Heteronuclear filters in two-dimensional [¹H, ¹H]-NMR spectroscopy: combined use with isotope labelling for studies of macromolecular conformation and intermolecular interactions

<jats:p>The use of heteronuclear filters enables the editing of complex <jats:sup>1</jats:sup>H nuclear magnetic resonance (NMR) spectra into simplified subspectra containing a lesser number of resonance lines, which are then more easily amenable to detailed spectral analysis. This editing is based on the creation of heteronuclear two-spin or multiple-spin coherence and discrimination between protons that do or do not participate in these heteronuclear coherences. In principle, heteronuclear editing can be used in conjunction with one-dimensional or multidimensional <jats:sup>1</jats:sup>H-NMR experiments for studies of a wide variety of low-molecular-weight compounds or macromolecular systems, and is implicitely applied in a wide range of heteronuclear NMR experiments with proton detection (e.g. Bax <jats:italic>et al.</jats:italic> 1983; Griffey & Redfield, 1987). In the present article we shall focus on the use of heteronuclear filters in two-dimensional (2D) [<jats:sup>1</jats:sup>H, <jats:sup>1</jats:sup>H]-NMR experiments. The selection of the material covered was primarily motivated by its impact on the practice of protein structure determination in solution, and on NMR studies of intermolecular interactions with biological macromolecules. Section 2 surveys potential applications of heteronuclear filters in this area. The remainder of the article is devoted to an introduction of the theoretical principles used in heteronuclear filters, and to a detailed description of the experimental implementation of these measurements. In writing the review we tried to minimize redundancy with the recent article in <jats:italic>Quarterly Review of Biophysics</jats:italic> by Griffey & Redfield (1987) and to concentrate on experiments that were introduced during the period 1986–9.</jats:p>