Published 28 June 2011
Jean-Marie Lehn: an evolutionary chemist
Between the laws of the universe and the rules of life lies a bridge. That bridge, said Nobel laureate Jean-Marie Lehn today, is chemistry.
Lehn made his point by asking a simple and intriguing question at the start of his lecture: how does matter become complex? How did elementary particles eventually gave rise to the thinking organisms that we are?
The answer is self organization, said Lehn. Elementary particles join to form atoms on their own, just like ants join to form a colony. In between the atom and the organism, there’s chemistry.“Chemistry is all about making keys for locks and locks for keys”, is how Lehn defined his scientific discipline. And it is true: chemists design and make molecules so that they fit and bind to other ones, just like the keys that fit in their locks.
Being the clever chemist that he is, Lehn took this approach one step further. Given the right set of molecules, he showed, the molecules can self-assemble into a larger structure, without any tinkering on the chemist’s part. He gave several examples of such self-organizing structures that he has made this way, such as molecular grids and nanocylinders. All it took for the nanoscopic cylinder to form was a mix of three linear molecules, four flat ones and 12 ions.
Designed self-organizing systems only have one problem: they are still limited by the imagination of the designer. Lehn has also worked on a way to self-assemble complex molecules in a truly dynamic way, based on the evolutionary principles of variation and selection.
Genetic variation and natural selection are evolution’s powerful duo. Taken together, they ‘produce’ organisms that fit to their respective environments. In a chemical setting, the genetic variation is mirrored by the diversity of molecules in the initial mix. This library of molecules should be sticky to some degree, but they shouldn’t bind each other so tightly that all evolvability is gone. Natural selection is replaced by artificial selection: the experimenter can select for anything he wants to select for.
Lehn gave the example of creating a drug that binds to a specific enzyme. In this example, the enzyme is the ‘lock’ while the drug is the ‘key’. As the keys mutate into different keys, the enzyme will eventually recognize and bind the key that fits best: the drug is self-assembling. The power of this approach ithout knowing what kind of key will fit best, and without building millions of different keys, the one that fits is still found.
There is not a single class of molecules that is required in evolutionary chemistry. In his talk, Lehn mentioned dynamic peptides, carbohydrates and polynucleotides. As with biological evolution, the possibilities of chemical evolution seem endless. Let the molecules evolve!
Today’s lecture by Jean-Marie Lehn: