Principles of Fluorescence Spectroscopy

218 SOLVENT AND ENVIRONMENTAL EFFECTS
Figure 6.20. Emission spectra of the lipid-like Prodan derivative
Patman at various temperatures in propylene glycol (top) and in solvents
of different polarities (bottom). Revised and reprinted from [41].
Copyright © 1983, American Chemical Society.
The large spectral shifts displayed by Prodan allowed
its use in imaging the phase state of membranes. 53–54 When
using fluorescence microscopy it is difficult to record the
entire emission spectrum for each point in the image. The
need for emission spectra was avoided by defining a wavelength-ratiometric
parameter that represented the emission
spectrum. This parameter is defined analogously to fluores-
Figure 6.22. Derivatives of Prodan.
cence polarization. This parameter was named the generalized
polarization (GP) and is given by
GP I B I R
I B I R
(6.20)
where I B and I R are the steady state intensities at a shorter
blue (B) wavelength and a longer red (R) wavelength,
respectively.
Figure 6.21. Charge separation in the excited state of Prodan (6-propionyl-2-(dimethylamino) naphthalene.