title: Dipeptide interactions with Zn(II)-cyclen artificial model for molecular recognition.
abstract: The Zn(II)-cyclen-dipeptide ternary systems (where cyclen is abbreviated as L and dipeptide is glycylglycine (HL(1)) or glycyl-(S)-alanine (HL(2))) were investigated by potentiometry applying both "out-of-cell" and direct titrations and by (1) H NMR spectroscopy. Especially, the (1)H NMR study was found to be very efficient to estimate speciation in the systems. The results obtained under full equilibria indicated two main species, [Zn(L)(HL(1,2))](2+) and [Zn(L)(L(1,2))](+), in both the systems. In the [Zn(L)(HL(1,2))](2+) complex, presence of carbonyl-carboxylate chelate was confirmed, and in the [Zn(L)(L(1,2))](+) species, the peptide coordination is re-organized to carbonyl-amine chelate or only terminal amino group is coordinated. Equilibrium constants describing [Zn(L)](2+)-dipeptide interaction are relatively low, log K = 3.4 for Gly-Gly and 4.1 for Gly-(S)-Ala, respectively. Nevertheless, the values are slightly higher than stability constants for interaction of Zn(II) with the dipeptides (i.e. [Zn(L(1,2))](+) species) where a chelate formation is expected. It indicates that interaction between Zn(II) ion in [Zn(L)](2+) and the dipeptides should be supported by some additional interactions. Potentiometry carried out under non-equilibrum condition showed different species where these additional stabilizing forces play more important role.
authors: Department of Inorganic Chemistry, Institute of Chemistry, P.J.Šafárik University, Moyzesova 11, 04154, Košice, Slovak Republic.
authors: I
authors: I
authors: Rostášová
authors: M
authors: M
authors: Vilková
authors: Z
authors: Z
authors: Vargová
authors: M
authors: M
authors: Walko
authors: M
authors: M
authors: Almáši
authors: J
authors: J
authors: Imrich
authors: P
authors: P
authors: Hermann
authors: I
authors: I
authors: Lukeš
mesh_terms: D000080027:Cyclams; D004151:Dipeptides / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015032:Zinc / Q000737:chemistry*
chemical_list: D000080027:Cyclams; D004151:Dipeptides; D006571:Heterocyclic Compounds; C038072:cyclen; D015032:Zinc
keywords: NMR spectroscopy; Zn(II)-cyclen complex; molecular recognition; potentiometry; solution study