APS & TEMED in acid gels

[Elizabeth Rogers]

On 22 Jan 1997, Bernard Murray wrote:

> In article <1997Jan22.123448.9875 at news.iup.edu>, jford at grove.iup.edu says...
> >
> >If you can the amounts of APS and TEMED, you will change the kinetics of 
> >gelation (great, that's what you want).
> 
> Agreed.  You can also control kinetics by changing the temperature.
> 
> >  You will also change the porosity of 
> >the gel - the relative amount of cross-linking.
> 
> Is this really true?  I was under the impression that the porosity
> was governed by the % acrylamide and by the ratio of acrylamide/bis
> (or other cross-linker).  The concentration of TEMED and/or persulphate
> shouldn't have any effect unless they become limiting - so that the
> gel fails to polymerise completely no matter how long it is left.
> Since they only catalyse the polymerisation of the acrylamide monomer
> they play no real role in the eventual structure of the gel.
> 	Can someone correct or confirm my assumption?
> 		Bernard
> 
> Bernard Murray, Ph.D.
> bernard at elsie.nci.nih.gov (National Cancer Institute, NIH, Bethesda MD, USA)
> 
> 
>Yes, the amt of initiators DOES affect the gel.  Increasing the amt of
TEMED and APS shortens the polymer chain length.  In extreme cases excess
initiator can produce a gel solution which does not appear to polymerize
at all.  This from  Bio-Rad bulletin 1156.  On the other hand, I routinely
add extra TEMED to speed up my sequencing gel polymerization without any
apparent effects.  Depends on how analytical your gel has to be I guess.