The PCR process has evolved significantly from the days of switching tubes between water baths at different temperatures to amplify DNA. Today, it seems that there are a wide array of PCR machines available, giving the consumer an assortment of machines to choose from in a range of prices and sizes. Recently, our lab required a new PCR machine and we decided to purchase a PTC-200 from MJ Research (now owned by Bio-Rad) based on the following reasons.
Aesthetically, the PTC-200 is pleasing and it fits into small spaces making it convenient in a cramped lab setting (be certain to leave space for the vents on the side of the machine!). One of the unique features of this machine is the opportunity to upgrade with interchangeable heating blocks that can be easily exchanged within the apparatus. Bio-Rad really did their homework and developed a wide range of different blocks including a regular 96 well block, a dual 48-well block, a gradient temperature block and most recently, a block which allows the machine to be used for real-time PCR. However, my recommendation would be to go for the dual block unit, as it gives you the chance to run each block independently and thus, you essentially have two PCR machines for the price of one. If your needs only warrant a fixed 96-well block system, I would say to go for the PTC-100, as this is a less expensive version of the PTC-200.
The PTC-200 has a Peltier heat pump system that allows for rapid heating and cooling at a rate of up to 3 ºC / second. This not only makes for rapid PCRs, but better specificity of PCR reactions due to quick ramp times between the steps of denaturation, annealing and extension. The results from this machine were very consistent and I found complete uniformity across each block (no difference between tubes at the edges of blocks and in the middle). Another use for the dual block version is performing optimization of primer annealing temperatures on new primer sets. Once a PCR reaction is optimized on the machine, subsequent experiments with the set conditions repeat consistently, even when using another PTC-200 machine. In our lab, we have obtained excellent results with this machine performing routine genotyping, RT-PCR and large DNA fragment amplifications (+5kb).
The only downside to this machine is the display size for entering and editing PCR programs. The GeneAmp has a better display as it shows the entire PCR program on the screen (and is more colorful). In contrast, the PTC-200 only displays a few lines of a given program at one time on the screen.
Overall, I would say that after trying many different PCR machines, this is by far my favorite. As the winner of “The Scientist’s Best Instrument for Under $25,000” in 2002, it certainly gets my vote.
Barry Hudson, Ph.D.
Post-Doctoral Fellow
Columbia University