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Microscopic answers to humanity’s looming questions about food, water, and energy
MIT NEWS OFFICE, Microscopic answers to humanity’s looming questions about food, water, and energy, May 04, 2017

When society is faced with the threat of environmental uncertainty, potential scientific solutions to global crises are a welcomed and important subject. On April 25, the MIT Department of Chemistry and the School of Science held an alumni and friends reception, where invited guests gathered in the Samberg Conference Center for an evening of food, drink, and talks by professors Mircea Dincă and Gabriela Schlau-Cohen, who shared their insights on basic science research that can help address global challenges in food, water, and energy availability.

Reverse-engineering the photosynthetic machine

Photosynthesis makes plants into machines that are extraordinarily efficient at capturing and transferring solar energy and turning it into food. If we understand how these machines work, we can not only adapt what we learn to improve solar technology, but also to optimize photosynthesis in plants to increase crop yields. However, since the photosynthetic “machine” works at an incredibly small scale, researchers need new tools and approaches to be able to observe it working at the level of single molecules and femtoseconds.

Gabriela Schlau-Cohen shared how she is developing single-molecule and ultrafast spectroscopies that are capable of exploring the energetic and structural dynamics of photosynthesis. By studying these tiny details, Schlau-Cohen believes we can solve some of the world’s major problems — such as our growing demand for food and our need for clean, sustainable energy. “We can solve some of society’s biggest problems by learning from nature’s smallest organisms,” Schlau-Cohen said.

In one study, Schlau-Cohen used moss and algae to understand a “molecular switch” protein that turns photosynthesis on and off in response to the availability of sunlight. Under sunny conditions, the switch is turned on, and the absorbed energy is dissipated as heat. On cloudy days, the switch is turned off and the energy is available to drive the reactions of photosynthesis. By observing this switch’s fluorescence under a powerful microscope, Schlau-Cohen was able to determine that the switch either gets turned on abruptly by one protein (in the event of the sun reappearing from behind a cloud) or gradually by a different protein (as the sun rises for the day).

Schlau-Cohen’s discovery may prove useful in meeting the world’s growing demand for food — which is rapidly outpacing current supply with a major shortfall predicted as early as 2030. By removing the gradual-change protein switch entirely, it may be possible to engineer plants that ramp up photosynthesis more aggressively when sunlight becomes available and to increase crop yield.

In another study, Schlau-Cohen concentrated on the capability of photosynthetic organisms to convert absorbed sunlight to electricity with a near-unity quantum efficiency — a remarkable feat that solar technology cannot yet match. We know that plant cells achieve this efficiency by transporting energy through a specialized network of proteins to reach a central location, but how the molecular machinery works to produce such an efficient directional energy flow is still a mystery.

Schlau-Cohen observed a type of photosynthetic bacteria that employs an adjustable antenna made up of a network of proteins that absorb solar energy. She found that on sunny days, the antennae were smaller, whereas cloudy days yielded larger antennae. Absorbed energy flowed through thousands of pathways within the protein antenna to reach a central location where electricity was generated. To understand how protein organization directed energy flow, Schlau-Cohen rebuilt the protein network and then measured energy with two ultra-fast, femtosecond lasers, one serving as a pump that simulates the sun and excites the sample, and another as a probe that functions as a camera to see what happens to the energy after the initial excitation. The energy moved 30 percent faster through the rebuilt protein network, revealing a possible pathway to obtaining the faster rates of energy transfer that are required for increasing the reliability and power density of solar panels.

Water from thin air

Instead of looking to nature for solutions to human-made problems, Mircea Dincă takes a different approach: “Fundamentally, I love making new stuffand then figuring out how it can help others,” he said.

Dincă develops new kinds of metal organic frameworks (MOFs), a type of material that has long been used for gas storage and separation. But MOFs also have promising and relatively unexplored electronic properties with applications to the storage and consumption of energy and global environmental concerns. The Dincă lab has spent the last five years focusing on the development of a new class of highly porous materials. If one were to unfold the internal surface area of one gram of the material, it would cover an entire football field. It has by far the largest surface area of any material known to humankind. Dincă said his work on water sorption in MOFs has led to the isolation of particularly tunable “sponges on steroids” that can produce fresh water by absorbing moisture from air.

Dincă was inspired to use his unique sponges to address the large and growing world need for fresh water. Approximately one third of the population currently lives under severe water stress. By 2030, it is estimated that that statistic will increase to half the world, with a third of the population being entirely without fresh water.

Much of the world’s water supply is inaccessible in ice caps or in the salty ocean — or in the air as vapor. To extract water from the atmosphere, Dincă’s high-capacity MOF sponges could be affixed to the roof of a house. During the night, when the humidity rises, the material would suck up water from the atmosphere, and then during the day, the sun would heat the sponge and release the vapors. Once they are condensed, fresh water could be collected.

Basic research is crucial to our future

“Chemistry is everywhere,” Department of Chemistry head Tim Jamison told the guests. The work that occurs within the boundaries of the MIT campus is among the most crucial to the future of both science and society.

The basic science that Schlau-Cohen and Dincă pursue lays the groundwork for technological advances that can address some of our society’s most challenging problems, and not just in ways that we can predict, such as improving solar technology, increasing crop yields, or extracting atmospheric water, but also in ways that we cannot yet imagine.