Doctoral Exit Seminar

DESIGN AND SYNTHESIS OF NOVEL LIGANDS FOR BIOORTHOGONAL CATALYSIS, ASYMMETRIC SYNTHESIS, AND FERROMAGNETIC BEHAVIOR

mnlo230 — Tue, 01 Apr 2025 20:14:28 +0000

DESIGN AND SYNTHESIS OF NOVEL LIGANDS FOR BIOORTHOGONAL CATALYSIS, ASYMMETRIC SYNTHESIS, AND FERROMAGNETIC BEHAVIOR mnlo230 Tue, 04/01/2025 - 04:14 pm

Small molecule metal complexes have diverse applications including usage as catalysts, single molecule magnets, photosensitizers and pharmaceuticals. Nature itself frequently takes advantage of such complexes for fundamental biological processes. For example, heme-based iron complexes provide O₂ for cellular respiration, while the active site of carbonic anhydrase catalyzes the hydration of CO₂. Now it is our turn to define and exploit the chemical characteristics of such metal complexes. This body of work is specific to the development and application of novel aminated ligands that, when coordinated to various metal centers, can be used for an assortment of applications. The first research project in this work reports a new benzimidazole-based ligand, which dimerizes upon coordination to afford a trinuclear Cu(I) complex. Due to the linear geometry of the Cu(I) metal centers, paired with the strong nitrogen coordinating groups, the resulting complex is resistant to oxidation in both air and water, even in the presence of strong oxidants. The complex is shown to be efficient in the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and used to tag anticancer drug candidates in vitro. The complex is fully characterized, and a catalytic cycle is proposed. The next project focuses on a series of amidine-based ligands featuring chiral functional groups proximal to the coordinating site. In doing so, the reaction of achiral substrates may be influenced to promote the formation of one enantiomeric product over the other. The ligands are shown to be active in catalyzing the hydroxymethylation of silyl enol ethers in the presence of bismuth chloride in aqueous solutions. The reaction is optimized and yields are reported. In the final research project, Ni(II) dimer complexes are investigated for their magnetic behavior. For octahedral Ni(II) dimers bridged by a common anion, it has previously been established that the ferromagnetic superexchange between the Ni(II) metal centers can be enhanced as the angle of the bridging anion approaches 90 degrees. Novel imidazole and pyridine-based ligands are synthesized to add to the catalogue of chlorine-bridged complexes in the literature. Further, their bromine-bridged analogues are synthesized in order to determine the effect the identity of the halide bridge has on the magnetic properties of the complex. These three projects, while functionally different with individual aims, fundamentally share the goal of probing the chemical space that influences intrinsic properties of unique metal complexes.

Date:

Tuesday, April 29, 2025 - 02:00 pm

Location:

CP 114

Event Series:

��vlog�ٷ�� Department Seminar

Doctoral Exit Seminar

Read more about DESIGN AND SYNTHESIS OF NOVEL LIGANDS FOR BIOORTHOGONAL CATALYSIS, ASYMMETRIC SYNTHESIS, AND FERROMAGNETIC BEHAVIOR

Enhancing Carbon Capture by Examining Degradation in Aqueous Amine Solvents and Developing Targeted Mitigation Systems to Reduce Key Environmental Impacts

mnlo230 — Mon, 31 Mar 2025 16:52:12 +0000

Enhancing Carbon Capture by Examining Degradation in Aqueous Amine Solvents and Developing Targeted Mitigation Systems to Reduce Key Environmental Impacts mnlo230 Mon, 03/31/2025 - 12:52 pm

Global CO₂ emissions from industrial, power generation and transportation sources has led to the call for increased implementation of carbon capture strategies. The most developed of these is point source carbon capture, which refers to the process of capturing CO₂ directly from large (point) source emitters, before the CO₂ is released into the atmosphere. The challenge becomes separating CO₂ from the other components of the emitted gas, mainly nitrogen. Therefore, these processes typically involve the use of aqueous solutions of amines to absorb (capture) CO₂ from the gas stream, where the CO₂ and the basic amine in water react to form a carbamate and/or bicarbonate, depending on the specific amine used. An advantage when using amine solutions is that this reaction is reversible, as the absorbed CO₂ is released when the solution is heated allowing the amine to be reused in multiple cycles of absorption and regeneration.

This type of amine-based carbon capture works well, but it is not without some drawbacks. The temperature swings needed for this desorption process not only requires significant energy input but can also lead to gradual degradation of the amine, commonly referred to as thermal degradation. This can lead to solvent losses, reduced performance, and higher operational costs. In addition, the solvent can degrade due to exposure to oxygen and other contaminants present in the gas (such as SO₂, NOx). This oxidative degradation can lead to the formation of unwanted byproducts, some of which are regulated volatile organic compounds. To avoid unintended environmental effects, the amine degradation pathways need to be carefully understood and managed. Amine degradation can produce a combination of different species generating a complex matrix that when coupled with the high pH environment, can make degradation remediation challenging. This dissertation focuses on the degradation by-products of amine solvents in carbon capture systems and how the chemical differences between the amine and water impacts the volatility and the removal of these degradation compounds. A better understanding of theses impacts allows for the development of mitigation strategies minimizing any environmental impacts.

Mitigation of the unwanted degradation byproducts is achieved by either removing the contaminants from the solvent or capturing and neutralizing them within the system. First, an assessment was performed to understand the effectiveness of activated carbon adsorption, with implications for treating high pH solutions. While there were some benefits to this methodology, activated carbon adsorption was not completely effective and presented several limitations such as metal leaching from the activated carbon material. Given this, it is necessary to expand into other areas of degradation mitigation. First understanding the potential for emissions of any degradation products, including compounds such as aldehydes, is crucial given their known environmental and human health hazards. These emissions may be impacted by the composition of the amine solvent used, therefore the Henry’s volatility coefficient of acetaldehyde in relevant amine solutions were determined as a surrogate for other classes of potential degradation compounds. The volatility was determined to be significantly higher from the amine solvent when compared to water, which is critical fundamental information in aiding the development of proper mitigation strategies that can be implemented within capture systems.

Current engineering controls within CO₂ capture plants involve the use of water wash systems to reduce amine emissions, however some degradation products are also captured by this system which allows for their targeted neutralization. The composition of the wash-water poses yet another unique challenge as the complex matrix and increased the pH make it difficult to treat via traditional water treatment methods. An electrochemical-mediated treatment method was developed and evaluated to facilitate the decomposition of N-nitrosamines and aldehydes. The experimental results showed that even in the presence of this complex matrix, highly efficient decomposition of these hazardous compounds can be achieved.

Date:

Tuesday, April 22, 2025 - 10:00 am

Location:

CP 114

Event Series:

Doctoral Exit Seminar

��vlog�ٷ�� Department Seminar

Read more about Enhancing Carbon Capture by Examining Degradation in Aqueous Amine Solvents and Developing Targeted Mitigation Systems to Reduce Key Environmental Impacts

Towards Automating the Study and Discovery of Electroactive Π-Conjugated Molecules

mnlo230 — Fri, 28 Mar 2025 17:14:48 +0000

Towards Automating the Study and Discovery of Electroactive Π-Conjugated Molecules mnlo230 Fri, 03/28/2025 - 01:14 pm

��vlog�ٷ�� is entering a new paradigm of automation and data-driven discovery. Automated discovery is grounded in well-curated “big data.” As generative and predictive models fueled by simulation data see growing success, emerging robotic automation enables the generation of unprecedented volumes of experimental data. Automation-powered, data-driven approaches hold tremendous potential for groundbreaking insights and innovations, particularly in the study and discovery of electroactive π-conjugated molecules. Realizing this potential, however, requires democratizing chemical data and the automation needed to generate and use it. There is a need to expand access to the tools for findable, accessible, interoperable, and reusable (FAIR) data management and experimental automation. This dissertation contends that efficient discovery in the realm of electroactive π-conjugated molecules requires a coalition of automation and data-driven design with chemists and chemical intuition; this necessitates both large-scale FAIR data and intuitive man-machine interfaces. This dissertation investigates the automation of big-data generation, management, and analysis in the context of studying small electroactive π-conjugated molecules. First, this work examines the philosophical and historical foundations underpinning chemical data ontologies upon which automation and data-driven approaches depend. It advocates for interdisciplinary collaboration between philosophers and chemists to create more realistic, intuitive, and FAIR-compliant data structures. Then, this dissertation explores data generation and management in practice by producing computational data for over 40,000 electroactive molecules via automated high-throughput quantum chemical calculations and building a management infrastructure for the resulting data. It next demonstrates the insights gained through analyzing big data with a study of dihedral angle rotations in π-conjugated systems. The results demonstrate the ability of data-empowered machine learning (ML) to inexpensively automate the estimation of experiment-aligned for mesoscale properties. Likewise, it discusses how big data can be utilized for informing the selection of similarity measures, a key metric in many automated discovery applications. This work finally transitions to the automated generation of experimental data. It overviews a software developed for translating experimental protocols to robotic actions, validating the system by reproducing well-reported electrochemical experiments. Overall, this dissertation offers a path through effective organization, generation, management, and use of chemical data towards the automated study and discovery of electroactive π-conjugated molecules.

