ABSTRACT
This chapter discusses the structure and dynamics of a paramagnetic metal chelate determine its ability to enhance water proton relaxation rates and that relaxivity is the key parameter in the evaluation of a paramagnetic chelate for magnetic resonance imaging applications. As anticipated above, an important parameter in the determination of the relaxivity is represented by the reorientational time of the magnetic vector joining the paramagnetic center and the protons of the coordinated water molecule. The presence of coordinating groups like phosphonates, carboxylates, carboxo-amide, etc., introduces a number of polar atoms around the coordination cage that promote the organization of water molecules in the second coordination sphere. Targeting human serum albumin represents another topic that has been widely investigated in the last decade, and it has provided a number of insights that can also be used to understand the binding of paramagnetic chelates to other proteins.
