how to calculate the molar absorption coefficient of a protein?

Eugene Gussakovsky gussak at
Fri Jun 11 02:08:53 EST 1999

Bob wrote:

> Is there any web site that would calculate the absorption coefficient of a
> protein on the basis of the number of tryptophans, tyrosins, Phe, disulfide
> bonds...
> Or if not, what is the formula?
> Thanks, Rob

Hi, Rob,

Try a good paper by Pace et al. (1995) in Protein Science 4,2411-2423. But pay
attention that there are no any method to exactly calculate an extinction
coefficient. A calculated value can be used for estimation only (however the
estimation may be quite good!). I'd recommend to measure (i) using Biuret or
other absolute method of the protein concentration determination and (ii)
applying a procedure for light scattering subtraction at the absorption spectra

Best wishes


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