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Clark Receives NSF Early Career Award

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Joseph Clark, assistant professor of chemistry, has received a National Science Foundation CAREER award for his work developing molecules that facilitate pharmaceutical drug design and evaluation.

Clark will receive $650,000 for his research into the use of tritium, the radioactive isotope of hydrogen, for the selective labeling of small molecules and drug candidates. Selective tritiation of drugs plays a critical role in determining how animals (including humans) metabolize them. Typically, scientists incorporate carbon-14 into the molecular structure of new drugs for FDA-mandated metabolic and safety testing; this isotope of carbon allows researchers to track the pathway and the behavior of drug molecules in the body without harming human subjects.

However, the worldwide supply of C-14 is produced primarily at one facility in Russia, and Russia’s ongoing war with Ukraine has caused a worldwide shortage. The shortage poses a potential threat to all small-molecule drugs awaiting approval from regulatory authorities in the U.S. and Europe. Clark and his team will research the use of tritium as a mainstream alternative radiolabeling strategy, thereby reducing the reliance on C-14 for most clinical metabolism studies in humans.

“Tritium is more difficult to use because it sits on the periphery of a molecule, which makes it less stable, or more prone to metabolic oxidation,” Clark said. “My team will research how to add specific amounts of tritium at sites less prone to oxidation and how to measure the purity and structure of these molecules. The United States produces tritium for research and government use, and there are several international suppliers in North America and Europe; if we can make it the new gold standard for drug tracing, we can solve the C-14 crisis and develop new medications more quickly and less expensively.”

NSF created CAREER to recognize and support early-career faculty who can serve as role models in their institutions while advancing research that benefits their state and the nation. In addition to Clark, researchers Doowon Kim, assistant professor of computer science, and Joon Sue Lee, assistant professor of physics and astronomy, also received NSF CAREER awards for their work in designing phishing detectors and developing new materials for quantum technology, respectively.

“We are incredibly proud of this year’s recipients,” said Deb Crawford, vice chancellor for research, innovation, and economic development. “Their efforts will lead to groundbreaking discoveries and inspire students at all levels to experience the excitement and fulfillment of scientific exploration. Their work has significant state and national impact.”

Clark began his career at Marquette University, and joined the chemistry faculty at the University of Tennessee, Knoxville in 2024. His research focuses on the development of selective transition metal-catalyzed reactions. Read more about Clark’s research here.

A student works in the Baccile lab.

Baccile Awarded $1.8 Million Grant for Pioneering Research on Five-Carbon Metabolism

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Headshot Joshua Baccile

Assistant Professor Joshua Baccile has been awarded a Maximizing Investigators’ Research (MIRA) award from the NIH. The MIRA grant, unlike many other grants, is awarded to support a researcher’s collective vision for their lab. Baccile’s lab is focused on investigating the role of five-carbon metabolism in the human body, which could impact long-term health.

“Our cells make cholesterol through a metabolic pathway called the isoprenoid pathway and many of the most largely prescribed drugs target this pathway. Statins are the most common example of these,” said Baccile.

Statins, commonly prescribed for high cholesterol, generally work by reducing the number of five-carbon precursors in the isoprenoid pathway. However, the underlying function of these five-carbon precursors is not well understood.

Baccile’s research examines what else these molecules do in the body beyond contributing to high levels of cholesterol. His team has made derivatives of two precursor molecules that can be introduced into cells. This allows his team to test for a variety of effects.

“We want to figure out what other molecules they make. We want to be able to control where they go, how many of them go there, and we want to be able to track them,” said Baccile. “Our goal is to expand the scope of what’s known about the isoprenoid pathway.”

Baccile’s lab was the first to develop functional derivatives of these 5-carbon precursors that can be used in experimentation. This work has the potential to discover the underlying purpose of a poorly understood metabolic pathway in the human body, which could impact several areas of human health.

Because of its foundational nature, Baccile’s research has generated international interest and opportunities for collaboration with other teams investigating the complexities of the human body.

“When we do science, we’re trying to discover unknowns which, in our case, are about human cellular physiology,” said Baccile. “This research is important because it will help us understand a really important pathway in basic human biology. These molecules are implicated in cardiac diseases, neurodegenerative diseases, and cancer. If we know more about them and how they work, we can create better treatments and therapies that target some of the most common issues in human health today.”

Baccile also plans to leverage his MIRA grant to continue, and potentially expand, his existing community college research fellowship program. This program provides summer research opportunities for area community college students interested in transferring into a four-year program.

“A critical function of academic research labs is the training of students and future scientists who will continue to ask these questions and make new discoveries,” said Baccile. He describes his graduate students as instrumental to the early research and publications that build into grants like the MIRA.

The NIH MIRA grant will provide $1.8 million to the Baccile lab over the course of five years.

