[RASMB] frictional ratio

[Borries Demeler]

Hi Holger,

the actual frictional ratio for an unfolded polypeptide chain is
dependent on the length of the peptide. The longer the chain, the larger
the value. So 2.3 may be correct for a certain length but not others.
Sorry, I don't really have an empirical formula available short of the
rod/ellipsoid formulas, but that may work as a first approximation if
you have an axial ratio for your peptide, which you can get from the 
thickness and the length of the polypeptide chain.

You can find a calculator in UltraScan under "Simulation" that will
give you the frictional ratio for a given axial ratio. 

Good luck, -Borries

> 
> Hi everybody,
> 
> I remember that the frictional ratio for a fully unfolded polypeptide 
> chain is around 2.3; but I can't remember the actual reference. Any hints?
> 
> A happy, peaceful and healthy 2006 to all!
> 
> Holger
> 
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