Duke Research Blog

Following the people and events that make up the research community at Duke.

Category: Chemistry (Page 1 of 5)

Can Science Explain Everything? An Exploration of Faith

The Veritas Forum, Feb. 1 in Penn Pavilion

I found out about this year’s Veritas Forum an hour before it started — a friend, who two years ago helped me explore Christianity (I grew up non-religious and was curious), mentioned it when we ran into each other at the Brodhead Center.

So, to avoid my academic responsibilities, I instead listened to Duke physics professor Ronen Plesser, a non-practicing Jew, Troy Van Voorhis, a Christian who teaches chemistry at MIT, and moderator Ehsan Samei, a professor of radiology and biomedical engineering at Duke. They discussed the God Hypothesis and how it fit in with their views as hard scientists.

Ehsan Samei

As someone who has relied on the scientific method instead of an omniscient, higher power to understand the natural world, I found it amazing how the speakers used relatable examples to demonstrate their belief that humans cannot explain everything. They started answering the classic question “Why is the sky blue?,” using more and more complex chemistry and physics as answers only led to more questions.

At some point, science-based explanations about how and why molecules move the way they do and where they come from didn’t suffice — at some point, it just seems like something, or someone, is responsible for the unexplainable.

Troy Van Voorhis of MIT

Something that Van Voorhis said particularly stuck in my mind. Reproducibility and objectivity form the “bedrock of science,” but are also it’s “grand limitations.” They are essential to corroborating the results of a scientific study or experiment, but can they really confirm something as scientific truth? When does reproducibility adequately overcome variation in data, and can something be defined as truly objective?

So, I sat there in the audience, thinking about alternatives to explaining morals, ethics, and the feeling of being human since, to paraphrase Plesser, science just doesn’t cut it in these cases. He elaborated on faith after branching off Van Voorhis’ point of view. Plesser’s explanation made the overlap of science and religion become more and more prominent. As someone who also does not practice a religion, I felt that his comparison of faith in science and faith in religion comforting.

Ronan Plesser

Even though I still struggle to fully accept Christ, I was aware of the similarities of the path to scientific and spiritual enlightenment. In science, incessant questioning of our surroundings is necessary to understand the Truths of our world (“otherwise we wouldn’t be publishing papers and we would be out of our jobs!”), as are the calls to God to come down and help people improve themselves. It is impossible, then, to avoid faith entirely since being human inherently involves belief in some sort of system.

I was wowed by the connections that the three men were making between the seemingly divergent areas. I was even more astonished, though, by their emphasis on humility. They exemplified the need for understanding and patience when describing scientific theories and religious ideologies. To be humble is to accept that people have differences and to acknowledge these differences is the only way to reduce conflicts between religion and science.

Post by Stella Wang

Farewell, Electrons: Future Electronics May Ride on New Three-in-One Particle

“Trion” may sound like the name of one of the theoretical particles blamed for mucking up operations aboard the Starship Enterprise.

But believe it or not, trions are real — and they may soon play a key role in electronic devices. Duke researchers have for the first time pinned down some of the behaviors of these one-of-a-kind particles, a first step towards putting them to work in electronics.

A carbon nanotube, shaped like a rod, is wrapped in a helical coating of polymer

Three-in-one particles called trions — carrying charge, energy and spin — zoom through special polymer-wrapped carbon nanotubes at room temperature. Credit: Yusong Bai.

Trions are what scientists call “quasiparticles,” bundles of energy, electric charge and spin that zoom around inside semiconductors.

“Trions display unique properties that you won’t be able to find in conventional particles like electrons, holes (positive charges) and excitons (electron-hole pairs that are formed when light interacts with certain materials),” said Yusong Bai, a postdoctoral scholar in the chemistry department at Duke. “Because of their unique properties, trions could be used in new electronics such as photovoltaics, photodetectors, or in spintronics.”

Usually these properties – energy, charge and spin – are carried by separate particles. For example, excitons carry the light energy that powers solar cells, and electrons or holes carry the electric charge that drives electronic devices. But trions are essentially three-in-one particles, combining these elements together into a single entity – hence the “tri” in trion.

A diagram of how a trion is formed in carbon nanotubes.

A trion is born when a particle called a polaron (top) marries an exciton (middle). Credit: Yusong Bai.

“A trion is this hybrid that involves a charge marrying an exciton to become a uniquely distinct particle,” said Michael Therien, the William R. Kenan, Jr. Professor of Chemistry at Duke. “And the reason why people are excited about trions is because they are a new way to manipulate spin, charge, and the energy of absorbed light, all simultaneously.”

Until recently, scientists hadn’t given trions much attention because they could only be found in semiconductors at extremely low temperatures – around 2 Kelvin, or -271 Celcius. A few years ago, researchers observed trions in carbon nanotubes at room temperature, opening up the potential to use them in real electronic devices.

