DNA computers are becoming more complex

Researchers from the University of Liege (Belgium) and the Hebrew University of Jerusalem (Israel) have created a logic gate – the basic element of a digital circuit performing an elementary logical operation – based on DNA molecules.

The logic gate outputs one or another output signal depending on the input signals.

In this case, scientists managed to implement logic gates that perform various logical functions, in particular, the "exclusive OR" function. Such a logic element generates an output signal ("1") if the values of the signals at its two inputs do not match: there is a signal at one input ("1"), and there is no signal at the other ("0").

The key elements of the system were complementary DNA strands, which form a strong connection with each other. To directly observe the signals coming in at the input and output, the scientists attached fluorescent molecules to them. When only one strand was present at the entrance, the molecule emitted a glow, and when there were two strands, their fluorescence was mutually extinguished. Molecules were added to each of the two complementary strands, which fluoresced (and represented the value "1" at the output) when the strands were separated from each other. If both filaments were fed to the input, the fluorescence was suppressed when they were combined, which corresponded to the zero output value. 

In addition to creating a single working logic gate, scientists have also obtained a system of sequentially operating valves that implement various logical functions:

Truth table and fluorescence intensity
for elements AND (right) and OR-NOT (left).
The letters a, b, c, d correspond to the 1, 2, 3 and 4 rows of the table.
(Illustration by the authors of the work.)

The authors tested in vitro how useful the device they created could be for medicine. Scientists have linked a logic gate with a molecule capable of inactivating thrombin, an enzyme that causes blood clotting. Normally, blood clotting allows you to avoid bleeding, but with cardiovascular diseases, the blood clots that form pose a serious danger to human life. In the scheme created by scientists, the thrombin inactivator was released only if the valve "bumped" into the enzyme.

The results of the work are published in the journal Nature Nanotechnology (Johann Elbaz et al., DNA computing circuits using libraries of DNAzyme subunits), a short summary (DNA logic gates herald injectable computers) – in the journal NewScientist.

Theoretically, the development of this work could lead to the creation of a DNA computer capable of working inside the body and, for example, regulating the release of drugs, releasing them only where necessary.

Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the Tape.<url> and "Compulents"03.06.2010