{HEAD ~ Reactions} were terminated by {TAIL ~ rapid filtration} and the radioactivity bound to the filters counted by liquid scintillation spectrophotometry 
terminated by
{ HEAD ~ Reactions } were terminated by { TAIL ~ rapid filtration } and the radioactivity bound to the filters counted by liquid scintillation spectrophotometry
HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH