Binding of defensin to Lp(a) and its components assessed using the optical biosensor. Defensin (9 nmol/L to 10 μmol/L) was incubated with immobilized Lp(a) (5,000 RU; A) or its components: LDL (445 RU; B), native apo(a) (1,400 RU; C), and recombinant apo(a) (900 RU; D). The interaction of defensin with a high surface density of immobilized BSA (2,400 RU) is shown in the insert to (D). Both the association and dissociation phases are shown. The inserts in (A) through (C) show both dR/dt × R plots (at 5 μmol/L defensin) and the binding isotherms at equilibrium to each component.