Measuring radiofrequency fields in NMR spectroscopy using offset-dependent nutation profiles

The application of NMR spectroscopy for studying molecular and reaction dynamics relies crucially on the measurement of the magnitude of radiofrequency (RF) fields that are used to nutate or lock the nuclear magnetization. Here, we report a method for measuring RF field amplitudes that leverages the intrinsic modulations observed in offset-dependent NMR nutation profiles of small molecules. Such nutation profiles are exquisitely sensitive to the magnitude of the RF field, and B-1 values ranging from 1 to 2000 Hz, as well the inhomogeneity in B-1 distributions, can be determined with high accuracy and precision using this approach. In order to measure B-1 fields associated with NMR experiments carried out on protein or nucleic acids, where these modulations are obscured by the large transverse relaxation rate constants of the analyte, our approach can be used in conjunction with a suitable external small molecule standard, expanding the scope of the method for large biomolecules. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

The method leverages intrinsic modulations observed in offset-dependent NMR nutation profiles of small molecules to measure RF field amplitudes accurately and precisely. It can determine B-1 values ranging from 1 to 2000 Hz, as well as the inhomogeneity in B-1 distributions. The approach can be used in conjunction with a suitable external small molecule standard for large biomolecules where modulations are obscured by high transverse relaxation rate constants.