Potentiometric and spectroscopic studies on the copper(II) complexes formed by oligopeptides containing histidine with a protection at the terminal amino group

Copper(II) and zinc(II) complexes of the peptides Ac-HisValHis-NH 2 and Ac-HisValGlyAsp-NH 2 related to the active site of the enzyme CuZnSOD

“…Similar binding was reported for the [CuAH À2 ] species of HisValHis system in our previous paper, too [12]. The transformation of the terminal amino group to an amide function significantly decreases the metal ion affinity of the ligands, but the formation of similar [(N À ,N À ,N À ,N(im)] coordination mode has been reported for the [CuAH À3 ] species of ZGlyGlyHis at high pH values [25]. The spectral parameters of this complex (g k ¼ 2:180, A k ¼ 202 Â 10 À4 cm À1 and k max ¼ 540 nm) are in very good agreement with those of Ac-HisValHis-NH 2 in Table 2.…”

“…The values in Table 2 strongly support the presence of a 4N complex as shown by Scheme 2(b). Deprotonation and coordination of the amide functions promoted by the anchoring imidazole side chains have already been reported [25] and the existence of a 7-membered chelate at the N-termini has also been published for the copper(II) complex of a very similar tetrapeptide Ac-HisGlyHisGlyOH [17]. The metal ion speciation of the systems, Cu(II)-Ac-HisValHis-NH 2 and Cu(II)-AcHisGlyHisGlyOH, is very similar and the same macrochelate is suggested for [CuA] 2þ , but the spectral parameters of both [CuAH À2 ] and [CuAH À3 ] À species are rather different in the two systems.…”

“…The existence of a species in low concentration can be observed in the EPR spectra before precipitation. Its spectral parameters Scheme 2. correspond to the coordination of 2N donor atoms suggesting the [CuBH À1 ] stoichiometry containing imidazole and amide donor functions [25]. Deprotonation and metal ion coordination of the subsequent amide functions result in the dissolution of the hydroxo complexes and the species [CuBH À3 ] 2À and [CuBH À4 ] 3À are present in solution above pH 10.…”

A multi-approach study of the interaction of the Cu(II) and Ni(II) ions with alanylglycylhistamine, a mimicking pseudopeptide of the serum albumine N-terminal residue

“…Cu(II) and Ni(II) cations are well known for their ability to interact with histidyl residues in peptides, particularly with those containing the N-terminal sequence X-Y-His that is encountered in serum albumine [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This protein, the most abundant one in mammalian blood serum, is involved in the transport of these ions.…”

Crystal structure, spectroscopy and ferromagnetostructural behavior of the complex [CuII(L)(Cl)(L´)]•H2O (L = 2-aminomethylbenzimidazole, L´= L-isoleucinate)

“…[1][2][3][4] These systems are found in biological molecules and carry out important functions as photosynthesis, 5 reversible dioxygen linking, 6 electron transfer, 7 peroxidation, 8 among others. On the other hand, the benzimidazole moiety and some of its derivatives present in molecules as vitamin B 12 5 and Cu II -benzimidazole complexes have been reported.…”