Hi,
Time-resolved fluorescence anisotropy is used for analyzing rotational diffusion. So my question is, can one measure the translational diffusion by fluorescence anisotropy (steady-state or time-resolved) ?
Thanks.
The rotational diffusion coefficient can be measured by fluorescence anisotropy, not the translational diffusion coefficient, I think.
http://www.horiba.com/fileadmin/uploads/Scientific/Documents/Fluorescence/Tech_Note2_-_Anisotropy.pdf
Fluorescence correlation spectroscopy (FCS) will give information about translation diffusion coefficient (http://www.fcsxpert.com/classroom/analysis/fcs_param.html). Fluorescence anisotropy will give rotational diffusion coefficient.
Fluorescence depolarization directly yields the rotational diffusion coefficient or the different rotational diffusion coefficients for anisotropic structures. The translational diffusion coefficient can only be calculated on this basis if the structure is known (e.g. for rods or ellipsoids). E.g. for ellipsoids the Perrin equations can be used. However, this is rather indirect and needs knowledge you might not have. It is easier to extract the translational diffusion coefficient directly from FCS experiments. Often FCS machines on confocal setups can do both types of experiments (e.g. MicroTime system from PicoQuant). However, if you do not have such a system, also photon correlation spectroscopy might work if the used laser does not excite the fluorophore or if the fluorescence light can be filtered from the scattered light.
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