Immobilization of lipid vesicles on polymer support via an amphiphilic peptidic anchor: application to a membrane enzyme.

To immobilize lipid vesicles on a polymer support, we have used a peptidic anchor with the following sequence: Ala-Ala-Leu-Leu-Leu-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-A la-Ala-Ala-Ala-Ala-Ala-Ala-Trp-Lys-Lys-Lys-Lys-Lys-Lys. This amphiphilic peptide was previously designed in our group to interact spontaneously and strongly with vesicles without perturbing their permeability. At the end of the solid-phase peptide synthesis, the peptide was left on the polymer beads and this novel polymer-peptide system was used for vesicle immobilization. It was shown that this polymer-peptide system could immobilize as much as 200 micromol of lipids per gram of dry resin. The amount of immobilized vesicles was decreased by a reduction of the proportion of the negatively charged lipids in the vesicles, indicating the importance of electrostatic interactions in the immobilization of the vesicles. The integrity of the vesicles was mostly preserved after the immobilization. This new polymer-peptide system was used easily and successfully to immobilize a membrane-bound enzyme, gamma-glutamyl transpeptidase. The activity of the membrane-bound enzyme was studied by monitoring the release of p-nitroaniline. The activity of the enzyme was still retained, even after being re-used eight times, indicating the strong immobilization of the enzyme in its active form. The polymer-peptide support could be regenerated by washing with ethanol and reused.