Copper(ii) complexes of terminally protected pentapeptides containing three histidyl residues in alternating positions, Ac-His-Xaa-His-Yaa-His-NH 2

C. Kállay, K. Várnagy, Gerasimos Malandrinos, Nick Hadjiliadis, Daniele Sanna, I. Sóvágó

Research output: Contribution to journalArticle

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Abstract

Copper(ii) complexes of the pentapeptides Ac-HisAlaHisValHis-NH 2, Ac-HisValHisAlaHis-NH2, Ac-HisProHisAlaHis-NH 2, Ac-HisAlaHisProHis-NH2, Ac-HisGlyHisValHis-NH 2 and Ac-HisValHisGlyHis-NH2 have been studied by potentiometric, UV-Vis, CD and EPR spectroscopic methods. It has been found that the pentapeptides are efficient ligands for the complexation with copper(ii) and exhibit an outstanding versatility in the co-ordination geometry of complexes. The presence of three histidyl residues provides a high possibility for the formation of macrochelates via the exclusive binding of imidazole-N donor atoms. The macrochelation suppresses, but cannot preclude the deprotonation and metal ion co-ordination of amide functions and the species [CuH-2L] and [Cu2H-4L] predominate at physiological pH in equimolar solutions and in the presence of excess metal ions, respectively. It is also clear from the data that both C-terminal and internal histidyl residues can work as the anchoring sites for metal binding and subsequent amide deprotonation resulting in the formation of co-ordination isomers and dinuclear species in equimolar solutions and in the presence of excess metal ions, respectively. In more alkaline solutions (pH ∼10) a third amide function can be deprotonated and co-ordinated in the species [CuH -3L]- with (N-,N-,N -,Nim) co-ordination. The dinuclear species [Cu 2H-5L]- and [Cu2H -6L]2- containing hydroxide ions and/or imidazolato bridges are formed at high pH in the presence of excess of metal ions. The insertion of one proline into the sequence preceding histidyl residues hinders the deprotonation of amide functions at that site and the formation of only mononuclear complexes was observed with these peptides.

Original languageEnglish
Pages (from-to)4545-4552
Number of pages8
JournalDalton Transactions
Issue number38
DOIs
Publication statusPublished - 2006

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Amides
Deprotonation
Metal ions
Copper
Complexation
Proline
Isomers
Paramagnetic resonance
Metals
Ligands
Atoms
Peptides
Geometry

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Copper(ii) complexes of terminally protected pentapeptides containing three histidyl residues in alternating positions, Ac-His-Xaa-His-Yaa-His-NH 2 . / Kállay, C.; Várnagy, K.; Malandrinos, Gerasimos; Hadjiliadis, Nick; Sanna, Daniele; Sóvágó, I.

In: Dalton Transactions, No. 38, 2006, p. 4545-4552.

Research output: Contribution to journalArticle

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title = "Copper(ii) complexes of terminally protected pentapeptides containing three histidyl residues in alternating positions, Ac-His-Xaa-His-Yaa-His-NH 2",
abstract = "Copper(ii) complexes of the pentapeptides Ac-HisAlaHisValHis-NH 2, Ac-HisValHisAlaHis-NH2, Ac-HisProHisAlaHis-NH 2, Ac-HisAlaHisProHis-NH2, Ac-HisGlyHisValHis-NH 2 and Ac-HisValHisGlyHis-NH2 have been studied by potentiometric, UV-Vis, CD and EPR spectroscopic methods. It has been found that the pentapeptides are efficient ligands for the complexation with copper(ii) and exhibit an outstanding versatility in the co-ordination geometry of complexes. The presence of three histidyl residues provides a high possibility for the formation of macrochelates via the exclusive binding of imidazole-N donor atoms. The macrochelation suppresses, but cannot preclude the deprotonation and metal ion co-ordination of amide functions and the species [CuH-2L] and [Cu2H-4L] predominate at physiological pH in equimolar solutions and in the presence of excess metal ions, respectively. It is also clear from the data that both C-terminal and internal histidyl residues can work as the anchoring sites for metal binding and subsequent amide deprotonation resulting in the formation of co-ordination isomers and dinuclear species in equimolar solutions and in the presence of excess metal ions, respectively. In more alkaline solutions (pH ∼10) a third amide function can be deprotonated and co-ordinated in the species [CuH -3L]- with (N-,N-,N -,Nim) co-ordination. The dinuclear species [Cu 2H-5L]- and [Cu2H -6L]2- containing hydroxide ions and/or imidazolato bridges are formed at high pH in the presence of excess of metal ions. The insertion of one proline into the sequence preceding histidyl residues hinders the deprotonation of amide functions at that site and the formation of only mononuclear complexes was observed with these peptides.",
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T1 - Copper(ii) complexes of terminally protected pentapeptides containing three histidyl residues in alternating positions, Ac-His-Xaa-His-Yaa-His-NH 2

AU - Kállay, C.

AU - Várnagy, K.

AU - Malandrinos, Gerasimos

AU - Hadjiliadis, Nick

AU - Sanna, Daniele

AU - Sóvágó, I.

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