A small peptide catalyst combines light absorption with recognition of the molecule entering a reaction. In a peer-reviewed laboratory study, four amino acids positioned these functions to favour one mirror-image molecular form. Different spatial arrangements gave different selectivity, and cooling improved some reactions. The experiments demonstrate a compact chemical design, without establishing industrial-scale manufacture or the overall energy budget.
Four-amino-acid peptides selected between mirror-image molecular forms in light-driven reactions. The peer-reviewed laboratory study places a molecule-recognition component at one end of the catalyst and a light-absorbing component at the other. Two amino acids connect the ends, arranging the interacting parts within a small chemical structure.[1], [2]
Pyroglutamic acid holds the reacting molecule through hydrogen bonds, while a thioxanthone-containing amino acid absorbs light and transfers energy to it. Proline and aminoisobutyric acid form the connecting backbone. Of four arrangements tested, the configuration called 6a was selective, whereas the others performed poorly. Nuclear magnetic resonance measurements and molecular dynamics calculations examined how the active components were positioned.[1]
Experiments used light-emitting diodes at 425 nanometres for deracemisation, which enriches one mirror-image form, and ring-forming cycloaddition reactions. The first allene example exceeded 99 per cent yield with a 96:4 ratio between the two forms. Some other products reached ratios of 95:5–98:2. Cooling to minus 70 degrees improved selectivity.[1]
Experiments were performed at a scale of 30 micromoles, with some setups using dichloromethane solvent. In one experiment, 70 per cent of the catalyst was recovered. The work demonstrated a compact design joining molecular recognition and light harvesting; industrial scale-up, energy consumption and overall environmental effects were not compared.[1]
