Electrophoresis for Very small peptides

[William Tivol]

Lee, Hee-Bong (leehbong at CC.KANGWON.AC.KR) wrote:
:      I have been doing enzymatic mapping of  protein(550KDa)
:      A terrible problem of SDS-PAGE for very small peptides(1000~10
:      000Da) and the protein(550kDa) in same gel was occured.
:      Good resolution of very small peptide have to be needed!!!!

Dear Hee-Bong,
	A gel with a gradient of acrylamide could do it.  The upper part
would have lower concentration and would be more porous, so it would
separate the higher-mass molecules.  All the lower-mass molecules would
travel together until they encountered the lower part of the gel where
the acrylamide concentration was greater; then they would separate.
The gel can have either a continuous gradient or a step depending on
what is more convenient for your experiment.  I think that some of
these gels are available commercially here, but I don't know whether
this is true for your country.  If they are not available, just pre-
pare the lower section of the gel with a concentration which will
give you the needed resolution for the small peptides (you will have
to try this with suitable standards), then polymerize the upper section
on top of the (already polymerized) lower section.  Adding a stacking
gel may also help the resolution, if you can use one in your system.
Good luck.
				Yours,
				Bill Tivol