To evaluate the interaction of the peptide with C1q by SPR, we utilized a BI-3000 instrument to measure the affinity of three inhibitory peptides E23A, Δ8-22, and PA (ligand) with human C1q (analyte). The peptide ligands were immobilized on a dextran coated sensor chip with PBS running buffer. The analyte binding was measured in PBS-Tween 20 (0.01%) at a flow rate of 20 µL/min. Surface regeneration after C1q injection was accomplished by injecting 10 mM NaOH. The mean equilibrium dissociation constants (KD) were 6.08 nM for E23A, 5.43 nM for?8-22, and 33.3 nM for PA (Table 1), respectively. Figure 2 depicts the SPR sensorgrams, which were fitted by the 1:1 model with the mass transport.
