DFT investigation and molecular dynamic simulation on the selectivecomplexation of cis-cyclic nanopeptides with alkaline earth metalions

Abstract

Three types of the cyclic peptides constructed of four sequences of glycine<br><br>(CP1) and alanine (CP2) and two sequences of glycine-valine molecules (CP3)<br><br>have been employed for selective complexation with Be2+, Mg2+, Ca2+, Sr2+ and<br><br>Ba2+ metal ions. Obtained data, from the density functional theory, showed that all<br><br>CPs have the most stable complexes with Be2+ ion, because of maximum<br><br>interaction with oxygen atoms of the CPs. Moreover, the most stable complex is<br><br>found for Be2+-CP2. All of the CPs make four-dentate stable complexes with Mg2+,<br><br>Ca2+, Sr2+ and Ba2+ metal ions in the gas phase through the oxygen atoms of CO<br><br>groups of CPs, while CP3 makes bidentate stable complexes with Mg2+, Ca2+ and<br><br>Sr2+ ions in water.<br><br>Natural bond orbital analysis indicates that charge transfers from oxygen and<br><br>nitrogen atoms of CPs to the metal ions reveals that electrostatic interaction<br><br>between the metal ion and CPs is an important factor in complexation. Quantum<br><br>theory of atoms in molecule investigation confirmed that the most stable bond was<br><br>found in Be2+ ion and oxygen atom of the CPs. These findings were in agreement<br><br>with the molecular dynamic simulations.