Figure 1. One-site binding model. (A) The simulated titration curves for P with L as a function of [L]t/[P]t ratio using Eq. 14. The colors used to illustrate the Kd are: red, 0.1 μM; blue, 1 μM; green, 10 μM; orange, 100 μM. The initial value of [P]t is 0.1 mM. (B) The calculated 1H/15N-HSQC cross-peaks of P during titration with L using Kd of (a) 0.1 μM, (b) 1 μM, (c) 10 μM, or (d) 100 μM. The cross-peak color changes gradually from blue to purple according to the [L]t/[P]t ratio. The black cross-peak indicates the bound state (PL).
Figure 2. Two-site binding model: one protein and two ligands. (A) The calculated 1H/15N-HSQC cross-peaks of P during titration with L using Kd,2 of 1 μM and Kd,1 of (a) 0.01 μM, (b) 0.1 μM, (c) 1 μM, or (d) 10 μM. The cross-peak color changes gradually from blue to purple according to the [L]t/[P]t ratio. The black cross-peak indicates the two bound states (PL and PL2). (B) The simulated titration curves for P (a: peak A; b: peak B in Figure 2A) with L as a function of [L]t/[P]t ratio using Eq. 29 (Kd,2 = 1 μM). The colors used to illustrate the Kd,1 are: red, 0.01 μM; blue, 0.1 μM; green, 1 μM; orange, 10 μM. The initial value of [P]t is 0.1 mM.
Figure 3. Two-site binding model: two proteins and one ligand. (A) The simulated titration curves for P with L as a function of [L]t/[P]t ratio using Eq. 44 (a: Kd,2 = 1 μM and various Kd,1; b: Kd,1 = 1 μM and various Kd,2). The initial value of [P]tis 0.1 mM. (B) The calculated 1H/15N-HSQC cross-peaks of P during titration with L using (a) Kd,2 of 1 μM and various Kd,1 values and (a) Kd,1 of 1 μM and various Kd,2 values. The cross-peak color changes gradually from blue to purple according to the [L]t/[P]t ratio. The black cross-peak indicates the two bound states (PL and P2L).
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