Protein quantification with Ammoniumsulfate present?!
bowers at shore.net
Tue Jun 9 13:59:26 EST 1998
There is a commercial copper/biuret based protein assay which claims no
interference up to 40% ammonium sulfate. It uses a "universal
precipitant" to pellet protein first. No claim is stated for precision,
but the standard curves published look good with a threshold sensitivity
of 0.5ug protein/tube. It is called the "Non-Interfering Protein
AssayTM", sold by Geno Technology, Inc. 3830 Washington Blvd, St. Louis,
MO 63108, USA tel 314-534-0075 fax 314-534-1147.
Another option is to diafilter your fractions in centrifugal
concentrators. We offer a simple, cost effective reusable microfuge
system which accepts up to 750uL and concentrates rapidly to 7uL with
quantitative recovery. If you are interested, the system is described at
http://www.orbio.com. You can Email me for information about distribution
In article <35726aaf.702161 at news.fu-berlin.de>,
deleteme_cpeter at zedat.fu-berlin.de says...
>I am doing hydrophobic interaction chromatography with ammoniumsulfate
>and need to quantify the protein content of the fractions (down to 20
>microgram/ml) which contain 0-3M ammoniumsulfate. Bradford gives
>unreliable results, no matter what I use as a blank. BCA and BioRads
>DC-Assay do not work at all with AS present. Protein precipitation
>with TCA prior to Bradford gives some sort of linear standard curve
>but only with a high standard deviation and not very reproducible. I
>am currently trying UV 260nm and SDS-PAGE scanning, but both have
>severe drawbacks (sensitivity and time/labour intensity, resp.).
>Does anybody have any proposals about how to get a reliable protein
>concentration in samples containing ammoniumsulfate from 0 to 3 M?
>Thanks in advance.....
>PhD Student (Biotechnology)
>cpeter at zedat dot fu-berlin dot de
>>Alles wird gut!<(Beate)
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