Interleaved spatial/spectral encoding in ultrafast 2D NMR spectroscopy

International audience ; The possibility to record a full 2D spectrum in less than a second using ultrafast 2D NMR(UF2DNMR) is beneficial in many applications. However, the spatial encoding process onwhich UF2DNMR is based sets specific constraints on the spectral width and resolution of theresulting spectra. To overcome these limitations, a tailored encoding method usingspatial/spectral pulses (SPSP) can be employed as an alternative to the traditional linearspatial encoding of interactions. Here we analyze and further develop this alternative spatialencoding strategy. We first carry out numerical simulations to describe the features ofbidimensional SPSP pulses. Sidebands are identified along the spectral dimension of theexcitation profile. An interleaved excitation scheme is then developed and implementedexperimentally to suppress the unwanted signals that arise from these harmonic sidebands.Two examples are shown to illustrate the potential of the proposed approach. An ultrafastselective TOCSY spectrum is recorded to access sub-spectra and fully assign 1H NMRresonances of individual residues of cyclosporin A. An ultrafast HSQC spectrum of a mixtureof metabolites is recorded with an optimized spectral width in the spatially encodeddimension.