The method also allows for the identification of {HEAD ~ nucleic acids} that have facilitating {TAIL ~ activities} as measured by their ability to facilitate formation of a covalent bond between the nucleic acid, including its associated functional unit, and its target 
The method also allows for the identification of { HEAD ~ nucleic acids } that have facilitating { TAIL ~ activities } as measured by their ability to facilitate formation of a covalent bond between the nucleic acid , including its associated functional unit , and its target
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH