TABLE 2.

Summary of the equilibrium dissociation and rate constants of S20 and MF23-1 antibodies^a

Antibody	KD (M)b	kd (s−1)	ka (M−1 s−1)	Chi2
S20 scFv monomer
Immobilized LPS	5.6 × 10−7	2.9 × 10−3	5.2 × 103	2.53
2 repeating units	4.7 × 10−6	5.1 × 10−3	1.1 × 103	0.25
3 repeating units	1.1 × 10−6	4.7 × 10−3	4.4 × 103	0.60
S20 scFv dimer
Immobilized LPS	2.1 × 10−8c	1.2 × 10−4	5.9 × 103	2.04
2 repeating units	ND	ND	ND	ND
3 repeating units	ND	ND	ND	ND
MF23-1 MAb
Immobilized LPS	ND	ND	ND	ND
2 repeating units	8.8 × 10−5d			0.53
3 repeating units	1.8 × 10−5d			0.96
MF23-1 Fab
Immobilized LPS	ND	ND	ND	ND
2 repeating units	ND	ND	ND	ND
3 repeating units	2.7 × 10−5d			0.74

^aAntibodies were flowed over captured O6a, 6d LPS-containing liposomes and O6a, 6d repeating unit oligosaccharides (1, 2, or 3) were flowed over immobilized antibodies. No binding was detected for 1-repeating-unit oligosaccharides.

^bK_D, equilibrium dissociation constant (K_D = k_d/k_a, where k_d is the dissociation rate constant and k_a is the association rate constant). ND, not determined.

^cApparent equilibrium dissociation constant, K_D^app, due to avid binding.

^dDetermined by steady-state affinity.