Measuring peptide concentration
AEVDOKIMOZ at cinci.rr.com
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
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 NOuchicago.edu> wrote in message
news:pyul8.311$s4.23478 at news.uchicago.edu...
> Use Protparam tool at www.expasy.ch/tools 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.
> "JB" <j.bukczynskiDELETE_ME at utoronto.ca> wrote in message
> news:b87a9ugslasbigp8lm4dhkqc4p0soe0se7 at 4ax.com...
> > 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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