From: Thomas M Laue <tml@christa.unh.edu>
  To  : RASMB group <rasmb@bbri.eri.harvard.edu>
  Date: Tue, 24 May 1994 09:41:53 -0400 (EDT)

V-bar

Preston Hensley and I were chatting about molecular weight determinations
on molecules where the mass is already well established (e.g. by mass
spec). Most times the correction of the buoyant mass yields a good
estimate of the "correct" monomer mass. However, we have noted some that
produce distinct errors. The culprit is almost surely the estimated v-bar.
We were wondering if there are some correlations in these errors and other
aspects of the structure. For example, Preston noted that Ab molecular
weights are often "too low," indicating that the estimated v-bar is
likewise too low. We have noted that coagulogen (unrelated to Ab in any
way) suffers from this same sort of error. What is curious is that both
molecules have a fair number of disulfide bonds. Does anyone else have 
examples of this? Is there information available that we are not aware of?
Thank you!
Tom Laue