engleski

Thermodynamic and structural studies of the complexation of homocyclopeptides with halides and structural anions in acetonitrile

The development of artificial anion receptors that mimic natural systems in their ability to efficiently and selectively bind a target anion has recently become an area of intense focus within supramolecular chemistry.1 Cyclic peptides present promising synthetic scaffolds for selective anion binding due to the amide group hydrogen bond properties, and also because of the macrocyclic ring flexibility and the variability of the subunits.2–4 By the combination of the thermodynamic and structural characterization of the cyclopeptide-anion complexes formed in the solution it is possible to obtain a detailed insight into the energetics of complexation and in the relationship of the receptor structure and its affinity towards particular anion. In this work, two cyclopeptide receptors were studied, L1 that contains five lysine subunits with amino groups of the side chains protected by a BOC group (Lys-BOC) and L2 that is comprised of six Lys-BOC subunits. These receptors bind anions directly through interactions with the peptide backbone or with the carbamate protons of BOC groups. Complexation affinities of L1 and L2 ligands toward halogen (Cl–, Br–, I–) and structural anions (ClO4–, HSO4–, H2PO4–, NO3–, NO2–, SCN–) in acetonitrile were investigated by means of mass spectrometry, 1H NMR and isothermal microcalorimetric titrations. More information about the structural characteristics of the cyclopeptide binding sites and microscopic image of the anion binding processes was gained by molecular dynamics simulations with explicit solvent molecules.

ciklopeptidi, anioni, kompleksiranje

nije evidentirano