Processing methods for nucleic acid data storage

A method for purifying a pool of nucleic acid molecules encoding digital information, the method comprising:

• (a) obtaining a first pool comprising capped target nucleic acid molecules and non-target nucleic acid molecules;
• (b) reducing a volume of the first pool to obtain a second pool comprising enriched concentrations of the target nucleic acid molecules and non-target nucleic acid molecules;
• (c) performing a buffer exchange on the second pool to obtain a third pool comprising the target nucleic acid molecules and non-target nucleic acid molecules in a laboratory-compatible medium;
• (d) isolating, using size selection, the target nucleic acid molecules from the non-target nucleic acid molecules to obtain a fourth pool comprising the target nucleic acid molecules, wherein the size selection comprises adding to the third pool an exonuclease that selectively degrades exposed linear ends of nucleic acid molecules and degrading exposed linear ends of non-target nucleic acid molecules;
• and
• (e) amplifying the target nucleic acid molecules in the fourth pool to obtain a fifth pool comprising an enriched concentration of the target nucleic acid molecules;
• wherein the target nucleic acid molecules comprise a sequence library that encodes information;
• wherein the target nucleic acid molecules comprise fully-assembled nucleic acid molecules, each comprising concatenated nucleic acid fragments;
• and
• wherein the non-target nucleic acid molecules comprise at least one of partially-assembled nucleic acid molecules, un-assembled nucleic acid fragments, or single-stranded nucleic acid fragments.