“…Two main methods exist for distinguishing and recovering these molecules. The fi rst, selection by auto-modifi cation, is used with nucleic acids that posses self-processing (3,4,7,8,9,12,17,18,35,50,51,81,90) or ligase activity (5,20,26,40,96); these can be discriminated by their size. When selecting molecules with autophosphorylation (71) or acylation activity (44), active molecules can be recovered by affi nity chromatography.…”