© Thermo Hybaid. Issue 1.0, January 2002
63
APPENDIX III
Px2 THERMAL CYCLER
In Situ
Block Application Notes
Overview
The Px2
In Situ
module with flat block has been designed for the precise control of temperature on up
to four standard microscope slides (dimensions 76mm x 26mm x 1mm). Flat blocks are supplied with
a Humidity Chamber, which can be used to reduce sample drying.
Temperature Control
The
In Situ
block can perform all the control functions of the standard Px2 reaction tube block with
the exceptions of Active Tube Control and Simulated Tube Control. Instead, the
Simulated Slide
Control
option is used which minimises the time lag between the block reaching target temperature
and the sample on the surface of the slide achieving target temperature. At the start of running a
program on an
In Situ
module the
SIM SLIDE
option should be selected as the control mode (see
Figure 5.1
). The heated lid is not operational under this control mode.
The performance of the
In Situ
module has been measured using miniature thermistor probes attached
to the surface of slides. Optimum results across four standard slides (1mm thickness) with the
humidity chamber in place have been obtained using a
calibration factor
of 25. Using a higher
calibration factor accelerates the approach to target temperature, but results in a degree of overshoot.
Conversely, a lower calibration factor slows the approach to target temperature, but minimises any
overshoot. A calibration factor of zero would be equivalent to block control when using
SIM
SLIDE
.
Protocol Transfer
When transferring protocols from a conventional 'block control' machine, it is important to consider
the effect of using Px2's 'Simulated Slide' control. On conventional thermal cyclers, the programmed
temperatures commonly refer to the temperature achieved by the block and not the microscope slide.
Consequently, a sample on the top surface of a glass slide will be significantly cooler than the block
temperature. The Px2’s 'Simulated Slide' control overcomes this problem by using an algorithm to
ensure the temperature achieved by samples on the surface of the slides is as close as possible to the
programmed temperature.
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