Conversely, {HEAD ~ the nucleic acid region} may serve to facilitate {TAIL ~ a covalent interaction} between the attached functional unit and a given target 
serve to facilitate
Conversely , { HEAD ~ the nucleic acid region } may serve to facilitate { TAIL ~ a covalent interaction } between the attached functional unit and a given target
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH