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. 2008 Sep 16;6(33):393–400. doi: 10.1098/rsif.2008.0236

Figure 1.

Figure 1

A logic gate, such as the NAND gate shown here, can be easily implemented using a molecular system. In (a) the standard symbol for the (i) NAND gate and (ii) its Boolean table representation are shown. In (b) is shown an example of the molecular implementation based on two proteins (A and B, which can be present or absent) activating a given gene coding for a protein C which defines the output of the gate. Moreover, signalling cascades also allow defining logic blocks. In (c) we give an example of such scenario for our NAND system. Here a protein P can be activated if two inputs A and B (external signals) are present. In that case, it makes a transition P→P* to an active form. If C=[P] is the measured output, then a NAND gate is obtained.