BLOOMINGTON, Ind. -- Chemists at Indiana University Bloomington have designed a molecule that binds chloride ions -- but can be conveniently compelled to release the ions in the presence of ultraviolet light.
Reporting in the Journal of the American Chemical Society today (online), IU Bloomington chemist Amar Flood and Ph.D. student Yuran Hua explain how they designed the molecule, how it works and, just as importantly, how they know it works.
"One of the things we like most about this system is that the mechanism is predictable -- and it functions in the way we propose," said Flood, who led the project.
Chloride is a relatively common element on Earth, ubiquitous in seawater and in the bodies of living organisms.
"We have two main goals with this research," Flood said. "The first is to design an effective and flexible system for the removal of toxic, negatively charged ions from the environment or industrial waste. The second goal is to develop scientific and even medical applications. If a molecule similar to ours could be made water soluble and non-toxic, it could, say, benefit people with cystic fibrosis, who have a problem with chloride ions accumulating outside of certain cells."
Many organic molecules exist that can bind positively charged ions, or cations, and this has much to do with the fact that it is easy to synthesize organic molecules with negatively charged parts. Synthesizing organic molecules that bind negatively charged ions, or anions, like chloride, presents special challenges.
The binding molecule or "foldamer" Flood and Hua designed is both a folding molecule and a (small) polymer, meaning the foldamer's constituent parts can be synthesized with relative ease. Under visible light of 436 nanometers (nm), the foldamer prefers a tight spiral structure that allows specially configured residues to interact with each other, which improves stability, and creates an attractive pocket f
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