Functional unit may be added which covalently react and couple the ligand to {HEAD ~ the target molecule}, catalytic groups may be added to aid in the selection of protease or nuclease activity, and reporter molecules such as biotin or fluorescein may be added for use as {TAIL ~ diagnostic reagents} 
Functional unit may be added which covalently react and couple the ligand to { HEAD ~ the target molecule } , catalytic groups may be added to aid in the selection of protease or nuclease activity , and reporter molecules such as biotin or fluorescein may be added for use as { TAIL ~ diagnostic reagents }
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