MJ Research DNA Engine Dyad PTC-220, Operation Manual, Page: 30 / 157

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DNA Engine Dyad Operations Manual
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 determine the optimum
pressure required for certain vessels. Once this pressure has been determined, the
thumbwheel position may be marked with a colored 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 “Adjust-
ing 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 instruc-
tions).
• 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), MJ Research 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.
Caution: If you use oil in the block, use only mineral oil. Never use silicone oil.
It can damage the Alpha unit.
One exception to this recommendation involves the use of volatile radioactive 35 S nucle-
otides. A small amount of oil in the block can help prevent escape of these compounds. See
Appendix 4-B of this chapter for important information regarding safe use of these com-
pounds in polypropylene tubes and polypropylene and polycarbonate microplates. A sec-
ond exception involves the use of thick-wall 0.5ml tubes. Certain brands of these tubes fit
poorly in the block, in which case, oil may somewhat improve thermal contact. Whenever
possible, use high-quality thin-wall tubes intended for thermal cycling (see Appendix 4-A of
this chapter for a tube and plate selection chart).