  Living cells communicate information about physiological conditions by
producing signaling molecules in a specific timed manner. Different conditions
can result in the same total amount of a signaling molecule, differing only in
the pattern of the molecular concentration over time. Such temporally coded
information can be completely invisible to even state-of-the-art molecular
sensors with high chemical specificity that respond only to the total amount of
the signaling molecule. Here, we demonstrate design principles for circuits
with temporal specificity, that is, molecular circuits that respond to specific
temporal patterns in a molecular concentration. We consider pulsatile patterns
in a molecular concentration characterized by three fundamental temporal
features - time period, duty fraction and number of pulses. We develop circuits
that respond to each one of these features while being insensitive to the
others. We demonstrate our design principles using abstract Chemical Reaction
Networks and with explicit simulations of DNA strand displacement reactions. In
this way, our work develops building blocks for temporal pattern recognition
through molecular computation.
