Why Comets Are Like Deep Fried Ice Cream

Astronomers tinkering with ice and organics in the lab may have discovered why comets are encased in a hard, outer crust.

Using an icebox-like instrument nicknamed Himalaya, the researchers show that fluffy ice on the surface of a comet would crystalize and harden as the comet heads toward the sun and warms up. As the water-ice crystals form, becoming denser and more ordered, other molecules containing carbon would be expelled to the comet's surface. The result is a crunchy comet crust sprinkled with organic dust.

"A comet is like deep fried ice cream," said Murthy Gudipati, a principal scientist at JPL and corresponding author of a recent study appearing in The Journal of Physical Chemistry. "The crust is made of crystalline ice, while the interior is colder and more porous. The organics are like a final layer of chocolate on top."

The lead author of the study is Antti Lignell, a postdoctoral scholar in Caltech's Division of Chemistry and Chemical Engineering, who formerly worked with Gudipati at JPL. Caltech manages JPL for NASA.

Read the full story at JPL News.

Written by Whitney Clavin

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Six from Caltech Elected to National Academy of Engineering

Six members of the Caltech community—Caltech professors Harry Atwater, Mory Gharib (PhD '83), Robert Grubbs, and Guruswami (Ravi) Ravichandran, and JPL staff members Dan M. Goebel and Graeme L. Stephens—have been elected to the National Academy of Engineering (NAE), an honor considered among the highest professional distinctions accorded to an engineer. The academy welcomed 67 new American members and 12 foreign members this year. Included among the new class are four Caltech alumni, Dana Powers (BS '70, PhD '75), Michael Tsapatsis (MS '91, PhD '94), Vigor Yang (PhD '84), and Ajit Yoganathan (PhD '78).

Harry Atwater, the Howard Hughes Professor of Applied Physics and Materials Science and director of the Resnick Sustainability Institute, was cited for his contributions to plasmonics—the study of plasmons, coordinated waves of electrons on the surfaces of metals. Atwater is developing plasmonic devices for controlling light on a nanometer scale. Such devices could be important for the eventual creation of quantum computers and more efficient photovoltaic cells in solar panels.

Mory Gharib is the vice provost for research and the Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering. His election citation notes his contributions to fluid flow visualization techniques and the engineering of bioinspired medical devices. Gharib's biomechanical studies are often coupled with medical engineering; for example, by studying the fluid dynamics of the human cardiovascular system, he and his group are better able to develop new types of prosthetic heart valves.

Dan M. Goebel, a senior research scientist at JPL, was honored for his contributions to low-temperature plasma sources for thin-film manufacturing, plasma materials interactions, and electric propulsion.

Robert Grubbs, the Victor and Elizabeth Atkins Professor of Chemistry and corecipient of the 2005 Nobel Prize in Chemistry, was elected for the development of catalysts that have enabled commercial products. For example, Grubbs and his team developed a new method for synthesizing organosilanes—basic chemical building blocks. Normally these molecules are made with expensive and rare precious metals, but Grubbs's group has found a way to catalyze the reaction using a cheap and abundant potassium compound.

Guruswami (Ravi) Ravichandran is the John E. Goode, Jr., Professor of Aerospace, professor of mechanical engineering, and director of the Graduate Aerospace Laboratories (GALCIT). He is cited by the NAE for his contributions to the mechanics of dynamic deformation, damage, and failure of engineering materials. Ravichandran has studied the behavior of polymers under high pressures and strains, and how the peeling of an adhesive material—like Scotch Tape—may be modeled as a crack propagating in a medium.

Graeme L. Stephens, the director of JPL's Center for Climate Sciences, was elected by the Academy for the elucidation of Earth's cloud system and radiation balance.

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Potassium Salt Outperforms Precious Metals As a Catalyst

A team of Caltech chemists has discovered a method for producing a group of silicon-containing organic chemicals without relying on expensive precious metal catalysts. Instead, the new technique uses as a catalyst a cheap, abundant chemical that is commonly found in chemistry labs around the world—potassium tert-butoxide—to help create a host of products ranging from new medicines to advanced materials. And it turns out that the potassium salt is more effective than state-of-the-art precious metal complexes at running very challenging chemical reactions.

