FRAG is a shiftable detectable species which provides {TAIL ~ a detectable species} when released from {HEAD ~ the reducible compound}, and 
FRAG is a shiftable detectable species which provides { TAIL ~ a detectable species } when released from { HEAD ~ the reducible compound } , and
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH