Heteroditopic Binding of Magnetic Resonance Contrast Agents for Increased Relaxivity

Kept within bounds: For peptide-targeted contrast agents, internal motion limits the relaxivity gain. A focused library approach identified an N-terminal thymine peptide nucleic acid (PNA) that reaches an additional binding pocket on the protein fibrin. The heteroditopic binding rigidifies the molecule upon binding, resulting in increased protein-bound relaxivity (see picture).