Streaked Protein Gels
Streaks – example 1
This one isn't so bad. The lane with the streaks
(left of lane 5) is quite usable, in fact. The
streaks came about because a portion of the more
concentrated proteins in the membrane fraction
precipated during the stacking process, then returned
to solution after a fairly short time. Because
of slight imperfections in the separating gel surface
(it may have been allowed to dry a little before
adding the stacking gel), the protein concentration
was not uniform across the lane, and streaks rather
than a uniform darker background are the result.
The electric field was quite uniform, and diffusion
minimal, otherwise the streaks would not remain
as narrow vertical lines.
Streaks – example 2
The fourth lane is streaked due to the effect described
above. The electrical field was affected by the non-uniform
concentration in the fourth lane (the dark one with
streaks),, causing a narrowing of the bands.
Note that the dye front was lost in this gel
- it was allowed to run too long.
Streaks – example 3
This one kind of stinks. Evidently, this group did
not use an overlay after pouring the first gel layer.
The result was a separating gel with the very rough
top that you see here. As samples were stacked they
were disproportionately concentrated in the 'valleys,'
where the proteins precipitated. The precipitates
re-dissolved gradually during the run, forming streaks
instead of resolving into discrete bands.