July 2, 2006
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Scientific American (05/06) Vol. 294, No. 5, P. 44; Shapiro, Ehud; Benenson, Yaakov
Computers composed of biological molecules do not seem so far-fetched in consideration of the fact that natural molecular machines process information in much the same manner as the Turing machine. Both the Turing machine and natural automata have demonstrated the ability to store data in strings of symbols, process these strings in a stepwise pattern, and modify or add symbols in keeping with fixed rules. DNA and enzymes assembled into a Turing-like automaton can carry out computations, receive input from other molecules, and produce a discernible output, such as a signal or a therapeutic drug. This organic device illustrates the feasibility of the concept and could find useful application as a medical tool. In a DNA computer, the ribosome reads data encoded in gene transcripts, or messenger RNAs (mRNAs), and converts it into amino acid sequences to form proteins; mRNA's symbolic alphabet consists of nucleotide trios or codons that each correlate to a specific amino acid. The ribosome processes the mRNA strand on a codon-by-codon basis, and the proper amino acid is delivered by transfer RNA (tRNA) molecules, which verify the codon match and then release the amino acid to join the expanding chain. Scientists Ehud Shapiro and Yaakov Benenson created an autonomous, programmable molecular computer that could run itself on its input molecule and theoretically process any input molecule with a fixed number of hardware and software molecules without ever running down, and they have outlined a biomolecular Turing machine that harnesses the molecules' ability to identify symbols and assemble molecular subunits together. Once they proved that DNA/enzyme automata can perform abstract yes-or-no computations, the scientists developed a device that can determine whether disease indicators are present and release a drug molecule if the diagnosis is positive.
For the complete article, see http://www.sciam.com/
Posted by rab5 at 12:51 PM
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