Date:

Thursday, April 17, 2025 - 10:00 am

Location:

CP 114

Event Series:

��vlog�ٷ�� Department Seminar

Doctoral Exit Seminar

Read more about Towards Automating the Study and Discovery of Electroactive Π-Conjugated Molecules

Catalytic Deoxygenation of Oleaginous Biomass to Renewable Diesel and Sustainable Aviation Fuel via Decarboxylation/Decarbonylation

mnlo230 — Fri, 28 Mar 2025 12:59:41 +0000

Catalytic Deoxygenation of Oleaginous Biomass to Renewable Diesel and Sustainable Aviation Fuel via Decarboxylation/Decarbonylation mnlo230 Fri, 03/28/2025 - 08:59 am

Several technologies have been developed to produce hydrocarbon biofuels – renewable diesel (RD) and sustainable aviation fuel (SAF) – from fats, oils, and greases (FOG), with the hydroprocessing of esters and fatty acids (HEFA) representing one of the most mature pathways. In its current form, HEFA is mainly reliant on the hydrodeoxygenation (HDO) reaction, which has several drawbacks since HDO requires large amounts and pressures of hydrogen, feedstocks of high purity and cost, as well as problematic sulfided catalysts that risk contaminating the biofuel product with sulfur. A process based on decarboxylation/decarbonylation (deCO_x) offers an attractive alternative to HDO, since it requires lower amounts and pressures of hydrogen, feedstocks of low purity and cost, and simple supported metal catalysts. Herein, several geographically distributed oleaginous feedstocks – ranging from municipal waste feeds (brown grease) to pine chemicals (tall oil and rosin) – were upgraded to RD and SAF via deCOx. Powdered and engineered Ni-based catalysts were used for FOG-to-RD conversion via deCO_x, evaluating deoxygenation over reducible and non-reducible oxides.

Engineered alumina-based catalyst showed superior deoxygenation activity and stability for up to 300 hours on stream. Similarly, quantitative conversion of FOG to SAF was achieved over bifunctional Ni-Cu-based catalysts with zeolitic supports, with deCO_x and isomerization occurring in a single step. Initial screening studies performed in a semi-batch reactor revealed that upgrading distilled tall oil (DTO) over a Ni-Cu-based catalyst afforded all types of hydrocarbons comprising SAF, namely n-alkanes, iso-alkanes, cycloalkanes, and aromatics. The same combination of feed, catalyst, and reaction conditions were applied in a fixed-bed reactor for a continuous experiment, consisting of two 72-hour cycles with catalyst regeneration in between. DTO conversion remained quantitative (~100%), with aromatic yields ≥80% regardless of time-on-stream. Most liquid products fell within the carbon number and boiling point range of jet fuel across all samples. Notably, the reaction produced all hydrocarbon classes found in SAF, with particular abundance of aromatic hydrocarbons. Since ~20% aromatics are required to swell elastomeric seals and prevent leaks in aircraft fuel systems, seal compatibility testing confirmed that the aromatics-rich SAF blendstock exhibited a volume swell percentage comparable to qualified SAF blends. Catalysts used for deoxygenation reactions were characterized using various techniques – including N₂ physisorption, X-ray diffraction, X-ray photoelectron spectroscopy, microscopy, and temperature-programmed methods – to rationalize trends, propose reaction pathways, and elucidate structure-activity relationships. Finally, to evaluate the economic and environmental feasibility of this technology, techno-economic and lifecycle analyses were conducted on an integrated plant combining catalytic deoxygenation and hydrothermal gasification, producing hydrogen for converting tall oil fatty acid to SAF. The analyses revealed a minimum fuel-selling price of USD$0.39/L – lower than that of existing SAF pathways (USD$1.4/L) – with greenhouse gas emissions of 5.1g CO₂-eq/MJ, which is 94% lower than fossil jet fuel (85g CO₂-eq/MJ).

