Excited state proton transfer and solvent relaxation of a 3-hydroxyflavone probe in lipid bilayers.
The photophysics of a ratiometric fluorescent probe, N-[[4'- N, N-diethylamino-3-hydroxy-6-flavonyl]methyl]- N-methyl- N-(3-sulfopropyl)-1-dodecanaminium, inner salt (F2N12S), incorporated into phospholipid unilamellar vesicles is presented. The reconstructed time-resolved emission spectra (TRES) unravels a unique feature in the photophysics of this probe. TRES exhibit signatures of both an excited-state intramolecular proton transfer (ESIPT) and a dynamic Stokes shift associated with solvent relaxation in the lipid bilayer. The ESIPT is fast, being characterized by a risetime of approximately 30-40 ps that provides an equilibrium to be established between the excited normal (N*) and the ESIPT tautomer (T*) on a time scale of 100 ps. On the other hand, the solvent relaxation displays a bimodal decay kinetics with an average relaxation time of approximately 1 ns. The observed slow solvent relaxation dynamics likely embodies a response of nonspecific dipolar solvation coupled with formation of probe-water H-bonds as well as the relocation of the fluorophore in the lipid bilayer. Taking into account that ESIPT and solvent relaxation are governed by different physicochemical properties of the probe microenvironment, the present study provides a physical background for the multiparametric sensing of lipid bilayers using ESIPT based probes.
Das
Ranjan
R
Photophysique des Interactions Biomoléculaires, UMR 7175 du CNRS, Institut Gilbert Laustriat, Faculté de Pharmacie, Université Louis Pasteur, 67401 Illkirch, France. Ranjan.Das@pharma.u-strasbg.fr
Klymchenko
Andrey S
AS
Duportail
Guy
G
Mély
Yves
Y
D005419:Flavonoids / Q000737:chemistry*; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D011522:Protons; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D005419:Flavonoids; D008051:Lipid Bilayers; D011522:Protons; D012997:Solvents; C041477:3-hydroxyflavone