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Author: Kayla Benson

Heberle Lab’s Latest Achievements

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Research in the Heberle Lab is aimed at elucidating the structure and function of biological membranes, with a focus on the plasma membrane.

Fred A. Heberle is coauthor of the recently published book Characterization of Biological Membranes. This book explores the high importance  of membranes in the fields of biology, pharmaceutical chemistry and medicine, since much of what happens in a cell or in a virus involves biological membranes. This book is an excellent introduction to the area, which explains how modern analytical methods can be applied to study biological membranes and membrane proteins and the bioprocesses they are involved to.

Heberle was also awarded $1.7M from the National Institutes of Health (NIH) for The Research Project (R01). The R01 is the original and historically oldest grant mechanism used by NIH. The R01 provides support for health-related research and development based on the mission of the NIH. The Heberle Lab aims to extend membrane studies through an unprecedented integration of lipidomics, biophysical experiments, cryogenic transmission electron microscopy (cryoEM), and advanced molecular simulations, to test their central hypothesis that compositionally asymmetric membranes have unique biophysical properties resulting from robust coupling between lateral and transverse membrane organization. 

The Heberle Lab had a journal cover on Nanoscale for their work on “Transverse lipid organization dictates bending fluctuations in model plasma membranes.” 

The Heberle Lab published their research “Direct label-free imaging of nanodomains in biomimetic and biological membranes by cryogenic electron microscopy” in Proceedings of the National Academy of Sciences of the USA. They worked with a collaborative team to capture the first direct images of tiny cell membrane domains known as lipid rafts. The images were published as a journal cover in PNAS. 

PNAS also published the Heberle Lab’s collaborative research “How cholesterol stiffens unsaturated lipid membranes.”  Their observations that cholesterol causes local stiffening in DOPC membranes indicate that a reassessment of existing concepts is necessary. These findings have far-reaching implications in understanding cholesterol’s role in biology and its applications in bioengineering and drug design.

Xue Group’s Recent Research

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The Xue group has published multiple papers this year. This group’s research focuses on three areas: spectroscopic studies of molecular magnetism, synthesis and characterization of transition metal complexes, and the development of new chemical analyses. 

 Inorganic Chemistry published their work “Inter-Kramers Transitions and Spin–Phonon Couplings in a Lanthanide-Based Single-Molecule Magnet.” Spin–phonon coupling plays a critical role in magnetic relaxation in single-molecule magnets (SMMs) and molecular qubits. This research shows spin–phonon couplings between IR-active phonons in a lanthanide molecular complex and Kramers doublets (from the crystal field). This study unveils and measures the spin–phonon couplings in a typical lanthanide complex and throw light on the origin of the spin–phonon entanglement.

Chinese Journal of Inorganic Chemistry published the group’s work on “Direct Observation of Magnetic Transitions in a Nickel(II) Complex with Large Anisotropy.” 

Chemosphere published their work “Sustained Release of Persulfate from Inert Inorganic Materials for Groundwater Remediation.” This work demonstrates the potential feasibility of sustained persulfate release from inert matrices for groundwater treatment.

They also have an invited review for the Comprehensive Coordination III  on Tantalum in press. 

Campagna Gives Talk for Harvard’s MSI Seminar Series

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The Microbial Sciences Initiative (MSI) at Harvard University is an interdisciplinary science program aimed at a comprehensive understanding of the richest biological reservoir of the planet, the microbial world.

Shawn Campagna presented a talk for this series titled “Using Metabolomics to Understand the Function of Environmentally Relevant Microbial Consortia.”

 

Calhoun Lab Featured Cover in J. Phys. Chem. C

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The Calhoun Lab was published in the Journal of Physical Chemistry C for their research “Leaving the Limits of Linearity for Light Microscopy” and it is a perspective on the recent advances in the field of nonlinear microscopy. This article is also the featured cover for the November 12, 2020 issue.

