| The design and implementation of a synthetic genetic circuit analogous to a clocked Set-Reset latch is presented. The circuit consists of a pair of co-repressing transcription factors comprising a switch, and two input promoters used to change the state of the switch. The inputs are gated using terminator structures. The terminator activities are modulated by the intracellular level of an antitermination protein acting as the system clock. Deterministic and stochastic simulation models were used to predict the circuit's behaviour. The circuit was cloned into a pair of plasmids used to transform Escherichia coli bacteria. The circuit behaviour was monitored using the fluorescence signal from a green fluorescent protein that indicated the current latch state. Experimental characterization of the circuit did not confirm that the circuit met the design criteria. Plasmid copy number of the circuit was found to have a significant effect on latch state stability. |