Bai used a laser probing technique to study how trions behave in carefully engineered and highly uniform carbon nanotubes. He examined basic properties including how they are formed, how fast they move and how long they live.

He was surprised to find that under certain conditions, these unusual particles were actually quite easy to create and control.

“We found these particles are very stable in materials like carbon nanotubes, which can be used in a new generation of electronics,” Bai said. “This study is the first step in understanding how we might take advantage of their unique properties.”

The team published their results Jan. 8 in the Proceedings of the National Academy of Sciences.

Dynamics of charged excitons in electronically and morphologically homogeneous single-walled carbon nanotubes,” Yusong Bai, Jean-Hubert Olivier, George Bullard, Chaoren Liu and Michael J. Therien. Proceedings of the National Academy of Sciences, Jan. 8, 2018 (online) DOI: 10.1073/pnas.1712971115

Post by Kara Manke

Glitter and Jell-O Reveal the Science of Oobleck

A black and white image showing a circular disk dropping into a container of oobleck

Mixing black glitter with oobleck allowed researchers to track the movement of individual cornstarch particles after a sudden impact. A computer program locked onto pieces of glitter and illustrated their motion. Credit: Melody Lim.

What do gelatin and glitter have to do with serious science? For some experiments, a lot! Duke alumna Melody Lim used jiggly Jell-O and a just a pinch of glitter to solve a scientific mystery about the curious goo many like to call oobleck.

To the uninitiated, oobleck is almost magic. The simple mixture of cornstarch and water feels solid if you squeeze it, but moments later runs through your fingers like water. You can dance across a bathtub full of oobleck, but stand still for too long and you will be sucked into a goopy mess. Not surprisingly, the stuff is a Youtube favorite.

Oobleck is an example of what scientists call a non-Newtonian fluid, a liquid whose viscosity – how easily it changes shape and flows – depends upon the force that is applied. But exactly how it is that this material switches from solid to liquid and back again has remained a mystery to scientists.

A piece of gelatin being squeezed viewed through a circular polarizer

This blogger mixed up a batch of jello to see the photoelastic effect for herself. When viewed with polarized light – from an iPhone screen and a circular polarizer – the jello changes color when squeezed.

“Water is simple to understand, and so is cornstarch,” said Lim, ’16, who is currently a graduate student at the University of Chicago. “However, a combination of the two produces this ‘liquid’ that ripples and flows, solidifies beneath your feet if you run on it, then turns back into a liquid if you stop running and stand still. I wanted to know why.”

The question beguiling scientists was whether sudden impact causes the cornstarch particles to “jam” into a solid like cement, or whether the suspension remains liquid but simply moves too slowly for its liquid-like properties to be apparent — similar to what happens if you skip a rock off the surface of a lake.

“There are these two opposing pictures,” said Robert Behringer, James B. Duke Professor of Physics at Duke. “Either you squish the material and turn it into cement temporarily, or you simply transmit the stress from the impactor straight to the boundary.”

Lim did two sets of experiments to find out which way oobleck works. In one experiment, she mixed black glitter into a transparent channel filled with oobleck, and then used a high-speed camera to watch how the material responded to the impact. The glitter let her track the motion of individual particles after the disc hit.

A piece of gelatin changes color when you squeeze it.

The photoelastic effect in gelatin.

Her video shows that the particles near the impact site jam and become solid, forming what the researchers call a “mass shock” wave that travels slowly through the suspension.

In a second set of experiments, Lim placed the oobleck in a container lined with gelatin, the main ingredient in Jell-O – besides sugar and food dye, of course. Gelatin is what is called a photoelastic material, which means that applying pressure bends light that travels through it, like a prism.

“Next time you eat Jell-O, get out your sunglasses and get somebody else’s sunglasses and look between them,” Behringer said. “Because if you give it a shake you should see all these stress patterns bouncing around.”

After the metal disc hit the oobleck, the gelatin let Lim see how fast the resulting pressure wave traveled through the material and reached the boundary.

A black and white image showing pressure waves traveling through a transparent material after impact

The researchers poured oobleck into a clear container lined with gelatin, a material that bends light when a pressure is applied to it. They saw that the force of a sudden impact is rapidly transmitted through the oobleck and to the boundary with the gelatin. Credit: Melody Lim.

They found that when the impact is sudden, the pressure wave traveled to the gelatin boundary faster than the “mass shock” wave. This means that the reason oobleck appears solid after a sudden impact is because the force of the collision is quickly transmitted to a solid boundary.

“If you are running across the water, that actually puts you into an impact velocity range where the pressure wave is significantly faster than the mass shock,” Behringer said. “Whereas if you try to walk across it, the impact speeds are slow, and the system actually doesn’t have the ability to transport the momentum quickly through the material and so you just sink in.”