"We have shown for the first time that you can efficiently make carbon–silicon bonds with a safe and inexpensive catalyst based on potassium rather than ultrarare precious metals like platinum, palladium, and iridium," says Anton Toutov, a graduate student working in the laboratory of Bob Grubbs, Caltech's Victor and Elizabeth Atkins Professor of Chemistry. "We're very excited because this new method is not only 'greener' and more efficient, but it is also thousands of times less expensive than what's currently out there for making useful chemical building blocks. This is a technology that the chemical industry could readily adopt."

The finding marks one of the first cases in which catalysis—the use of catalysts to make certain reactions occur faster, more readily, or at all—moves away from being a practice that is fundamentally unsustainable. While the precious metals in most catalysts are rare and could eventually run out, potassium is an abundant element on Earth.

The team describes its new "green" chemistry technique in the February 5 issue of the journal Nature. The lead authors on the paper are Toutov and Wen-bo (Boger) Liu, a postdoctoral scholar at Caltech. Toutov recently won the Dow Sustainability Innovation Student Challenge Award (SISCA) grand prize for this work, in a competition held at Caltech's Resnick Sustainability Institute.

"The first time I spoke about this at a conference, people were stunned," says Grubbs, corecipient of the 2005 Nobel Prize in Chemistry. "I added three slides about this chemistry to the end of my talk, and afterward it was all anyone wanted to talk about."

Coauthor Brian Stoltz, professor of chemistry at Caltech, says the reason for this strong response is that while the chemistry the catalyst drives is challenging, potassium tert-butoxide is so seemingly simple. The white, free-flowing powder—similar to common table salt in appearance—provides a straightforward and environmentally friendly way to run a reaction that involves replacing a carbon–hydrogen bond with a carbon–silicon bond to produce molecules known as organosilanes.

These organic molecules are of particular interest because they serve as powerful chemical building blocks for medicinal chemists to use in the creation of new pharmaceuticals. They also hold promise in the development of new materials for use in products such as LCD screens and organic solar cells, could be important in the development of new pesticides, and are being incorporated into novel medical imaging tools.

"To be able to do this type of reaction, which is one of the most-studied problems in the world of chemistry, with potassium tert-butoxide—a material that's not precious-metal based but still catalytically active—was a total shocker," Stoltz says.

The current project got its start a couple of years ago when coauthor Alexey Fedorov—then a postdoctoral scholar in the Grubbs lab (now at ETH Zürich)—was working on a completely different problem. He was trying to break carbon–oxygen bonds in biomass using simple silicon-containing compounds, metals, and potassium tert-butoxide, which is a common additive. During that process, he ran a control experiment—one without a metal catalyst—leaving only potassium tert-butoxide as the reagent. Remarkably, the reaction still worked. And when Toutov—who was working with Fedorov—analyzed the reaction further, he realized that in addition to the expected products, the reaction was making small amounts of organosilanes. This was unexpected since organosilanes are very challenging to produce.

"I thought that was impossible, so I went back and checked it many times," Toutov says. "Sure enough, it checked out!"

Bolstered by the finding, Toutov refined the reaction so that it would create only a single desired organosilane in high yield under mild conditions, with hydrogen gas as the only byproduct. Then he expanded the scope of the reaction to produce industrially useful chemicals such as molecules needed for new materials and derivatives of pharmaceutical substances.

Having demonstrated the broad applicability of the reaction, Toutov teamed up with Liu from Stoltz's group to further develop the chemistry for the synthesis of building blocks relevant to the preparation of new human medicines, a field in which Stoltz has been active for over a decade.

But before delving too deeply into additional applications, the chemists sought the assistance of Nathan Dalleska, director of the Environmental Analysis Center in the Ronald and Maxine Linde Center for Global Environmental Science at Caltech to perform one more test with a mass spectrometer that geologists use to detect extremely minute quantities of metals. They were trying to detect some tiny amount of those precious metals that could be contaminating their experiments—something that might explain why they were getting these seemingly impossible results from potassium tert-butoxide alone.

"But there was nothing there," says Stoltz. "We made our own potassium tert-butoxide and also bought it from various vendors, and yet the chemistry continued to work just the same. We had to really convince ourselves that it was true, that there were no precious metals in there. Eventually, we had to just decide to believe it."

