Bio-Rad Sequi-Gen GT Sequencing Cell - Manual (Page 7)

Features Benefits
A universal base accepts all gel dimensions, Modular system allows different sized
including wide and narrow gel formats of gels to be used with the same lower buffer
various lengths chamber
Injection molded parts Provides years of rigorous use
Chemically tempered glass plates Resists cracking due to overheating
and rough handling
One-piece, lever-operated clamps Conveniently and easily slides onto gel
sandwich, and shields edges of glass plates
from operator contact
Molded chambers with pour spouts or Easy and safe radioactive buffer disposal
drain ports
Machined vinyl spacers and Uniform thickness of combs and spacers
sharkstooth combs reduces well-to-well leakage during
sample loading
Sequi-Gen GT Buffer Heat Dissipation
Uneven dissipation of the Joule heat produced by the gel during electrophoresis causes
electrophoresis artifacts. “Smiling” is a common artifact that develops when a gel sandwich
loses heat more efficiently at the edges than in the center. When a gel runs hotter in the
center, the electrical resistance decreases, and more current flows down the center. As the
current flow increases, the gel heats even more. Thus a positive feedback loop is set up which
results in the lanes near the center of the gel running hotter, and therefore faster, than the
lanes near the edges. Smiling can lead to ambiguity in reading the sequence.
The Sequi-Gen GT cell employs natural convection and conduction of the upper buffer
to distribute heat evenly. The problems of uneven heat dissipation are avoided. Complicated,
expensive thermostatic plates are not necessary.
A thin, transparent, upper buffer chamber, called an IPC (Integral Plate Chamber), acts as
a heat sink across the full area of the gel. Convection occurs any time a slight temperature
gradient develops, mixing the buffer (and heat) to prevent smile patterns from developing.
Convection is the most effective way to distribute heat evenly. The upper buffer dampens
temperature fluctuations in the gel, and adds to the reproducibility of each run. The contact
between the buffer and the gel plate is direct and uniform. Thermal and physical stresses are
reduced. The sample loading wells are always at the same temperature as the gel, resulting in
fewer re-annealing problems. Bubbles of gas, generated by electrolysis along the cathode,
rise through the buffer. These bubbles also help to prevent temperature gradients from
forming by stirring the upper buffer while rising to the top of the IPC chamber.
Sequi-Gen GT Gel Casting
Because of their large size, casting sequencing gels has traditionally been extremely
problematic. Taping the bottom or sides of the glass plate sandwich is time consuming and
does not always result in a perfect seal. Thus, vacuum grease is required to seal corners and
edges. The user must then “wrestle” with the gel mold in order to pour the gel correctly.
Sliding glass plates, or plate dropping methods always result in acrylamide spills and waste.
Cleaning the hazardous neurotoxin after the spills is also time consuming.
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