“If you’d told me when I started that I would line a narrow container with Jell-o, add cornstarch, water, and black glitter, drop a piece of metal on it, then publish a paper on the results, I would have laughed at you,” Lim said.

CITATION: “Force and Mass Dynamics in Non-Newtonian Suspensions,” Melody X. Lim, Jonathan Barés, Hu Zheng and Robert P. Behringer. Physical Review Letters, Nov. 3, 2017. DOI: 10.1103/PhysRevLett.119.184501

Post by Kara Manke

Cheating Time to Watch Liquids do the Slow Dance

Colorful spheres simulating liquid molecules shift around inside a cube shape

The team’s new algorithm is able to simulate molecular configurations of supercooled liquids below the glass transition. The properties of these configurations are helping to solve a 70-year paradox about the entropy of glasses. Credit: Misaki Ozawa and Andrea Ninarello, Université de Montpellier.

If you could put on a pair of swimming goggles, shrink yourself down like a character from The Magic School Bus and take a deep dive inside a liquid, you would see a crowd of molecules all partying like it’s 1999.

All this frenetic wiggling makes it easy for molecules to rearrange themselves and for the liquid as a whole to change shape. But for supercooled liquids — liquids like honey that are cooled below their freezing point without crystallizing – the lower temperature slows down the dancing like Etta James’ “At Last.” Lower the temperature enough, and the slow-down can be so dramatic that it takes centuries or even millennia for the molecules to rearrange and the liquid to move.

Scientists can’t study processes that last longer than their careers. But Duke chemists and their Simons Foundation collaborators have found a way to cheat time, simulating the slow dance of deeply supercooled liquids. Along the way, they have found new physical properties of “aged” supercooled liquids and glasses.

A droplet rises above a surface of water

Credit: Ruben Alexander via Flickr.

To understand just how slow deeply supercooled liquids move, consider the world’s longest-running experiment, the University of Queensland’s Pitch Drop Experiment. A single drop of pitch forms every eight to thirteen years — and this pitch is moving faster than deeply supercooled liquids.

“Experimentally there is a limit to what you can observe, because even if you managed to do it over your entire career, that is still a maximum of 50 years,” said Patrick Charbonneau, an associate professor of chemistry and physics at Duke. “For many people that was considered a hard glass ceiling, beyond which you couldn’t study the behavior of supercooled liquids.”

Charbonneau, who is an expert on numerical simulations, said that using computers to simulate the behavior of supercooled liquids has even steeper time limitations. He estimates that, given the current rate of computer advancement, it would take 50 to 100 years before computers would be powerful enough for simulations to exceed experimental capabilities – and even then the simulations would take months.

To break this glass ceiling, the Charbonneau group collaborated with Ludovic Berthier and his team, who were developing an algorithm to bypass these time constraints. Rather than taking months or years to simulate how each molecule in a supercooled liquids jiggles around until the molecules rearrange, the algorithm picks individual molecules to swap places with each other, creating new molecular configurations.

This allows the team to explore new configurations that could take millennia to form naturally. These “deeply supercooled liquids and ultra-aged glasses” liquids are at a lower energy, and more stable, than any observed before.

“We were cheating time in the sense that we didn’t have to follow the dynamics of the system,” Charbonneau said. “We were able to simulate deeply supercooled liquids well beyond is possible in experiments, and it opened up a lot of possibilities.”

Two columns of blue and red spheres represent simulations of vapor-deposited glasses.

Glasses that are grown one layer at a time have a much different structure than bulk glasses. The team used their new algorithm to study how molecules in these glasses rearrange, and found that at low temperatures (right), only the molecules at the surface are mobile. The results may be used to design better types of glass for drug delivery or protective coatings. Credit: Elijah Flenner.

Last summer, the team used this technique to discover a new phase transition in low-temperature glasses. They recently published two additional studies, one of which sheds light on the “Kauzmann paradox,” a 70-year question about the entropy of supercooled liquids below the glass transition. The second explores the formation of vapor-deposited glasses, which have applications in drug delivery and protective coatings.

“Nature has only one way to equilibrate, by just following the molecular dynamics,” said Sho Yaida, a postdoctoral fellow in Charbonneau’s lab. “But the great thing about numerical simulations is you can tweak the algorithm to accelerate your experiment.”

Configurational entropy measurements in extremely supercooled liquids that break the glass ceiling.” Ludovic Berthier, Patrick Charbonneau, Daniele Coslovich, Andrea Ninarello, Misaki Ozawa and Sho Yaida. PNAS, Oct. 24, 2017. DOI: 10.1073/pnas.1706860114

The origin of ultrastability in vapor-deposited glasses.” Ludovic Berthier, Patrick Charbonneau, Elijah Flenner and Francesco Zamponi. PRL, Nov. 1, 2017. DOI: 10.1103/PhysRevLett.119.188002

Post by Kara Manke

Designing Drugs Aimed at a Different Part of Life’s Code

Individual RNA molecules fluoresce inside a breast cancer cell.

