4
Probable Cause
1. Sample focused for insufficient
number of volthours.
2. Gradient drift (over focusing.
1. Enzyme is inactive at its pI.
2. Cofactor removed during focus-
ing.
Sample is applied too close to its
isoelectric point.
Solution(s)
1. Apply the sample at different
sites. Note the Vh´s for coal-
escence.
2. Stop the run sooner. Find the
correct volthours for focusing)
as in 1 above).
1. Try changing the pH of the gel
after the run in an appropriate
buffer. This might result in band
diffusion, however.
2. Add cofactors to the detection
solution.
Try the other two application points.
Symptoms
Proteins do
not reach
their pI
Loss of enzyme
activity
Sample
precipitates at
the site of
application
Trouble Shooting Guide
