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Updated: Jan 20, 2026

A Femtoliter Droplet Array for Massively Parallel Protein Synthesis from Single DNA Molecules
Published on: June 20, 2020
Accurate high-throughput screening based on digital protein synthesis in a massively parallel femtoliter droplet
Yi Zhang1,2, Yoshihiro Minagawa2, Hiroto Kizoe2
1SUGAR Program, X-star, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan.
Abstract:
We report a general strategy based on digital counting principle that enables an efficient acquisition of enzyme mutants with desired activities from just a few clones within a day. We prepared a high-density femtoliter droplet array, consisting of 1 million uniform droplets per 1 cm2 to carry out high-throughput protein synthesis and screening. Single DNA molecules were randomly distributed into each droplet following a Poisson process to initiate the protein synthesis with coupled cell-free transcription and translation reactions and then recovered by a microcapillary. The protein yield in each droplet was proportional to the number of DNA molecules, meaning that droplets with apparent intensities higher than the Poisson distribution-predicted maximum can be readily identified as the exact hits exhibiting the desired increased activity. We improved the activity of an alkaline phosphatase up to near 20-fold by using less than 10 nl of reagents.
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