should exclude the CA analyte and act as a negative control,
while the other three should form Tb(ligand)(CA) ternary
complexes, depending on the steric constraints imposed by the
receptor ligand on the size and shape of the binding pocket.
TABLE V
STABILITYCONSTANTS FORTB^3 þANDGD^3 þWITHVARIOUSLINEAR ANDMACROCYCLIC
LIGANDS.Type Ligand Coord. no. logKTb logKGd References
Linear EDTA 6 17.92 17.35 ( 137 )
DTPA 8 22.71 22.46 ( 137 )
Cyclic DO2A 6 – 19.42 ( 138 )
DO3A 7 – 21.0 ( 96 )
DOTA 8 24.8 24.6 (96,138)
FIG.9 Linear (EDTA) and cyclic (DO2A, DO3A, and DOTA) ligands
utilized for determining binding stoichiometries. EDTA and DO2A are
hexadentate, DO3A is heptadentate, and DOTA is octadentate.
24 MORGAN L. CABLEet al.