  Biochemical computing is an emerging field of unconventional computing that
attempts to process information with biomolecules and biological objects using
digital logic. In this work we survey filtering in general, in biochemical
computing, and summarize the experimental realization of an AND logic gate with
sigmoid response in one of the inputs. The logic gate is realized with
electrode-immobilized glucose-6-phosphate dehydrogenase enzyme that catalyzes a
reaction corresponding to the Boolean AND functions. A kinetic model is also
developed and used to evaluate the extent to which the performance of the
experimentally realized logic gate is close to optimal.
