who we are and what we do

"Nothing happens unless first we dream."Carl Sandburg

Graham R. Fleming
Nancy Turley NancyT.jpg Tiffb2.jpg Tiff Dressen

Naomi S. Ginsberg
Photosynthesis is the process used by plants to turn the energy from sunlight into chemicals like starch and sugar. We study the very first stage of photosynthesis that happens in a few trillionths of a second! Sunlight is absorbed by chlorophyll molecules inside the plant leaves. Once a chlorophyll molecule absorbs some light, its electrons become 'excited.' That is, the electrons have enough energy to dance around. Plants turn this energy into sugars in particular locations inside the plant leaves. Therefore, the extra energy on an excited chlorophyll molecule has to travel to these locations. Though there are many different possible directions that the energy could travel, it almost always arrives at the right place. As the energy travels, it passes through many different chlorophyll molecules that are held in place by proteins. We try to figure out how the particular arrangements of chlorophylls enable this process to work so well. Because it happens so quickly, we use extremely short pulses of laser light, rather than actual sunlight, to do our studies.

Jahan Dawlaty
Jahan and Doran:
We want to learn how the teeny-tiny little factories inside the leaf work. How do they use sunlight to make sugar? We have instruments that make little bursts of light, just like the sunlight, but in very, very short flashes. These instruments are called lasers. You can make a small burst of light too. You can turn on the switch for the room light, and then very, very quickly turn it off. The light will probably be on for just long enough for you to blink once. Our instruments make light flashes that are much, much faster than the speed of your eye blinking.
Doran Bennett

Why do we need these fast blinking flashes of light to study the tiny little factories in the leaf? Just like a car has an engine, wheels, and body, these factories also have different components. The difference is that the parts of the tiny factories move very fast, much faster than the speed of your eye blinking. We use our fast blinking lasers to see how fast each components moves. The little burst of light from our laser goes and jiggles one part of the tiny factory. Then that part goes and jiggles another one, which goes on to move other parts and so on. We use many bursts of light to understand the jiggling, and wiggling and twisting and turning of the components of these little factories.
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Hohjai Lee
You can imagine how miserable our life is when the TV signal sent by the broadcasting center would not reach the TV antenna smoothly. To see a clear TV programs in your living room, your TV antenna and the antenna of the broadcasting center should be well coupled for a good TV signal transfer. The solar energy received by a leaf is transferred very quickly between various pigments inside. The coupling between pigments here is very important to explain the efficient energy transfer but the measurement of the degree of coupling is hard because they are tightly surrounded by proteins.

I am interested in measuring the degree of the coupling between two photosynthetic pigments. I am using two-color photon echo technique. I use pulses of two different colors simply because I need to access two pigments which are absorbing different colors. The technique tells us how a molecular state of a pigment fluctuates when a molecular state of the other pigment fluctuate; If they fluctuate exactly together, I will have a large signal. If they fluctuate randomly (different way), I will have no signal.

Matt Graham
Eighteen years ago a cylindrical formation of carbon atoms was discovered and called the single-walled carbon nanotube (SWNT). Today, this simple molecule remains at the forefront of the push and promise of nanotechnology. While its unparelled tensile strength and electrical properties as a "nano-wire" have already been commercialized, its enormous optical potential has yet to be understood or harnessed. The Fleming group is contributing to realization of this potential by using advanced time-resolved spectroscopic techniques which can map-out SWNT electronic structure and can characterize optical properties. This information will be of crucial importance to steer the next generation of carbon nanotube application based devices such as LEDs, solar voltaics and quantum computing.

Gabriela Schlau-Cohen
When you look outside, you see green plants and green leaves on trees. The reason plants are green is because there are molecules, called chlorophyll, in the leaves that can hold onto certain colors of light, every color that’s not green. That means the only color that doesn’t get trapped by these molecules is green, so that is all you can see. Generally, all these plants put the chlorophyll molecules next to each other in the same way. That is, the space between one chlorophyll and its neighbor in one plant is the same as in another. Our research studies why these molecules are placed next to each other in the way that they are.

