Captain John Mullan and the Engineers' Problem

"Captain Mullan's survey and construction of this wagon-road from Walla Walla to Fort Benton was really an off-shoot of the great work instituted by an act of Congress in February, 1853, calling for a thorough survey of all the several routes possible for a transcontinental railroad... It was the work of Stevens and his faithful subordinate Mullan, which opened the way for the railroad.

Multiplexed Target Detection Using DNA-Binding Dye Chemistry in Droplet Digital PCR

Two years ago, we described the first droplet digital PCR (ddPCR) system aimed at empowering all researchers with a tool that removes the substantial uncertainties associated with using the analogue standard, quantitative real-time PCR (qPCR). This system enabled TaqMan hydrolysis probe-based assays for the absolute quantification of nucleic acids. Due to significant advancements in droplet chemistry and buoyed by the multiple benefits associated with dye-based target detection, we have created a “second generation” ddPCR system compatible with both TaqMan-probe and DNA-binding dye detection chemistries. Herein, we describe the operating characteristics of DNA-binding dye based ddPCR and offer a side-by-side comparison to TaqMan probe detection. By partitioning each sample prior to thermal cycling, we demonstrate that it is now possible to use a DNA-binding dye for the quantification of multiple target species from a single reaction. The increased resolution associated with partitioning also made it possible to visualize and account for signals arising from nonspecific amplification products. We expect that the ability to combine the precision of ddPCR with both DNA-binding dye and TaqMan probe detection chemistries will further enable the research community to answer complex and diverse genetic questions