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