Individual RNA molecules fluoresce inside a breast cancer cell. Credit: Sunjong Kwon, Oregon Health & Science University, via Flickr.

Most drugs work by tinkering with the behavior of proteins. Like meddlesome coworkers, these molecules are designed to latch onto their target proteins and keep them from doing what they need to do.

If a protein is responsible for speeding up a reaction, the drug helps slow the reaction down. If a protein serves as a gatekeeper to a cell, regulating what gets in and what stays out, a drug changes how many molecules it lets through.

But proteins aren’t the only doers and shakers in our bodies. Scientists are finding that strings of RNA — known primarily for their role in shuttling genetic information from nucleus-bound DNA to the cell’s protein-manufacturing machinery — can also play a major role in regulating disease.

A portrait of Amanda Hargrove

Amanda Hargrove is an assistant professor of chemistry at Duke University.

“There has been what some people are calling an RNA revolution,” said Amanda Hargrove, assistant professor of chemistry at Duke. “In some diseases, non-coding RNAs, or RNAs that don’t turn into protein, seem to be the best predictors of disease, and even to be driving the disease.”

Hargrove and her team at Duke are working to design new types of drugs that target RNA rather than proteins. RNA-targeted drug molecules have the potential help treat diseases like prostate cancer and HIV, but finding them is no easy task. Most drugs have been designed to interfere with proteins, and just don’t have the same effects on RNA.

Part of the problem is that proteins and RNA have many fundamental differences, Hargrove said. While proteins are made of strings of twenty amino acids that can twist into myriad different shapes, RNA is made of strings of only four bases — adenine, guanine, cytosine and uracil.

“People have been screening drugs for different kinds of RNA for quite a while, and historically have not had a lot of success,” Hargrove said. “This begged the question, since RNA has such chemically different properties than proteins, is there something different about the small molecules that we need in order to target RNA?”

To find out, graduate student Brittany Morgan and research associate Jordan Forte combed the scientific literature to identify 104 small molecules that are known interact with specific types of RNA. They then analyzed 20 different properties of these molecules, and compared their properties to those of collections of drug molecules known to interact with proteins.

The team found significant differences in shape, atomic composition, and charge between the RNA-active molecules and the protein-active molecules. They plan to use the results to compile a collection of molecules, called a library, that are chosen to better “speak the language” of the RNA-active molecules. They hope this collection of molecules will be more likely to interact with RNA in therapeutically beneficial ways.

“We found that there are differences between the RNA-targeted molecules and the protein-targeted drugs, and some of them are pretty striking,” Hargrove said. “What that means is that we could start to enrich our screening libraries with these types of molecules, and make these types of molecules, to have better luck at targeting RNA.”

Discovery of Key Physicochemical, Structural, and Spatial Properties of RNA-Targeted Bioactive Ligands.” Brittany S. Morgan, Jordan E. Forte, Rebecca N. Culver, Yuqi Zhang and Amanda Hargrove. Angewandte Chemie, Sept. 18, 2017. DOI: 10.1002/anie.201707641

Kara J. Manke, PhDPost by Kara Manke

Lab-Made Protein Chomps Co-Factor Like a Big Ol' Gator

A protein is illustrated to look like an alligator mouth

The synthetic protein clamps down on the porphyrin like the jaws of an alligator. Credit: Nicholas Polizzi.

Proteins have the power to turbo-charge biochemical reactions inside the body.

Without the help of types of proteins called enzymes, the reaction that builds DNA could take over 130,000 years to complete. Enzymes cut that time down to just a few milliseconds.

To rev up chemical reactions, many proteins team up with smaller molecules or metals called cofactors. Chemists would like to design proteins that bind to non-biological cofactors in order to speed up chemical reactions not found in nature. But first, they have to figure out how to create man-made proteins that attach to new cofactors in exactly the right way, and that is no easy feat.

A team of chemists at Duke and UC San Francisco is the first to solve this protein design puzzle. The team created a synthetic protein that tightly binds a non-biological catalyst, a type of molecule called porphyrin that is capable of stealing electrons from other molecules when it absorbs light.

“To be able to combine man-made catalysts with proteins would be really big in the chemistry field because then you could combine the power of an enzyme with that of a reaction that isn’t found in nature,” said former Duke graduate student Nicholas Polizzi, who is now a postdoctoral researcher in William DeGrado’s lab at UCSF.

