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MIT Team Creates Mutating Molecule

In a step toward synthetic "life," Professor Julius Rebek and colleagues in chemistry have created molecules that can both reproduce themselves and mutate, or change their form in response to an environmental stress.

The work, reported in Science last month, "provides a model for evolution at the molecular level and brings synthetic life closer to reality," said Professor Rebek, the Camille Dreyfus Professor of Chemistry. His colleagues in the work, which is supported by the National Science Foundation, are postdoctoral associate Jong-In Hong, graduate student Qing Feng, and postdoctoral fellow Vincent Rotello.

The research was also reported in Chemical & Engineering News last month. C&EN said that "In the MIT experiments, two replicating molecules that are structurally very similar are allowed to compete for a limited amount of material from which they are both made." The molecules reproduce themselves, catalyzing their own replication and each other's.

Upon irradiation with ultraviolet light, one of the molecules mutates to form a third type that is more effective than either of the two original molecules at gobbling up the chemicals it needs to reproduce.

Specifically, the molecule that mutates contains a nitro group that is cleaved from the molecule when exposed to ultraviolet light.

Two years ago another group led by Professor Rebek created molecules capable of reproducing themselves. At the time, the next step was to create molecules that could both reproduce themselves and mutate-two of three criteria for Darwinian evolution and a goal achieved in the current work.

But to be considered truly "lifelike," the molecules must meet the third criterion of Darwinian evolution: natural selection, or competition among mutants resulting in a superior molecule that can pass on its characteristics to "offspring."

As noted in the C&EN article, however, natural selection requires at least two mutants, and the Rebek group has only one. As a result, they are currently working to create others.

The magazine concluded its story with a prediction from biochemist Gerald F. Joyce of the Scripps Research Institute: "By the end of this decade, someone-and the odds are good it will be Rebek-is going to make a self-sustained chemical system capable of undergoing Darwinian evolution."

A version of this article appeared in the March 11, 1992 issue of MIT Tech Talk (Volume 36, Number 23).

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