Biological systems that capture the energy in sunlight and convert it to the energy of chemical bonds come in many varieties, but they all have two basic parts: the light harvesting complexes, or antennae, and the reaction center complexes. The antennae consist of many pigment molecules that absorb photons and pass the excitation energy to the reaction centers.
In the reaction centers, the excitation energy sets off a chain of reactions that create ATP, a molecule often called the energy currency of the cell because the energy stored ATP powers most cellular work. Cellular organelles selectively break those bonds in ATP molecules when they need an energy hit for cellular work.
Green bacteria, which live in the lower layers of ponds, lakes and marine environments, and in the surface layers of sediments, have evolved large and efficient light-harvesting antennae very different from those found in plants bathing in sunlight on Earth's surface.
The antennae consist of highly organized three-dimensional systems of as many as 250,000 pigment molecules that absorb light and funnel the light energy through a pigment/protein complex called a baseplate to a reaction center, where it triggers chemical reactions that ultimately produce ATP.
In plants and algae (and in the baseplate in the green bacteria) photo pigments are bound to protein scaffolds, which space and orient the pigment molecules in such a way that energy is efficiently transferred between them.
But chlorosomes don't have a protein scaffold. Instead the pigment molecules self -assemble into a structure that supports the rapid migration of excitation energy.
This is intriguing because it suggests chlorosome mimics might be easier to incorporate in the design of solar devices than biomimetics that are made of proteins as well as pigments.
The goal of the work described in the latest
|Contact: Diana Lutz|
Washington University in St. Louis