Date:

Tuesday, April 15, 2025 - 10:00 am

Location:

CP 114

Event Series:

��vlog�ٷ�� Department Seminar

Doctoral Exit Seminar

Read more about Catalytic Deoxygenation of Oleaginous Biomass to Renewable Diesel and Sustainable Aviation Fuel via Decarboxylation/Decarbonylation

Redox control in a fused bifurcating electron transfer flavoprotein and significance of a H-bond interaction that contributes to flavin redox tuning and activation for covalent modification

mnlo230 — Fri, 28 Mar 2025 12:40:18 +0000

Redox control in a fused bifurcating electron transfer flavoprotein and significance of a H-bond interaction that contributes to flavin redox tuning and activation for covalent modification mnlo230 Fri, 03/28/2025 - 08:40 am

In absence of O₂ as terminal electron acceptors in anaerobic bacteria and archaea, carbohydrate metabolism is 15 times lesser efficient compared to aerobic energy metabolism resulting in energy deficit conditions. Despite their meager resources these anaerobes, they were able to generate H₂and a chemiosmotic potential able to drive energy demanding reactions such as CO₂ or N₂ fixation. These observations raised concerns as production of high energy reductants (H₂) from mediocre fuels (NADH) defied the laws of thermodynamics.

In 2008, a known mechanism “electron bifurcation” but with flavins as redox mediators instead of quinones was able to overcome the thermodynamic problems behind the machinery for H₂ production and was termed as flavin based electron bifurcation (FBEB). FBEB couples an energetically uphill electron transfer to a downhill electron transfer, making the process favorable overall while generating high energy reductants from mediocre and abundant fuel.

A relatively simply system that exemplifies FBEB is the bifurcating electron transfer flavoproteins (bETF). bETFs are usually heterodimeric flavoproteins comprised of two subunits- larger EtfA formed by domain I and domain II and smaller EtfB formed by domain III. Domains I and III form the base of the protein whereas domain II sits on top of the base and is known to be dynamic, shuttling towards and away from the base. bETFs contain two non-covalently bound flavins- bifurcating FAD (Bf- FAD) is situated at the interface of domain I and domain III and electron transfer FAD (ET-FAD) is positioned in domain II. Although the two flavins are chemically identical, they demonstrate contrasting reactivities to facilitate an efficient electron bifurcation.

Thus, it is very crucial to understand the molecular basis of this mechanism implemented by these systems (bETFs) naturally which could be applied to man-made devices to satisfy their high energy needs.

Electron gating is a must to facilitate the mechanism which allows only one electron to access the exergonic pathway forcing the second electron to flow in the uphill direction, the major crux of the FBEB mechanism. A conformational gate has been proposed, to enforce this, but differential redox tuning of the two flavins is also required. The polypeptide environment of these bETFs tune the reactivities of the two flavins via non-covalent interactions thus conferring them contrasting reactivities : ET-FAD carries out 1 electron chemistry whereas Bf-FAD does 2 electron chemistry enabling it to capture maximum reducing power from NADH. Free flavins in solution can accumulate up to 1% semiquinone in solution when [OX]=[HQ]. Thus, it is very unique how nature facilitates ways to an efficient mechanism.

These bETFs share several conserved reactions in the ET site that stabilizes the ASQ (anionic semiquinone) state of ET-FAD. The unusually high E^o_(OX/ASQ) of ET-FAD has been attributed in part to a 99% conserved Arg and a 100 % conserved Ser or Thr. However, replacement of these does not suffice to suppress the ASQ of the ET-FAD, indicating that the site employs additional interaction(s) as well.

