|
Solvent Effects
on Merocyanine 540 (M540) Spectra - A Biological Probe
Bae, Sue1
and Arnold, Bradley1
University of Maryland Baltimore County1
Abstract-
Merocyanine 540 (M540) is an anionic, lipophillic fluorescence dye that
has been used predominantly as a photosensitizer in treatment of human
cancer cells and as an external probe in studies of cellular membranes.
Solvent effects have been evaluated using the solvatochromic shift method
(Lippert, Bakhshiev, and Kawski-Chamma-Viallet correlations). These
methods attempt to correlate the solvent dielectric constant and refractive
index with absorption maxima of the probe. It will be shown that fitting
the band shape (i.e. bandwidth, coefficient and frequency) is much more
sensitive that correlating band frequency alone. This method not only
allows the accurate determination of the solvent polarity function but
also allows the study of the homogeneity of the microenvironment in
heterogeneous samples. The electronic absorption and fluorescence emission
spectra of M540 were determined in several solvents of differing polarity.
These studies were extended to M540 embedded in PC lipid bilayer membranes
and vesicle samples. Influences of additive such as cholesterol and
valinomycin as well as ionic strength and cell potential were investigated.
These results were correlated with the results of Stark spectroscopy
of polymer sample and lipid bilayer membranes.
Keywords: Solvatochromism,
Merocyanine 540, Lipid membrane
|