Graduate student authors include Marea Blake and Brandon Colon.  Blake is currently pursuing her Ph.D. in Chemistry at the University of Tennessee, Knoxville. Her current research focuses on probing small molecule-membrane interactions in living cells using nonlinear techniques such as second harmonic generation and two-photon fluorescence.

Colon received his B.S. degree (2016) in Chemistry from the University of West Florida in Pensacola, FL. He is a doctoral student at the University of Tennessee under the tutelage of Prof. Tessa Calhoun. He has been investigating the use of total internal reflection illumination geometries to apply nonlinear microscopy techniques to microfluidic samples.

In this paper, the group highlights recent developments within the past couple of years pertaining to how nonlinear microscopy methods such as transient absorption, 2D nonlinear microscopy, second order processes, and quantum microscopy are being implemented to probe different timescales, access information on interfaces and illuminate samples with novel excitation schemes. 

“Our group actually uses a few of these methods (such as TAM, SHG and TIR geometry excitation) in our lab so it was really exciting getting to portray that in this perspective and explore the directions they can grow,” Blake said.

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.

ORI Names Campagna Interim Director of Strategic Programs

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President Randy Boyd shared some developments at the Oak Ridge Institute at UT (ORI at UT). A national search for the first executive director and vice provost of the Oak Ridge Institute at UT is underway.

Shawn Campagna
Shawn Campagna

ORNL Director Thomas Zacharia and Randy Boyd, in consultation with UT Knoxville Chancellor Donde Plowman and UT Health Science Center Chancellor Steve Schwab, have named Michelle Buchanan, ORNL deputy for science and technology, and Stacey Patterson, UT System vice president for research, as interim co-directors of ORI at UT until a director is named. Suresh Babu, a UT-ORNL Governor’s Chair for Advanced Manufacturing and Bredesen Center Director, will serve as ORI at UT’s interim education director. Shawn Campagna, UT Knoxville associate department head of chemistry and Director of Science Alliance, will serve as the interim director of strategic programs. Jean Mercer, UT Knoxville assistant vice chancellor for research and director of the office of sponsored programs, will serve as interim director of operations.

Collier at Kennesaw State University

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Graham Collier, originally from Fayetteville, North Carolina, received his BS in chemistry in 2011 from the University of North Carolina Wilmington. Upon graduation, Collier enrolled in the graduate program at the University of North Carolina at Charlotte and studied porphyrin chromophores under the direction of Michael Walter. After graduating in 2013, Collier enrolled in the chemistry doctoral program at UT with a concentration in polymer chemistry.
 
Collier’s dissertation entailed studying structure-property relationships of purine-based polymers and chromophores under the guidance of Mike Kilbey. Collier received his PhD in 2017 and began his position as postdoctoral research associate at Georgia Tech studying conjugated polymers for electrochromic under the mentorship of John Reynolds. Collier joined the faculty of Kennesaw State University as a tenure-track assistant professor of Chemistry in the Department of Chemistry and Biochemistry in fall of 2020.
 
Research in the Collier Group resides at the interface of organic, polymer, and materials chemistry. “We are interested in utilizing precise monomer synthesis to incorporate functional building blocks into polymeric materials with targeted macromolecular properties,” said Collier. “Specific interests include synthesis and characterization of conjugated polymer and molecule systems to understand how structure influences optical and electrochemical properties.”
 
Research in the Collier Research Group at KSU will involve the synthesis and characterization of organic molecules and polymers that find applicability in thin film electronics. The group will work to develop new polymers and molecules by manipulating their fundamental chemical structure to obtain targeted properties.
 
 
 
 

 

Vogiatzis Lab Published in Physical Chemistry Letters

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The Vogiatzis Lab published their work “Direct Identification of Mixed-Metal Centers in Metal−Organic Frameworks: Cu3(BTC)2 Transmetalated with Rh2+ Ions” in a collaborative piece in The Journal of Physical Chemistry Letters.

