At a conference not long ago, someone asked me what journal I work for. When I replied BioTechniques, the response was: “The PCR journal”. While we are definitely not just a PCR journal, a quick glance through back issues of BioTechniques reveals that, circa 1990, PCR was the all rage. New PCR techniques and applications graced the pages of this journal on a regular monthly basis.
And why not? At the time, PCR was emerging as one of the most important techniques in molecular biology. Fast forward 20 plus years to 2013, and PCR remains the workhorse of the biomedical research lab. In fact, many of the methods from those early BioTechniques articles are still in use today.
This month, we provide two amazing examples of the PCR legacy BioTechniques has been a part of with the latest installments in our 30th anniversary Gem series. Deciding on articles to celebrate 30 years of publishing innovative PCR techniques and was no small feat for the editors; a great number of transformative methodologies have been published in these pages during the past three decades. But in the end, we were able to identify two articles that provide something above and beyond their useful methods–these articles are a glimpse into the incredible, and often underappreciated, history of BioTechniques.
The first selection is a 1992 article by Sykes et al. entitled “Quantitation of targets for PCR by use of limiting dilution”. The idea of making PCR a quantitative rather than qualitative method was established in the mid-1990s as techniques such as quantitative real-time PCR (qPCR) gained traction. But Sykes et al. proposed something different: a method to quantitate initial template numbers directly by amplifying individual or limited numbers of molecules from a starting sample. The approach also allowed users to deal with mixed template samples where a vast excess of competing targets were present. This concept of limiting dilution PCR was further advanced in 1999 by Vogelstein and Kinzler, who termed the methodology “digital PCR”. Currently, an expanding number of applications are being developed for digital PCR to meet the growing need for quantitative assessment of samples.
Our second Gem article, entitled “Continuous fluorescence monitoring of rapid cycle DNA amplification”, was published in 1997 by Carl Wittwer and his colleagues at the University of Utah. Real-time monitoring of PCR amplification can provide insights into staring template quantities as well as details on the efficiency of amplification reactions. In 1997, the main approaches for such real-time monitoring were through the use of specially designed fluorescent primers where the fluorescent probe portion is cleaved during polymerase extension or the use of “molecular beacons” where hybridization results in a conformational change to the fluorophore that can be then be detected. Wittwer and colleagues suggested a third, non-primer based alternative–SYBR green detection of amplification products. Prior to amplification, SYBR green fluorescence is minimal. But after incorporation into a double-stranded DNA amplification product, fluorescence increases, providing a way to detect amplification during PCR.
Both PCR Gem selections illustrate the impact straightforward ideas can have on our ability to do research. In the case of limiting dilution PCR, the work of Sykes et al. and that of Vogelstein and Kinzler paved the way for current research aimed at understanding gene transcription, as well as single cell analysis. And SYBR green remains a critical methodology in the qPCR toolkit as noted in a special commentary article from Kent Vrana (page 312).
We hope that you enjoy the articles in our special Gem section (page 311) as much as we have enjoyed revisiting these articles ourselves. It's good to be remembered as “The PCR journal”.
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