The fleeting and ultra-weak interactions between proteins in our body allow countless biochemical processes to take place. When the systems go awry we see misfolding problems and aggregation that gives rise to the symptoms of diseases, such as cystic fibrosis and Parkinson's disease. Now, Jens Jørgen Led of the University of Copenhagen, Denmark, and his colleagues have demonstrated how nuclear magnetic resonance (NMR) spectroscopy can reveal the details of these interactions and help explain how it is that proteins can "scan" each other so rapidly and "know" which ones to work with in healthy biochemical processes. The team exploited the contrast agent gadodiamide from the well-known medical sibling of NMR, magnetic resonance imaging (MRI). "It was already acknowledged that proteins find one another via ultra-weak interactions, but no one knew how to measure them. Now we can," says Led. He hopes that other researchers will now take this work and use it to develop our models of proteins perhaps even in living systems too.