TABLE 2.

Ionic strength dependence of association rate constant of F425 B4a1, b12, and Ab21 for binding to distinct variants of gp120

Values of association rate constant k_a were obtained by global analyses of sensorograms generated after injection of serial 2-fold dilutions of F425 B4a1 (25 to 0.049 nm), b12 (0.0049 (0.019)–5 nm, for binding to gp120 BaL, JRCSF, and CN54; 0.0049 (0.039)–10 nm, for binding to gp120 92RW020; and 0.039–20 nm, for binding to gp120 96ZM651), and of heme-exposed Ab21 (125 to 0.488 (0.244) nm) onto sensor chips with immobilized variants of gp120. The interactions were studied in HBS-EP buffer containing different concentration of NaCl, 0.05, 0.15, and 0.45 m. The global analyses were performed by fitting experimental data by using Langmuir binding with a drifting baseline kinetic model. In case of b12 binding to gp120 BaL, JRCSF, and CN54, at 0.05 m NaCl, due to possible involvement of mass transport, the experimental data were fitted by using Langmuir binding kinetic model with correction for mass transport artifacts. The values presented are mean ± S.D. of three independent fits of the experimental data.

	F425 B4a1			b12			Ab21-heme
	0.05 m	NaCl 0.15 m	0. 45 m	0.05 m	NaCl 0.15 m	0. 45 m	0.05 m	NaCl 0.15 m	0.45 m
	ka ×105m−1 s−1 (mean ± S.D.)
92RW020	2.5 ± 0.006	2.05 ± 0.01	1.47 ±0.006	57.3 ± 2.2	12.2 ± 0.001	4.6 ± 0.47	1.12 ± 0.021	0.99 ± 0.014	0.92 ± 0.012
BaL	4.05 ± 0.1	4.1 ± 0.069	2.01 ± 0.023	477 ± 4.6	15.2 ± 0.001	7.58 ± 0	0.98 ± 0.02	0.97 ± 0.012	0.49 ± 0.009
JRCSF	3.14 ± 0.023	3.19 ± 0.026	1.79 ± 0.011	150 ± 4.2	15.5 ± 0.01	6.22 ± 0.9	1.38 ± 0.023	0.9 ± 0.008	0.92 ± 0.018
CN54	3.21 ± 0.021	3.04 ± 0.055	1.91 ± 0.01	600 ± 5.7	6.44 ± 0.6	4.17 ± 0.1	0.62 ± 0.014	0.77 ± 0.017	0.36 ± 0.003
96ZM651	1.1 ± 0.006	0.56 ± 0.026	0.28 ± 0.13	50 ± 1.2	5.16 ± 0.38	#	1.1 ± 0.006	1.26 ± 0	1.04 ± 0.02
93TH975	#	#	#	0.24 ± 0.04	#	#	0.78 ± 0.03	0.68 ± 0.008	0.48 ± 0.02