Two-dimensional NMR from a single pulse: Reconstructing heteronuclear 2D spectra via off-resonance decoupling and...

NMR spectroscopy is ubiquitous in many areas of science, including chemistry, material science, biophysics, and structural biology. Heteronuclear two-dimensional (2D) NMR experiments form the basis of several NMR-based investigations, especially those involving biomolecules like proteins. However, in solution, as the molecule of interest becomes larger, transverse relaxation times of the spins of interest become shorter. This makes it difficult to record 2D ¹H-¹³C or ¹H-¹⁵N correlation maps of large protein molecules using standard Fourier transform-based experiments as they contain transfer delays that are long compared to the short relaxation times. Herein, we explore the possibility of leveraging deep neural networks (DNNs) to obtain 2D correlation maps of proteins while eliminating transfer delays from experiments. In this study, we show that 2D methyl ¹H-¹³C correlation maps can be obtained from experiments containing only a single ¹H excitation pulse followed by off-resonance ¹³C continuous-wave decoupling. A DNN was successfully trained to reconstruct the 2D ¹H-¹³C correlation map from datasets recorded with two ¹³C decoupling fields using protein samples enriched with isoleucine, leucine, and valine (ILV) ¹³CHD₂ methyl-groups in a ²H background. The efficacy of this strategy is demonstrated by using the DNN to reconstruct methyl ¹H-¹³C correlation maps of the ~8 kDa FF domain from human HYPA/FBP11, the ~18 kDa T4 phage lysozyme, the ~360 kDa α₇α₇ particle from the Thermoplasma acidophilum proteasome and a ~530 kDa ancestrally reconstructed L₈S₈ Rubisco complex. This study illustrates the potential for improving the sensitivity and resolution of NMR spectra by designing experiments tailored for use with DNNs.