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lundi 16 février 2004

Scientists at The Scripps Research Institute (TSRI) have constructed a single strand of DNA that spontaneously folds into a highly rigid, nanoscale octahedron. These clonable structures represent a breakthrough because they can be manipulated with the standard tools of molecular biology and can easily be cloned, replicated, amplified, evolved, and adapted for various applications. This opens the way to future nanotools and to the minuscule computers of tomorrow.

Before going further down, let's look at one of these clonable structures.

Here is an image of "a clonable DNA octahedron, roughly the size of a small virus, visualized using cryo-electron microscopy and single-particle reconstruction analysis. False colors indicate relative electron density." (Credit: Michael E. Pique, TSRI)

A clonable DNA octahedron
"Now we have biological control, and not just synthetic chemical control, over the production of rigid, wireframe DNA objects," says Research Associate William Shih, of TSRI, [who led the research with Professor Gerald Joyce, also from TSRI.]

So, how did they build this octahedron?

Similar to a piece of paper folded into an origami box, the strand of DNA that Shih and Joyce designed folds into a compact octahedron -- a structure consisting of twelve edges, six vertices, and eight triangular faces. The structure is about 22 nanometers in overall diameter.
Shih and Joyce constructed a 1669-nucleotide strand of DNA that they designed to have a number of self-complementary regions, which would induce the strand to fold back on itself to form a sturdy octahedron. Folding the DNA into the octahedral structures simply required the heating and then cooling of solutions containing the DNA, magnesium ions, and a few accessory molecules. And, indeed, the DNA spontaneously folded into the target structure.

And what will we do with these structures?

The DNA octahedra could possibly form scaffolds that host proteins for the purposes of x-ray crystallography, which depends on growing well-ordered crystals composed of arrays of molecules.
Another potential application is in the area of electronics and computing. Computers, which rely on the movement and storage of charges, can potentially be built with nano-scale transistors, but one of the big challenges to accomplishing this is organizing these components into integrated circuits. Structures like the ones that Shih and Joyce have developed might someday guide the assembly of nanoscale circuits that extend computing performance beyond the limits set by silicon integrated circuit technology.

So we are quite far from any real products.

Anyway, the research work, "A 1.7-kilobase single-stranded DNA that folds into a nanoscale octahedron," has been published by Nature on February 12, making the cover. You also can read the abstract.

Sources: The Scripps Research Institute, February 11, 2004; Nature, February 12, 2004

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