DNA Engine Tetrad 2 Thermal Cycler Operations Manual
4-10
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5. For microplate sealing films or mats that require additional pressure, turn the
thumbwheel clockwise an extra half turn past the point of initial contact to set
an appropriate lid pressure.
Caution:
Do not turn the thumbwheel more than three-quarters of a turn. This can
make it hard or impossible to close the lid and puts excessive strain on
the latch holding the lid closed.
An extra half to three-quarters of a turn ensures the correct pressure for most
types of reaction vessels. Some empirical testing may be required to deter-
mine the optimum pressure required for certain vessels. Once this pressure
has been determined, the thumbwheel position may be marked with a col-
ored marking pen or piece of tape.
Note:
As an aid in gauging how much the thumbwheel has been turned, mark it at the
quarter turn positions, or every sixth “bump” on the thumbwheel (there are 24 total “bumps”).
Loading Sample Vessels into the Block
When using a small number of tubes, load at least one empty tube in each corner of
the block to ensure that the Hot Bonnet lid exerts even pressure on the sample tubes
(see “Adjusting the Hot Bonnet Lid’s Pressure,” above).
To ensure uniform heating and cooling of samples, sample vessels must be in complete
contact with the block. Adequate contact is ensured by always doing the following:
•
Ensure that the block is clean before loading samples (see Chapter 9 for cleaning
instructions).
•
Firmly press individual tubes or the microplate into the block wells.
Using Oil to Thermally Couple Sample Vessels to the Block
With two exceptions (see below), Bio-Rad Laboratories does not recommend using
oil to thermally couple sample vessels to the block, for the following reasons:
•
Calculated-control protocols do not run accurately when oil is used.
•
Oil traps dirt, which interferes with thermal contact between vessels and the block.
