Chapter 15: High-resolution Applications of Shuttle Field-cycling NMR

High-resolution shuttle field-cycling relaxometry has proven to be a robust technique for characterizing ³¹P in biological molecules, particularly phospholipids. Instrument and sample requirements and constraints for the Redfield “spin spa”, typical R₁ profiles covering 0.002–11.74 T and the relaxation mechanisms responsible for different features are reviewed. With this as background, results analyzing several biological systems are examined to highlight how different parameters extracted from the data can be used to measure the dynamics of ligands bound to proteins, emphasizing the use of paramagnetic relaxation enhancement (PR₁E) at low fields to identify novel moderate-affinity sites for phospholipids on amphitropic proteins.