From: E.braswell <BRASS@UCONNVM.UConn.Edu>
  To  : rasmb@alpha.bbri.org
  Date: Wed, 17 May 00 22:51:19 EDT

thin cells

Hi Everybody! We made ultra thin cells for absorption studies
of self associating dyes in the early 80s.  We made them from
all kinds of sheet plastic including the thinnest from the red plastic
gasket material supplied by Beckman (around .03-.05 mm when squeezed
I think).  We cut the compartments out with ticket punches and
with scapels.  We also have used thin cells for interference studies of
high concentration protein solutions (30 to 50 mg/ml, but beware of
nonideality problems). Focusing
is probably not as important with absorption as it is with interference.
For interference we usually refocus the optics carefully by a procedure which
Jeff Lary has worked out.  For 3 mm cells we use spacers
to properly place the focus point (thanks to Les Holiday who gave us
a set) rather than refocusing the instrument. However if you ignore proper
focusing you will notice differences at fairly high gradients (Allen).
I know this sounds like what a number of others have said, but I hope that
another voice will add courage to those who wish to try thin cells.
                                    Emory

Emory H. Braswell
Professor of Biophysics and Head,
National Analytical Ultracentrifugation Facility
U-149
University of Connecticut
STORRS, CT 06269-3149
TEL 860 486 5032
FAX         5005
E.BRASWELL@UCONN.EDU