PMA™ is a high affinity photoreactive DNA binding dye developed by Biotium (40019). The dye is weakly fluorescent by itself but becomes highly fluorescent upon 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 cell membrane-impermeable and thus can be used to selectively modify DNA from dead cells with compromised membrane integrity, while leaving DNA from viable cells intact. PMA inhibits PCR amplification of modified DNA templates by a combination of removal of modified DNA during purification and inhibition of template amplification by DNA polymerases. Consequently the dye is useful in the selective detection of viable pathogenic cells by quantitative real-time PCR. PMA Enhancer for Gram Negative Bacteria was designed to improve PMA-mediated discrimination between live and dead gram-negative bacteria. PMA Enhancer is provided as a 5X solution, and is added to a sample before the addition of PMA. 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. Thus, PMA plus Enhancer is the optimal way to perform viability PCR on gram-negative bacteria. Note: PMA Enhancer is not intended for use when gram-positive bacteria are to be detected. PMA Enhancer may adversely affect the amplification of live cell DNA from gram-positive bacteria. Also see our PMA Real-Time Bacterial Viability Kits.
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