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