This thesis demonstrates that a conserved His (H290 in bETF from Acidaminococcus fermentans) is critical, for the stability of ET-FAD_ASQ. Variants of bETF in which H290 was replaced demonstrated lower accumulation of ET-FAD_ASQ and perturbation of ET- flavin’s E^o’_Ox/SQ by 150 mV and E^o’_SQ/HQ by 100 mV. Additionally, we demonstrated that the non-covalent interactions responsible for stabilizing the one electron reactivity of ET-FAD is also responsible for activating the methide intermediate responsible for covalent modification of ET-FAD in these systems.

In this study we have also biochemically characterized a monomeric ETF from a thermophilic archaeon Sulfolobus acidocaldarius showing that it qualifies as a bETF. The SaETF retains optical features unique to reported bETFs drawing attention to similar flavin environments, a must for redox tuning. Moreover, via UV-vis spectroscopy and spectroelectrochemistry we were able to demonstrate the contrasting reactivities of the two flavins.

SaETF model demonstrates conservation of residues in the ET site responsible for modulation of one electron reactivity of ET-FAD in the established heterodimeric ETFs, and an ^ETE^o_(OX/ASQ)of -21 mV confirms the stabilization of ^ETASQ. Finally, SaETF even replicates the side effect of ASQ stabilization that is seen in established ETFs, that the ET-FAD of SaETF is prone to covalent modification. Thus, in ongoing work, we have documented the formation of different covalently modified FADs, showing that the aerobic/anaerobic nature of the atmosphere dictates products formed, and reflected on the potent nucleophile and the reaction mechanism that allows us to refine our prior proposals for the mechanism of flavin modification.

Date:

Wednesday, April 9, 2025 - 02:00 pm

Location:

CP 114

Event Series:

Doctoral Exit Seminar

��vlog�ٷ�� Department Seminar

Read more about Redox control in a fused bifurcating electron transfer flavoprotein and significance of a H-bond interaction that contributes to flavin redox tuning and activation for covalent modification

Biophysical and biochemical characteristics of bifurcating electron transfer flavoproteins (bETFs) and redox tuning of electron transfer FAD (ET-FAD) to facilitate electron gating in bETFs

mnlo230 — Thu, 27 Mar 2025 14:56:59 +0000

Biophysical and biochemical characteristics of bifurcating electron transfer flavoproteins (bETFs) and redox tuning of electron transfer FAD (ET-FAD) to facilitate electron gating in bETFs mnlo230 Thu, 03/27/2025 - 10:56 am

Due to the presence of O2 as electron acceptors in aerobes, the energy metabolism is 15 times more efficient than anaerobic metabolism. Krebs’s cycle and oxidative phosphorylation results in the production of additional 36 mols of ATP in aerobes. However, it was observed in Clostridium kluyveri that during pyruvate fermentation to butyrate, H2 was generated. This mitigated energy deficit in bacteria and archaea but raised concerns as to how could mediocre fuels generate H2, a high energy reductant. This endergonic transfer violated the laws of thermodynamics suggesting the tight coupling to an exergonic reaction paying off for the endergonic transfer. This led to the discovery of Flavin based electron bifurcation (FBEB) in 2008 which could answer the mechanistic details behind the tight coupling of an exergonic pathway to an endergonic pathway leading to the production high energy fuel from mediocre ones. Thus, FBEB is considered as the third mode of energy conservation and is crucial for bacteria and archaea to carry out CO2 and N2 fixation. Bifurcating electron transfer flavoproteins (bETF) are heterodimeric flavoproteins that carry out FBEB. bETFs are comprised of two subunits- larger EtfA formed by domain I and domain II and smaller EtfB formed by domain III. Domains I and III form the base of the protein whereas domain II sits on top of the base and is known to be dynamic shuttling towards and away from the base. bETFs contain two non-covalently bound flavins- bifurcating FAD (Bf- FAD) situated at the interface of domain I and domain III and electron transfer FAD (ET-FAD) positioned in domain II. In FBEB, NADH is a natural substrate for these bETFs which donates 2 e- in the form of a hydride completely reducing the Bf-FAD. From the reduced HQBf-FAD, one e- goes downhill to the high potential acceptor (ET-FAD in this case) and the second e- flows uphill to a low potential acceptor (flavodoxin or ferredoxin). The two pathways are tightly coupled, and the overall energetics of the system is retained. Electron gating is crucial towards the mechanism of the reaction which allows the second e- to flow uphill instead of downhill in the favorable direction. Apart from the protein dynamics which prevents the flow of the second electron to the exergonic pathway, tuning ET-FAD’s 1 e- reactivity allowing it to do 1 e- chemistry unlike Bf-FAD’s 2 e- chemistry is crucial for electron gating. Flavins can accumulate up to 1% semiquinone in solution. Contrasting reactivities of the two FAD’s is highly unique in these systems as these are the polypeptide environment of the respective FAD that tunes their potential over a wide range of reactivity. It is very important to understand the properties and reactivities of these bETFs in order to be able to make it potable to mankind to produce high energy fuel from mediocre and abundant ones. My study involves the biophysical and biochemical characterization of a thermophilic flavoprotein to establish it as a bifurcating ETF and H-bonding from a conserved histidine residue in ETFs that is responsible for tuning ET-FAD’s 1 e- reactivity and unusual formation of 8-amino flavin in the ET-site.

