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