protein concentration

Torsten Boerchers borcher at
Fri Sep 29 04:25:42 EST 1995

I agree with shaun about amino acid analysis as
the method giving "the truth". Be aware that 
Bradford and BCA tests vary by more than a factor
of two for different proteins, they thus give
a good estimate if you determine total protein
in a mixture bad may give large errors when using
for purified proteins. 
The calculation of concentration from absorbance at 280 nm
based on the amino acid composition is described by 
Gill, S.C.  and von Hippel, P.H., Anal.  Biochem
182;  319-326 (1989) and is valid only for denatured protein
solutions (in structured proteins you have hypso- or
bathochromic effects). The calculated is implemented
in the programme peptidesort of the GCG package.
Hope this helps
                          Torsten Boerchers                            /
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