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Materials

Shaken And Stirred Self-Replication

Different-sized molecules can come from one combinatorial library, depending on the agitation method

by Stu Borman
March 22, 2010 | A version of this story appeared in Volume 88, Issue 12

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In a dynamic combinatorial chemistry system, oxidation of an aromatic dithiol (left) yields a variety of macrocycles, including the hexamer (right).
In a dynamic combinatorial chemistry system, oxidation of an aromatic dithiol (left) yields a variety of macrocycles, including the hexamer (right).

Different self-replicating molecules can be synthesized from the same dynamic combinatorial library, depending on whether the starting solution is shaken, stirred, or unagitated, researchers find (Science 2010, 327, 1502). Sijbren Otto of the University of Groningen, in the Netherlands, and coworkers oxidized a peptide-derivatized aromatic dithiol, inducing it to oligomerize via disulfide formation into macrocycles of various size, which were in equilibrium with one another. Some of the macrocycles stack noncovalently, forming fibers that remove them from the equilibrium. When the dithiol solution is left alone, small macrocycles form, but fibers and larger macrocycles, such as hexamers and heptamers, do not. When the solution is shaken, hexamers and hexamer-based fibers dominate. And when the solution is stirred, which generates greater shear stress, heptamer and heptameric-fiber formation is favored. “I’m not aware of previous studies that show any differences between shaking and stirring in the outcome of a covalent synthesis,” Otto says. The researchers believe mechanosensitive self-assembly represents a promising method for the discovery of self-replicating molecules, self-synthesizing materials, and noncovalent polymers.

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