Artificial reporter gene providing MRI contrast based on proton exchange

Existing magnetic resonance reporter genes all rely on the presence of ( super) paramagnetic substances and employ water relaxation to gain contrast. We designed a nonmetallic, biodegradable, lysine rich-protein ( LRP) reporter, the prototype of a potential family of genetically engineered reporters expressing artificial proteins with frequency-selective contrast. This endogenous contrast, based on transfer of radiofrequency labeling from the reporter's amide protons to water protons, can be switched on and off.