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Hoefer DALT System
Preparation for Gradient Gel Casting
Amersham Biosciences
17
3. For a linear gradient, straighten the divider, with its upper end almost touching the
left wall at the height determined by the volume of water.
4. To make a funnel for introducing heavy solution into the left side, bend the
remaining top of the divider to the right.
5. Tighten the faceplate screws and close the pinch clamps on the tubing that runs out
of the gradient maker before adding water or gel solutions.
6. Using water in place of gel solution, put half the required volume in the right
chamber and the other half in the left chamber.
7. Adjust the angle of the gradient divider so that the level of liquid in the “heavy”
chamber is about 2 cm below the level of liquid in the “light” chamber.
You may use tape or wax pencil on the outside of the gradient maker to record the
angle of the gradient divider. Avoid using marker ink that can only be removed with
methanol. Most solvents, including methanol, can craze the plastic parts of the
gradient maker.
8. Open the pinch clamps to remove the water, or pour the water out of the top of the
gradient maker.
Repeat this procedure whenever the required volume of acrylamide solution changes as
a result of changing the number or thickness of gels you are casting.
Calibrating the Peristaltic Pump
Install the pump head and tubing to the pump controller, as directed in the manual
supplied with the pump. Calibrate the pump flow before the first use, and after every
ten to twenty uses, to assure proper flow rates.
This calibration procedure assumes a desired flow rate of 440 ml/min for a full tank of
gels (2000 ml acrylamide) and 325 ml/min for 12 gels.
1. Place the inlet side of the tubing in a beaker that contains one liter of water.
2. Place the outlet side of the tubing in a 1-liter graduated cylinder.
3. Set the flow speed at approximately 3 – 3.5 on the dial and start the pump.
4. Stop the flow of liquid after exactly 2 minutes.
5. Measure the water in the outlet cylinder and divide by 2 to determine the flow in
ml/min.
6. To determine the appropriate flow setting, divide the desired flow rate by the flow
rate in step 5; multiply this result times the flow speed used in step 3.
Example.
You want to cast a full tank of gels and determine the flow rate is
500 ml/min when you set the flow rate at 3. For a flow rate of 440 ml/min:
(440
÷
500)
× 3 = 2222....6666
= the appropriate flow rate setting to deliver 440 ml/min
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