Variants of {HEAD ~ thymidine kinase}, {TAIL ~ nucleic acids} encoding them, and methods of using them 
Variants of { HEAD ~ thymidine kinase } , { TAIL ~ nucleic acids } encoding them , and methods of using them
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH