Fluorescence emission polarization studies

Alternatively, an ordered, stable array of macromolecules may evolve at the surface with increasing time and/or bulk concentration. Since the excitation light is plane-polarized, the decay in emission signal may be a reflection of preferential orientation of 7-globulin molecules with time or enhanced surface packing densities. Fluorescence emission polarization studies should tell us more about this in the future. 

One of the easiest and most commonly used techniques to study the anisotropic optical properties of dye molecules is fluorescence anisotropy (FA). A dilute solution of the dye is excited with vertically polarized light and the fluorescence emission polarized parallel (I ) and perpendicular (I ) to the electric field vector of the exciting beam are detected with a 90 -scattering geometry, see figure 1. The FA is defined as ... 

Any factor that affects the size or shape of a molecule, the hindered movement of a fluorophore within a molecule, or the energy transfer within the molecule will affect the measured depolarization of its fluorescence emission. Therefore, the conformation of humic fractions in solution can be studied as a function of pH, ionic strength, temperature, and other factors by depolarization measurements. The principle of the method is that excitation of fluorescent samples with polarized light stimulates... 

The emitted light is detected along y through a polarizer oriented either along z (Fz) or along x (Fx). In fluorescence polarization studies with continuous excitation (steady-state experiments), the emission anisotropy r and the emission polarization p are defined in eqs 8a and 8b. 

Model compound and difference spectral studies have been carried out on tyrosine and related compounds by Wetlaufer (1956), Laskowski (1957), Edelhoch (1958), Chervenka (1959), Bigelow and Geschwind (1960), Yanari and Bovey (1960), and Foss (1961) (see also Section VI,Z)). Studies of the fluorescence of tyrosine—activation spectrum, fluorescence emission spectrum, and quantum yield—have been reported by Teale and Weber (1957). The pH-dependence of the fluorescence of tyrosine and related compounds was studied by White (1959) fluorescence-polarization studies from the same laboratory were reported by Weber (1960a) for simple compounds, and for proteins (Weber, 1960b). Teale (1960) has carried out extensive studies on the fluorescence characteristics of a score of proteins. 

Aminophenoxazone dyes were studied by Otsuki and Taguchi94 with respect to their solvatochromic behavior in non-hydrogen-bonding polar solvents. The absorption spectra of 7-A,A-dimethylamino-3-phenoxazone (77), its 7-A,A-diethylamino analog and its 1-methyl analog were measured in several neat solvents and in aqueous dioxane solutions and the peak positions correlated linearly with the jt scale. The fluorescence emission peak, however, was not linear with jt. ... 

Fluorescence Polarization Studies of PMA and PAA. Time-resolved fluorescence polarization measurements are potentially a powerful means for studying molecular mobility. The fluorescence anisotropy function r(t) may be generated by monitoring the decay of vertically (Iv(t)) and horizontally (Ijj(t)) polarized components of emission following excitation by vertically polarized light pulses (Equation 1). 

Direct evidence of energy migration in the different films was found in polarized fluorescence emission studies. The fluorescence anisotropy indicated that intramolecular energy migration (with a Dexter hopping mechanism) existed in both the solution and spin-cast films. Further energy migration and transfer studies were... 

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