Date:

Wednesday, April 9, 2025 - 02:00 pm

Location:

CP 114

Event Series:

��vlog�ٷ�� Department Seminar

Doctoral Exit Seminar

Read more about Biophysical and biochemical characteristics of bifurcating electron transfer flavoproteins (bETFs) and redox tuning of electron transfer FAD (ET-FAD) to facilitate electron gating in bETFs

Methodological Innovations for Improved Cancer Treatment and Enzyme Activity Insight

mnlo230 — Tue, 13 Aug 2024 13:08:15 +0000

Methodological Innovations for Improved Cancer Treatment and Enzyme Activity Insight mnlo230 Tue, 08/13/2024 - 09:08 am

The mortality rate of cancer establishes it as a leading global health concern, prompting significant investment into cancer research. While the effects of cancer are well known, the understanding of specific sources of cancer therapy resistance are not. In this study, our goal was to develop innovative methods to address current shortcomings in cancer treatment and understanding. To do this, we studied exosome-mimetic nanovesicles as an immunotherapeutic platform and fluorescence lifetime imaging as a means to measure cancer-associated enzyme activity at a single cell level.

Through the use of a novel method of production, we generated nanovesicles from dendritic cells in high yields and leveraged the antigen-presenting and costimulatory properties of dendritic cells for induction of a T cell immune response. We demonstrate that these nanovesicles are able to present antigens in functional immune stimulatory complexes and retain parental ability to activate CD8+ T cells. Additionally, these nanovesicles were shown to mediate activation of T cells through indirect means. Here, nanovesicles are taken up by bystander dendritic cells, thereby delivering antigen to the dendritic cell and conferring T cell stimulatory capability. Next, we investigated the application of fluorescence lifetime imaging to measure cancer-associated cytochrome P450 enzyme activity at the single-cell level. We demonstrated this approach provides detailed insights into cellular heterogeneity and localized enzyme activity. Additionally, we showed that sensitivity and dynamic range can be tuned to enzyme activity and levels by altering excitation and emission wavelengths.

These advancements offer new and promising avenues to enhance nanoparticle-based immunotherapy and understanding of the role of enzyme activity and cellular heterogeneity in cancer progression. Ultimately, the methods developed contribute to improving therapeutic strategies and personalized medicine.

