Exit Seminar "Developments in Gold(III) Scaffolds for Protein Bioconjugation and Enhanced Anticancer Activity"
Site-selective modifications of target proteins using specifically designed small molecules is a powerful tool that has been extensively utilized for drug discovery. Small molecules can modify proteins either covalently or non-covalently depending on their structures and intrinsic chemical reactivity. Covalent chemical modification presents a more stable and often irreversible interaction with target proteins; unlike non-covalent binders, which form weak, reversible interactions with protein. Therefore, covalent modifiers represent an effective class of therapeutics due to their stability and irreversibility once bound to target proteins of interest. I hypothesized that tuning biocompatible, high-valent gold(III) complexes toward nucleophile-induced reductive elimination will lead to covalent protein modification by arylation. While most proteins are expressed amongst all cell types; protein overexpression is a common phenomenon in several cancer types due to their rapid proliferative phenotype and mutations compared to healthy non-cancerous cells. The nucleophilic amino acid side chains in proteins can be used as reactive handles for covalent modifications. Amongst the naturally occurring amino acids; cysteine, the most intrinsically nucleophilic, contains a highly reactive thiol functional group. This innate nucleophilicity provides a framework for covalent modification with electrophiles, which includes but is not limited to electron-deficient metal centers (e.g., Au and Pd).
Although there are previous reports successfully identifying transition metals as suitable chemical modifiers, specifically, tuning gold(III) complexes for selective binding offers a unique strategy for chemotherapeutics. Gold(III) metal centers are innately acidic and react with softer bases such as phosphorous and sulfur unlike the traditionally used late transition metals. Secondly, gold(III) complexes are known to target proteins over DNA, unlike other common transition metal complexes such as platinum and ruthenium. Combining the innate ability of gold(III) complexes to interact with proteins and the high affinity for cysteine thiols, rationale design of highly selective protein modifiers and efficient chemotherapeutics is possible.
My work focused on tuning the reactivity of cyclometalated gold(III) complexes for cysteine arylation and ligand-directed bioconjugation using Metal-mediated Ligand Affinity Chemistry (MLAC) have been elucidated to modify biomolecules including antibodies and undruggable protein targets such as KRAS. While developing cyclometalated gold(III) complexes discussed herein, a unique class chiral gold(III) complexes bearing diamine or phosphine ligands led to other applications including improved anticancer activity in comparison to first generation of gold(III) complexes. A key highlight is the development of stable organometallic gold(III) macrocycles with potent in vitro and in vivo anticancer action in aggressive cancer types including triple negative breast cancer (TNBC).
KEYWORDS: Site-selective protein modification, gold complexes, covalent binders, cysteine arylation, anticancer
Abstract: A thiol molecule, 2,6-pyridinediamidoethanethiol (PB9), was synthesized based on the pyridine-2,6-dicarboxamide scaffold with appended cysteamine group. PB9 acts as an effective chelator for Pb(II) due to multiple binding sites (N3S2) through irreversible binding precipitating Pb(II). Removal of aqueous Pb(II) from solution was demonstrated by exploring the effects of time, initial PB9:Pb(II) ratios, pH, exposure time, and solution temperature. After 15 min the Pb(II) concentrations were reduced from 50 ppm to 0.3 ppm (99.4%) and 0.25 ppm (99.5%) for PB9:Pb ratios of 1:1 and 2:1, respectively. Removal of >93% Pb(II) was observed over multiple pH values with negligible susceptibility for leaching over time. The thermodynamic studies reveal the removal of Pb(II) from solution is an entropically driven spontaneous process. Solution-state studies (UV-Vis, 1H-NMR, 13C NMR) along with solid-state (IR, Raman, and thermal studies) for L/Pb(II) compounds were performed. UV-vis displays a global maximum at 274 nm and a local maximum at 327 nm for ligand-to-metal charge transfer S- 3p -> Pb2+ 6p, and intraatomic Pb2+ 6s2 -> Pb2+ 6p transitions. A Probable molecular structure designed is PB9 behaving like a bis-deprotonated ligand with an N3S2 donor set to give Pb(II) a pentagonal environment with non-stereochemically active s electrons is proposed. However, the existence of a cyclic oligomeric (PB9)4(Pb)4 or polymer (PB9)?