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