Metal Ion Binding of the $\alpha$ – $\gamma$ Hybrid Cyclic Peptide Nanotubes—A The

The quantum mechanics/molecular mechanics ONIOM calculations have been performed to study the structure and metal-ion binding properties of all-trans cyclo[1R-3S-γ-Acc- Gly]₃ hexapeptide nanotube (TAG)₃PNT. The intersubunit distances and tube angle of (TAG)₃PNT exhibited the sturdy nature of (TAG)₃ stacks upon Li⁺, K⁺, Mg²⁺, and Zn²⁺ enclosure. The calculated dimer binding energies of (TAG)₃PNT and its ionic complexes confirm that the building blocks are bound by C=O...H-N hydrogen bond interactions. The binding energy of (TAG)₃PNT with ions interacting at the surface cavity exhibit the affinity of ions at the entrance of the channel and the many-body analysis for the ion interacting at the central region substantiates the major contribution of two-body interactions to the total binding energy. In general, the binding energies of (TAG) ₃PNT metal ion interacting complexes with well-maintained channel shows α-γ hybrid cyclic peptides as the promising peptidic nanochannels of biological interests.