A young Asian man wearing a blue lab coat and clear safety glasses is using a glove box in a lab. A shadow of his image is reflected in the glove box window

Baccile’s Grant Prepares Community College Students for Four-Year Programs

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A young Asian man wearing a blue lab coat and clear safety glasses is using a glove box in a lab. A shadow of his image is reflected in the glove box window

Joshua Baccile, assistant professor in the Department of Chemistry, is leveraging a National Science Foundation (NSF) grant to provide summer research opportunities to community college students. He hopes the program will encourage more students to pursue a four-year degree.

The NSF requires all submissions to not only detail the proposed research, but to address the broader impacts of that research. NSF broader impacts are described as tangible societal benefits that go beyond the research’s contribution to the greater body of knowledge, and ensure that publicly funded research contributes to a public good.

Baccile addressed the broader impact question in his proposal by creating a summer research internship for community college students who are interested in pursuing a bachelor’s degree in chemistry or a closely related field. His goal was to tailor a comprehensive research program that would provide hands-on experience and professional development opportunities, and help ease the transition from community college to a four-year program.

“This program is important to me because I started out in community college. There is often a bit of a gap between the skills developed in a two-year program and the skills needed to succeed in a four-year program,” said Baccile. “When I was an undergraduate student, my summer research experience was critical to my continued pursuit of chemistry and I wanted to create an opportunity like that for our local community college students.”

To get the program running, Baccile had to first build a relationship with local community colleges and establish a pool of interested students. He reached out to Pellissippi State Community College (PSCC) via a colleague and visited the campus repeatedly to discuss the program with the college’s organic chemistry students. When the program began accepting applications, the response from students was overwhelmingly positive.  

“In the first year, we had a number of qualified applicants that we were forced to turn down because I simply didn’t have room for them in my lab,” said Baccile. “It was immediately clear this is an opportunity students want.”

Now in its second year, Baccile’s program has expanded beyond his own lab to include the research groups of Mike Best and Johnathan Brantley, fellow faculty members in the chemistry department. The addition of these labs has allowed the program to support more qualified students, a trend Baccile hopes to continue.

He notes that, thus far, all of the students who have participated in the summer internship program have gone on to four-year institutions in Tennessee, including UT’s chemistry department.

“This program is establishing pathways to four-year degree programs for Tennessee residents through research experiences. Not only is this helping individual students expand their future opportunities, it’s directly contributing to the state’s workforce development goals,” said Baccile.

Chemistry is a growing industry in the state of Tennessee. In the last six years, industry partners have made investments in excess of $400 million and created more than 2,000 jobs. Qualified and capable chemists will continue to be in-demand in Tennessee for the foreseeable future, and Baccile strongly believes that research experiences directly impact whether a student continues to work in the field of chemistry.

“My undergraduate summer research experience is the reason I’m a chemist,” said Baccile. “I think early exposure to research significantly improves the chances of students discovering their own passion for chemistry, and I am dedicated to extending the same invaluable opportunity I benefitted from to current and future community college students.”

The NSF proposal that funds Baccile’s summer research program has one year remaining. However, he hopes to find a way to continue and even expand the program into something more permanent in the future.

Dr. Baccile and graduate student Zack Hulsey stand with two young women in front of a case of lab supplies. They are wearing lab coats and safety glasses and are all smiling.
Dr. Baccile and graduate student Hima Davit stand with a young male student. They are smiling.
Dr. Baccile and graduate student Robert Maraski stand with a male student in front of a glove box. They are smiling.
water jug

UT Professors Investigate Solutions for “Forever Chemicals”

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University of Tennessee, Knoxville faculty members Shawn Campagna, professor and associate department head in chemistry, and Frank Loeffler, Governor’s Chair professor in microbiology, have made a discovery that could lead to new capabilities for managing environmental contamination.

Commercially used per- and polyfluoroalkyl substances (PFAS) were developed in the 1940’s and made their way into a variety of common household products. Today, PFAS are used for plastic and rubber manufacturing and in food wrappers, umbrellas, firefighting foam and more.

PFAS have also been called “forever chemicals” due to their resistance to breaking down in both the environment and the human body. PFAS have been discovered lingering in rivers, Arctic sea ice, human breast milk and in the blood of 97% of Americans. Most troublesome is their potential impact on human health and PFAS have been linked to metabolic disruption, obesity, diabetes, immune suppression, and cancer.

Loeffler and Campagna’s work, recently published in Environmental Science and Technology, explores a potential avenue for decreasing broad contamination with these chemicals. Their team found that a naturally occurring soil bacterium, Pseudomonas sp. strain 273, was capable of degrading and detoxifying 1,10-difluorodecane, a fluorinated compound that could be a model for dealing with PFAS. Surprisingly, this bacterium was also able to use the fluorine containing byproducts to build lipid bilayers, or cellular membranes, which indicates that we don’t yet know all that we should about the fate of this type of compounds in biological systems.

