Bio-Rad Mini-PROTEAN® 3 Dodeca™ Cell - Manual (Page 9)

Section 4
Troubleshooting Guide
Problem Cause Solution
1. Smile effect – band pattern a. Center of the gel running a. Improper cooling.
curves upward at both sides of hotter than either end Use cooling coil and
the gel refrigerated circulator
to maintain buffer
temperature of 20 ºC.
b. Power conditions are b. Decrease voltage from
excessive 200 V to 150 V or fill
buffer to maximum
volume.
2. Run takes unusually long a. Ion depletion in running a. Prepare and use fresh
time. buffer (lower tank) buffer.
b. Running buffer too b. Check buffer protocol
concentrated in the and dilute buffer if
clamp assembly necessary.
3. Changes in protein mobility a. Ion depletion in running a. Prepare and use fresh
or band sharpness. buffer (lower tank) buffer.
4. Clamp assembly leaks a. Improper assembly a. Be sure the green
gasket is clean, free of
cuts, and is inserted
completely into the
core.
b. Be sure the gel
sandwich or gel
cassette is seated at the
bottom of the clamping
frame before closing
the clamps.
5. SDS is precipitating. a. Running buffer is too cold. a. Set the refrigerated
circulator to maintain a
buffer temperature of
18–20 ºC.
6. Vertical streaking of protein a. Sample overload or a. Dilute sample,
precipitation selectively remove
predominant protein in
the sample, or reduce
voltage by about 25%
to minimize streaking.
b. The ratio of SDS to
protein should be
enough to coat each
protein molecule,
generally 1.4:1. It may
require more SDS for
some membrane
protein samples.
7. Lateral band spreading a. Diffusion out of the wells a. Minimize the time
prior to turning on the between sample
current application and power
start up.
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