TABLE 2.

SPR measurements of the effect of the H66N change on gp120-sCD4 binding

gp120 protein	Kona (M−1 s−1)	Koffb (s−1)	Kd (nM)
KB9	1.1 × 104	1.9 × 10−4	17
KB9-H66N	1.1 × 104	2.8 × 10−4	24
ADA N197S	9.3 × 103	6.4 × 10−4	69
ADA N197S-H66N	7.3 × 103	1.1 × 10−3	140

^aK_on, on-rate constant.

^bK_off, off-rate constant.