Temperature-Dependent Solid-State NMR Proton Chemical-Shift Values and Hydrogen Bonding

J Phys Chem B. 2021 Jun 17;125(23):6222-6230. doi: 10.1021/acs.jpcb.1c04061. Epub 2021 Jun 7.

Abstract

Temperature-dependent NMR experiments are often complicated by rather long magnetic-field equilibration times, for example, occurring upon a change of sample temperature. We demonstrate that the fast temporal stabilization of a magnetic field can be achieved by actively stabilizing the temperature of the magnet bore, which allows quantification of the weak temperature dependence of a proton chemical shift, which can be diagnostic for the presence of hydrogen bonds. Hydrogen bonding plays a central role in molecular recognition events from both fields, chemistry and biology. Their direct detection by standard structure-determination techniques, such as X-ray crystallography or cryo-electron microscopy, remains challenging due to the difficulties of approaching the required resolution, on the order of 1 Å. We, herein, explore a spectroscopic approach using solid-state NMR to identify protons engaged in hydrogen bonds and explore the measurement of proton chemical-shift temperature coefficients. Using the examples of a phosphorylated amino acid and the protein ubiquitin, we show that fast magic-angle spinning (MAS) experiments at 100 kHz yield sufficient resolution in proton-detected spectra to quantify the rather small chemical-shift changes upon temperature variations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy
  • Hydrogen Bonding
  • Magnetic Resonance Spectroscopy
  • Protons*
  • Temperature

Substances

  • Protons