Bio-Rad PROTEAN® Plus Hinged Spacer Plates and Combs - Manual (Page 4)

1.1 Specifications
Model 385 Gradient Former
Overall size
10 cm x 15 cm x 15 cm (with piston in chamber)
Weight 405 g without piston; piston 65 g
Capacity 2 x 56 ml
Model 395 Gradient Former
Overall size 16.5 cm x 11.2 cm x 18 cm (without piston)
Weight 730 g without piston; piston 310 g
Chamber volume 2 x 400 ml
Practical capacity 2 x 350 ml
Construction of Model 385 and 395 Gradient Formers
Body machined from an acrylic block
Valve stem Delrin ®
Stopcock one-way plastic stopcock, Luer taper
Piston Delrin
Tubing Tygon ® 1/8" ID
Section 2
Pouring a Linear Gradient Gel
2.1 Calculating the Chamber Volumes
Each chamber's volume is one-half the total volume of the gel. The volume of the tubing
and the stir bar, however, can affect the measurement of the total volume. Section 2.2, step 10,
discusses tubing volume.
Adding the stir bar to the mixing chamber increases the volume in the mixing chamber.
If not compensated for, this increased volume would divide itself between the two chambers
when the valve stem was opened. However, when the stirring motor is turned on, a vortex is
created, which compensates for the increase in mixing chamber volume, since the bottom of
the vortex becomes the level at which the other chamber equalizes.
To calculate the volume of solution required for each chamber, multiply the spacer thick-
ness in cm by the length of the gel in cm, by the width of the gel in cm, and divide by 2.
2.2 Pouring the Gel from the Top
The heavy solution is poured into the mixing chamber since it enters the sandwich first,
flowing to the bottom. The light solution, which flows into the gel last, is poured into the
reservoir chamber.
Note: We advise you to familiarize yourself thoroughly with the sequence of operations
starting with step 6. The best guarantee of reproducibility from gradient to gradient is
careful technique on the part of the operator.
1. Set up the gel sandwich in the usual manner.
2. Arrange the tubing in the peristaltic pump so there is as short a distance as possible
between the stopcock opening and the pump, and between the pump and the gel sandwich.
Cut the tubing as necessary.
3. Attach the needle to the end of the tubing and tape it to the top of the gel sandwich near
the center.
2