Stereospecific Isotopic Labeling of Methyl Groups for NMR Spectroscopic Studies of High‐Molecular‐Weight Proteins

Sometimes less is more: 13C1H3methyl isotopomers can be biosynthetically incorporated specifically into the pro-S methyl groups of leucine and valine residues in large protein assemblies within a perdeuterated background by using an acetolactate precursor. This stereospecific labeling strategy considerably enhances NMR spectra for large protein assemblies.