“Completion of SELEX” refers to the point in the Systematic Evolution of Ligands by EXponential enrichment (SELEX)workflow where iterative selection rounds have produced an enriched nucleic-acid pool (DNA or RNA) that contains high-affinity, high-specificity binding sequences (aptamers) for a defined target, and further rounds provide diminishing improvements. In practical terms, completion is less a single universal round number and more a decision point supported by enrichment evidence, performance metrics, and downstream readiness. 1) SELEX in One Picture (Why “Completion” Exists at All) SELEX is an iterative evolutionary loop performed in vitro: Start with a diverse library (randomized nucleic-acid sequences). Bind the library to a target (protein, small molecule, cell surface, complex mixture, etc.). Partition: separate binders from non-binders (the critical “selection” step). Elute and amplify the binders (PCR for DNA; RT-PCR for RNA). Repeat with increasing stringency (less target, harsher washes, counter-selection, etc.). “Completion” matters because every additional round costs time, introduces amplification bias, and can over-enrich “fast amplifiers” rather than “best binders.” Modern practice treats completion as an optimization endpoint, not a ritual number of rounds. 2) What “Completion of SELEX” Typically Means (Conceptual Definition) A common knowledge-centered definition is: The pool has converged toward one…
