chemistry

UK Chemistry Alum Bryan Ingoglia Works to Improve Molecular Construction

Bryan Ingoglia is currently (May 2018) a graduate student in the Department of Chemistry at Massachusetts Institute of Technology. 

Brian grew up in Northern Kentucky, came to UK with the intention to obtain a degree in biology and attend medical school.  Like many undergraduate students, Brian’s interests changed as he took more advanced courses and became involved in undergraduate research. He decided to pursue graduate studies in chemistry and, near the completion of his graduate degree, he provided answers to a few questions.

CANCELLED - Macromolecular Receptors for Chemical Fingerprinting in Aqueous Media

**CANCELLED**

Marco Bonizzoni

Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, AL, USA.
Alabama Water Institute, The University of Alabama, Tuscaloosa, AL, USA.

E-mail: marco.bonizzoni@ua.edu

Abstract: Artificial supramolecular receptors often rely on weak intermolecular interactions for their chemical recognition properties, so they may struggle to work in competitive media, chief among 

which are water solutions. However, aqueous media are very important in analytical, environmental, and biomedical applications, so it is valuable to adapt our supramolecular tools to them. With the right tools, even the weakest noncovalent interactions can be pressed into service in aqueous media. We have been using water-soluble polymers (e.g. dendrimers, hydrogels, conjugated polymers) as scaffolds to build multivalent supramolecular sensors that take advantage of the large number of interactions and of the preorganization of receptor sites afforded by such scaffolds, resulting in improved affinity in buffered aqueous solutions near neutral pH. We have successfully built systems for the detection of interesting guest families, including carboxylate anions, simple saccharides, heavy metal cations, and polycyclic aromatic hydrocarbons. These are examples of a general approach with two key advantages. On the one hand, installing known receptor chemistry on a polymer scaffold affords a modular approach to multivalency with minimal design and synthesis effort. This improves the apparent strength of weaker interactions and allows them to overcome desolvation costs in water. On the other hand, water-soluble macromolecular scaffolds impart solubility to water-incompatible receptor families.

This simple approach is particularly valuable when designing chemical fingerprinting systems (sometimes referred to as an “electronic nose” or “tongue”) that typically require many different receptors, each one poorly selective, and recovers selectivity from judicious interpretation of the ensemble response.

**CANCELLED**

Date: 
Friday, September 3, 2021 - 4:00pm to 5:00pm
Location: 
CP-114
Type of Event (for grouping events):

Mass spectrometry method development for the discovery and characterization of secondary metabolites

Abstract: Secondary metabolites are organic compounds produced by an organism for reasons other than growth and development. In plants, secondary metabolites generally act as defense agents produced to deter predators and inhibit other competitive species. For humans, these compounds can often have a beneficial effect and are pursued and utilized as natural pharmaceuticals. The development of sensitive, high-throughput analytical screening methods for plant derived metabolites is crucial for natural pharmaceutical product discovery and plant metabolomic profiling. Here, metabolomic profiling methods were developed using a microfluidic capillary zone electrophoresis device and evaluated against traditional separation approaches. An alkaloid screening assay was constructed to analyze transgenic mutant plant extracts for novel metabolites. Putatively identified novel features were detected, elucidated, and then isolated and purified for pharmaceutical evaluation. Additionally, methods for the analysis of polyphenolic plant-derived secondary metabolites, such as cannabinoids, were also developed and evaluated. In this case, the occurrence of cross-instrumental variation was addressed, given the tight legal restrictions regarding commercialization the products in question. Lastly, the microfluidic CZE-MS methods were further applied for both primary and secondary metabolite profiling in a DMPK assay. This assay was developed to inclusively monitor metabolic changes as a response to varying concentrations of a therapeutic in circulation. The metabolomic methods developed and evaluated in this work displayed high sensitivity, efficiency, and accuracy and can be utilized across a wide variety of applications.

Attend the seminar here. Password 618011.

Date: 
Friday, July 16, 2021 - 10:00am to 11:00am
Location: 
Zoom
Type of Event (for grouping events):

Synthesis, Crystal Engineering, and Material Properties of Small-Molecule Organic Semiconductors

Abstract: Small-molecule organic materials are of increasing interest for electronic and photonic devices due to their solution processability and tunability, allowing devices to be fabricated at low temperature on flexible substrates and offering utility in specialized applications. This tunability is the result of functionalization through careful synthetic strategy to influence both material properties and solid-state arrangement, both crucial variables in device applications. Functionalization of a core molecule with various substituents allows the fine-tuning of optical and electronic properties, and functionalization with solubilizing groups allows some degree of control over the solid-state order, or crystal packing. These combinations of core chromophores with varying substituents are systematically evaluated to develop structure-function relationships that can be applied to numerous applications. In this work, heteroacenes are investigated for singlet fission and triplet harvesting, with known crystal engineering strategies applied to optimize crystal packing and maximize relevant solid-state interactions. Further, a class of antiaromatic compounds are investigated using the same approaches to build up structure-function relationships and provide insight into the properties of a relatively understudied core molecule.

Attend the seminar here.

Date: 
Tuesday, July 27, 2021 - 11:00am to 12:00pm
Location: 
Zoom
Type of Event (for grouping events):

Understanding and Controlling Electrochemistry for Electrolyzers and Batteries

Professor Andrew Gewirth

The University of Illinois at Urbana-Champaign

Understanding and Controlling Electrochemistry for Electrolyzers and Batteries

Abstract:

This talk addresses the electrochemical reactivity associated with electrolyzers and batteries.  Relevant to electrolyzers we show that electrodeposition of CuAg or CuSn alloy films under suitable conditions yields high surface area catalysts for the active and selective electroreduction of CO2 to multi-carbon hydrocarbons and oxygenates.  Alloy films containing Sn exhibit greater efficiency for CO production relative to either Cu along or CuAg at low overpotentials.   In-situ Raman and electroanalysis studies suggest the origin of the high selectivity towards C2 products to be a combined effect of the diminished stabilization of the Cu2O overlayer and the optimal availability of the CO intermediate due to the Ag or Sn incorporated in the alloy.  Sn-containing films exhibit less Cu2O relative to either the Ag-containing or neat Cu films, likely due to the increased oxophilicity of the admixed Sn.  Incorporation of a polymer into the Cu electrodeposit leads to very active CO2 reduction electrocatalysis due to pH changes at the electrified interface.  Vibrational spectroscopy is used to evaluate the pH at the interface during electrolyzer operation.

Relevant to batteries, we discuss solid electrolytes (SEs) which have become a practical option for lithium ion and lithium metal batteries due to their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates whose excellent ionic conductivities at room temperature approach those of commercially-utilized electrolytes. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare solid electrolyte counterparts due to decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface. Spectroscopic and structural studies on these latter materials lead to new formulations and artificial SEI materials exhibiting advantageous properties.

Host: ECS UK chapter

Date: 
Wednesday, October 6, 2021 - 4:00pm to 5:00pm
Location: 
Zoom
Type of Event (for grouping events):

Advances and challenges in understanding the electrocatalytic conversion of carbon dioxide to fuels

Professor Marc T. M. Koper

Leiden University, Netherlands

Advances and challenges in understanding the electrocatalytic conversion of carbon dioxide to fuels

Abstract:

The electrocatalytic reduction of carbon dioxide is a promising approach for storing (excess) renewable electricity as chemicalenergy in fuels. Here, I will discuss recent advances and challenges in the understanding of electrochemical CO2 reduction. I will summarize existing models for the initial activation of CO2 on the electrocatalyst and their importance for understanding selectivity. Carbon–carbon bond formation is also a key mechanistic step in CO2 electroreduction to high-density and high-value fuels. I will show that both the initial CO2 activation and C–C bond formation are influenced by an intricate interplay between surface structure (both on the nano- and on the mesoscale), electrolyte effects (pH, buffer strength, ion effects) and mass transport conditions. This complex interplay is currently still far from being completely understood.

Y.Y.Birdja, E.Perez-Gallent, M.C.Figueiredo, A.J.Göttle, F.Calle-Vallejo, M.T.M.Koper, Nature Energy 4 (2019) 732-745

Host: ECS UK chapter

Date: 
Wednesday, September 8, 2021 - 10:00am to 11:00am
Location: 
Zoom - https://uky.zoom.us/j/83419323701?pwd=YUZuc25QVDJZemlDR3JiVHlZZURXdz09
Type of Event (for grouping events):

Alysia Kohlbrand, Former UK Chemistry ChemCat President, Presses on to Graduate School in Chemistry during the Pandemic

Alysia Kohlbrand graduated from the University of Kentucky in 2019 with double majors in Chemistry and Neuroscience.

This interview is part of a series conducted by the department called, "UK Chemistry Alumni: Where Are They Now." This interview was coordinated by Dr. Arthur Cammers.

Exit Seminar - Investigation of Multidrug Efflux Pump Acrab-Tolc in E.Coli: Assembly and Degradation of the Complex and the Dynamics of ACRB

