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Self-assembly now easier to control

14 May 2009 NWO (Netherlands Organization for Scientific Research)

Researchers regulate the formation of G-quadruplexes

Nature has long perfected the construction of nanomachines, but David González and his fellow researchers from Eindhoven University of Technology and Utrecht University under the leadership of Spinoza Award winner Bert Meijer, have brought the construction of artificial supramolecular structures a step closer by. The researchers managed to carefully control the self-assembly of guanosine, one of the building blocks of our DNA. Their research results were published by Nature Chemistry on 19 April.

The natural world is a shining example when it comes to the self-assembly of molecules. However, it has not disclosed all of its secrets yet. Controlling the shape and structure of self-assembled systems continues to be a stumbling block for scientists. Yet such structures, in which the different molecules cooperate with each other, can have unrivalled characteristics. Self-assembly could provide the way forward for the future mass production of nanomaterials, nanodrugs and nanoelectronics.

Control

A quadruplex of four DNA strands is an example of such a self-assembling structure. Guanosine molecules bind together to form such a G-quadruplex. The researchers managed to influence the formation of G-quadruplexes, using Coulombic interactions. They produced structures with 8, 12, 16, or even 24 guanosine molecules.

During the formation of G-quadruplexes, positively charged alkali metal ions are incorporated in the interior of the structure. Negatively charged anions, however, fall on the outside of the structure and are therefore exposed to the surrounding medium. Coulomb's law describes the forces that two electrical charges exert on each other. According to this law, that force depends on the distance between the negatively and positively charged ions and on the stabilising characteristics of the solution in which the self-assembly takes place. The negatively charged ions on the outside of the structure are of course exposed to this solution, as a result of which the solution determines the stability of the structure to a large extent.

By varying the two different factors, distance and solution, the researchers could regulate the formation of the G-quadruplexes. For example, they could build structures with different numbers of molecules. A structure with exactly 24 guanosine molecules had not previously been artificially constructed. This new perspective therefore provides opportunities for the regulation of self-assembling structures.

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