title: Fluorescent amino acid undergoing excited state intramolecular proton transfer for site-specific probing and imaging of peptide interactions.
abstract: Fluorescent amino acids bearing environment-sensitive fluorophores are highly valuable tools for site-selective probing of peptide/ligand interactions. Herein, we synthesized a fluorescent l-amino acid bearing the 4'-methoxy-3-hydroxyflavone fluorophore (M3HFaa) that shows dual emission, as a result of an excited state intramolecular proton transfer (ESIPT). The dual emission of M3HFaa was found to be substantially more sensitive to hydration as compared to previous analogues. By replacing the Ala30 and Trp37 residues of a HIV-1 nucleocapsid peptide, M3HFaa was observed to preserve the peptide structure and functions. Interaction of the labeled peptides with nucleic acids and lipid vesicles produced a strong switch in their dual emission, favoring the emission of the ESIPT product. This switch was associated with the appearance of long-lived fluorescence lifetimes for the ESIPT product, as a consequence of the rigid environment in the complexes that restricted the relative motions of the M3HFaa aromatic moieties. The strongest restriction and thus the longest fluorescence lifetimes were observed at position 37 in complexes with nucleic acids, where the probe likely stacks with the nucleobases. Based on the dependence of the lifetime values on the nature of the ligand and the labeled position, two-photon fluorescence lifetime imaging was used to identify the binding partners of the labeled peptides microinjected into living cells. Thus, M3HFaa appears as a sensitive tool for monitoring site selectively peptide interactions in solution and living cells.
authors.affiliation: Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Université de Strasbourg, Faculté de Pharmacie, 74, Route du Rhin, 67401 Illkirch Cedex, France.
authors.forename: Marianna
authors.initials: M
authors.lastname: Sholokh
authors.forename: Oleksandr M
authors.initials: OM
authors.lastname: Zamotaiev
authors.forename: Ranjan
authors.initials: R
authors.lastname: Das
authors.forename: Viktoriia Y
authors.initials: VY
authors.lastname: Postupalenko
authors.forename: Ludovic
authors.initials: L
authors.lastname: Richert
authors.forename: Denis
authors.initials: D
authors.lastname: Dujardin
authors.forename: Olga A
authors.initials: OA
authors.lastname: Zaporozhets
authors.forename: Vasyl G
authors.initials: VG
authors.lastname: Pivovarenko
authors.forename: Andrey S
authors.initials: AS
authors.lastname: Klymchenko
authors.forename: Yves
authors.initials: Y
authors.lastname: Mély
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D047309:Flavones / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D008958:Models, Molecular; D008968:Molecular Conformation; D057054:Molecular Imaging; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011522:Protons
chemical_list: D000596:Amino Acids; D047309:Flavones; D005456:Fluorescent Dyes; D010455:Peptides; D011522:Protons