comparing incorporation by HIV RT of said analog with incorporation by a mammalian DNA polymerase, therefrom determining whether said {HEAD ~ analog} is incorporated preferentially by {TAIL ~ HIV RT} 
is incorporated preferentially by
comparing incorporation by HIV RT of said analog with incorporation by a mammalian DNA polymerase , therefrom determining whether said { HEAD ~ analog } is incorporated preferentially by { TAIL ~ HIV RT }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL