All-DNA finite-state automata with finite memory

Biomolecular logic devices can be applied for sensing and nanomedicine. We built three DNA tweezers that are activated by the inputs H+/OH-; Hg2+/cysteine; nucleic acid linker/complementary antilinker to yield a 16-states finite-state automaton. The outputs of the automata are the configuration of the respective tweezers (opened or closed) determined by observing fluorescence from a fluorophore/quencher pair at the end of the arms of the tweezers. The system exhibits a memory because each current state and output depend not only on the source configuration but also on past states and inputs.