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UV absorption of protein

John Philo "jphilo*NO SPAM12*" at mailway.com
Fri Jan 5 19:21:46 EST 2001

I think you are seeing the absorbance due to oxidized DTT---I can't
remember the wavelength maximum for that offhand, but it definitely
absorbs strongly in the far UV (the reduced form has far less

John Philo
Alliance Protein Laboratories

"B.H.Kang" wrote:
> I prepared the protein with histidine tag in bacterial cell and purified
> with Ni resin.
> For the quantitation of my protein, I check the UV absorption.
> Surprisingly, the maximun absorbance was at 260 nm instead of 280 nm
> and the absorbance was slightly increased comparing the real concentration
> of the protein.
> Is this usual case?
> I think that my protein has no significant nucleic acid contamination.
> And the buffer contains 1 mM DTT,
> The sample buffer was used for baseline of UV absorbance.
> I didn't know the reason...
> Thanks and happy new year...!

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