Date:

Tuesday, August 20, 2024 - 10:00 am

Location:

CP 114

Event Series:

��vlog�ٷ�� Department Seminar

Doctoral Exit Seminar

Read more about Methodological Innovations for Improved Cancer Treatment and Enzyme Activity Insight

Effect of pi-conjugated ligands and A* site organic cations on the energetic properties and photovoltaic performance of metal halide perovskites

mnlo230 — Mon, 01 Apr 2024 19:01:24 +0000

Effect of pi-conjugated ligands and A* site organic cations on the energetic properties and photovoltaic performance of metal halide perovskites mnlo230 Mon, 04/01/2024 - 03:01 pm

Metal halide perovskites have gained interest in optoelectronic applications such as photovoltaics, lasers, LEDs, transistors, and photodetectors due to their excellent semiconducting properties considering their low cost. Metal halide perovskite (HP) photovoltaics have rapidly increased in power conversion efficiency (PCE), which now exceeds 25%. HPs have gained attention in these applications due to their high tolerance towards defects, long charge carrier diffusion lengths, high charge carrier mobility, high optical absorption, and bandgaps that are tunable over a large range. Even though HP photovoltaic PCEs are improved these are still not commercially available due to them showing lower stability and energy loss due to severe charge recombination at the surface and interfaces in the device . Treating the HP surface with surface ligands has become a promising approach to improve photovoltaic performance, defect passivation, and interfacial energetics. In this dissertation, the influence of ammonium functionalized p – conjugated ligands on MAPbI3 perovskite energetics, photovoltaic performance, and interfacial charge transfer is investigated. With the thiophene ligands, a drastic PCE drop was observed for p-i-n devices, and improved PCE was obtained for n-i-p devices. With PDI surface ligands no significant change was observed for photovoltaic performance. Two-dimensional metal halide perovskites (2D HP) have captured interest in the field due to their improved stability against air, moisture, and light relative to their 3D counterparts. 2D HPs have a layered structure, where the organic spacer cations are sandwiched between layers of inorganic octahedra. This organic layer in 2D HPs adds additional protection against moisture and oxygen ingression and other degradation pathways . These materials are used as the active layer in LEDs and solar cells and as capping layers in 3D HPs. 2D perovskites demonstrate remarkable structural variabilities, where the properties can be modified by changing the layer thickness, the halide anion, and the spacer cation. To make devices with 2D perovskites we need to understand the influence of the organic spacer cations on the optoelectronic properties of these materials . In this work, we investigate the influence of the dipole magnitude and the direction of a series of functionalized PEAI derivatives as organic spacer cations on the ionization energy and the electron affinity of 2D tin halide perovskites. However, determining ionization energy and electron affinity in HPs could be quite difficult as several methods are being used in data interpretation for HPs . In this work, we propose a method to assign the energy levels in 2D HPs by correcting for the instrumental resolution in ultraviolet and inverse photoemission spectroscopy.

Date:

Monday, April 15, 2024 - 10:00 am

Location:

CP 114

Event Series:

Doctoral Exit Seminar

��vlog�ٷ�� Department Seminar

Read more about Effect of pi-conjugated ligands and A* site organic cations on the energetic properties and photovoltaic performance of metal halide perovskites

Mechanism of Action of Gold-based Anticancer Small Molecules

mnlo230 — Wed, 20 Mar 2024 17:26:57 +0000

Mechanism of Action of Gold-based Anticancer Small Molecules mnlo230 Wed, 03/20/2024 - 01:26 pm

The current standard of care (platinum-based drugs) for the treatment of different forms of malignancy have been very effective in the clinic, however the negative side effects associated with the administration of these platinum based-drugs remains an unsolved problem. Gold based molecules are among a few metal complexes that have been developed over the years in search for better chemotherapy drugs. While the anticancer mechanism of action of platinum-based drugs is well known to involve DNA damage, the mechanism of action of gold based small molecules remains a subject of debate. It is understood that gold-based complexes exhibit non-cisplatin like anticancer mechanism of action, hence the potential to overcome resistance seen in patients with recurrent tumors after initial remission with platinum-based drugs. Herein, we report efforts to elucidate the mechanism of action of novel gold-based anticancer agents with very potent inhibitory effect against triple negative breast cancers and ovarian cancer. A recurring observation from the mechanism of action studies is the perturbation of mitochondria physiology by these complexes. These includes; perturbation of mitochondria bioenergetics, depolarization of mitochondria membrane potential of the cells, increased mitochondria ROS production, depletion of mitochondria DNA, and disruption of mitochondria dynamics. Modified versions of the lead molecules were developed as probes to monitor in vitro localization of the complexes and facilitate elucidation of the mechanism of action. Target identification studies with a biotinylated lead complex unveiled heme oxygenase 2 (HMOX2) as a novel target in gold medicinal chemistry. Preliminary target validation studies revealed for the first time, HMOX2 as an upstream regulator of the MYC proto-oncogene. These findings uncover a new strategy for targeting tumor cells and reinforces the belief that small molecules can serve as probes to interrogate the complex cancer biology system and unveil new strategies for development of better chemotherapeutic agents.

