From: Cole, James L <jim_cole@merck.com>
  To  : 'Borries Demeler' <demeler@bioc09.v19.uthscsa.edu>
  Date: Fri, 01 Oct 1999 18:04:19 -0400

RE: "fringe" extinction coefficient

	Bo:
	The inteference equivalent of an extinction coefficient is the
refractive index increment (dn/dc). It is pretty constant among proteins but
it does depend on wavelength.  I use a value of dn/dc=0.186 ml/mg. For 675
nm light and a 1.2 cm path this gives a fringe displacement of 3.31 for a 1
mg/ml solution. There is a nice discussion of this stuff, and table of dn/dc
values for various proteins,  in the the monograph that Tom Laue wrote for
Beckman about which optical system to use. It is available as a PDF file at:

	http://www.beckman.com/Beckman/biorsrch/prodinfo/xla/pdf/a_1821a.pdf

	Good luck.
	Jim