The nucleic acid region of {HEAD ~ the nucleic acid ligand} serve in whole or in part as {TAIL ~ ligands} to a given target 
The nucleic acid region of { HEAD ~ the nucleic acid ligand } serve in whole or in part as { TAIL ~ ligands } to a given target
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH