title: Structural optimization of Zn(II)-activated magnetic resonance imaging probes.
abstract: We report the structural optimization and mechanistic investigation of a series of bioactivated magnetic resonance imaging contrast agents that transform from low relaxivity to high relaxivity in the presence of Zn(II). The change in relaxivity results from a structural transformation of the complex that alters the coordination environment about the Gd(III) center. Here, we have performed a series of systematic modifications to determine the structure that provides the optimal change in relaxivity in response to the presence of Zn(II). Relaxivity measurements in the presence and absence of Zn(II) were used in conjunction with measurements regarding water access (namely, number of water molecules bound) to the Gd(III) center and temperature-dependent (13)C NMR spectroscopy to determine how the coordination environment about the Gd(III) center is affected by the distance between the Zn(II)-binding domain and the Gd(III) chelate, the number of functional groups on the Zn(II)-binding domain, and the presence of Zn(II). The results of this study provide valuable insight into the design principles for future bioactivated magnetic resonance probes.
authors.affiliation: Departments of Chemistry, Molecular Biosciences, Neurobiology, Biomedical Engineering, and Radiology, and ‡Department of Chemistry, and Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208-3113, United States.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Matosziuk
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Leibowitz
authors.forename: Marie C
authors.initials: MC
authors.lastname: Heffern
authors.forename: Keith W
authors.initials: KW
authors.lastname: MacRenaris
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ratner
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Meade
mesh_terms: D002614:Chelating Agents / Q000737:chemistry; D060326:Chemistry Techniques, Synthetic; D003287:Contrast Media / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D013329:Structure-Activity Relationship; D013696:Temperature; D015032:Zinc / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D003287:Contrast Media; D005682:Gadolinium; D015032:Zinc