TABLE 1.

Kinetic parameters for binding of full-length gp120, b121a, and b122a to b12 by surface plasmon resonance

Protein	b12a
	kon	koff	KD
	m−1 s−1	s−1	m
gp120b	6 × 104	4.6 × 10−3	7.6 × 10−8 ± 0.8 × 10−8
b121a	2 × 102	6.9 × 10−3	34.5 × 10−6 ± 15.6 × 10−6
b122a	6.6 × 102	5.6 × 10−3	8.4 × 10−6 ± 0.5 × 10−6

^a The non-neutralizing antibody b6 binds gp120 with a k_on of 1.1 × 10⁵ m⁻¹ s⁻¹. There was very slow dissociation; hence, k_off could not be measured. However, the published K_D is 0.013 pm (7). There was no detectable binding of b121a or b122a to b6.

^b Both full-length and core gp120 bind b12 with similar affinity.