Table 1. Gd³⁺ and Zn²⁺ binding affinity and selectivity of Gd-DTPA and ProCA1 variants.

	DTPA	ProCA1	ProCA1.GRPR	ProCA1.B10	ProCA1.G10
Kd Gd , M	3.5 × 10−23 *	8.7 × 10−13 *	2.1 ± 0.6 × 10−12	5.1 ± 0.1 × 10−12	1.3 ± 0.1 × 10−12
Kd Zn, M	5.1 × 10−19 *	1.9 × 10−7 *	4.1 ± 2.0 × 10−6	9.0 ± 0.1 × 10−6	4.6 ± 0.4 × 10−6
log (KGd/KZn)	4.2	5.4	6.3	6.3	6.5
r1, mM−1s−1, 1.4 T	3.5	25.9 ± 2.6	42.0 ± 2.6	47.5 ± 0.1	49.2 ± 0.2
r2, mM−1s−1, 1.4 T	5	41.2 ± 3.3	78.9 ± 2.6	80.3 ± 0.7	92.0 ± 0.1

^*from references²¹.