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

TL;DR

This paper introduces a precise method for measuring RF field amplitudes in NMR spectroscopy using offset-dependent nutation profiles, applicable to small molecules and large biomolecules with high accuracy.

Contribution

The authors develop a novel approach leveraging offset-dependent nutation profiles to accurately measure RF fields in NMR, including in complex biological samples.

Findings

High accuracy measurement of B1 fields from 1-2000 Hz

Effective in determining B1 inhomogeneity

Applicable to both small molecules and large biomolecules

Abstract

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 B1 values ranging from 1-2000 Hz, as well the inhomogeneity in B1 distributions, can be determined with high accuracy and precision using this approach. In order to measure B1 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.