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article imageScientists create genetic transistors for biological computers

By JohnThomas Didymus     Mar 30, 2013 in Science
A team at Stanford say they have created a biological transistor. Transistors are the basic units used to build computers. A biological transistor is thus the first step toward building biological computers that can be incorporated into living systems.
The researchers, in a paper titled "Amplifying Genetic Logic Gates," published in the journal Science on Friday, 28 March 2013, described their invention of a system of genetic transistors which they dubbed "transcriptors," which they say can be incorporated into biological cells and programmed such that when certain prescribed conditions are met they could turn on to make a cell or group of cells perform specific functions such as directing self-destruction of cancerous cells.
According to the researchers, the achievement means that in the future engineers will be building and incorporating biological computers into human bodies that monitor activities at the cellular level, store information and mediate defensive responses to pathological changes in the body, such as making a cell stop producing insulin or causing a cancerous cell to self-destruct.
The implication of the research is that in the future it will be possible to fit humans with biological computers inside their cells that could monitor the internal environment for build up of toxins and other conditions indicative of development of disease.
The biological computers could be programmed to screen for cancer, infections or even turn cell reproduction on and off.
According to Extreme Tech, the biological transcriptor is essentially the biological analog of the digital transistor. Just as transistors control the flow of electricity in a circuit, transcriptors control flow of RNA polymerase along DNA using enzymes.
Jerome Bonnet, one of the researchers, said: "The choice of enzymes is important. We have been careful to select enzymes that function in bacteria, fungi, plants and animals, so that bio-computers can be engineered within a variety of organisms."
The researchers are optimistic that their biological transistor or "transcriptor" would eventually become the basis of living computers of the future incorporated into living systems to perform vital tasks that will revolutionize the medical sciences.
Lead researcher Drew Endy, explained to San Jose Mercury News: "We're going to be able to put computers into any living cell you want. We're not going to replace the silicon computers. We're not going to replace your phone or your laptop. But we're going to get computing working in places where silicon would never work."
Mercury News reports that UC Berkeley biochemical engineer Jay Keasling, said that the work "clearly demonstrates the power of synthetic biology and could revolutionize how we compute in the future."
The power of biological computers in application to solving medical problems is that they can be programmed to provide true-false answers to practically any biological question that a physician may pose about the internal environment indicative of disease. They can also be used as "counters" to monitor growth of cancerous tissues.
The video above is a tutorial by Endy that explains how transcriptors and "transcriptor-enabled genetic logic" work. It is also a primer detailing the basics of their paper "Amplifying Genetic Logic Gates."
The researchers have demonstrated the application of their new invention using E. Coli bacteria. The researchers explain in their study abstract:
"We developed a three-terminal device architecture, termed the transcriptor, that uses bacteriophage serine integrases to control the flow of RNA polymerase along DNA... We realize permanent amplifying AND, NAND, OR, XOR, NOR, and XNOR gates actuated across common control signal ranges... The single-layer digital logic architecture developed here enables engineering of amplifying logic gates to control transcription rates within and across diverse organisms.
The abstract illustrates that transcriptors work like transistors in electronic circuits which amplify signals enabling a small current to turn on a larger one. Transcriptors will perform the function of signal amplification such that a small change in an enzyme activity can activate amplifying logic gates that control transcription rates in biological organisms.
But as Extreme Tech points out:
You need more than just...[logic] gates to make a computer, though. You also need somewhere to store data (memory, RAM), and some way to connect all of the transcriptors and memory together (a bus)...
According to Mercury News, the researchers explain that their genetic transcriptor is the third and final component in a 10-year research project to deliver the essential building blocks of a biological computer.
Last year, the team delivered the two other essential components needed to build a biological computer. Mercury News reports:
The first was a type of rewritable digital data storage within DNA. Information can be stored inside cells by flipping DNA sequences back and forth between two possible orientations to represent and store "0'' and "1'' that represent one "bit' of computer data. The other was a mechanism for transmitting genetic data from cell to cell, a biological Internet.
Now that the researchers have devised the biological analog of an electronic transistor what is now required is further R&D to put the building blocks together into functional biological computers.
The researchers said that implanting biological computers into living systems could help information gathering not only about the biological systems but also their environment. Endy explained: "For example, suppose we could partner with microbes and plants to record events, natural or otherwise, and convert this information into easily observed signals. That would greatly expand our ability to monitor the environment."
Endy and his colleagues have published some of their work under a public domain license in the hope that it will stimulate research studies to the goal of functional biological computers
More about transistors, Cells, Computers, biological computers
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