| Abstract: | Complex formation of valinomycin with Ba2+ ions was investigated by circular dichroism spectroscopy. The results indicated that Ba2+ forms entirely different types of complexes when compared with K+. The data with perchlorate salt showed evidence for the formation of less stable V2C (peptide sandwich), VC (1:1), and VC2 (ion sandwich) complexes followed by a stable final complex upon gradual addition of salt (V stands for valinomycin and C for the cation). This final complex possibly has a flat structure with no internal hydrogen bonds, similar to that of valinomycin in highly polar solvents. The possible complexation mechanism and the role played by anions and isopropyl side chains are highlighted. |
