Bio-Computer Closer with Molecular Transistors

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Crunching data on conventional computers requires electrons. But scientists have been working toward biological computers that can store, retrieve and process data using chemical reactions.

To that end, Jerome Bonnet, a postdoctoral scholar in bioengineering at Stanford University, and his colleagues report today in the journal Science building a transistor out of DNA and RNA. Their research brings bio-computers one step closer to reality. Such devices would not look like the silicon-based computers we know and use today. There would be no keyboard or monitor. Instead, the computations would happen inside a living cell.

In a press release from the university, Drew Endy, assistant professor of bioengineering and the paper’s senior author said, “Biological computers can be used to study and reprogram living systems, monitor environments and improve cellular therapeutics.”

The bio-computers could be used not only to precisely test drug reactions inside a cell, for example, but could do so over a particular time period and save the information for retrieval or retesting later.

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The component Bonnet and his team developed is a transistor, a device essential to every computing device. In silicon-based computers, transistors control the flow of electrons over a circuit, a simple action that produces the 1s or 0s of binary code — the basic units of information in a computer. Two transistors together form a logic gate, which is what allows a computer to manage mathematical operations.

A typical computer chip has millions of transistors.

The Stanford team’s biological transistor uses enzymes — or integrases — to control the flow of specific protein, RNA polymerase, as it travels along a strand of DNA. Linking multiple transcriptors together creates logic gates that allow for both information storage and logical operations. This transcriptor is the third and final component necessary to making the biological computer.

The other two components — storing information within DNA and transmitting information from cell to cell — were developed in Endy’s lab last year. With this third ability of performing logical operations, the scientists have all three basic elements of a working computer. One that works inside a cell, that is.

By controlling the flow of RNA, the transcriptor is able to produce a kind of binary code, the 1s and 0s that make up “Boolean logic.” That ability could help scientists test whether cells have been exposed to a drug and if so, how that drug was distributed among the cells. Such a system could also be used to tell whether cells have started or stopped dividing when exposed to particular drug.

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Bonnet’s transcriptors could also amplify signals. In conventional electronics that send or receive radio signals, transistors are used to amplify signals. Transcriptors could be used in a similar way to amplify a gene that codes for a certain protein, for example.

This means that cells could be manipulated a lot more precisely, making biotechnology a much more exact science.

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