Fluorescence Polarization

Polarized vs. Unpolarized Light

Polarized light needs a polarizing filter to single out one specific polarization. Unpolarized light has all rotations of polarized light

Transition Moment

selective ex. of molecules

the way the molecule is rotated

the plane in which the photon needs to match

Polarized light absorption

Polarized light beam only absorbs closely to the transition moment of the molecule

Rotational Diffusion

If the molecule is fluor. and the fluor. em. is parallel to the transition moment, then the em. is polarized. During that nano second to emit the photon, there is a kinetic battle going on btwn the fluor lifetime and rot. dif. which causes depolarization

Factors impacting rot. dif. rate

Viscosity = resistance to flow

low viscosity, rot. dif. rapid, and sample rapidly depolarizes

high viscosity, rot dif slow, and we will see polarized fluor emission

Size

-small molecules rotate easily

-big molecules are harder to turn

Depolarization

Most molecules have a partial depolarization, tilted before photon hits

Fluorine Dye

Binds a small fluorine molecule to a macromolecule and can show different degrees of hinderance of rot. diff. and shows how polarized a molecule is