Real-time kinetic analysis of interaction between interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R) using a resonant mirror optical biosensor

The real-time kinetic analysis of the interaction between interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R) was carried out by a resonant mirror optical biosensor, lAsys. The experimental results showed that the immobilization mass of sIL-2R was 0.42 ng mm(-2). IL-2 could specifically bind sIL-2R. The interaction response is dose-dependence of IL-2 in solution with a range of 150-2400 nM. Kinetic constants for IL-2 binding to sIL-2R were determined from the plots of the apparent association rate constant, K-on, versus the concentration of IL-2. For the interaction, k(ass) was 3.3 x 10(3) M-1 s(-1), k(diss) was 1.7 x 10(-3) s(-1), and K-D was 5.1 x 10(-7) M.