How very small changes in the peptide sequence of β-amyloids influence their redox properties. Electrochemical studies of copper complexes with Aβ(11-16) and pAβ(11-16)

Here we demonstrate a significant difference in redox behaviour of copper complexes with β-amyloids Aβ(11-x) and pAβ(11-x) which are models for important components of senile plaques. A small change in the peptide chain may enhance reactive oxygen species (ROS) formation which can severely damage nerve cells

Redox Activity of Copper(II) Complexes with NSFRY Pentapeptide and Its Analogues.

The influence of cation-π interactions on the electrochemical properties of copper(II) complexes with synthesized pentapeptide C-terminal fragment of Atrial Natriuretic Factor (ANF) hormone was studied in this work. Molecular modeling performed for Cu(II)-NSFRY-NH2 complex indicated that the cation-π interactions between Tyr and Cu(II), and also between Phe-Arg led to specific conformation defined as peptide box, in which the metal cation is isolated from the solvent by peptide ligand. Voltammetry experiments enabled to compare the redox properties and stability of copper(II) complexes with NSFRY-NH2 and its analogues (namely: NSFRA-NH2, NSFRF-NH2, NSAAY-NH2, NSAAA-NH2, AAAAA-NH2) as well as to evaluate the contribution of individual amino acid residues to these properties. The obtained results led to the conclusion, that cation-π interactions play a crucial role in the effective stabilization of copper(II) complexes with the fragments of ANF peptide hormone and therefore could control the redox processes in other metalloproteins

Cyclic voltammograms recorded in 0.5 mM aqueous solution of Cu(II)-NSFRY-NH₂ complex (black solid line) and NSFRY-NH₂ peptide (black dashed line) at pH 6.0; Cu(II)-AAAAA-NH₂ complex (red solid line) and AAAAA-NH₂ peptide (red dashed line) at pH 6.5; Cu(II)-NSFRA-NH₂

<p>Cyclic voltammograms recorded in 0.5 mM aqueous solution of Cu(II)-NSFRY-NH₂ complex (black solid line) and NSFRY-NH₂ peptide (black dashed line) at pH 6.0; Cu(II)-AAAAA-NH₂ complex (red solid line) and AAAAA-NH₂ peptide (red dashed line) at pH 6.5; Cu(II)-NSFRA-NH₂</p

Cyclic voltammograms recorded in 0.5 mM aqueous solution of Cu(II)-NSFRY-NH₂ complex (solid line) and NSFRY-NH₂ peptide (dashed line) at pH 11.0.

<p>Cyclic voltammograms recorded in 0.5 mM aqueous solution of Cu(II)-NSFRY-NH₂ complex (solid line) and NSFRY-NH₂ peptide (dashed line) at pH 11.0.</p

Cyclic voltammograms recorded in 0.5 mM aqueous solution of Cu(II)-NSFRY-NH₂ complex (black solid line) and NSFRY-NH₂ peptide (black dashed line) at pH 6.7; Cu(II)-AAAAA-NH₂ complex (red solid line) and AAAAA-NH₂ peptide (red dashed line) at pH 8.0; Cu(II)-NSFRA-NH₂ complex (blue solid line) and NSFRA-NH₂ peptide (blue dashed line) at pH 7.1.

<p>Cyclic voltammograms recorded in 0.5 mM aqueous solution of Cu(II)-NSFRY-NH₂ complex (black solid line) and NSFRY-NH₂ peptide (black dashed line) at pH 6.7; Cu(II)-AAAAA-NH₂ complex (red solid line) and AAAAA-NH₂ peptide (red dashed line) at pH 8.0; Cu(II)-NSFRA-NH₂ complex (blue solid line) and NSFRA-NH₂ peptide (blue dashed line) at pH 7.1.</p

Various complex species formed at the appropriate pH (values given in brackets), determined on the basis of spectroscopic and potentiometric measurement [13] (the pH value for Cu(II)-NSAAY-NH₂ 4N complex was estimated on the basis of UV-Vis spectra measured in the present work).

<p>Various complex species formed at the appropriate pH (values given in brackets), determined on the basis of spectroscopic and potentiometric measurement [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160256#pone.0160256.ref013" target="_blank">13</a>] (the pH value for Cu(II)-NSAAY-NH₂ 4N complex was estimated on the basis of UV-Vis spectra measured in the present work).</p

Redox Activity of Copper(II) Complexes with NSFRY Pentapeptide and Its Analogues - Fig 3

<p>(A), (C) Cyclic and (B) DP voltammograms recorded in 0.5 mM aqueous solution of Cu(II)-peptide complexes (solid lines) and free peptides (dashed lines) at pH 9.0. Only in the case of Cu(II)-AAAAA-NH₂ complex (red line) and AAAAA-NH₂ peptide (red dashed line) the measurements were performed at pH 11.0.</p

Calculated structures of the Cu(II)-NSFRY-NH₂ complex.

<p>Ball model–left side–and the stick model–on the right side.</p