title: Molecular factors that determine Curie spin relaxation in dysprosium complexes.
abstract: Dysprosium complexes can serve as transverse relaxation (T(2)) agents for water protons through chemical exchange and the Curie spin relaxation mechanism. Using a pair of matched dysprosium(III) complexes, Dy-L1 (contains one inner-sphere water) and Dy-L2 (no inner-sphere water), it is shown that the transverse relaxation of bulk water is predominantly an inner-sphere effect. The kinetics of water exchange at Dy-L1 were determined by (17)O NMR. Proton transverse relaxation by Dy-L1 at high fields is governed primarily through a large chemical shift difference between free and bound water. Dy-L1 forms a noncovalent adduct with human serum albumin which dramatically lengthens the rotational correlation time, tau(R), causing the dipole-dipole component of the Curie spin mechanism to become significant and transverse relaxivity to increase by 3-8 times that of the unbound chelate. These findings aid in the design of new molecular species as efficient r(2) agents.
authors.affiliation: EPIX Medical, Inc., Cambridge, Massachusetts 02142-1118, USA. pcaravan@epixmed.com
authors.forename: P
authors.initials: P
authors.lastname: Caravan
authors.forename: M T
authors.initials: MT
authors.lastname: Greenfield
authors.forename: J W
authors.initials: JW
authors.lastname: Bulte
mesh_terms: D003287:Contrast Media; D004419:Dysprosium / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D012709:Serum Albumin; D014867:Water
chemical_list: D003287:Contrast Media; D012709:Serum Albumin; D014867:Water; D004419:Dysprosium