pH- and Thermo-Induced Specific Permeability of Chiral Amino Acids through the Peptide Grafted Poly(N-isopropylamide) Network Membrane

In this article we prepared an amphiphilic peptide, (L-Leu-L-Lys)(8), grafted poly(N-isopropylacrylamide) network membrane. The graft content of the peptide and the content of the cross-linker were 4% and 16%, respectively. We investigated the permeability of L- and D- phenylalanine through this membrane. The pH- and thermo-induced permeability changes of the network membrane were observed. Under the neutral condition (pH 6.5 and 20 degrees C), the peptide grafted PNIPAm network membrane showed a significant difference between the permeability of L-phenylalanine and D-phenylalanine. The maximum permselectivity (alpha=2.6) was achieved under this condition. At temperatures above the LCST of PNIPAm, PNIPAm polymers become hydrophobic; hence, the membrane shrunk. And under these conditions the permeable path for L- and D- phenylalanine was formed in the membrane which results in the non-permselectivity through this membrane.