The Fluorescence and Infrared Absorption Probe para-Cyanophenylalanine: Effect of Labeling on the Behavior of Different Membrane-Interacting Peptides.

Total syntheses and complete characterizations of singly substituted PheCN-based analogs of alamethicin AlaP, which is active on model and natural membranes, and the TM peptide, which inserts in a transmembrane orientation in lipid bilayers, are reported. The syntheses of the AlaP analogs were performed in solution, while those of TM and its analogs were carried out by solid phase. Using the cyanophenyl fluorescence and infrared (IR) absorption probe, an in-depth investigation of the self-association, membrane-interacting, permeabilizing, and orientation properties of these peptides were conducted. The aromatic residue incorporated induces only a negligible modification to the properties of the parent peptides. The Phe(CN) IR absorption band was located between 2228 and 2230 cm 21 for all peptides, irrespective of the position of labeling. By contrast, as the width of this band varied significantly with the depth of probe insertion in the bilayer, it could represent a good marker of the PheCN position in phospholipid membranes. (C) 2015 Wiley Periodicals, Inc.