Imaging protein-protein interactions in living subjects

Only over the last three years methods have been developed to study protein-protein interactions occurring inside the intact cells within small living animals. This has been made possible by the explosion of non-invasive small-animal imaging technologies and the rapidly expanding field of molecular imaging, with technologies including bioluminescence imaging, fluorescence imaging, positron emission tomography (PET), and single photon emission computed tomography (SPECT). The first two techniques depend on light transmission through the animal, while the latter two depend on gamma ray transmission through the animal; in each case, the appropriate reporter genes or split-reporter genes are needed, along with the corresponding reporter probes. Other imaging technologies, such as magnetic resonance imaging (MRI) are also used for molecular imaging. but have not yet been validated specifically for imaging protein-protein interactions. The focus of this article is primarily on optical technologies for imaging protein-protein interactions.