New
research at Concordia University is bringing us one step closer to
clean energy. It is possible to extend the length of time a battery-like
enzyme can store energy from seconds to hours, a study published in the
Journal of The American Chemical Society shows.

Concordia
Associate Professor László Kálmán—along with his colleagues in the
Department of Physics, graduate students Sasmit Deshmukh and Kai
Tang—has been working with an enzyme found in bacteria that is crucial
for capturing solar energy. Light induces a charge separation in the
enzyme, causing one end to become negatively charged and the other
positively charged, much like in a battery.

In
nature, the energy created is used immediately, but Kálmán says that to
store that electrical potential, he and his colleagues had to find a
way to keep the enzyme in a charge-separated state for a longer period
of time.

“We
had to create a situation where the charges don’t want to or are not
allowed to go back, and that’s what we did in this study,” he says.

Kálmán
and his colleagues showed that by adding different molecules, they were
able to alter the shape of the enzyme and, thus, extend the lifespan of
its electrical potential.

In
its natural configuration, the enzyme is perfectly embedded in the
cell’s outer layer, known as the lipid membrane. The enzyme’s structure
allows it to quickly recombine the charges and recover from a
charge-separated state.

However,
when different lipid molecules make up the membrane, as in Kálmán’s
experiments, there is a mismatch between the shape of the membrane and
the enzyme embedded within it. Both the enzyme and the membrane end up
changing their shapes to find a good fit. The changes make it more
difficult for the enzyme to recombine the charges, thereby allowing the
electrical potential to last much longer.

“What
we’re doing is similar to placing a race car on snow-covered streets,”
says Kálmán. The surrounding conditions prevent the race car from
performing as it would on a racetrack, just like the different lipids
prevent the enzyme from recombining the charges as efficiently as it
does under normal circumstances.

Photosynthesis
is suspected to have existed for billions of years. “All of our food,
our energy sources (gasoline, coal)—everything is a product of some
ancient photosynthetic activity,” says Kálmán.

But
he adds that the main reason researchers are turning to these ancient
natural systems is because they are carbon neutral and use resources
that are in abundance: sun, carbon dioxide and water. Researchers are
using nature’s battery to inspire more sustainable, man-made energy
converting systems.

For
a peek into the future of these technologies, Kálmán points to medical
applications and biocompatible batteries. Imagine batteries made of
enzymes and other biological molecules. These could be used to, for
example, monitor a patient from the inside post-surgery. Unlike
traditional batteries that contain toxic metals, biocompatible batteries
could be left inside the body without causing harm.

“We’re
far from that right now but these devices are currently being explored
and developed,” says Kálmán. “We have to take things step by step but,
hopefully, we’ll get there one day in the not-too-distant future.”

Lipid binding to the carotenoid binding site in photosynthetic reaction centers

Source:  Concordia University