Raman spectroscopy was used to establish direct evidence of heterometallic metal centers in a metal–organic framework (MOF). The Cu3(BTC)2 MOF HKUST-1 (BTC3– = benzenetricarboxylate) was transmetalated by heating it in a solution of RhCl3 to substitute Rh2+ ions for Cu2+ ions in the dinuclear paddlewheel nodes of the framework. In addition to the Cu–Cu and Rh–Rh stretching modes, Raman spectra of (CuxRh1–x)3(BTC)2 show the Cu–Rh stretching mode, indicating that mixed-metal Cu–Rh nodes are formed after transmetalation.

Density functional theory studies confirmed the assignment of a Raman peak at 285 cm–1 to the Cu–Rh stretching vibration. Electron paramagnetic resonance spectroscopy experiments further supported the conclusion that Rh2+ ions are substituted into the paddlewheel nodes of Cu3(BTC)2 to form an isostructural heterometallic MOF, and electron microscopy studies showed that Rh and Cu are homogeneously distributed in (CuxRh1–x)3(BTC)2 on the nanoscale.

Brantley & Long’s Collaborative Research

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The Brantley Lab and the Long Group published collaborative research “Vinyl-addition polymerizations of cycloallenes: synthetic access to congeners of cyclic-olefin polymers” in Polymer Chemistry. Co-first authors include Nick Galan with the Brantley Lab and Justin Burroughs with the Long Group. 

Their research demonstrates that vinyl-addition polymerization of cycloallenes is a potentially valuable strategy for preparing tunable analogues of cycloolefin polymers. Cycloallenes can be polymerized in a well-controlled manner at room temperature using a simple Ni catalyst. 

“This route does not require high strain monomers to achieve cyclic motif incorporation, and copolymerization with acyclic monomers is possible, but not required to achieve good conversion,” Galan said. “Taken together, these results suggest that vinyl-addition polymerizations of cyclic allenes could provide a reliable synthetic route toward heretofore inaccessible materials.”

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Do Lab Published in Analytical Chemistry

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The Do Lab published their research “Cytotoxicity of α-Helical, Staphylococcus aureus PSMα3 Investigated by Post-Ion-Mobility Dissociation Mass Spectrometry” in Analytical Chemistry.

Staphylococcus aureus, a major bacterial human pathogen, secretes phenol-soluble modulin (PSM) peptides to stimulate inflammatory responses and kill human cells. PSMα3 is the prominent member of the PSM family and exerts its toxic function via the formation of cross-α fibrils. The fibril structure of PSMα3 resembles the eukaryotic amyloid fibrils found in the brain of Alzheimer’s disease patient, but each unit is an α-helix peptide and not a β-strand.

In this study, the Do Lab investigated how oligomeric structures and interactions with cell membrane mimetics could determine peptide cytotoxicity. To overcome the dynamic nature of interaction and aggregation process, they use ion mobility spectrometry mass spectrometry (IMS-MS) to measure the molecular shapes of the oligomeric species.

Due to the weakly-bound nature of these oligomers, it is possible for them to dissociate within the mass spectrometer. This phenomenon, called post-ion mobility dissociation, has been well documented in the past but has not been considered in previous biomolecular self-assembly studies.

The Do Lab took advantage of this typically undesired phenomenon to elucidate the molecular structures of the oligomers and determine the number of detergent molecules (which mimic the lipids in cell membrane) required to stabilize the complexes.

Consequently, the most toxic PSMα3 variant was shown to preserve its α-helical signature and required the smallest number of detergent molecules, indicating that a key virulence factor of toxic PSMα3 lies in its ability to quickly insert into the cell membrane. The same approach can be applied to similar peptide systems. Amber Gray, first author and graduate student said, “Ultimately, our study highlights the ambiguity previously present in IMS-MS data and sheds new insight into the interpretation of such data in biomolecular self-assembly studies.”

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