library_construction_protocol: The protein of interest was incubated with the randomized library and run on a non-denaturing polyacrylamide gel at 4 ⁰C. Bound fragments were excised and purified using phenol:chloroform:isoamyl extraction. An aliquot was then used for an additional round of selection and extraction. Illumina adapters and barcodes and were then added to the selected libraries usng 4 cycle PCR, and samples were sent for sequencing. A hand-mixed library containing a 16 bp randomized region was ordered from IDT with standard desalting. The library was made double stranded using the Klenow reaction.