band shift in SDS PAGE with mercaptoethanol

[MarkusM]

In a recent SDS-PAGE experiment I saw a very strange (and reproducable)
phenomenon:

BSA (and also HSA) boiled with 5% beta-mercaptoethanol (5min, 70°C) showed a
higher molecular weight (around 66kD; so this should be correct) but BSA (or
HSA) not boiled with 5% 2-ME had a band at around 55kD.

Just boiling alone also leads to bands at 55kD as does not pretreating the
sample at all before loading.

The 55kD band in the no-treatment lane right beside the 66kD band in the 5%
2-ME lane seems slightly tilted upwards which could suggest some kind of
different running behaviour?

I can not explain this phenomenon.. Does anyone have a possible explanation?

Gel was 8% separating, 4% stacking. The buffer system has a pH of 6.8.
BSA and HSA solutions are prepared in PBS. 9µg are loaded per well.
Electrophoresis at 180V (constant) for 2h.


-- 
View this message in context: http://www.nabble.com/band-shift-in-SDS-PAGE-with-mercaptoethanol-tf4205066.html#a11961238
Sent from the Bio.net - Methods mailing list archive at Nabble.com.