Solvent relaxation behaviour of n-anthroyloxy fatty acids in PC-vesicles and paraffin oil: a time-resolved emission spectra study

Abstract

Time-resolved fluorescence measurements were performed for a set of n-anthroyloxy fatty acids (n-AS; n = 2, 3, 6, 9, 12, 16) in both solvent and vesicle systems. The Stokes' shifts and the mean relaxation times calculated from the time-resolved emission spectra (TRES) are shown to be strongly dependent on the position of the fluorophore in small unilamellar vesicles (SUV) composed of phosphatidylcholine (PC), while they are essentially independent of the fluorophore position in isotropic paraffin oil. The concept of an intramolecular relaxation process which had been suggested to explain the wavelength dependence of the emission behaviour of the n-AS dyes in viscous solvents is supported by semiempirical calculations showing that a more planar conformation is favoured in the excited compared to the ground state. However, in order to explain the results in vesicle systems, the concept of intramolecular relaxation is not sufficient. Rather, we show that intermolecular solvent relaxation processes play the dominant role for the wavelength dependent emission behaviour in polar, viscous environments.

A new fluorescent probe with stimulated emission and multiphoton absorption properties

“…Therefore, the intramolecular relaxation and solvent relaxation process are responsible for the ns time dependent shift in emission wavelength. Similar results have been observed for quinine sulfate dication and for n-anthroyloxy fatty acids [26,27].…”

“…At later times the emission spectrum is shifted to longer wavelengths. At these longer times, besides the intramolecular relaxation of the solute [26], the solvent has already relaxed around the excited-state dipole. Therefore, the red shifted emission can be observed from the relaxed fluorophores.…”

Time-Dependent Stokes Shifts of Fluorescent Dyes in the Hydrophobic Backbone Region of a Phospholipid Bilayer: Combination of Fluorescence Spectroscopy and Ab Initio Calculations

“…28 Semiempirical calculations also have been performed on this molecule. 14 The absorption spectra of this molecule exhibit anthracenelike structure with a negligible solvent shift. This is in accord with the fact that both the ground-and the excited-state dipole moments are rather low.…”

Imaging Cellular Dynamics with Spectral Relaxation Imaging Microscopy: Distinct Spectral Dynamics in Golgi Membranes of Living Cells

“…It is important to emphasize that the analysis presented here is based on a simple model and only yields an apparent spectral relaxation time. For many systems undergoing spectral relaxation the correlation functions are typically non-exponential and characterized by the sum of two or more exponentially-decaying processes2829. The interpretation of faster or slower dynamics could therefore also be interpreted as changes in the proportion of faster processes relative to slower processes.…”