(Pb)? structure is evident by broad melting point, insolubility in most common solvents, and amorphous powder XRD. PB9 also exhibits high sensitivity and selectivity towards Fe3+ over other metal ions, acts as a naked-eye detector showing colorless to yellow, and by fluorescent quenching. The quenching efficiency found by Stern-Volmer is 7.42 ± 0.03 × 103 M-1 with a higher apparent association constant of 9.537 X 103 M-1. A linear range of Fe3+ (0- 80 µM) with a detection limit of 0.59 µM (0.003 ppm) was found. The obtained detection limit was much lower than the maximum allowance limit of Fe3+ (0.3 ppm) regulated by EPA in drinking water. Since Pb(II) removal using PB9 was higher than 15 ppb (EPA limit), a separate study was conducted to explore the use of thiol molecule (AB9) which was already developed in our lab previously. Thus, 2,2'-(isophthalolybis(azanaediyl))bis-3-mercaptopropanoic acid (AB9) was coupled to amine-functionalized silica and silica-coated magnetic nanoparticles (with Fe3O4 core). Results revealed successful fabrication of AB9 on mesoporous silica and MNPs surfaces without introducing crystalline impurities. Indeed, an added advantage for AB9-MNP over AB9-silica is its superparamagnetic nature where a magnet was used to isolate the Pb(II)-containing (solid) composite from the treated water. The >99.9% removal of Pb(II) was obtained by AB9-MNPs with detectable Pb(II) dropping to below 15 ppb EPA level. The obtained equilibrium results were in good agreement with the Langmuir model suggesting a dominant chemical adsorption mechanism on AB9- composites with monolayer coverage with maximum adsorption capacities of 24.80 and 56.40 mg/g respectively for AB9-silica and AB9-MNP implying the thiol group improved the adsorption capacity of Pb(II). This eco-friendly modification with rapid magnetic separation makes these AB9-MNPs a good candidate for aqueous Pb(II) removal
Exit Seminar: Synthesis and In Situ Characterization of Intercalated Transition Metal Oxide Nanomaterials Investigated for Novel Cathode Applications
Abstract: To develop an effective battery cathode material that can be useful for future batteries, the thermal stability and ion migration dynamics need to be well understood. In situ transmission electron microscopy (TEM) is a popular and proven technique to study the evolution of local structures during the dynamic processes in the cathode materials. This dissertation will demonstrate the application of high-resolution imaging and in situ heating and biasing in the TEM to study the structure and composition, morphology change, and ion migration in the cathode materials. The three chapters in this dissertation will be focused on the two cathode materials: zeta (?) vanadium pentoxide, and chromium intercalated sodium manganese oxide. The first project demonstrates the effect of in situ heating method, nanowire size, sodium content, and vacuum condition on the thermal stability of zeta (?) vanadium pentoxide in real-time in the TEM. The second project concentrates on in situ biasing in the TEM to study the sodium ion migration, silver exsolution, and negative differential resistance phenomenon in the zeta (?) vanadium pentoxide. The third project concentrates on the synthesis and characterization of chromium incorporated sodium manganese oxide. The works presented here show the capability of in situ TEM imaging techniques to study the dynamic changes in the structure and composition of the nanomaterials during the heating and biasing processes.
Department of Biomedical Engineering and Simpson Querrey Institute
Northwestern University, Evanston, IL
Abstract: Direct measurement and stimulation of ionic, biomolecular, cellular, and tissue-scale activity is a staple of bioelectronic diagnosis and/or therapy. Such bi-directional interfacing can be enhanced by a unique set of properties imparted by organic electronic materials. These materials, based on conjugated polymers, can be adapted for use in biological settings and show significant molecular-level interaction with their local environment, readily swell, and provide soft, seamless mechanical matching with tissue. At the same time, their swelling and mixed conduction allows for enhanced ionic-electronic coupling for transduction of biosignals. Structure-transport properties allow us to better understand and design these active materials, providing further insight into the role of molecular design and processing on ionic and electronic transport, charging phenomena, and stability for the development of high-performance devices. Such properties stress the importance of bulk transport processes and serve to enable new capabilities in bioelectronics. In this talk I will discuss the design of new organic mixed conductors and future design rules for performance and stability. I will demonstrate how such materials properties relax design constraints and enable new device concepts and unique form factors, allowing for flexible amplification systems for electrophysiological recordings, and electroactive scaffolds to modulate tissue state and/or cell fate. New materials design continues to fill critical need gaps for challenging problems in bio-electronic interfacing.
