Separation Of Chloroform From A Dilute Solution Using A Cyclic Peptide Nanotube:A Molecular Dynamics Study

In this work,multiple molecular dynamics(MD)simulations have been performed to investigate the transport properties of pure chloroform in five a-CPNTs and the adsorption characteristics of four hydrophobic a-CPNTs to the chloroform component from a CHCl3/water solution.The simlution results indicate that it is difficult for CHCl3 molecules to spontaneously enter five ?-CPNTs-8�((W?))4,5,8x(A(?))4,5 and 8�(Q(?))4 from a pure chloroform solution.But once entering,CHCl3 molecules may be trapped in individual midplane regions.On average,about 7 and 13 chloroform molecules may exist in an octa-CPNT and a deca-CPNT,forming single and double chains,respectively.Exchange and cross events between neighboring CHCl3 molecules may occasionally occur in a deca-CPNT.Chloroform molecules in CHCl3/water solutions with different concentrations were absolutely adsorbed on the surfaces of four hydrophobic ?-CPNTs�8x((W?))4,5 and 8�(A(?))4,5,distributing symmetrically along the tube axes.The binding constants of chloroform with four CPNTs were computed to be 1.87?4.42.Sporadic CHCI3 molecules can spontaneously entered a CPNT from a solution,and are confined in midplane regions.CHCl3 molecules in an octa-CPNT tend to exist near the tube axis,while double radial distribution peaks appear in a deca-CPNT.Chloroform molecules inside and outside a CPNT both tend to keep their dipoles perpendicular to the tube axis.Four hydrophobic a-CPNTs all possess excellent adsorption properties to the chloroform component in a dilute chloroform solution.When the number of chloroform molecules in a solution is more than 60,the adsorption efficiencies of four a-CPNTs to chloroform are higher than 95%.Nevertheless,when the number of chloroform molecules is very small(e.g.,10),the adsorption efficiency of chloroform in a CPNT is affected by the CPNT diameter and side chain structures.Relatively,8�((W?))4 has better adsorption property to chloroform among four hydrophobic ?-CPNTs.