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. 2021 Dec 7;12:7106. doi: 10.1038/s41467-021-26933-1

Fig. 1. A modified multiparameter particle display (MPPD) selection scheme for generating indole-modified aptamers.

Fig. 1

1) DNA library molecules are hybridized to magnetic beads coated with forward primers, and 2) emulsion PCR is performed to create aptamer particles that each display many copies of a single sequence. dTTP is substituted with the modified base 5-indolyl-dUTP at this step to produce base-modified aptamers. 3) The emulsions are broken and 4) the aptamer particles are converted to single-stranded DNA via NaOH treatment. 5) The aptamer particles are incubated with RNase B (RB) and RNase A (RA), where each protein is labeled with a spectrally orthogonal fluorophore. 6) Fluorescence-activated cell sorting (FACS) separates aptamer particles that generate a strong RB-specific signal and minimal RA-specific signal (quadrant IV of the FACS plot). 7) The aptamers are subjected to a ‘reverse-transcription’ step to produce natural DNA, which is either used as the template for an additional round of screening or 8) characterized via high-throughput sequencing.