“We were able to figure out the design criteria necessary to place that porphyrin in a protein to within a very high accuracy,” Polizzi said. “That was a really big stepping stone to be able to design new protein-cofactor combinations not seen in nature.”

Proteins are made of chains of hundreds or thousands of smaller amino acids that twist and loop into complex 3-D shapes that can interlock with other molecules like pieces of a jigsaw puzzle. To catalyze chemical reactions, protein-cofactor combinations hold two or more molecules in precisely-shaped pockets that keep the molecules in just the right positions, and provide the right environment, for a chemical reaction to occur.

An illustration of a protein jigsaw puzzle

Chemists at Duke and UCSF designed a synthetic protein that tightly binds a non-biological molecule. Credit: Nicholas Polizzi.

Millions of years of evolution have created proteins that fold into the shapes that tightly grip specific cofactors and provide the perfect environments to catalyze chemical reactions.

For over 25 years, chemists have used what they know about protein folding to design synthetic amino acid sequences that twist up into useful shapes. But so far, they have been unable to design a protein that binds a non-biological cofactor with the precision necessary to power complex new chemical reactions.

Polizzi said this may be because these designs focused primarily on the “binding site” where cofactors and reacting molecules fit into the protein, while ignoring the rest of the structure. “What I did differently is that I considered essentially the entire interior of protein as the binding site for the porphyrin, as opposed to just a few amino acids that touch the porphyrin,” Polizzi said.

To understand how this works, you can think of the protein as the mouth of an alligator, said Michael Therien, William R. Kenan Jr. Professor of Chemistry at Duke. The protein latches onto a cofactor in the same way that an alligator uses its front teeth to chomp down on dinner. But for the front teeth to get a strong grip, the jaw and back teeth also have to be designed correctly.

“The new concept here is that the non-binding region of the protein is held in a shape that allows the binding region to work,” Therien said.

“We called the protein ‘gator’ in the lab,” Polizzi said.

The jaws of the gator protein actually clamp down so hard on the porphyrin cofactor that the whole structure is too rigid to catalyze a reaction, Polizzi said. But with a few tweaks to loosen up the structure, he thinks he can get it to work.

“In this reaction, often times you need a little bit of wiggle room in the protein for it to move. And there was no wiggle room in our protein, everything fit too perfectly,” Polizzi said.

CITATION: “De novo design of a hyperstable non-natural protein-ligand complex with sub-A accuracy.” Nicholas F. Polizzi, Yibing Wu, Thomas Lemmin, Alison M. Maxwell, Shao-Qing Zhang, Jeff Rawson, David N. Beratan, Michael J. Therien and William F. DeGrado. Nature Chemistry, Aug. 21, 2017. DOI: 10.1038/nchem.2846

Kara J. Manke, PhDPost by Kara Manke

A Summer Well-Spent In and Around Toxic Waste Sites

Edison, NJ is just 40 miles from Manhattan and 70 miles from Philadelphia. It’s also home to the US EPA’s Emergency Response Team (ERT), where I spent the summer as an intern.

Stella Wang and an EPA contractor used lifts to test oil being pumped out of these huge tanks. It was found to be contaminated with mercury, benzene and lead.

At the start of my internship, I had little idea of how ERT functioned. Unlike the 10 regional offices of the Environmental Protection Agency, ERT is a “headquarters” or Washington, DC-based group, which means it responds to incidents all over the country such as oil spills, train derailments, and natural disasters.

For example, my mentor, an air specialist who generally works from his cubicle in Edison, aided in the immediate aftermath of Hurricane Katrina by employing equipment to analyze air for hazardous pollutants. Other ERT team members have conducted sediment sampling to expedite the hazardous waste removal process, given consultation advice to other EPA members for long-term remedial site work, and led the innovation of new technology.

I was able to shadow and help my mentor and fellow ERT members with their Superfund site removal work. I created accurate maps showing injection well locations, learned how to use air monitoring instruments, and helped perform chemical lab experiments that will be employed for future site analysis.

Perhaps my favorite part of the internship was traveling to a myriad of active sites. At these sites, I not only got to see how ERT members worked with EPA’s on-scene coordinators, but also observed the physical removal and remediation processes. I was fortunate to visit a particular site multiple times — I witnessed the removal of contaminated oil from an abandoned lot as the summer progressed.

Stella Wang (left) and an EPA air specialist calibrating a air monitoring instrument before a public event.

At another site, I saw the beginning of an injection process intended to prevent the contamination of underground drinking water by hexavalent chromium. By pumping sodium lactate into underground wells, the hexavalent is converted into the insoluble and benign chromium-3 ion. If the injection process works, the community will no longer be threatened by this particular hazardous material.

