Precise protein concentration

Lena Zaitseva zaitseva at biochem.purdue.edu
Wed Jan 6 10:18:26 EST 1999

     We purified a membrane protein in the presence of non-ionic
detergent. Now we need to calculate precise protein concentration. It
appeared to be a real problem.
     Bradford method doesn't work at all. BCA method looks better, but
with BSA as control it doesn't give us reliable results (there is no
linear dependence of OD from concentration of our protein). For
UV-method it would be nice to unfold  protein to get the maximum
absorbency at 280 nm. However, guanidine-HCl and SDS lead to the protein
aggregation. We tried also make quantitative amino-acid analysis of the
protein, but  presence of high salt concentration (1.5 M) and glycerol
in the sample buffer is a problem in that case.
     Do you have any idea about that?
     Thanks for your suggestions.
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