title: Associating a negatively charged GdDOTA-derivative to the Pittsburgh compound B for targeting Aβ amyloid aggregates.
abstract: We have conjugated the tetraazacyclododecane-tetraacetate (DOTA) chelator to Pittsburgh compound B (PiB) forming negatively charged lanthanide complexes, Ln(L4), with targeting capabilities towards aggregated amyloid peptides. The amphiphilic Gd(L4) chelate undergoes micellar aggregation in aqueous solution, with a critical micellar concentration of 0.68 mM, lower than those for the neutral complexes of similar structure. A variable temperature (17)O NMR and NMRD study allowed the assessment of the water exchange rate, k ex (298) = 9.7 × 10(6) s(-1), about the double of GdDOTA, and for the description of the rotational dynamics for both the monomeric and the micellar forms of Gd(L4). With respect to the analogous neutral complexes, the negative charge induces a significant rigidity of the micelles formed, which is reflected by slower and more restricted local motion of the Gd(3+) centers as evidenced by higher relaxivities at 20-60 MHz. Surface Plasmon Resonance results indicate that the charge does not affect significantly the binding strength to Aβ1-40 [K d = 194 ± 11 μM for La(L4)], but it does enhance the affinity constant to human serum albumin [K a = 6530 ± 68 M(-1) for Gd(L4)], as compared to neutral counterparts. Protein-based NMR points to interaction of Gd(L4) with Aβ1-40 in the monomer state as well, in contrast to neutral complexes interacting only with the aggregated form. Circular dichroism spectroscopy monitored time- and temperature-dependent changes of the Aβ1-40 secondary structure, indicating that Gd(L4) stabilizes the random coil relative to the α-helix and β-sheet. TEM images confirm that the Gd(L4) complex reduces the formation of aggregated fibrils.
authors.affiliation: Centre de Biophysique Moléculaire, CNRS, UPR 4301, Université d'Orléans, Rue Charles Sadron, 45071, Orléans Cedex 2, France.|Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Calçada Martim de Freitas, 3000-393, Coimbra, Portugal.|Coimbra Chemistry Center, University of Coimbra, Rua Larga, 3004-535, Coimbra, Portugal.|Department of Chemistry, University of Texas at Dallas, Richardson, TX, 75083, USA.
authors.forename: André F
authors.initials: AF
authors.lastname: Martins
authors.affiliation: Coimbra Chemistry Center, University of Coimbra, Rua Larga, 3004-535, Coimbra, Portugal.
authors.forename: Alexandre C
authors.initials: AC
authors.lastname: Oliveira
authors.affiliation: Centre de Biophysique Moléculaire, CNRS, UPR 4301, Université d'Orléans, Rue Charles Sadron, 45071, Orléans Cedex 2, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Morfin
authors.affiliation: Instituto de Química Física "Rocasolano", C.S.I.C., Serrano 119, 28006, Madrid, Spain.
authors.forename: Douglas V
authors.initials: DV
authors.lastname: Laurents
authors.affiliation: Centre de Biophysique Moléculaire, CNRS, UPR 4301, Université d'Orléans, Rue Charles Sadron, 45071, Orléans Cedex 2, France.
authors.forename: Éva
authors.initials: É
authors.lastname: Tóth
authors.affiliation: Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Calçada Martim de Freitas, 3000-393, Coimbra, Portugal. geraldes@ci.uc.pt.|Coimbra Chemistry Center, University of Coimbra, Rua Larga, 3004-535, Coimbra, Portugal. geraldes@ci.uc.pt.
authors.forename: Carlos F G C
authors.initials: CF
authors.lastname: Geraldes
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D016229:Amyloid beta-Peptides; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate
keywords: 17O NMR; Alzheimer’s disease; Amyloid; Contrast agents; DOTAGA; Gadolinium; Lipari-Szabo approach; MRI; Relaxivity