BD Biosciences-Clontech of Palo Alto, Calif., has harnessed the power of a DNAzyme, the DNA equivalent of a ribozyme, in its new BD QZymeassay for quantitative PCR. The sensitive system, which can detect fewer than 10 copies of a target, can be used with any real-time thermocycler and works via a simple amplification and cleavage reaction.

Appended to the gene-specific 5' PCR primer is the inactive antisense strand of a phosphodiesterase DNAzyme. As double-stranded copies of the DNA target are produced the active, DNAzyme molecule binds and cleaves a previously dormant substrate, releasing a fluorescent signal that increases in proportion to the amount of amplified DNA. To measure more than one gene at the same time, researchers can use two different DNAzymes with unique spectral signals.

So far, beta testers "like the robustness of the system," says Abe Couse, senior product manager. Slated for an early 2004...

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