Definition of fluorescence anisotropy Fluorescence anisotropy

the anisotropy (r) of light source defined ratio of polarized component total intensity (




i

t




{\displaystyle i_{t}}

):

r
=




i

z


−

i

y





i

x


+

i

y


+

i

z







{\displaystyle r={\frac {i_{z}-i_{y}}{i_{x}+i_{y}+i_{z}}}}

when excitation polarized along z-axis, emission fluorophore symmetric around z-axis(figure). hence statistically have




i

x


=

i

y




{\displaystyle i_{x}=i_{y}}

.




i

y


=

i

⊥




{\displaystyle i_{y}=i_{\perp }}

, ,




i

z


=

i

∥




{\displaystyle i_{z}=i_{\parallel }}

, have

r
=




i

∥


−

i

⊥





i

∥


+
2

i

⊥





=




i

∥


−

i

⊥




i

t






{\displaystyle r={\frac {i_{\parallel }-i_{\perp }}{i_{\parallel }+2i_{\perp }}}={\frac {i_{\parallel }-i_{\perp }}{i_{t}}}}

.