# Understanding the Methyl-TROSY effect over a wide range of magnetic fields

## TL;DR

This paper develops a comprehensive model for methyl-TROSY relaxation interference across a wide magnetic field range, extending beyond the slow-tumbling approximation, enabling NMR studies of large proteins at various fields.

## Contribution

It introduces a new theoretical model describing methyl-TROSY effects over broad magnetic fields, including low and ultra-high fields, beyond previous approximations.

## Key findings

- Relaxation interference varies with magnetic field type.
- Methyl-TROSY can be applied from 0.33 T to 100 T.
- Fast methyl rotation enables broad field applicability.

## Abstract

The use of relaxation interference in the methyl Transverse Relaxation-Optimized SpectroscopY (TROSY) experiment has opened new avenues for the study of large proteins and protein assemblies in nuclear magnetic resonance. So far, the theoretical description of the methyl-TROSY experiment has been limited to the slow-tumbling approximation, which is correct for large proteins on high field spectrometers. In a recent paper, favorable relaxation interference was observed in the methyl groups of a small protein at a magnetic field as low as 0.33 T, well outside the slow-tumbling regime. Here, we present a model to describe relaxation interference in methyl groups over a broad range of magnetic fields, not limited to the slow-tumbling regime. We predict that the type of multiple-quantum transitions that show favorable relaxation properties change with the magnetic field. Under the condition of fast methyl-group rotation, methyl-TROSY experiments can be recorded over the entire range of magnetic fields from a fraction of 1 T up to 100 T.