Operation
Tech Support: 1-800-4BIORAD • 1-800-424-6723 • www.bio-rad.com
4-7
0.5 ml Tubes
Thick-walled 0.5 ml tubes may not fit tightly in thermal cycler wells and typically provide
poor thermal transfer, since these tubes were originally designed for centrifuges. For
best results, we recommend using thin-walled 0.5 ml tubes specifically designed for
thermal cycling. The higher quality brands provide a good and consistent fit. Bio-Rad
thin-walled 0.5 ml tubes are designed for precise block fit and tight sealing of reactions
down to 10 µl.
Thin-Walled vs. Thick-Walled Tubes
The thickness of sample tubes directly affects the speed of sample heating and thus
the amount of time required for incubations. Thick-walled tubes delay sample
heating, since heat transfers more slowly through the tubes’ walls. For the earliest
types of thermal cyclers, this delay mattered little. These machines’ ramping rates
were so slow (below 1°C/sec) that there was plenty of time for heat to transfer
through the tube wall to the sample, during a given incubation.
Modern thermal cyclers have much faster ramping rates (up to 2–3°C/second), so the
faster heat transfer provided by thin-walled tubes allows protocols to be significantly
shortened.
0.2 ml Tubes
All types of thin-walled 0.2 ml tubes may be used. Bio-Rad offers high-quality 0.2 ml
tubes in a number of styles, including individual and strip tubes.
Microplates
A variety of polycarbonate or polypropylene microplates can be used in Alpha units
as long as they fit the wells snugly. Polypropylene microplates are usually preferred
because they exhibit very low protein binding and, unlike polycarbonate microplates,
do not lose water vapor through the vessel walls. This allows smaller sample volumes
to be used—as little as 5–10 µl.
Several varieties of microplates are available from Bio-Rad (see the "Tube, Microplate,
and Sealing Selection Chart"), including Hard-Shell
®
thin-wall microplates. Hard-
Shell microplates feature a skirt and deck molded from a rigid, thermostable polymer
that completely resists the warping and shrinkage experienced with traditional one-
component plates. The rigid skirt improves robotic handling such that stackers and
robotic arms can grip and move Hard-Shell plates securely and reliably. In a separate
step, thin-wall wells are molded of virgin polypropylene selected for low DNA binding
and optimized for thermal cycling.
