Self-assembling molecular receptors.

Self-assembling molecular receptors

In the crowded chemical brew of every living cell, molecular and atomic subunits find each other and assemble into functioning enzymes, ribosomes -- the organelles that link amino acids into proteins -- and other cellular occupants. The elegance and efficiency of this self-assembly tactic, which cells mastered billions of years ago, has long captured chemists' admiration. Yet not until about a decade ago did scientists begin emulating the process in their laboratories.

For the most part, such efforts have focused on large components that combine to form even bigger molecular systems, which bind, for instance, charged atoms such as sodium or potassium ions. Scientists hope to use these so-called ionophores for such purposes as scavenging and removing sodium ions from complex solutions while leaving other kinds of ions behind.

Now, chemist Alanna Schepartz of Yale University and chemistry graduate student Jason P. McDevitt, who began the project as a Yale undergraduate, report developing self-assembling ionophore systems out of much smaller molecular subunits. The system's simplicity should allow finer structural and functional control than is possible with large systems, Schepartz says.

Nickel ions dissolved in chloroform serve as attractants for the molecular components also in the solution, she explains. The ring-shaped part of two of these molecules sticks to the nickel ion. Oxygen-containing molecular arms, whose length the chemists can control, stem from each ring and reach toward each other to form variously sized enclosures that embrace different ions with differing readiness.

In future studies, Schepartz says, she expects to design peptide-containing receptors by attaching short amino acid sequences to the rings.