Faculty Host: Dr. John Anthony
Innovation in Molecular Neuroscience
Schedule of Events - April 1, 2022
Registration and Continental Breakfast
Welcome - TBD
Dr. Erin Calipari
Dr. Tim Harris
Lunch & Break
Dr. Elizabeth Hillman
Break & Poster Session Set-Up
Dr. Baljit Khakh
|3:30 - 5:00pm||
Dr. Erin Calipari
Dr. Calipari received her PhD in Neuroscience in 2013 in the laboratory of Dr. Sara Jones at Wake Forest University School of Medicine where she studied how self-administered drugs altered dopaminergic function to drive addictive behaviors. She then went on to complete her postdoctoral training with Dr. Eric Nestler at Icahn School of Medicine at Mount Sinai, where she used circuit probing techniques to understand the temporally specific neural signals that underlie motivation and reward learning. She is currently an Assistant Professor at Vanderbilt University in the Department of Pharmacology. Her independent work seeks to characterize and modulate the precise circuits in the brain that underlie both adaptive and maladaptive processes in reward, motivation, and associative learning.
Dr. Tim Harris
Johns Hopkins University
Timothy Harris is a research professor in the Department of Biomedical Engineering. He leads the Applied Physics and Instrumentation Group at the HHMI Janelia Research Campus, and is the originator of the project that produced the Neuropixels Si probe for extracellular recording in animals, mostly mice, and rats. He shares his time between Janelia and Johns Hopkins and is working on projects to enable recording 10-20,000 neurons in rodents and 30-50,000 neurons in non-human primates, as well as stimulate with high resolution.
He received a BS in Chemistry at California Polytechnical State University, San Luis Obispo, and a PhD in Analytical Chemistry at Purdue University.
Dr. Elizabeth Hillman
Elizabeth Hillman is professor of biomedical engineering and radiology at Columbia University and a member of the Mortimer B. Zuckerman Mind Brain Behavior Institute and Kavli Institute for Brain Science at Columbia. Hillman received her undergraduate degree in physics and Ph.D. in medical physics and bioengineering at University College London and completed post-doctoral training at Massachusetts General Hospital/Harvard Medical School. In 2006, Hillman moved to Columbia University, founding the Laboratory for Functional Optical Imaging. Hillman’s research program focuses on the development and application of optical imaging and microscopy technologies to capture functional dynamics in the living brain. Most recently, she developed swept confocally aligned planar excitation (SCAPE) microscopy, a technique capable of very high speed volumetric imaging of neural activity in behaving organisms such as adult and larval Drosophila, zebrafish, C. elegans and the rodent brain. Hillman’s research program also includes exploring the interrelation between neural activity and blood flow in the brain, as the basis for signals detected by functional magnetic resonance imaging (fMRI). Hillman is a fellow of the Optical Society of America (OSA), the society of photo-optical instrumentation (SPIE) and the American Institute for Medical and Biological Engineering (AIMBE). She has received the OSA Adolf Lomb Medal for contributions to optics, as well as early career awards from the Wallace Coulter Foundation, National Science Foundation and Human Frontier Science Program.
Dr. Baljit Khakh
University of California, Los Angeles
Baljit Khakh completed his Ph.D. at the University of Cambridge in the laboratory of Patrick PA Humphrey. He completed postdoctoral fellowships in the laboratory of Graeme Henderson at the University of Bristol, and then in the laboratory of Henry A. Lester and Norman Davidson at California Institute of Technology. In 2001, Khakh became Group Leader at the MRC Laboratory of Molecular Biology in Cambridge, and in 2006 he moved to the University of California, Los Angeles where he is Professor of Physiology and Neurobiology. Khakh’s work has been recognized, including with the NIH Director's Pioneer Award, the Paul G. Allen Distinguished Investigator Award, and the Outstanding Investigator Award (R35) from NINDS.
2022 Naff Symposium Committee
Dr. Chris Richards - Chair
On September 28, 2021, the University of Kentucky inducted 27 former students into the 2020 Hall of Distinguished Alumni. The alumni are being honored for their meaningful contributions to the Commonwealth, nation, and the world. The prestigious event, held every five years, was postponed last year due to pandemic restrictions.
Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, AL, USA.
Alabama Water Institute, The University of Alabama, Tuscaloosa, AL, USA.
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.
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.