(653.6) Forster Resonance Energy Transfer in an Intrinsically Disordered Peptide

Poster Board Number: A152

Roman Martinez (Metropolitan State University of Denver), Joshua Martin (Metropolitan State University of Denver)

We report Forster Resonance Energy Transfer (FRET) studies of a 2-cyanophenylalanine-tryptophan donor-acceptor pair within an intrinsically disordered peptide (IDP) region of an olfactory marker protein. In the olfactory IDPs (OFP) examined, tryptophan occupies the N-terminus and 2-cyanophenylalanine (2-PheCN) is substituted in place of phenylalanine (Phe) at two different distances from that terminus; in OFP Long the 2-PheCN is at the C-terminus, whereas in OFP Short the nitrile derivatized amino acid is only two residues away from the tryptophan. While Phe is native to OFP, 2-PheCN exhibits a larger fluorescence quantum yield providing better spectroscopic selectivity. Further, addition of the nitrile group to phenylalanine has been reported to change the peptide structure only minimally, thus resulting in an unperturbed IDP structure. As such, OFP Long and Short allow for comparison of energy transfer efficiency between the donor and acceptor fluorophores at two distances. Additionally, examining OFP Long and Short in solvents that either promote or inhibit secondary structures provide model systems in which spectroscopic techniques are used to determine structural perturbations induced by environmental changes. Intriguing trends observed in the various solvents provide a site-specific view of an IDP structure and dynamics, which can be used to extrapolate applications of their manifestation in numerous human disease states.



The structure of the olfactory marker protein is shown on the left (adapted from R. K. Gitti, et al., Biochemistry, 2005, 44, 9673). The olfactory peptides (OFP Short and OFP Long) are sequence homologues of the Ω-loop 3, an intrinsically disordered region, with a 2-cyanophenylalanine (F2CN) in place of a phenylalanine (as shown in above sequences). Forster Resonance Energy Transfer experiments probe the intrinsically disordered peptides to determine the distance between the fluorophores, r.