Our bodies are made up by hundreds of billions of cells and now researchers at Stanford have managed to create a (sort of) computer that goes inside a cell and uses molecules available in the cell itself for performing computations.
Any computer has to carry out three basic operations: store data, transmit data and process data. The Stanford team made the news last year by succeeding to perform the first two operations using cellular processes and molecules. Now they have announced in a paper, published on March 28th on Science, to have succeeded in implementing the third missing part: create a functioning processing unit within the cell.
The basic processing unit in a computer is a XOR logic gate. If you can do a XOR operation you can do any other operation you can dream of. If you want to dig into the properties of XOR and how to combine it to perform any kind of processing you can read the explanation on Wikipedia.
You can see the basic scheme of this “processor” on the left. What the researchers did was to find out a way to use DNA and RNA to create this logic gate. They have called this a “transcriptor”, and it is a sort of biological transistor. It works using a well calibrated mixture of enzymes, and the researchers have chosen those that can be found normally in bacteria and other living cells so that indeed this transcriptor can operate inside a living cell.
A very weak signal that may not lead to the activation of a gene when processed by the transcriptor gets amplified (similarly to what happen in a transistor that amplifies and electrical signal) and therefore can activate the gene(s).
According to the researchers this transcriptor can be used to assess the presence of certain compound in a cell, and remember it for later use, it can tell a cell, on command, to produce a certain protein by activating a specific gene and so on. Actually, they claim the the range of applications is so broad that it is impossible to be defined by a single group and this is why they have opened up the results of their work by placing it in a public domain to let other teams to further polish the method and come up with other applications.