Function and design
Biometra TOne
16
3.2.1
Thermal block
The device is equipped with a thermal block.
Fig. 2
Opened device with thermal block
The thermal blocks are made of aluminum and coated with a special alloy. Aluminum
blocks offer high heating and cooling rates for fast protocol run times.
Once the lid is closed, the rubber seal of the heated lid ensures that the space around
the sample block is encapsulated. This enclosed space improves the uniformity of the
temperature inside the sample block and avoids the formation of condensed water dur-
ing the final cooling step of the PCR process. Furthermore, all sample blocks are per-
fectly sealed to prevent condensed water from penetrating into the Peltier elements un-
derneath the sample block and other parts of the electronics. The sealing protects the
Peltier elements and prolongs the working life of the device.
3.2.2
Temperature gradient
The annealing temperature has a major impact on the PCR reaction:
¡
If the selected annealing temperature is too low, the primers may anneal to nucleo-
tide sequences that are not fully complementary. The reaction will then be less spe-
cific and produce unwanted by-products.
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If the selected annealing temperature is too high, the thermal movement of the
primers may be so extended that they do not anneal properly. As a result, the prod-
uct is not formed at all or only inefficiently.
The ideal annealing temperature is about 5 … 10 °C below the average melting tempera-
ture of the primers. This usually corresponds to a temperature of 55 … 65 °C.