Abstract: The Resistant Nodulation Division (RND) super family member, tripartite AcrA-AcrB-TolC efflux pump is a major contributor in conferring multidrug-resistance in Escherichia coli. The structure of the pump complex, drug translocation by functional rotation mechanism has been widely studied through crosslinking studies, crystallography, and Cryo-EM efforts. Furthermore, the ClpXP system has been identified as important in degrading ssrA tagged AcrB. Despite all this data, the dynamics of assembly process of the pump and AcrB during functional rotation in the process of drug efflux, the proteases in degrading AcrB remains poorly understood. The focus of my thesis is understanding pump assembly process, dynamics of AcrB in functional rotation mechanism, and identifying the proteases that degrade ssrA tagged AcrB. First, I used disulfide bond crosslinking, minimum inhibitory concentration (MIC) and EtBr efflux assay in studying the importance of the relative flexibility at the inter-subunit interface by introducing 6 inter-subunit disulfide bonds into the periplasmic domain of AcrB using site directed mutagenesis. Based on MIC the double Cys mutants tested led to equal or higher susceptibility to AcrB substrates compared to their corresponding single mutants. EtBr accumulation assays was conducted utilizing DTT as the reducing agent. In two cases, the activities of the double Cys-mutants were partially restored by DTT reduction, confirming the importance of relative movement in the respective location for function. In the second project, I tested the effect of over-expressing functionally defective pump components in wild type E. coli cells to probe the pump assembly process. Incorporation of defective component is expected to reduce the efflux efficiency of the complex and leading to the so called “dominant negative” effect. We examined two groups of mutants defective in different aspects and found that none of them demonstrated the expected dominant negative effect, even at concentrations many folds higher than their genomic counterpart. Based on the data the assembly of the AcrAB-TolC complex appears to have a proof-read mechanism that effectively eliminated the formation of futile pump complex. Moreover, I utilized a novel tool- transposons library creation in studying the possible other proteases contribute to degradation of the AcrB-ssrA. The next generation sequencing identified already known ClpXP gene and MIC and western blot analysis confirmed the results. These, findings provide new insights to the dynamics of the AcrAB-TolC efflux pump in E. coli.  Key words: multidrug efflux pump, AcrB, assembly, disulfide, conformational changes, ssrA.

Join the seminar at

 https://uky.zoom.us/j/88673605310

Date: 
Friday, June 25, 2021 - 9:00am to 10:00am
Location: 
Zoom

Exit Seminar - Plasmon Mediated Single Molecule Fluorescence Enhancement in "Zero Mode Waveguides" (ZMWs)

Abstract:: Plasmonic nanostructures have been extensively studied for their potential application in numerous fields such as nanophotonics, biosensors, and bioimaging. One of the key properties of nanostructures that can be manipulated for practical applications is their capabilities to modulate the optical and photophysical properties of fluorophores residing nearby. Surface plasmons (SP), which can be defined as the collective oscillation of the delocalized electrons, are the fundamental characteristic of nanostructures that are primarily responsible for altering those properties. Elucidating fluorophores at the single-molecule level has received significant attention since more specific information can be extracted from single molecule-based studies, which otherwise, could be obscured in ensemble studies. However, single-molecule studies are inherently challenging because the signal from a single molecule is usually deem, which makes it difficult to detect. The situation is even worse in the case of a crowded environment due to higher background noise, such as cellular autofluorescences in the case of cell-based studies. Thus, one of the possible ways out of this single-molecule detection problem is to couple the fluorophore with a plasmonic nanostructure which can potentially enhance the fluorescence intensity of the single fluorophore leading to the improvement in signal to noise ratio. Throughout the projects presented here, I studied the fluorescence characteristics of single fluorophore molecules coupled in a plasmonic nano-aperture which is termed as Zero Mode Waveguides (ZMWs). I utilized single fluorophores of different origins, such as organic dyes and quantum dots (QDs), in ZMWs of different metallic compositions. By probing ZMWs made from the mixture of Aluminum and gold, with a range of ATTO dyes emitting across the visible wavelength, we found that the surface plasmon resonance of ZMWs is tunable by optimizing the metal ratio. Apart from the ATTO dyes, I investigated the photoluminescence (PL) behavior of single QDs in ZMWs and observed a significant enhancement in PL intensity and a substantial improvement in the blinking characteristics of the QDs, which are beneficial for the utility of QDs as a bio-imaging agent or a single-photon source. Single QDs in ZMWs exhibited a significant enhancement in biexciton quantum yield, which is crucial for their potential application in lasing where materials with a high optical gain are desired. I also examined the fluorescence properties of the single fluorophores in gold ZMWs in the presence of a gold nanoparticle (AuNP) and observed a more significant enhancement in fluorescence intensity in the gap between AuZMW and AuNP compared to the case of only AuZMW or only AuNP. The experimental design and the resulting findings throughout the three projects presented here should be a valuable resource for the future development of plasmon-mediated single-molecule studies.

Join the seminar at

https://uky.zoom.us/j/88903093777

Date: 
Thursday, June 24, 2021 - 1:00pm to 2:00pm
Location: 
Zoom

LGBTQ+ Chemists - Celebrate Pride Month

The Chemistry Department honors the amazing contributions of the LGBTQ+ community to the field of Chemistry. For more information on LGBTQ+ Chemists, please visit the following link.


LGBTQ+ chemists you should know about

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