Focused aptamer libraries are constructed in accordance with a proteome (i.e., complex mixture of native biomolecules). The libraries may be screened to identify one or more candidate aptamers with desired biological activities other than specific binding to a target. Aptamers which are selected or derivatives thereof may be used for those specific activities in biological systems. Any combination of deconvoluting a focused library (functional profiling), increasing frequencies of particular aptamers in a focused library (Laser SELEX), and decreasing frequencies of particular aptamers in a focused library (DeSELEX) may be performed prior to assaying biological activity.