The Palladium(II) Complex of Aβ4−16 as Suitable Model for Structural Studies of Biorelevant Copper(II) Complexes of N-Truncated Beta-Amyloids |
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Authors: | Mariusz Mital,Kosma Szutkowski,Karolina Bossak-Ahmad,Piotr Skrobecki,Simon C. Drew,Jarosł aw Poznań ski,Igor Zhukov,Tomasz Frą czyk,Wojciech Bal |
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Affiliation: | 1.Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warszawa, Poland; (M.M.); (K.B.-A.); (P.S.); (S.C.D.); (J.P.);2.NanoBioMedical Centre, Adam Mickiewicz University, 61-614 Poznań, Poland; |
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Abstract: | The A peptide is a major beta-amyloid species in the human brain, forming toxic aggregates related to Alzheimer’s Disease. It also strongly chelates Cu(II) at the N-terminal Phe-Arg-His ATCUN motif, as demonstrated in A and A model peptides. The resulting complex resists ROS generation and exchange processes and may help protect synapses from copper-related oxidative damage. Structural characterization of Cu(II)A complexes by NMR would help elucidate their biological function, but is precluded by Cu(II) paramagneticism. Instead we used an isostructural diamagnetic Pd(II)-A complex as a model. To avoid a kinetic trapping of Pd(II) in an inappropriate transient structure, we designed an appropriate pH-dependent synthetic procedure for ATCUN Pd(II)A, controlled by CD, fluorescence and ESI-MS. Its assignments and structure at pH 6.5 were obtained by TOCSY, NOESY, ROESY, H-C HSQC and H-N HSQC NMR experiments, for natural abundance C and N isotopes, aided by corresponding experiments for Pd(II)-Phe-Arg-His. The square-planar Pd(II)-ATCUN coordination was confirmed, with the rest of the peptide mostly unstructured. The diffusion rates of A, Pd(II)-A and their mixture determined using PGSE-NMR experiment suggested that the Pd(II) complex forms a supramolecular assembly with the apopeptide. These results confirm that Pd(II) substitution enables NMR studies of structural aspects of Cu(II)-A complexes. |
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Keywords: | Alzheimer’ s disease, Aβ peptide, NMR spectroscopy, 13C relaxation, Palladium(II), ATCUN motif |
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