INSPIRED BY PHOTOSYNTHESIS, ENGINEERS LONG AGO devised photovoltaic chips, or solar cells, that convert sunlight into electricity. But plants don't run on electricity. They rely instead on a special kind of chemical energy using ATP (for adenosine triphosphate) to fuel growth and reproduction.
At Arizona State University in Tempe, chemistry professors Thomas and Anna Moore and Devens Gust are pursuing a new approach to artificial photosynthesis--one that comes a lot closer than solar cells to what plants actually do. They devised a membrane that produces ATP when exposed to light. Their feat is featured in the Apr. 2 issue of Nature. The membrane is made from fatty molecules, called lipids, that are infused with synthetic compounds. When these chemicals absorb light, they pump hydrogen ions, or protons, across the membrane and through an enzyme derived from spinach. And this enzyme uses the proton energy to synthesize ATP.
Many hurdles remain before such a device could become useful to industry, including high costs. But someday, a membrane like this could provide energy for the synthesis of drugs or other useful proteins inside artificial cells. "Electrical energy has more than 100 years of history behind it," Thomas Moore points out. Proton-based energy, in contrast, "is still something that's unknown outside of living cells."