General pulse sequence elements that achieve sensitivity-enhanced coherence transfer from a heteronucleus to protons of arbitrary multiplicity are introduced. The building blocks are derived from the sensitivity-enhancement scheme introduced by Cavanagh et al. ((1991) J. Magn. Reson., 91, 429-436), which was used in conjunction with gradient coherence selection by Kay et al. ((1992) J. Am. Chem. Soc., 114, 10663-10665), as well as from a multiple-pulse sequence effecting a heteronuclear planar coupling Hamiltonian. The building blocks are incorporated into heteronuclear correlation experiments, in conjunction with coherence selection by the formation of a heteronuclear gradient echo. This allows for efficient water suppression without the need for water presaturation. The methods are demonstrated in HSQC-type experiments on a sample of a decapeptide in H2O. The novel pulse sequence elements can be incorporated into multidimensional experiments.

Novel strategies for sensitivity enhancement in heteronuclear multidimensional spectra are introduced and evaluated theoretically and experimentally. It is shown that in 3D sequences employing several Coherence Order Selective Coherence Transfer (COS-CT) steps, enhancement factors of up to 2 can be achieved. This sensitivity enhancement is compatible with the use of heteronuclear gradient echoes, yielding spectra with excellent water suppression. HNCO and HCCH-TOCSY pulse sequences are proposed and experimentally tested. These experiments employ recently developed coherence order selective pulse sequence elements, e.g., COS-INEPT and planar TOCSY for antiphase to in-phase transfers 2F(-)S(2)↔S(-) or in-phase COS-CT for in-phase transfer F(-)↔S(-), and the well-known isotropic TOCSY mixing sequences for homo- and heteronuclear in-phase transfer.

A new homonuclear Hartmann-Hahn-type mixing scheme is introduced that effects coherence transfer between resonances in two separated frequency bands. The mixing scheme relies on the irradiation of two-band selective shaped pulses that are expanded in an MLEV-16 supercycle. Similar to heteronuclear Hartmann-Hahn experiments, a planar effective coupling tensor is created. This novel mixing scheme is applied to C(α),C' transfer and to the transfer between C(β) and aromatic carbon spins.

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