PMA™ (propidium monoazide) is a high affinity photoreactive DNA binding dye invented by scientists at Biotium. The dye is weakly fluorescent by itself but becomes more fluorescent after binding to nucleic acids. It preferentially binds to dsDNA with high affinity. Upon photolysis, the photoreactive azido group on the dye is converted to a highly reactive nitrene radical, which readily reacts with any hydrocarbon moiety at the binding site to form a stable covalent nitrogen-carbon bond, thus resulting in permanent DNA modification. The dye is nearly completely cell membrane-impermeable, and thus can be selectively used to modify only exposed DNA from dead cells while leaving DNA from viable cells intact. This feature makes the dye highly useful in the selective detection of viable pathogenic cells by quantitative real-time PCR in the presence dead cells whose DNA has been PMA-modified and thus can not be amplified. 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.
Using our recommended protocol, 1 mg of PMA dye can be used to treat 78 samples with 50 uM dye and 500 uL sample size; optimal dye concentration and sample size may vary by strain or application. PMA dye is also available in H2O (40019), a convenient ready-to-use format.
Note: Scientists at Biotium have recently invented a new and improved dye for viability PCR, called PMAxx (40069). PMAxx functions in a manner very similar to PMA, but has much greater activity and ability to distinguish between live and dead bacteria. PMAxx can be used as a replacement for PMA in any bacterial viability-PCR assay. We recommend that customers interested in using PMA try PMAxx instead, for improved detection of viable bacteria.
For viability PCR of gram-negative bacteria we highly recommend using our new PMA Enhancer (31038) in conjunction with PMA. 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 Enhancer show a decrease in the signal from dead cells, with no change in the signal from live cells.
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 PMA or EMA dye, we recommend the use of Biotium’s PMA-Lite LED Photolysis Device (E90002), which is designed to conduct photolysis under controlled conditions.
- Molecular weight: 511
- Abs = 464 nm (before photolysis)
- Abs/Em = 510/610 nm (following photolysis and covalent attachment to DNA/RNA)
- Dark red solid soluble in DMSO or DMF
- Store at 4°C and protect from light at all times