSY mixing building block are proposed for different types of effective coherence-order-selective (COS) heteronuclear coherence-transfer mechanisms. They are based on the anisotropic behaviour of the involved HCP process that is easily described and analysed in terms of cartesian product-operator formalism. A number of different versions are given for in-phase to in-phase (II-COS: S-→ I-), in-phase to anti-phase (IA-COS: S- → 2I-Sz), in-phase to spin-state-selective (IS3-COS: S-→ 2I-Sα/β), anti-phase to in-phase (AI-COS: 2IzS- → I-), anti-phase to anti-phase (AA-COS: 2IzS- → 2I- Sz), anti-phase to spin-state-selective (AS3-COS: 2IzS- → 2I-Sα/β) and spin-state-selective to spin-state-selective (S3S3-COS: 2Iα/βS- → 2I-Sα/β) coherence transfers. The combination of the echo/anti-echo approach, heteronuclear gradient echoes and the preservation of equivalent pathways (PEP) methodology affords a general approach to obtain sensitivity-enhanced pure-absorption 2D spectra that can be used as interesting alternatives to conventional pulse-interrupted free-precession INEPT-based pulse schemes, such as HSQC-type and TROSY-type experiments. © 2004 Kluwer Academic Publishers.