{TAIL ~ The compounds} of this invention wherein R is CO2 H can be attached to a biomolecule through {HEAD ~ an amine group} or a hydroxyl group on the latter 
{ TAIL ~ The compounds } of this invention wherein R is CO2 H can be attached to a biomolecule through { HEAD ~ an amine group } or a hydroxyl group on the latter
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH