Associating a negatively charged GdDOTAderivative

Authors: André F Martins Alexandre C Oliveira JeanFrançois Morfin Douglas V Laurents Éva Tóth Carlos F G C Geraldes

Publish Date: 2015/11/27

Volume: 21, Issue: 1, Pages: 83-99

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Abstract

We have conjugated the tetraazacyclododecanetetraacetate DOTA chelator to Pittsburgh compound B PiB forming negatively charged lanthanide complexes LnL4 with targeting capabilities towards aggregated amyloid peptides The amphiphilic GdL4 chelate undergoes micellar aggregation in aqueous solution with a critical micellar concentration of 068 mM lower than those for the neutral complexes of similar structure A variable temperature 17O NMR and NMRD study allowed the assessment of the water exchange rate k ex 298  = 97 × 106 s−1 about the double of GdDOTA and for the description of the rotational dynamics for both the monomeric and the micellar forms of GdL4 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 Gd3+ 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 LaL4 but it does enhance the affinity constant to human serum albumin K a = 6530 ± 68 M−1 for GdL4 as compared to neutral counterparts Proteinbased NMR points to interaction of GdL4 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 temperaturedependent changes of the Aβ1–40 secondary structure indicating that GdL4 stabilizes the random coil relative to the αhelix and βsheet TEM images confirm that the GdL4 complex reduces the formation of aggregated fibrilsThis work was supported by the Portuguese Fundação para a Ciência e Tecnologia FCT grants SFRH/BD/46370/2008 to A F M REEQ/481/QUI/2006 RECI/QEQQFI/0168/2012 and CENTRO07CT62FEDER002012 by the Coimbra Chemistry Centre project PEstOE/QUI/UI0313/2014 the Rede Nacional de RMN REDE/1517/RMN/2005 in part by FEDER—European Regional Development Fund through the COMPETE Program Operational Program for Competitiveness and by the FrenchPortuguese PHC PESSOA project E T acknowledges support from La Ligue contre le Cancer and D V L the support of the Spanish Ministry of Science and Innovation grants CTQ 201021567C0202 and SAF201349179C22R This work was carried out in the frame of the European COST Actions TD1004 “Theragnostics Imaging and Therapy” and TD1007 “PETMRI”

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