ERT also acts in anticipation of possible contamination to protect the public. At largely attended events like the Democratic National Convention, a few ERT members will arrive with monitoring equipment. They pride themselves in their real-time data collection for a reason: throughout the event, they can detect whether a contaminant has been released and immediately instigate an emergency response to protect attendees.

Thanks to various ERT members, I felt accepted and welcome. They were open and patient with my never-ending questions about their career paths and other things. They’ve graciously taken me out to lunch so that they could get to know me better, ensuring my inclusion in their small community.

Of course, the experiences I had this summer, while brief, have taught me a tremendous amount and I have a clearer sense of how this division of the US federal government functions. But, it would be inaccurate and unjust to omit the impact that its people made on me.

Stella Wang, Duke 2019Guest post by Stella Wang, Class of 2019

Science on the Trail

Duke launches free two-week girls science camp in Pisgah National Forest.

Duke launches free two-week girls science camp in Pisgah National Forest.

DURHAM, N.C. — To listen to Destoni Carter from Raleigh’s Garner High School, you’d never know she had a phobia of snails. At least until her first backpacking trip, when a friend convinced her to let one glide over her outstretched palm.

Destoni Carter

Destoni Carter from Raleigh’s Garner High School was among eight high schoolers in a new two-week camp that combines science and backpacking.

Soon she started picking them up along the trail. She would collect a couple of snails, put them on a bed of rocks or soil or leaves, and watch to see whether they were speedier on one surface versus another, or at night versus the day.

The experiment was part of a not-so-typical science class.

From June 11-23, 2017, eight high school girls from across North Carolina and four Duke Ph.D. students left hot showers and clean sheets behind, strapped on their boots and packs, and ventured into Pisgah National Forest.

For the high schoolers, it was their first overnight hike. They experienced a lot of things you might expect on such a trip: Hefty packs. Sore muscles. Greasy hair. Crusty socks. But they also did research.

The girls, ages 15-17, were part of a new free summer science program, called Girls on outdoor Adventure for Leadership and Science, or GALS. Over the course of 13 days, they learned ecology, earth science and chemistry while backpacking with Duke scientists.

Duke ecology Ph.D. student Jacqueline Gerson came up with the idea for the program. “Backpacking is a great way to get people out of their comfort zones, and work on leadership development and teambuilding,” said Gerson, who also teamed up with co-instructors Emily Ury, Alice Carter and Emily Levy, all Ph.D. students in ecology or biology at Duke.

Marwa Hassan of Riverside High School in Durham studying stream ecology as part of a two-week summer science program in Pisgah National Forest. Photo by Savannah Midgette.

Marwa Hassan of Riverside High School in Durham studying stream ecology as part of a two-week summer science program in Pisgah National Forest. Photo by Savannah Midgette.

The students hauled 30- to 40-pound loads on their backs for up to five miles a day, through all types of weather. For the first week and a half they covered different themes each day: evolution, geology, soil formation, aquatic chemistry, contaminants. Then on the final leg they chose an independent project. Armed with hand lenses, water chemistry test strips, measuring tapes and other gear, each girl came up with a research question, and had two days to collect and analyze the data.

Briyete Garcia-Diaz of Kings Mountain High School surveyed rhododendrons and other trees at different distances from streambanks to see which species prefer wet soils.

Marwa Hassan of Riverside High School in Durham waded into creeks to net mayfly nymphs and caddisfly larvae to diagnose the health of the watershed.

Savannah Midgette of Manteo High School counted mosses and lichens on the sides of trees, but she also learned something about the secret of slug slime.

“If you lick a slug it makes your tongue go numb. It’s because of the protective coating they have,” Midgette said.

High schoolers head to the backcountry to learn the secret of slug slime and other discoveries of science and self in new girls camp

High schoolers head to the backcountry to learn the secret of slug slime and other discoveries of science and self in new girls camp

The hiking wasn’t always easy. On their second day they were still hours from camp when a thunderstorm rolled in. “We were still sore from the previous day. It started pouring. We were soaking wet and freezing. We did workouts to keep warm,” Midgette said.

At camp they took turns cooking. They stir fried chicken and vegetables and cooked pasta for dinner, and somebody even baked brownies for breakfast. Samantha Cardenas of Charlotte Country Day School discovered that meals that seem so-so at home taste heavenly in the backcountry.

“She would be like, ugh, chicken in a can? And then eat it and say: ‘That’s the most amazing thing I’ve ever had,’” said co-instructor Emily Ury.

Savannah Midgette and Briyete Garcia-Diaz drawing interactions within terrestrial systems as part of a new free summer science program called Girls on outdoor Adventure for Leadership and Science, or GALS. Learn more at https://sites.duke.edu/gals/.

Savannah Midgette and Briyete Garcia-Diaz drawing interactions within terrestrial systems as part of a new free summer science program called Girls on outdoor Adventure for Leadership and Science, or GALS. Learn more at https://sites.duke.edu/gals/.