“This research is important since fluorinated organic chemicals are emerging contaminants, and we do not yet know how and if they enter the food web,” said Campagna. “The fact that bacteria can incorporate breakdown products of these molecules into their biomass indicates that we don’t fully understand the environmental impact of these contaminants.”

This discovery developed from a long-standing series of collaborations between Campagna and Loeffler and leverages the capabilities of both the Center for Environmental Biotechnology and the Biological and Small Molecule Mass Spectrometry Core.

“There is a pressing need to demonstrate that natural degradation processes for PFAS exist – that they are not forever chemicals,” said Loeffler. “The new findings emerged through collaborative efforts at the interface of disciplines, specifically environmental microbiology and analytical chemistry. My group obtained and characterized the unique microorganism, and Dr. Campagna’s group had the instrumentation and expertise to perform the analytical procedures. The results are a product of teamwork and neither group individually would have succeeded.”

Campagna and Loeffler hope their work can lead to further discoveries of bacteria capable of degrading the entire range of fluorinated pollutants, which could lead to removing PFAS from contaminated areas like drinking water.

As part of the bipartisan infrastructure law funding initiative, the U.S. Environmental Protection Agency is making available $1 billion in grant funding, the first of $5 billion through the law. This initiative aims at reducing PFAS in drinking water specifically in communities facing disproportionate impacts.

Both Loeffler and Campagna have been contacted by the Tennessee Department of Environment and Conservation (TDEC) regarding state mandated PFAS monitoring in drinking water. Their capabilities are facilitating statewide efforts to improve the quality of life for all residents of the state of Tennessee.

Best Group Publishes ATP-Responsive Liposomes in JACS

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The research group of Michael Best in Tennessee Chemistry, led by graduate student Jinchao Lou, recently published an article describing the development of ATP-responsive liposomes in the Journal of the American Chemical Society. The nanocarriers reported in this work show strong prospects for enhancing clinical drug delivery applications.

Liposomes are highly effective nanocarriers for therapeutics due to their ability to encapsulate drugs with wide-ranging properties and enhance their circulation and delivery to cells. However, their potential could be improved by achieving control over the release of cargo to maximize drug potency and diseased-cell selectivity. While liposome-triggered release represents a vibrant field of research due to this significance, the toolbox for controlling liposome release remains limited and prior strategies face many challenges that obstruct clinical application.

The Best Group has explored a new paradigm for triggered release in which cargo escape is triggered only when liposomes encounter specific small molecule metabolites that are overly abundant in disease states. This is achieved using synthetic stimuli-responsive lipid switches designed to undergo programmed conformational changes upon the binding of small molecule targets, events that compromise membrane packing and thereby drive release.

In this work, Lou and co-workers developed liposomes that selectively respond to ATP over eleven other structurally similar phosphorylated small molecules. ATP is a critical target for metabolite-mediated drug delivery since this molecule is a universal energy source that is known to be heavily upregulated in-and-around cancer cells. This opens up the potential for selective drug delivery and release driven by overly abundant ATP associated with diseased cells.

This project also entailed a collaboration with the group of Dr. Francisco Barrera in the Tennessee Biochemistry & Cellular and Molecular Biology (BCMB) Department. Through cellular delivery and fluorescence imaging experiments, graduate student Jennifer Schuster showed that modulation of cellular ATP levels using drugs led to direct control of cellular delivery of ATP-responsive liposomes. These results demonstrate the key advancement that liposome delivery can be modulated by the cellular abundance of ATP.

A provisional patent has been filed for this ATP-responsive liposome technology. Additionally, the Best Group is currently working on advancing this platform for clinical delivery applications and developing liposomes that respond to other disease-associated small molecule metabolites.  

Darko Lab Published in Dalton Transactions

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The Darko Lab published their work “Tuning Rh(ii)-catalysed cyclopropanation with tethered thioether ligands” in Dalton Transactions. 

Dirhodium(II) paddlewheel complexes have high utility in diazo-mediated cyclopropanation reactions and ethyl diazoacetate is one of the most commonly used diazo compounds in this reaction. In this study, the lab reports efforts to use tethered thioether ligands to tune the reactivity of RhII-carbene mediated cyclopropanation of olefins with ethyl diazoacetate.

Microwave methods enabled the synthesis of a family of RhII complexes in which tethered thioether moieties were coordinated to axial sites of the complex. Different tether lengths and thioether substituents were screened to optimise cyclopropane yields and minimise side product formation.

Good yields were obtained when equimolar diazo and olefin were used. Structural and spectroscopic investigation revealed that tethered thioethers changed the electronic structure of the rhodium core, which was instrumental in the performance of the catalysts. Computational modelling of the catalysts provided further support that the tethered thioethers were responsible for increased yields.

