Theoretical Study on Cyclopeptides as the Nanocarriers for Li+, Na+, K+ and F−, Cl−, Br−

The interaction process between a series of cyclopeptide compounds cyclo(Gly)n (n=4,6,8) and monovalent ions (Li+, Na+, K+, F−, Cl−, and Br−) was studied using theoretical calculation. The mechanism of combination between the cyclo(Gly)n and ions was discussed through binding energy, Mulliken electron population, and hydrogen bond. It was found that for the same cyclopeptide the binding energy has the order of cyclo(Gly)n–Li+ > cyclo(Gly)n–Na+ > cyclo(Gly)n–K+ and cyclo(Gly)n–F− > cyclo(Gly)n–Br− > cyclo(Gly)n–Cl−. The binding energy manifests the stable complex of cyclo(Gly)n and ions can be formed, and the different energy shows the potential use of cyclo(Gly)n as nanocarriers for metal ions or the extractant for ions separation