From: Marc S. Lewis <mslewis@helix.nih.gov>
  To  : Borries Demeler <demeler@bioc09.v19.uthscsa.edu>
  Date: Fri, 1 Oct 1999 16:48:46 -0500

Re: "fringe" extinction coefficient

It is my recollection that, for the Model E, using the He-Ne laser at 632
nm (?) one obtained 3.2 fringes per mg/ml and for the Hg lamp, at a
wavelength I do not recall  but which you can look up in a Model E manual,
one obtained 4.0 fringes for the same concentration.  This is for 12 mm
optical pathlength cells.  There is, obviously, wavelength dependence, but
the dependence on amino acid composition of the protein was almost
non-existant and nobody seemed to bother with it.  I do not recall values
for various carbohydrates or nucleic acids.  You will have to adjust these
values for the XL-I since it has a different optical geometry.  The best
way that I can think of for obtaining the value you want is to do a
synthetic boundary run with an accurately prepared one percent BSA
solution.  I hope that this will be helpful.

Regards -

Marc Lewis

Marc S. Lewis, Ph. D., Chief
Molecular Interactions Resource
Bioengineering and Physical Science Program
Office of Research Services
National Institutes of Health
Buiding 13  Room 3N17
13 South Drive  MSC 5766
BETHESDA MD 20892-5766

Phone: 301-496-9044;  Fax:  301-496-6608