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fresh APS (former SDS-PAGE)

Nikolai Chitaev nikolaic at VISAR.WUSTL.EDU
Wed Nov 29 13:07:34 EST 1995

> From: pnh at cockleberry.ncifcrf.gov (Paul N Hengen)
> Subject: Re: SDS-PAGE
> Date: Tue, 28 Nov 1995 17:57:39 GMT

I wrote:
> : Poor (slow) polimerization of acrylamide means that your APS is dead.
> : If the APS is freshly made and problem persists - dead TEMED
> : (instead to adding more TEMED buy new).

Paul N Hengen sent a tip:
> To test if the APS is too old, put some in a test tube and add the correct
> volume of H20 to make 10 mg/ml. If you hear it snap, crackle, and pop, then
> it is still good. At one time I looked into why it does this and all I could
> figure is that some gas forms (I forget if it is hydrogen or oxygen?...somebody
> please tell me which) within the crystals when water is added to APS which
> causes them to pop. It is mentioned in Maniatis, but not explained why this
> happens.

I suggest for those of us who a litle bit odd of this "hubble-bubble sciense" of
testing APS :-), something more scientific.
Prepare solution of NaI in water and add your APS to it. If the color changes to
brown your APS is good. The reaction could be calibrated. The saturation of
colorization depends from NaI concentration, and the rate of colorization depends
from "how good the APS is".

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