|
Researchers at the Bio-SANS are using this new LED lighting tool to study the light response of the membrane stacks in blue-green algae found in almost every environment. Photo: Oak Ridge National Laboratory
|
Researchers at the Bio-SANS instrument at
the High Flux Isotope Reactor are getting a leg up in their research from a
"low tech" lighting tool that can be fixed to their samples and then
pushed directly into the neutron beam, to illuminate the response of layers of
cyanobacteria to changes in light.
"It's really low tech," says
Volker Urban, lead instrument scientist on the Bio-SANS, with a grin. "You
can buy the parts anywhere." The lighting tool is the work of graduate
student Brad O'Dell, a visiting intern from Cambridge University.
The device combines light-emitting diodes (LEDs) with the electronics that
drive the illumination.
Parts off the shelf it may be, but the
device facilitates research into biologically inspired solar cell devices,
important alternative energy-related research being conducted with funding from
the Photosynthetic Antenna Research
Center one of the Energy Frontier
Research Centers in the US.
Photosynthesis is the process by which
plants convert sunlight into energy. Bacteria, algae, and plants have natural
sensors called light-harvesting antenna systems that capture the sun's light
and transfer the energy to reaction centers, where the electron transfer for
photochemistry occurs. Such antenna complexes are highly specialized in nature,
allowing organisms to capture the maximum light energy available in their
environment.
Researchers at the Bio-SANS are now using
the new LED lighting tool to study the light response of the membrane stacks in
cyanobacteria, a blue-green algae found in almost every environment, from
oceans to fresh water to bare rock to soil.
At the Bio-SANS, the bacteria are loaded
into cuvettes, small sample holders that resemble tiny transparent banjos. An
LED is fixed to the top of each cuvette. The array is then pushed into the
sample holder and the neutron beam passes through a window, taking
"pictures" of the response of the layers of the bacteria to
variations in light from the attached LEDs.
"We push the samples into the neutron
beam—and then from the neutron scattering we can observe how the structure
changes, depending on how much light of which color we shine on the
samples," Urban says. "Ultimately, we want to find out how nature has
solved the problem of optimizing the efficient use of solar energy through
these intricate architectures of antennas. These collect sunlight and funnel
the light energy to reaction centers, where it is converted into chemical
energy that can be stored for further use," he says. "If those
fundamental principles are better understood then they can be used to create
new, more efficient solar panels." They have already made some
observations. "In a preliminary experiment, we could see with neutrons
that the membrane stacking in the cycnobacteria changes in response to light
on/ light off," Urban says. "With this new light in place, we can now
study this response more precisely, and in more detail: How does it depend on
the intensity and the color of the light?"
In related recent work, also funded by PARC,
Urban and his collaborators performed small-angle neutron scattering studies to
obtain structural information about the photosynthetic apparatus of the
light-harvesting chlorosome complex, the light-harvesting B808-866 complex, and
the bacterium Chloroflexus aurantiacus.
"To our knowledge, this was the first SANS report regarding the overall
photosynthetic machinery of Cfx.
Aurantiacus," Urban says.
Subsequently, the researchers studied in greater
detail the light harvesting antenna chlorosome. Chlorosomes, from green
photosynthetic bacteria, are the largest and one of the most efficient
light-harvesting antenna complexes found in nature. The chlorosome is able to
absorb solar energy and convert it into chemical energy under both low and high
light conditions. Its unique properties make it an attractive candidate for
developing biohybrid solar cell devices.
The paper that resulted was the first to
investigate the ionic strength effects of chlorosomes, whose size, shape, and
orientation of the light-harvesting complexes are critical to understand for
the phenomenon of electron transfer to semiconductor electrodes in solar
devices.
"These studies are useful
for developing biomimetic and bioanalytical solar cell devices, and for
demonstrating that chlorosomes are alternatives to other protein_pigment
complexes produced in photosynthetic organisms," Urban says.
SOURCE
