Facile synthesis of tetrafluorotyrosine and its application in pH triggered membrane lysis.

"Smart" peptides that lyse membranes in response to biological stimuli are of considerable interest. Herein, we report a facile synthesis of L-tetrafluorotyrosine (L-f(4)Y) and its utilization as a pH sensing element. The synthetic route affords gram quantities of L-f(4)Y within two days. Incorporation of this unnatural amino acid into magainin 2 gives a peptide that turns on its membrane-lytic activity upon mild acidification.