Benchtop NMR Spectroscopy of Prebiotically-Relevant Peptide Reactions Enabled by Salt-Induced Chemical Shift Dispersion

This Article describes a method that increases the chemical shift dispersion of signals in proton nuclear magnetic resonance (¹H NMR) spectra of peptides by the addition of salts to the sample. We demonstrate that the addition of potassium phosphate to aliquots of reactions of glycine peptides permits the measurement of their rate constants for hydrolysis by a 60 MHz benchtop instrument, which would otherwise be infeasible due to overlapping signals in the salt-free mixtures. The method is described in detail and validated by comparison to analysis on a 400 MHz spectrometer. The ability to use benchtop NMR spectroscopy to study reactions of simple peptides enables interested scientists at a broader array of institutionsnot just those institutions capable of affording high-field NMR instrumentsto participate in original research projects like those aimed at elucidating the chemistry that led to the origin of life on Earth.