From: Les Hicks <hicks@gpu.srv.ualberta.ca>
  To  : RASMB Bulletin Board <rasmb@alpha.bbri.org>
  Date: Fri, 12 May 2000 16:35:41 -0600

Sedimentation Equilibrium of highly concentrated protein solutions

Hi all,

    At the risk of asking a stupid question, here goes.  Is there any way to
perform a sedmentation equilibrium run on an approximately 50 mg/ml protein
solution?  Even with a 3 mm path length cell, I would think the fringes
would be too compressed at this concentration.  I was initially wondering
about using the absorbance optics at a higher wavelength (ie : where the OD
is app. 0.5) till I re-read Tom Laue's article "Choosing which optical
system of the Optima XL-I Analytical Ultracentrifuge to use".  I gather that
a problem would arise with an effective misalignment of the optics due to
the large refractive index gradient from the high protein concentration.
    If I used the interference optics at a relatively low speed would I
possibly be able to resolve the fringes to the cell bottom or would there be
the same problem with the interference optics due to the high refractive
index gradient?  We don't require an accurate Kd for this sample - we would
just like to know whether it's mainly monomeric, dimeric, or whatever at
this high concentration.

Regards, and have a good week-end.

Les



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Les Hicks
PENCE / Dept. of Biochemistry
Rm 3-36 Medical Sciences Bldg.
University of Alberta
Edmonton, Alberta, Canada
T6G 2H7

Phone : 780-492-3412
Cell     : 780-975-7741
FAX    : 780-492-0095
email   : hicks@gpu.srv.ualberta.ca
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