Date:

Thursday, April 18, 2024 - 01:00 pm

Location:

CP 114

Event Series:

Doctoral Exit Seminar

��vlog�ٷ�� Department Seminar

Read more about Mechanism of Action of Gold-based Anticancer Small Molecules

Investigation of dynamics of flavoproteins involved in flavin based electron bifurcation via small angle neutron scattering (SANS) and fluorine NMR

mnlo230 — Wed, 20 Mar 2024 17:25:13 +0000

Investigation of dynamics of flavoproteins involved in flavin based electron bifurcation via small angle neutron scattering (SANS) and fluorine NMR mnlo230 Wed, 03/20/2024 - 01:25 pm

Anaerobic bacteria and archaea thrive in seemingly inhospitable environments because they are extremely energy eﬃcient. Their eﬃciency is based in large part on their ability to conduct electron transfer bifurcation ('bifurcation') at strongly reducing potentials, thereby producing extremely potent reducing agents able to ﬁx nitrogen and make molecular hydrogen. This chemistry is made possible by the use of a ﬂavin as the site of bifurcation, supported by a specialized protein environment and mechanisms that control the ﬂow of individual electrons.

Bifurcating electron transfer ﬂavoproteins (Bf-ETFs) are versatile protein modules that provide the bifurcating capability associated with several metabolic functions. Bf-ETFs enable use of low-energy electron reserves such as NADH to charge the carriers ferredoxin and ﬂavodoxin with high-energy electrons. Bf-ETFs possess two ﬂavin adenine dinucleotide (FAD) cofactors. The bifurcating FAD (Bf-FAD) receives two electrons from NADH, and distributes them through two distinct pathways. One pathway involves exothermic electron transfer to a high- potential acceptor via the second FAD, the ET-FAD (electron transfer FAD). This provides the driving force to send the second electron to a lower potential (higher-energy) acceptor.

Investigations described herein elucidated the crystal structure and internal dynamics of ﬂavodoxin (Fld), a high-energy acceptor in the bifurcation process. 19F NMR was used to examine conformational heterogeneity and dynamics of Fld free in solution, to characterize the ﬂexibility of a 20-residue stretch of Fld's peptide chain that is believed to mediate interaction between Fld and ETF. Temperature-dependent NMR studies, alongside paramagnetic relaxation investigations comparing Fld in both its oxidized and semi-reduced forms, detailed internal dynamics pivotal to Fld's interactions with diverse partner proteins.

Complementary research explored conformational dynamics of ETF, employing small-angle neutron scattering (SANS). This revealed notable divergence from published structures, demonstrating presence of a more extended conformation in solution. Signiﬁcant reduction- triggered conformational change was also discerned via SANS by comparing the fully oxidized and reduced states of ETF. Molecular dynamics simulations-based data modeling suggests coexistence of multiple ETF conformations, ranging from extended to compact, in solution.

Finally, conformational consequences of complex formation between ETF and a partner protein were examined. We demonstrated isolation of a complex between ETF and its high- potential acceptor butyryl CoA dehydrogenase (BCD). Innovative application of segmental deuteration of BCD in combination with SANS, enabled comprehensive insights into the conformational adaptations made by ETF upon complex formation. Contrast variation SANS, utilizing 80% deuterated BCD, was used to identify the match point, paving the way for advanced analysis of the complex's structural dynamics.

This work enriches comprehension of the roles played by dynamics in bifurcation, and advances new technical approaches for future explorations of conformational changes within multidomain proteins.

Date:

Wednesday, April 17, 2024 - 01:00 pm

Location:

CP 114

Event Series:

Doctoral Exit Seminar

��vlog�ٷ�� Department Seminar

Read more about Investigation of dynamics of flavoproteins involved in flavin based electron bifurcation via small angle neutron scattering (SANS) and fluorine NMR