RMV, thanks again for your support and Fortran code (which I have successfully ported to python with the help of the cited papers [Fortran code is not that straight forward when you are used to python :-) ]).

Still I am wondering about one thing.
The long time diffusion should be calculated from a region where the r2com is more or less linear.

From the attached picture (r2com for 86 POPC) I would tend to use frames between ~6000 and ~13000.

Is this reasonable? I am somewhat unsure if it is okay to discard so much points.

Currently I am calculating r2com for different time windows to get a clue how this effects the shape of the curve.

Kind regards,
Bjoern

Attached Images
r2com.png