So far, the chemists do not know why the simple catalyst is able to drive these complex reactions. But Stoltz's lab is part of the Center for Selective C–H Functionalization, a National Science Foundation–funded Center for Chemical Innovation that involves 23 research groups from around the country. Through that center, the Caltech team has started working with Ken Houk's computational chemistry group at UCLA to investigate how the chemistry works from a mechanistic standpoint.

"It's pretty clear that it's functioning by a mechanism that is totally different than the way a precious metal would behave," says Stoltz. "That's going to inspire some people, including ourselves hopefully, to think about how to use and harness that reactivity."

Toutov says that unlike some other catalysts that stop working or become sensitive to air or water when scaled up from the single-gram scale, this new catalyst seems to be robust enough to be used at large, industrial scales. To demonstrate the industrial viability of the process, the Caltech team used the method to synthesize nearly 150 grams of a valuable organosilane—the largest amount of this chemical product that has been produced by a single catalytic reaction. The reaction required no solvent, generated hydrogen gas as the only byproduct, and proceeded at 45°C—the lowest reported temperature at which this reaction has successfully run, to date.

"This discovery just shows how little we in fact know about chemistry," says Stoltz. "People constantly try to tell us how mature our field is, but there is so much fundamental chemistry that we still don't understand."

Kerry Betz, an undergraduate student at Caltech, is a coauthor on the paper, "Silylation of C–H bonds in aromatic heterocycles by an Earth-abundant metal catalyst." The work was supported by the National Science Foundation. The Resnick Sustainability Institute at Caltech, Dow Chemical, the Natural Sciences and Engineering Research Council of Canada, and the Shanghai Institute of Organic Chemistry provided graduate and postdoctoral support. Fedorov's work on the original reaction was supported by BP. 

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Abundant Salt Makes High-Performing Catalyst
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Friday, February 13, 2015
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Backpocket Barnburner: A Lightning Quick Overview of Educational Theory

Caltech Professors Named Fellows of the AAAS

Caltech Professor of Astronomy George Djorgovski and chemist Bruce Brunschwig are among the 401 newly elected fellows of the American Association for the Advancement of Science (AAAS) for 2014.

The AAAS was formed in 1848 with the mission of "advancing science, engineering, and innovation throughout the world for the benefit of all people." The annual tradition of electing fellows began in 1874 to recognize scientists for their contributions toward this mission.

"The AAAS performs an essential role of promoting and protecting science and its benefits for society. This has never been more important than it is now," says Djorgovski, director of the Center for Data-Driven Discovery at Caltech. He was elected by his scientific peers to the AAAS's Section on Astronomy for his "leadership of the Virtual Observatory and the emerging field of astroinformatics, and considerable body of work on surveys and transient discovery." Astronomical data is exponentially growing in complexity and volume; the Virtual Observatory is an open, web-based research environment intended to organize, maintain, and explore the rich information content within these datasets.

"Science is being transformed by computing and information technology, and astronomy has been at the forefront of these developments," says Djorgovski.

Brunschwig, director of the Molecular Materials Research Center (MMRC) at Caltech, was elected to the AAAS's Section on Chemistry for his "pioneering contributions to the theoretical and physical understanding of electron transfer and its application to artificial photosynthesis." The MMRC is home to state-of-the-art instrumentation that facilitates cutting-edge interdisciplinary research in the fields of chemistry, surface science, and materials science. The center currently hosts myriad projects, including work on artificial photosynthesis and solar energy conversion.

"Bruce Brunschwig is a model for us to aspire to with his dedication to scholarship and his natural curiosity and inquisitiveness," says Brunschwig's colleague Nate Lewis, the George L. Argyros Professor of Chemistry at Caltech and the scientific director of the Joint Center for Artificial Photosynthesis. "His election as a fellow to the AAAS is well deserved."

Caltech is currently home to 42 fellows of the AAAS.

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Saturday, January 24, 2015
Center for Student Services 360 (Workshop Space) – Center for Student Services

The personal side of science

Wednesday, February 4, 2015
Center for Student Services 360 (Workshop Space) – Center for Student Services

Meet the Outreach Guys: James & Julius

Wednesday, February 18, 2015
Center for Student Services 360 (Workshop Space) – Center for Student Services

HALF TIME: A Mid-Quarter Meetup for TAs

How Do You Make a Greasy Protein?

