A University of Washington-led team, including Nobel Laureate David Baker, developed a generalizable molecular on/off protein switch that modulates binder dissociation rates by up to 6,000-fold, enabling precise timing of cytokine signaling. This methodological leap focuses on controlling interaction kinetics rather than just binding affinity, with applications demonstrated in IL-2 signaling to reduce toxic side effects. The advance could revolutionize safer, real-time drug activation and biosensing.