Hello,

I've recently fitted FRAP curves by the Soumpasis formula and I've created a fitting function in Origin for that purpose. It can fit with up to 2 diffusion components.The second function (SoumpasisB) can fit up to 2 components + an exponential bleaching component during the recovery.

Explanation of the variables:

tD1 and tD2 - the diffusion times

A1 - fraction of component 1

C - scaling factor = recovered intensity - intensity immediately after bleaching pulse

The rest differs for the 2 functions:

Soumpasis:

I0 - intensity immediately after bleaching pulse

SoumpasisB:

B - background value after complete bleaching (I set it to the offset value of my camera)

I0 - intensity immediately after bleaching pulse - B

tB - exponential decay time of the bleaching

The number of free parameters with 2 diffusion components is quite high, so try to choose well the initial parameters, otherwise it may take a long time to converge or may not converge to the global minimum.

Hope it helps!

Thanks a ton Radek Machan! It works perfectly. I even modified it for a single component fit now.

Really thanks a lot!!

Aditya