Förster resonance energy transfer studies of an intrinsically disordered peptide using a cyanophenylalanine derivative.

Abstract

We report Förster Resonance Energy Transfer (FRET) studies of an intrinsically disordered peptide (IDP) using a phenylalanine derivative as the donor fluorophore. Due to its increased spectroscopic selectivity compared to phenylalanine, 2-cyanophenylalanine (2-PheCN) can be used as a site-specific probe of solvent environment and in FRET with tryptophan (Trp) as the acceptor for analysis of protein structure with an R0 of roughly 16 Å. Replacing phenylalanine with 2-PheCN in a 12 residue, intrinsically disordered olfactory peptide (OFP) where tryptophan occupies the N-terminus position provides two model IDPs: OFP Long, where 2-PheCN occupies the C-terminus, and OFP Short, in which 2-PheCN is two residues away from Trp. Measurement of the FRET efficiency within various solvent environments that either promote or inhibit secondary structures allows for examination of structural changes in the IDPs induced by the solvent environment. As expected, the energy transfer is highly efficient, approximately 0.99, between the nearly proximal fluorophores in OFP Short for all solvents examined. However, surprisingly the largest FRET efficiency for OFP Long is observed in solvent inhibiting secondary structures. Future FRET studies of both OFP Long and OFP Short will further investigate the solvent environment and temperature dependencies of the dynamics and structure of the disordered olfactory peptides.