From: Steve Shire <sjs@gene.com>
  To  : Borries Demeler <demeler@bioc09.v19.uthscsa.edu>
  Date: Sat, 02 Oct 1999 10:02:32 -0700

Re: "fringe" extinction coefficient

Borries,
    Great question. I've often heard people state that the refractive
increment is essentially a constant value for most proteins. If you look at
the various tables available ( I believe the CRC handbook has values) the
numbers are actually all over the place. We did notice that for "families"
of proteins such as immunoglobulins we could probably use a constant value
of 0.187 (g/mL)-1 . WE applied this to a humanized monoclonal antibody we
have been  developing and got excellent agreement using combined UV
absorption and interference with other methods such as amino acid analysis
or an enzymatic digestion procedure developed by Tom Bewley. If you are
interested I can send you a copy of the applications note I wrote up for
Beckman.

     One final comment, it is unlikely that there is one value that should
be used especially with proteins that have a variety of glycosylation sites,
and this may be reflected in the existing tables. On the other hand, the
variability seen in the literature could be due to variability in protein
concentration determination.
     Steve


Borries Demeler wrote:

> Quick question:
>
> What is the interference equivalent to an extinction coefficient under
> absorbance optics, ie. how much of a fringe shift can I expect for a
> given concentration of protein? How much variation is there for different
> proteins? If it is constant, is there a published number and what is it?
>
> TIA, -Borries

--
Steven J. Shire, Ph.D.
Sr. Scientist and Group Leader
Pharmaceutical Research and Development Dept.
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