Surface plasmon resonance detection. Parameters of association and dissociation for rTapA-His and rTapB-His with rTprA were determined by surface plasmon resonance analysis (Biacore). Sensorgrams for the binding of rTapA-His or rTapB-His to rTprA immobilized on a CM5 sensor chip were overlaid at various concentrations of rTapA-His or rTapB-His. rTapA-His, rTapB-His, or bovine serum albumin (BSA) was injected at concentrations of 0.016, 0.08, 0.4, 2, and 10 mM. The Kd values of binding of rTprA to rTapA-His and rTapB-His were 1.89 × 10−4 M and 1.42 × 10−6 M, respectively. RU, resonance units.