Neural nets, neuromorphic computing and other manifestations of artificial intelligence are popular topics these days. You might think of this as art (as in the art of computing) imitating life. What about the other direction – does life ever imitate art in this same sense? A professor at ASU’s Biodesign Institute thinks it can, in this case by building circuits using ribonucleic acid or RNA.
The 5-cent story on RNA is that this is the intermediary in synthesizing protein, ultimately from DNA. DNA doesn’t create proteins directly; instead when a cell needs to produce a certain protein, it activates the protein’s gene – the portion of DNA that codes for that protein – and produces multiple copies of that piece of DNA in the form of RNA. These are then used to translate the genetic code into protein. Thus, RNA expands the quantity of a protein that can be made at one time from a gene.
Researchers showed that they could develop a switch in synthesized RNA (called a toehold switch). As I understand it, this is an RNA sequence which is folded over on itself (as in the right picture above) with bases bonded to each other and thus disabled from synthesizing proteins. But when certain trigger RNA sequences are present and bind to the toehold switch, the folded-over structure breaks open and can synthesize proteins.
At the simplest level the trigger can be a single complementary RNA sequence, which might be part of the cell’s natural RNA. You could consider this a basic logic gate. Starting from this elementary capability, the team went on to develop and validate more complex logic functions where two or more complementary RNA sequences occurring in the cell were required to trigger the hairpin (the folded-over structure) breaking open. Impressively, they were able to construct a 12-input logic function using AND, OR and NOT functions (specifically (A1 AND A2 AND NOT A1*) OR (B1 AND B2 AND NOT B2*) OR (C1 AND C2) OR (D1 AND D2) OR (E1 AND E2)) as the trigger.
OK – impressive, but so what? The so what is that this allows for intelligent detection of toxins and other signals, which may require complex logic conditions to accurately diagnose. This would then trigger the switch and synthesize corrective proteins. Which promises cell-level response to disease diagnosis and correction, perhaps even as far as for cancer. An especially interesting aspect of this work is that viruses, from the common cold to Zika, use RNA to infect cells and are always stubbornly resistant to conventional anti-infection methods. This approach could could take the fight to viruses on their own turf.
Perhaps not as immediately exciting to this audience as electronics-based health solutions, but with a little widened perspective, why limit your logic design aspirations to silicon? To learn more, read HERE and HERE.