Effect of the Peptidic Scaffold in Copper(II) Coordination and the Redox Properties of Short Histidine‐Containing Peptides. Issue 37 (28th July 2015)

• Record Type: Journal Article
• Authors: Fragoso, Ana; Carvalho, Tiago; Rousselot‐Pailley, Pierre; Correia dos Santos, Margarida M.; Delgado, Rita; Iranzo, Olga
• Is Part Of: Chemistry. Volume 21:Issue 37(2015)
• Page Start: 13100
• Page End: 13111
• Publication Date: 2015-07-28
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201501715
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>A linear decapeptide containing three His and one Asp residues and a β‐turn‐inducing dProPro unit was synthesised. A detailed potentiometric, mass spectrometric and spectroscopic study showed that at a 1:1 ratio of C<sub>Cu</sub>/C<sub>peptide</sub> this peptide formed a major [CuH(O<sub>dPro</sub>Asp)]<sup>2+</sup> species (pH range 5.5–7.0), in which the Cu<sup>2+</sup> ion was bound to the His and Asp residues in square‐planar or square‐pyramidal geometries. The stability constant corrected for protonated species (log <italic>K*</italic><inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgj2gd468ks" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="urn:x-wiley:09476539:media:CHEM201501715:tex2gif-inf-4" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mtext> </mml:mtext><mml:mrow><mml:mtext>CuH(O</mml:mtext><mml:msub><mml:mtext> </mml:mtext><mml:mrow><mml:mtext>dPro</mml:mtext></mml:mrow></mml:msub><mml:mtext>‐Asp)</mml:mtext></mml:mrow></mml:msub></mml:math></alternatives></inline-formula>=9.33) is almost equal to the value obtained for the parent [CuH(OAsp)]<sup>2+</sup> species (log <italic>K*</italic><sub>CuH(O‐Asp)</sub>=9.28), but lower than that obtained for the cyclic [CuH(CAsp)]<sup>2+</sup> complex (log <italic>K*</italic><sub>CuH(C‐Asp)</sub>=10.79) previously published. Thus, the replacement of the ProGly unit by the stronger β‐turn‐inducing dProPro unit did not generate a more stable copper(II) species, although the O<sub>dPro</sub>Asp peptide was structured in solution, as shown by circular dichroism (CD) spectroscopy. Interestingly, the calculated value of <italic>K</italic><sub>eff</sub> showed that this peptide behaved similarly to the OAsp or CAsp counterparts, depending on the pH value. The cyclic voltammetry data indicated that the most easily reducible species were [CuH(OAsp)]<sup>2+</sup> (<italic>E</italic>′<sup>0</sup>=262 mV versus a normal hydrogen electrode (NHE)) and [CuH(O<sub>dPro</sub>Asp)]<sup>2+</sup> (<italic>E</italic>′<sup>0</sup>=294 mV versus NHE) complexes, the peptidic scaffolds of which are open. A lower value was obtained for [CuH(CAsp)]<sup>2+</sup> (<italic>E</italic>′<sup>0</sup>=24 mV versus NHE). A different degree of non‐reversibility was observed for the three copper(II) complexes; this could reflect a different degree of flexibility in their respective peptidic scaffolds.</p> </abstract>