ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P19. Potentiometric and Spectroscopic Studies of Coordination Abilities of
Dehydrotripeptides Gly-∆Phe-His and His-Gly-∆Phe
J. Brasuń a , M. Makowski b , O. Gładysz a J. Świątek-Kozłowska a
a
Department of Inorganic Chemistry, Wroclaw Medical University, Szewska 38, 50-139 Wroclaw, Poland
e-mail: olimpia@chnorg.am.wroc.pl
b
Department of Chemistry, University of Opole, Oleska 48, 45-052 Opole, Poland
∆-aminoacids are unsaturated analogues of α-aminoacids and their biological activities and structural properties
were investigated [1-2] because they are constituents of many microbial proteins (fungal and bacterial
metabolities) as well antibiotics [3]. Also the coordination abilities compared to parent peptides were widely
studied [4-8]. These studies showed that ∆-peptides display unusual binding ability towards metal ions such as
Cu 2+ , Ni 2+ , Co 2+ , Zn 2+ [6-7].
The purpose of the present studies was to examine the stability of copper (II) complexes with dehydrotripeptides
Gly-∆Phe-His and His-Gly-∆Phe .
Using pH-metric titrations the protonation constants and stability constants of these ligands were found out and
also UV-Vis spectra were recorded.
Both investigated dehydro peptides form stable complexes with Cu (II) ions and the the stability constants
derived from potentiometric titrations were obtained with high accuracy. The potentiometric and spectrosciopic
results show that Gly-∆Phe-His forms six types of complexes with Cu (II) ions and since pH 4 complex CuL2 is
created. Although His-Gly-∆Phe forms also six complexes all of them involve only one ligand. The species
distribution of Gly-∆Phe-His/Cu(II) and His-Gly-∆Phe/Cu(II) solution (Fig.1 and Fig.2) will be discussed as well
as some likely complexes structure.
%Cu
100
90
80
70
60
50
40
30
20
10
0
CuL
free Cu
CuL
CuH -1L
CuH -1L 2
CuH -2L 2
CuH -3L 2
3 4 5 6 7 8 9 10 11
pH
_____________________________________________________________________
138
%Cu
100
90
80
70
60
50
40
30
20
10
0
free Cu (II)
CuHL
CuL
CuH -1L
CuH -2L
CuH -3L
3 4 5 6 7 8 9 10 11
pH
Fig. 1 Species distribution curves for Gly-∆Phe-His/Cu(II) Fig.2 Species distribution curves for His-Gly-∆Phe/Cu(II)
Refrences:
[1] B. Rzeszotarska, Z. Kubica, J. Tarnawski, Post. Biochem., 33, 533, (1987)
[2] T. P. Singh, P. Narula, H.C. Patel, Acta Cryst.Sect. B, 46, 539, (1990)
[3] A.F. Spatola, in: B. Weinstein, editor. Chemistry and Biochemistry of Amino Acids, Peptides and Proteins,
vol.VII, New York, , M. Dekker, 267, (1983).
[4] J. Świątek-Kozłowska., J. Brasuń, M. Łuczkowski., M. Makowski, J. Inorg. Biochem., 90, 106 (2002)
[5] M. Z. Siddiqui, Inter. Journal of Biol. Macromolecules, 26, 17, (1999);
[6] M. Jeżowska-Bojczuk, H. Kozłowski, Polyhedron, 10, Vol.19, 2331, (1991)
[7] M. Jeżowska-Bojczuk, H. Kozłowski, Polyhedron, 13, Vol.18, 2683, (1994)
[8] M. Jeżowska-Bojczuk, K. Varnagy, I. Sovago, G. Pitrzyński, M. Dyba, Y. Kubica, B. Rzeszotarska, L.
Smełka, H. Kozłowski, J.Chem. Soc., Dalton Trans., 3265 (1996)
[9] R. Hay, M. M. Hassan, C. You-Quan, Journal of Inorganic Biochemistry, 52, 17 (1993).
CuH -
L