Molar extinction coefficient of a protein at 280 nm.

[Chris Penington]

In article   writes:
>From: madi at biocell.fundp.ac.be (Marc DIEU)
>Subject: Molar extinction coefficient of a protein at 280 nm.
>Date: 16 Mar 1995 13:00:44 GMT


>Is it possible to determine the molar extinction coefficient at 280 nm
>of a given protein (epsilon 280 nm prot.) simply by additionning the
>individual molar extinction coefficients of the different aromatic
>residues which compose the sequence of the protein ? Is it correct or
>not ? 

It's possible to get an estimate.  Cantor and Schimmel (Biophysical
Chemistry, part 2, 1980) give a formula for estimating extinction
coefficients based solely on aromatic amino acid content of a protein. 
Its accurate to about +/- 25%.  Gill and von Hippel (Anal.  Biochem. 
182:319-326 (1989)) have also published a paper on this.  They consider
the contributions of trp, tyr and cys to absorbance.  Phe and his make
almost no contribution.  The calculated values are all within about
10% of the measured values for 18 "normal" globular proteins. 

	Chris

-- 
Chris Penington			       The opinions expressed are mine. NOT
Research School of Chemistry,          those of the school *or* the  university
Australian National University,
Canberra, ACT 0200			chrisp at rschp1.anu.edu.au