The students were chosen from a pool of over 90 applicants, said co-instructor Emily Levy. There was no fee to participate in the program. Thanks to donations from Duke Outdoor Adventures, Project WILD and others, the girls were able to borrow all the necessary camping gear, including raincoats, rain pants, backpacks, tents, sleeping bags, sleeping pads and stoves.

The students presented their projects on Friday, June 23 in Environment Hall on Duke’s West Campus. Standing in front of her poster in a crisp summer dress, Destoni Carter said going up and down steep hills was hard on her knees. But she’s proud to have made it to the summit of Shining Rock Mountain to see the stunning vistas from the white quartz outcrop near the top.

“I even have a little bit of calf muscle now,” Carter said.

Funding and support for GALS was provided by Duke’s Nicholas School of the Environment, Duke ecologist Nicolette Cagle, the Duke Graduate School and private donors via GoFundMe.

2017 GALS participants (left to right): Emily Levy of Duke, Destoni Carter of Garner High School, Zyrehia Polk of East Mecklenburg High School, Rose DeConto of Durham School of the Arts, Briyete Garcia-Diaz of Kings Mountain High School, Marwa Hassan of Riverside High School, Jackie Gerson of Duke, Daiana Mendoza of Harnett Central High School, Savannah Midgette of Manteo High School, Samantha Cardenas of Charlotte Country Day School and Alice Carter of Duke.

2017 GALS participants (left to right): Emily Levy of Duke, Destoni Carter of Garner High School, Zyrehia Polk of East Mecklenburg High School, Rose DeConto of Durham School of the Arts, Briyete Garcia-Diaz of Kings Mountain High School, Marwa Hassan of Riverside High School, Jackie Gerson of Duke, Daiana Mendoza of Harnett Central High School, Savannah Midgette of Manteo High School, Samantha Cardenas of Charlotte Country Day School and Alice Carter of Duke.


3D Virus Cam Catches Germs Red-Handed

A 3D plot of a virus wiggling around

The Duke team used their 3D virus cam to spy on this small lentivirus as it danced through a salt water solution.

Before germs like viruses can make you sick, they first have to make a landing on one of your cells — Mars Rover style — and then punch their way inside.

A team of physical chemists at Duke is building a microscope so powerful that it can spot these minuscule germs in the act of infection.

The team has created a new 3D “virus cam” that can spy on tiny viral germs as they wriggle around in real time. In a video caught by the microscope, you can watch as a lentivirus bounces and jitters through an area a little wider that a human hair.

Next, they hope to develop this technique into a multi-functional “magic camera” that will let them see not only the dancing viruses, but also the much larger cell membranes they are trying breech.

“Really what we are trying to investigate is the very first contacts of the virus with the cell surface — how it calls receptors, and how it sheds its envelope,” said group leader Kevin Welsher, assistant professor of chemistry at Duke. “We want to watch that process in real time, and to do that, we need to be able to lock on to the virus right from the first moment.”

A 3D plot spells out the name "Duke"

To test out the microscope, the team attached a fluorescent bead to a motion controller and tracked its movements as it spelled out a familiar name.

This isn’t the first microscope that can track real-time, 3D motions of individual particles. In fact, as a postdoctoral researcher at Princeton, Welsher built an earlier model and used it to track a bright fluorescent bead as it gets stuck in the membrane of a cell.

But the new virus cam, built by Duke postdoc Shangguo Hou, can track particles that are faster-moving and dimmer compared to earlier microscopes. “We were trying to overcome a speed limit, and we were trying to do so with the fewest number of photons collected possible,” Welsher said.

The ability to spot dimmer particles is particularly important when tracking viruses, Welsher said. These small bundles of proteins and DNA don’t naturally give off any light, so to see them under a microscope, researchers first have to stick something fluorescent on them. But many bright fluorescent particles, such as quantum dots, are pretty big compared to the size of most viruses. Attaching one is kind of like sticking a baseball onto a basketball – there is a good chance it might affect how the virus moves and interacts with cells.

The new microscope can detect the fainter light given off by much smaller fluorescent proteins – which, if the virus is a basketball, are approximately the size of a pea. Fluorescent proteins can also be inserted to the viral genome, which allows them to be incorporated into the virus as it is being assembled.

“That was the big move for us,” Welsher said, “We didn’t need to use a quantum dot, we didn’t need to use an artificial fluorescent bead. As long as the fluorescent protein was somewhere in the virus, we could spot it.” To create their viral video, Welsher’s team enlisted Duke’s Viral Vector Core to insert a yellow fluorescent protein into their lentivirus.

