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. 2014 Dec 28;87(3):1950–1956. doi: 10.1021/ac504330x

Figure 4.

Figure 4

MMP–substrate assay on the device. The two data traces indicate fluorescence obtained from two repeats of a sequence of droplets containing different MMP–substrate combinations. The FAM channel indicates fluorescence from the FRET peptide substrates cleaved by different MMPs. Alexa Fluor 546 dye is used to insert a few “beacon” droplets (green peaks in the Alexa Fluor 546 channel) into the droplet sequence without interfering with the assay channel. The presence of beacon droplets in the sequence at predetermined positions with respect to other droplets can be used as an indicator of the proper operation of the device without any unwanted droplet merging or splitting. The fluorescence from the nonbeacon droplets in the Alexa Fluor 546 channel is due to bleeding of some fluorescence from the FAM channel into the Alexa Fluor 546 channel.