Watson Lecture Preview

Every cell is encapsulated and protected by a thin membrane made of greasy molecules called lipids. Assemblies of equally greasy protein molecules span the membrane, forming passageways that control the flow of signaling molecules that, in turn, direct the cell's activities. Because of these proteins' key role in cell-to-cell communication, they have become a prime target for drug design. Professor of Biochemistry Bil Clemons is among those working out the structures of these proteins and, more fundamentally, the biological processes behind them. Clemons will discuss how cells assemble these proteins, and how they deliver them to the membrane, at 8 p.m. on Wednesday, January 7, in Caltech's Beckman Auditorium. Admission is free.

 

Q: What do you do?

A: I am nominally a structural biologist, but I'm really a crystallographer. We purify a protein in solution and then try to crystallize it, which is really, really hard. When we succeed, we make X-ray diffraction patterns of the crystals and work backwards from those patterns to calculate the precise position of every atom. This allows us to make a blueprint for the molecule, and the blueprint helps us understand how the molecule does what it does. That's my group's real interest—figuring out the biological mechanisms that underlie how a protein works. We want to understand, on a molecular level, the processes by which these proteins are targeted and inserted into the membrane.

Proteins are long chains of amino acids that assume very specific three-dimensional shapes, or conformations. The proteins we work on contain hundreds of amino acids and thousands of individual atoms. These proteins interact with other molecules as they do their jobs. When they do, their conformations change, so a large part of our work is trying to understand all these different interactions and motions.

A crystal contains millions of copies of the same molecule held in exactly one conformation, so in that sense, a crystal structure is just one snapshot of a series of biological motions. Eventually we'd like to make movies of all the conformational changes that occur during these interactions—or at least render the important frames. It's almost like producing a cheap cartoon, where the lead animator draws a few key cels, and the rest is filled in later.

 

Q: What do you get from a crystal structure?

A: We get the first glimpse of how something works. Every crystal structure provides a huge amount of information. The beauty of structural biology is that we get to be the first people to peek under the hood of a protein and draw a three-dimensional map of what we see. Science is vast, and most people work in very narrow fields, doing mechanistic studies and drug discovery and all sorts of things. Structural biologists create the platform for everyone else's studies.

 

Q: How did you get into this line of work?

A: Well, I'd like to say it was a series of happy accidents. I've always been passionate about science. In my heart, I think I was born a scientist. I always wanted to know how everything worked, and biochemistry fascinated me. There was so much complexity—so many ways to ask questions.

At Virginia Tech, I was lucky enough to have an undergraduate adviser, Walt Niehaus, who encouraged me to do research in his group. There was really no looking back after that. I just thought, "Wow. This is really fun. I like doing this." Meanwhile, I was paying my way through school. My senior year I was the student manager of one of the food-service facilities. I was working nearly 40 hours a week managing 40 employees plus spending another 20 hours in the lab and 20 hours in school. I wasn't able to look past that to what my future might be, but Walt pushed me to apply for grad school. It was eye-opening the first time he suggested I could do this for a living.

Walt's research was in basic biochemistry. There weren't any structural biologists at Virginia Tech at the time, but the Howard Hughes Medical Institute sent us a booklet with stereo pictures of protein structures. I thought, "You've got to be kidding me. We can look at these things in 3-D?" It blew my mind. So I went to grad school at the University of Utah to be a crystallographer, and I earned my PhD working on the molecular machinery responsible for making proteins. Then I did my postdoctoral work at Harvard Med, trying to understand the complex process of getting greasy membrane proteins into cell membranes. We solved the structure of an important piece of the puzzle there, and now that I'm at Caltech, which has major strengths in X-ray crystallography, we're filling in the details of the bigger picture.

 

 

Named for the late Caltech professor Earnest C. Watson, who founded the series in 1922, the Watson Lectures present Caltech and JPL researchers describing their work to the public. Many past Watson Lectures are available online at Caltech's iTunes U site.

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Douglas Smith
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Tuesday, December 2, 2014
Guggenheim 101 (Lees-Kubota Lecture Hall) – Guggenheim Aeronautical Laboratory

PUSD: Annual Open Enrollment

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