Isotope Labeling Methods for Protein Dynamics Studies

Protein structure determination by solution NMR spectroscopy has long relied on the uniform stable isotopic enrichment with 13C and 15N to alleviate resonance overlap and to allow multiple distance and angular restraints, at as many atomic sites as possible, to facilitate computing the optimal three-dimensional structural model.(1) Recently, the optimization of these labeling techniques has increased the range of protein sizes amendable to study, enhanced the quality of three-dimensional structures, and simplified the analysis of experimental data.(2) Similarly, the field of protein dynamics has benefited from advances in isotopic labeling techniques that have allowed researchers to study the motional properties of ever larger proteins over a broad range of timescales while more accurately describing the protein motions. In many ways, improvements in isotopic labeling for dynamics have mirrored those used in structural studies. However, spin-relaxation experiments designed for studying protein dynamics have their own unique requirements for residue labeling, requiring special developments in isotope enrichment techniques better suited for these demanding studies.