Measuring peptide concentration

Artem Evdokimov AEVDOKIMOZ at
Mon Mar 18 21:43:50 EST 2002

I disagree on one point : Expasy server does NOT calculate extinciton if you
don't have certain types of AA's in your sequence.
For example 'AAAAAA' results in

Extinction coefficients:

As there are no Trp, Tyr or Cys in the region considered, your protein
should not be visible by UV spectrophotometry.

There's a reason for it - while some absorption at 280 will indeed be
present, it won't be characteristic, and it would be overwhelmed by
non-specific absorption of crud.

Otherwise, way to go Emir :)

"Emir Khatipov" <khatipovNO at> wrote in message
news:pyul8.311$s4.23478 at
> Use Protparam tool at to calculate molar extinction
> coefficient of your peptide and use it for your spectrophotometric
> measurements. Peptides absorb light at 280nm even if they don't contain
> aromatic residues. I hope it is needless to say that you should use same
> DMSO in PBS as a reference. If you believe there are impurities in your
> samples, I would suggest determining absorption spectra of your peptide
> solutions at ~200-350nm (or at least 250-330nm). If your sample is pure,
> should see a nice peak at around 276-280nm. Be aware that peptide bond
> absorbs at 214nm, but there might be a lot of interference from impurities
> you may have in your sample.
> Emir
> "JB" <j.bukczynskiDELETE_ME at> wrote in message
> news:b87a9ugslasbigp8lm4dhkqc4p0soe0se7 at
> > Hi,
> >
> > Does anyone know how to measure peptide concentration using a
> > spectrophotometer? I have it dissolved in 10% DMSO in PBS. Any help
> > would be appreciated. Thanks,
> >
> > Jacob

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