SAXS

gregor

Hi all,
I'm currently trying to fit measured scattering data to theoretical curves unsing CRYSOL. Besides of constant crashing ("out of memory qwgsvid.c line 611") everything is okay...

With all my other projects so far it all worked fine, but at the moment I am fighting with larger differences (higher than usual...) at higher quantum moments, meaning the theoretical curve always has lower intensities at higher s than the measured data. I guess this is due to the different electron density of the solvent (or background scattering)? .... but the crysol manual only says:

"Solvent density (e/Å3). Default value is the electron density of pure water. Solvents with high salt concentration may have a somewhat higher electron density. User can adjust the value accordingly."

Is there any rule of thumb concerning salt concentrations and corresponding (approximate) solvent electron density? (e.g. my proteins were measured in 200mM NaCl, 50mM HEPES, 2mM DTT). CRC-handbook?

Thanks for any help,

Gregor

gregor

A too obvious solution? calculate electrons from H2O/Angstr. plus electrons of 200mM NaCl etc... ...(?)
I'll probably write an application for this if this turns out to be right..

gregor

....yep,,,, that was definitely too easy... sorry....

Alex

Hi Gregor

Does it also solve the problem of crashing? Can you also send me files with
experimental and theoretical data (EMBL address), as well as final value you used as solvent density?

Cheers
Alex