Microscopic answers to humanity’s looming questions in food, water, and energy
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When faced with the threat of environmental uncertainty, potential scientific solutions to global crises are a welcomed and important societal subject. On April 25, 2017, the 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 Dinca and Gabriela Schlau-Cohen sharing their basic science research—research that can help us address global challenges for food, water, and energy.
Reverse-engineering the photosynthetic machine
Photosynthesis turns plants into extraordinarily efficient machines at capturing and transferring solar energy and turning it into food. If we understood how these machines work, not only could we adapt what we learn to improve solar technology, but we could optimize photosynthesis in plants to increase crop yields. However, the photosynthetic “machine” works at a vastly small scale: researchers need to be able to observe it working at the level of single molecules and femtoseconds, which requires new tools and approaches.
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 biggest problems—such 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,” she 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 protein’s fluorescence under a powerful microscope, Schlau-Cohen determined that the switch either gets turned on by one protein abruptly (in the event of the sun reappearing from behind a cloud) or by a different protein gradually (as the sun rises for the day).
By removing the “gradual change” protein entirely, it may be possible to engineer plants to ramp up photosynthesis more aggressively when sunlight becomes available and increase crop yield. Schlau-Cohen’s discovery may prove useful in meeting the world’s growing demand for food—which is rapidly outpacing its current supply, with a major shortfall predicted as early as 2030.
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 remains mysterious.
Schlau-Cohen observed a type of photosynthetic bacteria that employs an adjustable antenna made up of a network of proteins that absorb solar energy, finding that on sunny days, the antenna is smaller, whereas cloudy days yield larger antennae. Absorbed energy flows through thousands of pathways within the protein antenna to reach a central location where electricity is 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 the other as a probe that functions as a camera to see what happens to the energy after the initial excitation. The energy moved 30% faster through the rebuilt protein network, revealing a possible pathway to obtaining the faster rates of energy transfer that are required for increased reliability and power density of a solar panel.
Water from thin air
Instead of looking to nature for solutions to human-made problems, Mircea Dinca takes a different approach: “Fundamentally, I love making new stuff and then figuring out how it can help others,” he said.
Dinca develops new kinds of metal organic frameworks (MOFs), a type of material that has long been used for gas storage and separation, but has promising and relatively unexplored electronic properties with applications to the storage and consumption of energy and global environmental concerns.
The Dinca Laboratory has spent the last 5 years focusing on the development of a new class of highly porous materials. If one were to unfold the internal surface area of 1 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. Dinca’s 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.
Dinca was inspired to use his MOF sponges to address a large and growing need for fresh water. Approximately one third of the global population lives under severe water stress, and by 2030, it is estimated that that statistic will increase to half the population. By that time, a third of the population will be without fresh water entirely. Much of the world’s water is inaccessible in ice caps or in the salty ocean—or in the air as vapor.
To extract water from the atmosphere, Dinca’s high-capacity MOF sponge 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’re condensed, fresh water could be collected.
Basic research is crucial to our future
“Chemistry is everywhere,” stated Department Head Tim Jamison. The work that occurs within the boundaries of the MIT campus is among the most crucial to the future of both science and society, he continued. The basic science that Schlau-Cohen and Dinca pursue lays the groundwork for technological advances that can address some of our society’s most challenging problems—not just in ways that we can predict, such as improving solar technology, increasing crop yields, or extracting atmospheric water, but in ways that we cannot yet imagine.