DLS at high protein concentration

Dear all,
I have a simple question on viscosity correction for DLS. In Stokes-Einstein
equation, the viscosity is referred to solvent viscosity. However, I was
told by someone that Rh at high protein concentration should be corrected by
solution viscosity, which is the viscosity of the protein solution. I do
not think that was right 'cause in that situation only the apparent Rh was
determined and the hydrodynamic non-ideality may exists. Any comment?
Thanks.

Chin

hi Chin,

Theorotically,
Rh related strongly to flow speed, too.
Ideal DLS works based on statistical mechanics in the absence of any
macroscopic flow, so such correction might not be significant compared
to other factors such as the ignorance of non-spherical particle
shape, etc.

By the way, over-concentrated protein solutions may lead to
out-of-range error of the photon detector since the overall diffraction
intensity goes too strong.


Zhao

Chin,

well, as a first order correction,
I think the empricial formulae will work anyway, as long as you can
get a straightline with good R^2.

Zhao