Self-made molecules do the double twist.

Self-made molecules do the double twist

Since the 1950s, when scientists uncovered the molecular structure of DNA, the double helix has symbolized biological phenomena as minute as a fruit-fly's eye and as grandiose as evolution. No wonder some chemists focus on making molecules to interact with such celebrity biochemicals or mimic their structures.

In the July 26 NATURE, Jean-Marie Lehn of the Universite Louis Pasteur in Strasbourg, France, and co-workers describe how they coaxed molecular segments to self-assemble into double-helical molecules with DNA-like appendages.

Several years ago, Lehn and other co-workers first reported making the frameworks that underlie these new, more complex molecules. Their twisty frameworks begin as pairs of pyridine molecules (benzene-like hexagonal rings containing a nitrogen atom) joined like Siamese twins and linked to other pairs via short organic 'spacer' units. Chains of these linked pyridine twins spontaneously braid into double helices around copper ions.

In their latest work, Lehn and his co-workers integrate biologically important molecules such as the nucleoside thymidine -- part of one of DNA's four nucleotide building blocks -- into the helical backbone.

Though nucleosides reside within DNA's double-helix backbone, they point out from the double-helical spine of Lehn's new synthetic structures. In a commentary that accompanies the report, chemist and artificial-helix maker Edwin C. Constable, of the University of Dundee in Scotland, describes the synthetic molecules' structure as a "curious 'inside-out' analogue to that of DNA." Unlike DNA, which overall carries a negative charge, Lehn's compounds are positively charged.

The new synthetic structures offer a means for studying how natural and lab-made double helices form and bind to other molecules, such as DNA. Constable speculates that double helices built around heavier metals, such as ruthenium or platinum, might bond to specific portions of nucleic acids, permitting researchers to "eavesdrop" on, says, drug-DNA interactions. These structures might even serve as light-activated "molecular-mines" that could destroy malfunctioning regions of DNA, he told SCIENCE NEWS.