PMAxx dye is a DNA modifier used for viability PCR, invented by scientists at Biotium. PMAxx is a new and improved version of our popular viability dye PMA (propidium monoazide). Like PMA, PMAxx is a photo-reactive dye that binds to dsDNA with high affinity. Upon photolysis with visible light, PMAxx dye becomes covalently attached to dsDNA. The PMAxx-modified dsDNA cannot be amplified by PCR. PMAxx dye is designed to be cell membrane-impermeable. Thus, in a population of live and dead cells, only dead cells are susceptible to DNA modification due to compromised cell membranes. This unique feature makes PMAxx highly useful in selective detection of live bacteria by qPCR.
PMAxx was designed by Biotium scientists to be a superior alternative to PMA. While PMA is generally effective at differentiating between live and dead bacteria by qPCR, it does not completely eliminate PCR products from dead cell DNA. This could potentially give false positive results. Biotium’s new dye PMAxx is much more effective at eliminating PCR amplification of dead cell DNA, and therefore provides the best discrimination between live and dead bacteria.
Since Biotium first developed PMA dye, there have been numerous publications on the use of the dye in pathogenic bacterial detection related to food and water safety, medical diagnosis and biodefense (download the PMA Reference List). PMAxx should be compatible with all existing PMA protocols, but with superior activity. Using our recommended protocol PMAxx can be used to treat twice the number of samples as PMA. One vial (100 uL) of PMAxx can be used to treat 160 samples using 25 uM dye with a 500 uL sample size; optimal dye concentration and sample size may vary by strain or application. We also continue to offer the classic PMA dye, in water (40019) or lyophilized format (40013).
For viability PCR of Gram-negative bacteria we highly recommend using our PMA Enhancer (31038) in conjunction with PMAxx. PMA Enhancer for Gram Negative Bacteria was designed to improve PMA-mediated discrimination between live and dead Gram-negative bacteria. When a sequence from a Gram-negative bacteria is amplified by PCR, samples pre-treated with dye and Enhancer show a decrease in the signal from dead cells, with no change in the signal from live cells. PMA Enhancer is particularly useful for samples in which bacteria were killed using mild methods such as low heat.
Biotium also provides strain-specific PMA Real-Time PCR Bacterial Viability kits with validated primers for 7 selected pathogens: M. tuberculosis, S. aureus, MRSA, Salmonella, E. coli, E. coli O157:H7 and Listeria. These kits provide everything that you need for the selective detection of your favorite species of live bacteria by real-time PCR. Don’t see your favorite strain? Let us know at firstname.lastname@example.org.
Real-Time PCR Bacterial Viability Kits
For photoactivation of PMAxx dye (or PMA or EMA), we recommend the use of Biotium’s PMA-Lite LED Photolysis Device (E90002), which is designed to conduct photolysis under controlled conditions.
- Abs = 466 nm (before photolysis)
- Abs/Em = ~510/~610 nm (following photolysis and covalent attachment to DNA/RNA)
- Dark red solution
- Store at -20°C and protect from light at all times