Table 1.

Kinetic parameters of immunogens for binding to different RBD conformation-specific ligands in PBS pH 7.4 at 25 °C.

Ligand	Parameter	Immunogens
		RS2	S2R	Spike
ACE2-hFc	ka (M−1s−1)	2.30 ± 0.01 × 105	5.15 ± 0.10 × 105	1.07 ± 0.01 × 105
	kd (s−1)	3.90 ± 0.02 × 10−4	1.49 ± 0.01 × 10−3	3.04 ± 0.07 × 10−5
	KD (M)	1.71 ± 0.01 × 10−9	2.99 ± 0.06 × 10−9	2.88 ± 0.16 × 10−10
CR3022	ka (M−1s−1)	3.43 ± 0.02 × 105	6.57 ± 0.07 × 105	6.17 ± 0.11 × 104
	kd (s−1)	4.13 ± 0.03 × 10−4	1.39 ± 0.01 × 10−3	2.45 ± 0.05 × 10−4
	KD (M)	1.21 ± 0.01 × 10−9	2.15 ± 0.03 × 10−9	4.06 ± 0.11 × 10−9
S309	ka (M−1s−1)	5.78 ± 0.08 × 104	5.31 ± 0.05 × 104	7.61 ± 0.13 × 104
	kd (s−1)	9.87 ± 0.26 × 10−5	ND	ND
	KD (M)	1.73 ± 0.05 × 10−9	ND	ND
ADG-2	ka (M−1s−1)	2.17 ± 0.01 × 105	2.26 ± 0.01 × 105	1.36 ± 0.01 × 105
	kd (s−1)	4.51 ± 0.23 × 10−5	ND	6.88 ± 0.06 × 10−5
	KD (M)	1.05 ± 0.05 × 10−10	ND	5.10 ± 0.20 × 10−10
H014	ka (M−1s−1)	4.52 ± 0.03 × 105	7.82 ± 0.05 × 105	7.38 ± 0.13 × 105
	kd (s−1)	3.49 ± 0.03 × 10−4	1.64 ± 0.01 × 10−3	1.66 ± 0.05 × 10−4
	KD (M)	7.78 ± 0.08 × 10−10	2.14 ± 0.03 × 10−9	2.30 ± 0.08 × 10−9

ND No dissociation.