Wydział Chemii

Teresa Kowalik-Jankowska

Anna Rajewska

Wioletta Szeszel-Fedorowicz

Danuta Konopińska

2005

Polyhedron

24

443-450

10.1016/j.poly.2004.12.005

Naukowa

Angielski

Artykuł

The proctolin (Arg–Tyr–Leu–Pro–Thr, RYLPT) analogues modified in fifth position of the peptide chain (RYLPP, RYLPI, RYLP–Dab, where Dab – 2,4-diamminobutyric acid) have been synthesised and their complexes with H⁺ and Cu²⁺ studied by potentiometry and spectroscopy (UV–Vis, CD and EPR) at 25 °C and I = 0.10 mol dm⁻³ (KNO₃). The results obtained support the earlier suggestion on the specific role of a proline residue as a “break-point” in copper complex formation with peptides. The presence of a proline residue into the fourth position of the proctolin analogues (RYLPP, RYLPI) leads in wide pH range of the existence the CuL and CuH₋₁L complexes with expected stabilities. Spectroscopic studies confirm that these are 2N {NH₂, N⁻, CO} and 3N {NH₂, 2N⁻, CO} species, respectively. The amine group of the Dab residue of the RYLP–Dab proctolin analogue, in whole pH range (2.5–10.5) is coordinated to the copper(II) ions, and the deprotonation and coordination of the second amide nitrogen atom to the metal ion is prevented. In solution in wide pH range (5–10.5) the 3N {NH₂, N⁻, CO, NH_2Dab} complex is present. Proctolin and its analogues modified in fifth position contain in the second position of the peptide sequence the Tyr residue and the CD results show that TyrO⁻–Cu²⁺ bonding is present at pH above 8.

https://doi.org/10.1016/j.poly.2004.12.005

http://www.elsevier.com