In article <199511291814.MAA07054 at visar.wustl.edu>,
nikolaic at VISAR.WUSTL.EDU (Nikolai Chitaev) wrote:
> > 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
> > 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
> testing APS :-), something more scientific.
> Prepare solution of NaI in water and add your APS to it. If the color
> brown your APS is good. The reaction could be calibrated. The saturation of
> colorization depends from NaI concentration, and the rate of
> from "how good the APS is".
If I can add something here. I know that every source says to use fresh
APS, but......I make 10% APS and freeze single use aliquots at -20 and it
works forever! Well I haven't tested the forever part but it works for at
least 6 months. Try it.
voellerj at gunet.georgetown.edu
Lombardi Cancer Center, Georgetown University
Washington DC, USA