Now that the virus-tracking microscope is up-and-running, the team is busy building a laser scanning microscope that will also be able to map cell surfaces nearby. “So if we know where the particle is, we can also image around it and reconstruct where the particle is going,” Welsher said. “We hope to adapt this to capturing viral infection in real time.”

Robust real-time 3D single-particle tracking using a dynamically moving laser spot,” Shangguo Hou, Xiaoqi Lang and Kevin Welsher. Optics Letters, June 15, 2017. DOI: 10.1364/OL.42.002390

Kara J. Manke, PhDPost by Kara Manke

Hidden No More: Women in STEM reflect on their Journeys

Back when she was a newly-minted Ph.D., Ayana Arce struggled to picture her future life as an experimental physicist. An African American woman in a field where the number of black women U.S. doctorates is still staggeringly small, Arce could not identify many role models who looked like her.

“I didn’t know what my life would look like as a black postdoc or faculty member,” Arce said.

But in the end, Arce – an associate professor of physics at Duke who went on to join the international team of physicists who discovered the Higgs Boson in 2012 — drew inspiration from her family.

“I looked to the women such as my mother who had had academic careers, and tried to think about how I could shape my life to look something like that, and I realized that it could be something I could make work,” Arce said.

Adrienne Stiff-Roberts, Fay Cobb Payton, Kyla McMullen, Robin Coger and Valerie Ashby on stage at the Hidden Figures No More panel discussion.

Adrienne Stiff-Roberts, Fay Cobb Payton, Kyla McMullen, Robin Coger and Valerie Ashby on stage at the Hidden Figures No More panel discussion. Credit: Chris Hildreth, Duke Photography.

Arce joined five other African American women faculty on the stage of Duke’s Griffith Film Theater March 23 for a warm and candid discussion on the joys and continuing challenges of their careers in science, technology, engineering and math (STEM) fields.

The panel, titled “Hidden Figures No More: Highlighting Phenomenal Women in STEM,” was inspired by Hidden Figures, a film which celebrates three pioneering African American women mathematicians who overcame racial segregation and prejudice to play pivotal roles in NASA’s first manned space flight.

The panel discussion was spearheaded by Johnna Frierson, Director of the Office of Diversity and Inclusion at the Pratt School of Engineering, and co-sponsored by the Duke Women’s Center. It was followed by a free screening of the film.

Though our society has made great strides since the days depicted in the film, women and minorities still remain under-represented in most STEM fields. Those who do pursue careers in STEM must overcome numerous hurdles, including unconscious bias and a lack of colleagues and role models who share their gender and race.

“In my field, at some of the smaller meetings, I am often the only black woman present at the conference, many times I’m the only black person at all,” said Adrienne Stiff-Roberts, an Associate Professor of Electrical and Computer Engineering at Duke. “In that atmosphere often it can be very challenging to engage with others in the way that you are supposed to, and you can feel like an outsider.”

Valerie Ashby and Ayana Arce onstage at the Hidden Figures No More panel discussion

Valerie Ashby and Ayana Arce shared their experiences. Credit: Chris Hildreth, Duke Photography

Stiff-Roberts and the other panelists have all excelled in the face of these challenges, making their marks in fields that include physics, chemistry, computer science, mechanical engineering and electrical engineering. On Thursday they shared their thoughts and experiences with a diverse audience of students, faculty, community members and more than a few kids.

Many of the panelists credited teams of mentors and sponsors for bolstering them when times got tough, and encouraged young scientists to form their own support squads.

Valerie Ashby, Dean at Duke’s Trinity College of Arts and Sciences, advised students to look for supporters who have a vision for what they can become, and are eager to help them get there. “Don’t assume that your help might come from people who you might expect your help to come from,” Ashby said.

The importance of cheerleading from friends, and particularly parents, can never be overestimated, the panelists said.

“Having someone who will celebrate every single positive with you is a beautiful thing,” said Ashby, in response to a mother seeking advice for how to support a daughter majoring in biomedical engineering. “If your daughter is like many of us, we’ll do 99 great things but if we do one wrong thing we will focus on the one wrong thing and think we can’t do anything.”

Women in STEM can also be important and powerful allies to each other, noted Kyla McMullen, an Assistant Professor of Computer and Information Science at the University of Florida.

“I have seen situations where a woman suggests something and then the male next her says the same thing and gets the credit,” McMullen said. “That still happens, but one thing that I see help is when women make an effort to reiterate the points made by other women so people can see who credit should be attributed to.”

With all the advice out there for young people who are striving to succeed in STEM – particularly women and underrepresented minorities – the panelists advocated that everyone to stay true to themselves, above all.

“I want to encourage everyone in the room – whether you are a budding scientist or woman scholar – you can be yourself,” Ashby said. “You should make up in your mind that you are going to be yourself, no matter what.”

Kara J. Manke, PhD

Post by Kara Manke

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