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