Active groups are {HEAD ~ any} of {TAIL ~ various pharmacologically or therapeutically active moieties}, including moieties useful for magnetic resonance contrast enhancement 
of
Active groups are { HEAD ~ any } of { TAIL ~ various pharmacologically or therapeutically active moieties } , including moieties useful for magnetic resonance contrast enhancement
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH