From: Jack Correia <jcorreia@fiona.umsmed.edu>
  To  : rasmb@bbri.harvard.edu
  Date: Tue, 20 Aug 1996 11:38:36 -0500

Re:Optics & Biophysics Ultracentrifuge Workshop on XLA Applications

Rasmbers,

        I'm passing on an observation that may be unique to our situation,
but may also be helpful in the future for others.  Just before XMAS we had a
PM done where bellows seals were replaced along with oil changes and routine
stuff.  For the next 6 weeks we had to clean the optics every 2 weeks or so;
the intensity at 230 nm would decay from 20,000 to < 5000, and a large dark
spot was very obvious on the lamp face.  We started to keep track of plateau
noise in every vel run to try to monitor the process as if it occurred
gardually, but it appears to be catastrophic, OK one run and terrible the
next.  I assumed either a small air leak was the problem (it did seem to
hold a vacumn) or a contaminant in the fresh oil.  Thus we got into the
habit of checking radial and wavelength intensities often.  But then after
those 6 weeks, the intensities were stable at ~20,000 at 230 nm????? and
have continued to be so up to the present??????  I am now knocking on the
hardest wood I can find (yes its my head) because I know this telling will
cause us trouble!

        During this time period, Feb, 1996 - present, we have done a lot of
low (4C) and high (37C) temperature work which requires preequilibration of
the rotor and the monochromator overnight at the desired temperature
(actually 2 degrees colder or warmer).  My hypothesis is long term pumping
cleans the system or keeps the seals firm, thus preventing optical problems.

        I just had another PM and, even though we are currently doing 25C
runs, we pumped overnight for a week on the assumption my hypothesis was
partially correct.  Its 8 days, 16 velocity runs and counting and the noise
is still OK.  

        So let me know if this helps anyone or if we're just being compulsive!

-------------------------------------------------------------------------------

        The Biophysics Ultracentrifuge Workshop on XLA Applications is now
set for the New Orleans meeting in March, 1997!  Look at the meeting
schedule when it appears for the time of the workshop.  Looking forward to
seeing ya'll in the French Quarter!  Here it is:

        1) Jack Correia, Univ. Miss Medical Center - "Sedimentation Studies
on Kinesin and NCD Motor Domain Constructs."

        2) Moncef Ladjimi, CNRS - "Self-association of the molecular
chaperone HSC70: Structural basis, molecular mechanism and regulation".

        3) Jim Lee, Univ. Texas at Galveston -  - What can sedimentation
tell me about biology?  A Story about HIV-1 Rev.

        4) Preston Hensley, Smith Kline - "The Interactions of IL-5 with
Therapeutic Monoclonal Antibodies."

        5) Tom Laue, Univ. New Hampshire - "A Prototype Fluorescence System
for the XLA"

        6) Arthur Rowe, Univ. Leicester - "Concentrated Solutions and Weak
Interactions: Studies Using Schlieren Optics and a New, On-Line AUC Imager"



|-------------------------------------------------------|
|   Dr. Jack Correia                                    |
|   Department of Biochemistry                          | 
|   Univ. of Miss. Medical Center                       |
|   2500 N. State St.                                   |
|   Jackson, MS 39216                                   |
|   (601) 984-1522                                      |
|   fax (601) 984-1501                                  |
|-------------------------------------------------------|