When a chlorophyll holds onto a certain color of light, it then passes that light to its neighbors and this happens many times. We use lasers to look at how long it takes to pass the light energy, which is part of figuring out where that light is going. We take the chlorophyll part out of plants and hit it with a laser beam. When the laser beam, which is a bunch of light energy, hits the chlorophylls, they hold onto some of that energy. If another beam comes along, and they still have the energy from the first beam, they cannot hold onto as much energy. We can measure the differences between the amount of energy they hold on to and that difference changes over time. That tells us how long the chlorophylls hold onto light before passing it to another chlorophyll. Then, when we understand more about how the light moves around in the chlorophylls, we can understand more about who the neighbors of each chlorophyll are and why they are put in the arrangement that they are.

Julia Zaks
Plants need sunlight to provide the energy for growth. However, absorbing more sunlight than they can use can be dangerous for plants. Because sunlight intensity fluctuates, the number of photons hitting a plant can quickly change from very few to very many. In order to protect themselves from damage by too many photons, plants are able to dump the excess energy that they absorb when they are hit by more photons than they can use. But we don't completely understand how plants dump this energy, or how the plant signals that energy needs to be dumped. In order to understand this regulation in plants, we are making a mathematical model of feedback regulation in plants and analyzing it to see if it can agree with experimental observations.

Jacqui Burchfield
Our bodies get our energy by eating food. However, plants don’t eat; they absorb the energy they need to grow from the sun in a process called photosynthesis. In photosynthesis, molecules called chlorophylls absorb light, which is a form of energy, and the plant converts this energy into sugar for food. While scientists would like to harvest energy from the sun the way plants do, we do not yet understand how plants adapt to changes in light levels. When a human gets too much sun, he or she can move inside to cool down, but plants have roots! Solar panels, like plants, are fixed in place, so knowing how plants adapt quickly to do more photosynthesis when the day gets cloudy but not get hurt when the sun comes back out will help us make better solar cells. Scientists already know that to avoid being injured by too much light; that is, more light than the plant can use in photosynthesis; plants grow molecules called “carotenoids.” Carotenoids can take extra energy from the chlorophylls, and we know that some carotenoids can do this because of their ability to have a chemical reaction with the chlorophyll. However, we do not know how this reaction, in which a carotenoid gives a small part of itself, an electron, to the chlorophyll, works. The Fleming lab is studying this reaction so that other scientists can make solar panels that work in all weather without getting damaged by too much light on sunny days.

Kapil Amarnath
As you guys can see in this video, the algae is a promising organism for us to use for making fuels using light, because it is easy to grow and won't take up farmland. Also, the entire process would be "carbon-neutral," meaning that the amount of carbon dioxide that is released due to burning the fuels is the same as that used from the atmosphere to make them. Right now, algae biofuels cost about $8 a gallon, and so it needs to be more cost efficient before going on the market. So, we need to know more about the biology of algae so that we can perhaps engineer algae to be more efficient. As a result, I am studying what happens inside algae as they respond to different light intensities.

Eleonora De Re
The desire to understand how nature works has always pushed humans to explore phenomena happening on ever shorter time scales. Till three hundreds of years ago, people were able to reconstruct processes with the duration of a blink of the eye: anything faster than this was considered instantaneous. The development of science and technology has enabled people to detect events happening on much shorter time scales: for example, at the end of the nineteen century, snapshot photography allowed us to "see" how the gallop of a horse happens.
However, atomic and molecular motions happening in chemical and biological systems have much shorter durations; in order to see these dynamics, we use a technique called ultrafast spectroscopy: this technique is a sort of ultrafast photography, in which the flash duration is of the order of a few trillionths of seconds. The laser pulses that we use are bursts of light of very short duration, able to capture a snapshot of the state of the material that we want to study. By putting together all of these snapshots, we are able to reconstruct the whole time evolution of the system that we are studying.

Emily Jane Glassman
While plants need energy from light to make food, too much energy can actually hurt the plants. If the plant is hurt too much, it can no longer make the energy it needs, and it could die. To prevent this from happening, plants have found a way to heal so that they can keep making energy. One complex of molecules that absorb light is particularly important for the plant to stay alive. Plants have many of these complexes in order to capture the light energy they need. Scientists know that if these complexes get damaged, they are repaired very quickly. However, because these complexes are so small, no one has seen exactly how the repair happens. Scientists are building a new type of microscope in order to see how these complexes are repaired.

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