Best Group Published in Chemistry and Physics of Lipids

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The Best Group’s article titled “Metabolic labeling of glycerophospholipids via clickable analogs derivatized at the lipid headgroup” was published in Chemistry and Physics of Lipids.

Metabolic labeling, in which substrate analogs containing diminutive tags can infiltrate biosynthetic pathways and generate labeled products in cells, has led to dramatic advancements in the means by which complex biomolecules can be detected and biological processes can be elucidated.

Within this realm, metabolic labeling of lipid products, particularly in a manner that is headgroup-specific, brings about a number of technical challenges including the complexity of lipid metabolic pathways as well as the simplicity of biosynthetic precursors to headgroup functionality. As such, only a handful of strategies for metabolic labeling of lipids have thus far been reported. However, these approaches provide enticing examples of how strategic modifications to substrate structures, particularly by introducing clickable moieties, can enable the hijacking of lipid biosynthesis.

Furthermore, early work in this field has led to an explosion in diverse applications by which these techniques have been exploited to answer key biological questions or detect and track various lipid-containing biological entities. In this article, the group reviews these efforts and emphasize recent advancements in the development and application of lipid metabolic labeling strategies.

Best Group’s Recent Work

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Recent work in the Best Group has culminated in the development of stimuli-responsive liposomes for drug delivery designed to release therapeutic cargo when they come into contact with diseased cells, specifically based on overexpressed enzymes and reactive oxygen species. “These smart liposomes show strong prospects for advancing drug delivery by targeting therapeutics directly to the site of the disease,” Jinchao Lou, graduate student in the Best Group, said.

Liposomes are effective nanocarriers for drug delivery due to their ability to encapsulate and deliver a wide variety of therapeutic cargo to cells. Nevertheless, liposome delivery would be improved by enhancing the ability to control the release of contents within diseased cells. Toward this end, stimuli-responsive liposomes, in which the drug carrier decomposes when it comes in contact with conditions associated with disease, are of great interest for enhancing drug potency while minimizing side effects.

While various stimuli have been explored for triggering liposome release, both enzymes and reactive oxygen species (ROS) provide excellent targets due to their key roles in biology and overabundance in diseased cells. In two separate papers, the Best Group presented a general approach to enzyme‐responsive liposomes exploiting targets that are commonly aberrant in disease, including esterases, phosphatases, and β‐galactosidases (Chem. Eur. J. 2020, 26, 8597-8607), as well as an ROS-responsive liposomal delivery platform (Bioconjugate Chem. 2020, 31, 2220-2230).

In both of the cases, responsive lipids designed to target each stimulus were designed and synthesized bearing a responsive headgroup attached via a self‐immolating linker to a non‐bilayer lipid scaffold. In this way, stimulus addition triggers chemical lipid decomposition in a manner that disrupts membrane integrity and releases contents. Release properties were fully characterized by fluorescence-based dye leakage assays, dynamic light scattering and electron microscopy, among other techniques.

Due to their recent works in this field, the Best group was also invited to write a review describing advances in the design of stimuli-responsive liposome strategies for drug delivery with an eye towards emerging trends in the field (Chem. Phys. Lipids. In Press. DOI 10.1016/j.chemphyslip.2020.104966). Smart liposomes show strong prospects for advancing drug delivery by targeting drugs directly to the site of the disease.

Campagna Group Published in Environmental Microbiology

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The Campagna Group has published a collaborative piece titled “Nitrogen flux into metabolites and microcystins changes in response to different nitrogen sources in Microcystis aeruginosa NIES-843” in Environmental Biology. 

The over-enrichment of nitrogen (N) in the environment has contributed to severe and recurring harmful cyanobacterial blooms, especially by the non-N2 -fixing Microcystis spp. N chemical speciation influences cyanobacterial growth, persistence and the production of the hepatotoxin microcystin, but the physiological mechanisms to explain these observations remain unresolved.

Stable-labelled isotopes and metabolomics were employed to address the influence of nitrate, ammonium, and urea on cellular physiology and production of microcystins in Microcystis aeruginosa NIES-843. Global metabolic changes were driven by both N speciation and diel cycling. Tracing 15 N-labelled nitrate, ammonium, and urea through the metabolome revealed N uptake, regardless of species, was linked to C assimilation.

The production of amino acids, like arginine, and other N-rich compounds corresponded with greater turnover of microcystins in cells grown on urea compared to nitrate and ammonium. However, 15 N was incorporated into microcystins from all N sources. The differences in N flux were attributed to the energetic efficiency of growth on each N source.

While N in general plays an important role in sustaining biomass, these data show that N-speciation induces physiological changes that culminate in differences in global metabolism, cellular microcystin quotas and congener composition.