Re: extinction coefficient
Roger Murphy (murphy_r@licre.ludwig.edu.au)
Fri, 10 Jul 1998 14:12:00 +1000
At 05:48 PM 09-07-98 -0700, you wrote:
>A well characterized protein with known molecular weight has a defined
>extinction coefficient for quantitating protein amount by UV analysis.
>However, when the protein is lyophilized, the gravimetric weight of the
>lyophilized material is much higher by about 20% than the value calculated
>from UV analysis. This preparation is also extremely pure which excludes
>impurities contributing to the overall weight. What can be happening and
>how would you test your hypothesis?
>
John,
Whenever you lyophilize a protein or peptide, you're also going to have the
counter ions associated with basic and/or acidic residues, depending upon
the pH of the solution/buffer you are drying down. Hence the increase in
weight....
Cheers,
Roger
Roger Murphy, Ph.D.
Biological Production Facility
Ludwig Institute for Cancer Research
Austin & Repatriation Medical Centre
Studley Road,
Heidelberg, Vic. 3084
Australia.
Tel 61-3-94965463
Fax 61-3-94965436
Email murphy_r@licre.ludwig.edu.au