Modeling
Cross-correlation curves are modeled according to a slightly more complicated mathematical function than applied in FCS. First of all, the effective superimposed observation volume in which the G and R channels form a single observation volume, in the solution:
where and are radial parameters and and are the axial parameters for the G and R channels respectively.
The diffusion time, for a doubly (G and R) fluorescent species is therefore described as follows:
where is the diffusion coefficient of the doubly fluorescent particle.
The cross-correlation curve generated from diffusing doubly labelled fluorescent particles can be modelled in separate channels as follows:
In the ideal case, the cross-correlation function is proportional to the concentration of the doubly labeled fluorescent complex:
with
Contrary to FCS, the intercept of the cross-correlation curve does not yield information about the doubly labelled fluorescent particles in solution.
Read more about this topic: Fluorescence Cross-correlation Spectroscopy
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