The fluorescence and infrared absorption probe para‐cyanophenylalanine: Effect of labeling on the behavior of different membrane‐interacting peptides

Abstract

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 PheCN IR absorption band was located between 2228 and 2230 cm(-1) 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.

Trichogin GA IV Alignment and Oligomerization in Phospholipid Bilayers

“…These findings were confirmed by polarized ATR‐FTIR spectroscopy, which allows the average orientation of helical peptides inside lipid bilayers to be determined (Figure , Table ). For these studies, we employed an unlabeled trichogin analogue and two sequences labeled with para ‐cyano(αMe)phenylalanine (PheCN), which had previously been investigated by exploiting the PheCN fluorescence and IR signals, and had been demonstrated to insert into the membrane . Table shows the dichroic ratio ( R ) for the amide I band in the region between 1600 and 1700 cm −1 , the order parameter ( S ), and the angle formed by the helix axis with the bilayer normal α .…”

Comparison of biological chromophores: photophysical properties of cyanophenylalanine derivatives

“…[27][28][29] Overall, 4-Phe CN has been used as an adaptive fluorescence reporter in various solvents and biological systems. [30][31][32][33][34] The utility of nitrile derivatives of phenylalanine (Phe CN ) as a spectroscopic probe in protein studies arises from several advantageous photophysical properties of the non-natural amino acid. First, both the molar absorptivity (e) and fluorescence quantum yield (F F ) of the Phe CN species are roughly 4 times larger than those of Phe (e = 200 M À1 cm À1 at 260 nm and F F = 0.024) 35,36 due to mixing of the np* state (located on the amino group) and the pp* state wavefunctions upon addition of the nitrile group to the phenyl ring.…”

Contributions and Limitations of Biophysical Approaches to Study of the Interactions between Amphiphilic Molecules and the Plant Plasma Membrane

“…In general, the percentage of fluorescent probe does not exceed a few molar percent (typically 1-5 probes for 100 molecules). Another method used to study biomolecule-lipid interactions by fluorescence is to synthesize an analogue of the target compound containing a fluorophore part [107,108]. For example, the fluorescent cyanophenylalanine was grafted onto alamethicin to study its interaction with the membrane [107].…”

“…Another method used to study biomolecule-lipid interactions by fluorescence is to synthesize an analogue of the target compound containing a fluorophore part [107,108]. For example, the fluorescent cyanophenylalanine was grafted onto alamethicin to study its interaction with the membrane [107]. Likewise, another strategy can be to use the fluorescent properties of a complex of two molecules that do not emit fluorescence separately.…”