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A Red-Shifted Chlorophyll
Published 2010 · Chemistry, Medicine
Chlorophyll Sees Red Among the first facts students learn about the natural world is that plants owe their green color to the pigment chlorophyll. There have actually been a handful of slightly different chlorophyll variants uncovered over the years, and Chen et al. (p. 1318, published online 19 August) have found another in bacteria from Shark Bay, Australia. The chlorophyll variant displayed a red-shifted absorption spectrum, which extended into the near-infrared region due to the insertion of a formyl group on the molecule's periphery. The precise cellular function of the pigment awaits further study. A natural chlorophyll is found to absorb further in the infrared than other light-harvesting chromophores in its class. Chlorophylls are essential for light-harvesting and energy transduction in photosynthesis. Four chemically distinct varieties have been known for the past 60 years. Here we report isolation of a fifth, which we designate chlorophyll f. Its in vitro absorption (706 nanometers) and fluorescence (722 nanometers) maxima are red-shifted compared to all other chlorophylls from oxygenic phototrophs. On the basis of the optical, mass, and nuclear magnetic resonance spectra, we propose that chlorophyll f is [2-formyl]-chlorophyll a (C55H70O6N4Mg). This finding suggests that oxygenic photosynthesis can be extended further into the infrared region and may open associated bioenergy applications.