Selecting The Correct Sample Vessel; 0.5 Ml Tubes; Microplates; Thin-Walled Vs. Thick-Walled Tubes - BIO RAD PTC-200 Operation Manual

DNA Engine Operations Manual

Selecting the Correct Sample Vessel

The DNA Engine cycler's wide variety of interchangeable Alpha units affords you great
scope in choosing sample vessels. Keep in mind that differences in tube and plate com-
position and wall thickness among the many brands available can affect reaction
performance. Protocols may require some adjustment to ensure optimum performance
when using a new vessel type. Bio-Rad offers a full range of tubes and microplates, man-
ufactured to the specifications of each type of Alpha unit to ensure a precise fit. See
chapter appendix 4-A for a complete list.

0.5 ml Tubes

Make sure thick-walled 0.5 ml tubes fit the wells snugly. Since these tubes were originally
designed for centrifuges, some brands may not fit tightly in thermal cycler wells. Thin-walled
0.5 ml tubes were specifically designed for thermal cycling, and the higher quality brands
provide a good and consistent fit. Bio-Rad provides thin- and thick-walled 0.5 ml tubes
designed for precise block fit.
0.2 ml Tubes
All types of thin-walled 0.2 ml tubes may be used. Bio-Rad sells high-quality 0.2 ml
tubes in a number of styles, including individual tubes and strips.

Microplates

A variety of 96-well polycarbonate or polypropylene microplates can be used in 96-well
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. Polypropylene microplates and com-
patible sealing systems are available from Bio-Rad. (See "Sealing Sample Vessels" on
the next page for a description of available sealing systems from Bio-Rad.)

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/sec), so the faster
heat transfer provided by thin-walled tubes allows protocols to be significantly short-
ened. On average, about 30 seconds can be saved per cycle by using thin-walled
tubes, for an overall savings of 15 minutes in a 30-cycle run.
4-6 Tech Support: 1-800-4BIORAD • 1-800-424-6723 • www.bio-rad.com