SELEX is {HEAD ~ an acronym} for {TAIL ~ Systematic Evolution} of Ligands by EXponential enrichment 
SELEX is { HEAD ~ an acronym } for { TAIL ~ Systematic Evolution } of Ligands by EXponential enrichment
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH