Cyclic peptides-assisted transport of metal ions across liquid-organic membrane

Abstract

The formation of alkali and alkaline-earth metal picrate complexes with cyclo(Pro-Gly) n ionophores (1, n = 3; 2, n = 4) can facilitate the migration of metal ions across a bulk liquid CH 2 Cl 2 membrane. The migration behavior was studied by measuring the solution absorption at 356 nm, using a UV/Vis spectrophotometer, and the rates can be determined by comparing the initial absorption of donor solutions with the absorption of the corresponding receiver solutions as the function of time. It was found that cyclic peptide 1 shows higher transport activity for the studied alkali and alkaline-earth metal ions than compound 2, which is related to the backbone flexibility of the cyclic peptides. The findings in this work suggest that the rate of ionophore-facilitated ion transport depends not only on the ability of complex formation in aqueous phase, but also on the ability of complex dissociation in organic phase.

Tetrakis(diisopropyl amide) substituted norbornadiene and quadricyclane are highly barium selective ligands

“…2 Various binding domains have been successfully established, e.g. calixarenes, [3][4][5] cyclic oligopeptides 6 or substituted crown ethers. 7 Especially the use of the lipophilic dicarbollyl-cobaltate anion in combination with a wide variety of donor ligands was extensively studied by Makrlík et al 8,9 Over the past two decades we have been investigating the well-established norbornadiene-quadricyclane system regarding the feasibility of active ion transport through artificial lipophilic membranes.…”