Biological Logic Gate II: Electronic GENOsensor

I am quite excited to see yet another biological logic gate article in ChemComm – this time a more biochemical favour. The system is also an AND gate. The inputs are contributed by 2 genes, gyrB and K-ras (this one is a famous oncogene), and the output is presented by the I/V characteristic.


Figure 1. The Basic Principle.

Here is how the system works (Figure 1). At the beginning, the two strands of DNA are restricted in closed loop structures, and they are known as ‘hairpins’. The 2 redox tags (MB and Fc) positioned on them can transfer 2 respective electrons to a proximal electrode (colored in yellow in the figure). If for some reason, the hairpin is released to become a straight strand, the redox tag is too far away to transmit the electron to the electrode, and a decrease in intensity of the I/V plot will be observed. This ‘proximity effect’ is indeed very common in molecular biology, and I believe my biological readers are definitely aware of something called ‘FRET’.

This is where the ‘logic’ comes into play: when the 2 corresponding single-stranded DNA comes to bind with each of this hairpin, the effect will the release of the hairpin and a decrease of I/V will be the output. For course, the output will be ‘1’ if both single-stranded DNAs (inputs) are present to release the two hairpins (outputs). The observed I/V characteristics on Figure 2 clearly illustrates the action of the genosensor. Impressive!


Figure 2. The work of the AND Genosensor.


Reference:

A reagentless and disposable electronic genosensor: from multiplexed analysis to molecular logic gates
Yun Xiang, Xiaoqing Qian, Ying Chen, Yuyong Zhang, Yaqin Chai and Ruo Yuan
Chem. Commun., 2011, Advance Article
DOI: 10.1039/C0CC04350H