Solution NMR of supramolecular complexes: providing new insights into function.

Solution NMR spectroscopy is an extremely powerful technology for the study of biomolecular dynamics and site-specific molecular interactions. An important limitation in the past has been molecule size, with molecular weights of targets seldom exceeding 50 kDa. New labeling technology and NMR experiments are changing this paradigm so that applications for investigating supramolecular complexes are starting to become feasible. Here we describe a strategy developed in our laboratory that involves the use of labeled methyl groups of isoleucine, leucine and valine residues in proteins as probes, along with experiments that significantly enhance the lifetimes of the resulting signals. We describe the application of these methods to a number of systems with molecular weights in the hundreds of kilodaltons.