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Chemistry Virtual Poster Session

Welcome to the Virtual Poster Session. Posters have been provided by various graduate research groups throughout the chemistry option. If you have any questions on the research being presented, we encourage you to reach out to the respective group contacts.

Agapie Group

Synthesis Mechanism Applications

Contact: arnett@caltech.edu, gbailey@caltech.edu, mabruening@caltech.edu, thhe@caltech.edu, gheim@caltech.edu, lie@caltech.edu, rribson@caltech.edu, ascott@caltech.edu, ashiau@caltech.edu, manar@caltech.edu, thevarna@caltech.edu, sxiong@caltech.edu

Arnold Lab

Directed Evolution Research

Contact: Kai Chen, Juner Zhang, Shilong Gao & Nat Goldberg

Blake Group

High Sensitivity Ultrafast THz Studies of Materials

This poster depicts our work on a single shot Kerr effect spectrometer for studying ultrafast molecular dynamics in liquids and charge transport properties of photovoltaic materials.

Contact: Kyle Virgil, Griffin Mead, Haw Wei Lin, Sarah E. Dutton, & Alex Froebel

Uncovering Material Charge Dynamics with Ultrafast Terahertz Spectroscopy

This poster describes a collaborative effort between Geoff Blake and Harry Atwater on synthesizing novel semiconductors for better photovoltaics and characterizing their electrical properties with terahertz time-domain spectroscopy (THz-TDS).

Contact: Kyle Virgil, Griffin Mead, Haw Wei Lin

Hunting for the Origins of Oxygen-bearing Complex Organic Molecules with Orion

Astrochemistry is the study of molecules in space. Using radio telescopes to observe molecules in stellar nurseries, which serve as interstellar laboratories, we can learn about what compounds are out there and how they form via rotational spectroscopy. Chemistry can also be used as a tool to probe the physical conditions of star-forming regions. In the Orion KL nebula, for example, we have observed methanol isotopologues to study the chemistry at the hydroxyl hydrogen in interstellar space and have also used these data to map the local physical conditions of the nebula.

Contact: Olivia Haper Wilkins

Cushings Lab

Exploring Light-Matter Interactions from X-rays to Microwaves

We develop spectroscopic techniques that span the microwave to soft X-ray regions and probe dynamics that occur on timescales ranging from femtoseconds to microseconds. Specifically, we have been building a THz pump, XUV probe set-up and an entangled photon interferometer. Additionally, we are working on expanding the scope of our spectroscopic experiments. If you are interested in building optical, mechanical, and vacuum set-ups, developing theory for understanding X-ray and optical data or designing, fabricating, and testing samples, talk to us!

Contact: Jonathan Michelsen, Bryce Hickam, Manni He, Isabel Klein, & Danika Nimlos

Fu Group

Photoinduced, Copper-Catalyzed Cross-Coupling

Despite the tremendous accomplishments that have been described in the development of metal-catalyzed cross-couplings to form carbon–carbon bonds (as exemplified by the Nobel Prize in Chemistry in 2010), many significant opportunities remain. For example, until recently there were relatively few examples of metal-catalyzed coupling reactions of alkyl electrophiles. To address this shortcoming, we are pursuing the discovery of nickel-based catalysts for the coupling of a wide range of alkyl electrophiles, including enantioconvergent reactions of racemic electrophiles. We have also recently begun to explore couplings of racemic nucleophiles, along with employing olefins as nucleophiles in cross-coupling. Mechanistic studies are a significant component of this research program.

Enantioconvergent, Nickel-Catalyzed Cross-Coupling

Copper catalysis

Although the alkylation of an amine with an alkyl halide is one of the first reactions of amines that is taught in organic chemistry, there have been few studies of transition-metal catalysis of this transformation. In collaboration with the Peters lab at Caltech, we are pursuing the use of light and a transition-metal catalyst to achieve a wide range of couplings of heteroatom nucleophiles with alkyl electrophiles. In contrast to most photoredox catalysis, we employ a single catalyst for the key photochemistry and bond-forming processes. Enantioconvergent reactions of racemic alkyl halides, as well as mechanistic studies, are being investigated.

Contact: Dylan Freas, Wanji (Wendy) Zhang, Hyungdo Cho, Robert Anderson, Xiaoyu (Dan) Tong

Goddard Lab

New Methods for de Novo Simulations and Applications to Catalysis, Materials, and Biochemistry

Hadt Lab

Hadt Lab at Caltech

The Hadt Lab specializes in combining innovative spectroscopic and computational methods to the study of transition metal complexes and materials. We emphasize a creative approach to describing the relationships between structure and function across interdisciplinary areas of chemistry, biology, physics, and materials science.

In the Hadt lab, we combine experimental and computational techniques towards exploring the magnetic field and vibrational mode-dependences that underlie vital physical phenomena in inorganic complexes. We're a physical-inorganic group, applying physical experimental techniques (including transient absorption spectroscopy) towards understanding the kinetics of inorganic systems. Our preprint studying the influence of spin-phonon interactions on spin-crossover and zero-field splitting in iron(II) complexes with computational methods can be found here: https://tinyurl.com/ZFSPaper

Contact: abarth@caltech.edu, rghadt@caltech.edu, nhigdon@caltech.edu

Hsieh-Wilson Lab

The Hsieh-Wilson lab uses chemical tools to investigate biological phenomena as they relate to neuroscience, cancer, and metabolism. We are particularly interested in elucidating the role of glycans in cell and organismal biology. We also develop new methods to synthesize, probe, and manipulate glycans both in vitro and in living organisms. Specifically, our interests lie in the following areas:

Chemical Approaches to Study Chondroitin Sulfate in Neuroplasticity and Neurodegeneration

Chemical Approaches to Studying the Biological Functions of Heparan Sulfate

Glycosaminoglycans (GAGs): GAGs such as chondroitin sulfate (CS) and heparan sulfate (HS) are a family of sulfated polysaccharides involved in neuroplasticity, brain development, inflammation, and cancer. Our research combines advanced organic synthesis with cutting-edge techniques in molecular biology, mass spectrometry-based proteomics, and neurobiology to explore the role of HS and CS in the brain.

Chemical Approaches to Studying O-Glynacylation of Proteins

O-GlcNAc Glycosylation: O-GlcNAc glycosylation is a dynamic, inducible post-translational modification that involves the covalent attachment of N-acetylglucosamine (GlcNAc) to serine and threonine residues of proteins. O-GlcNAc is essential for cell survival and plays important roles in many biological processes, including transcription, translation, cell division, and metabolism. Our lab focuses on understanding the functional roles of O-GlcNAc and its contributions to human diseases such as Alzheimer's disease, diabetes, and cancer. In the process, we develop new chemical, analytical, and bioinformatics approaches to detect, quantify, and study the modification.

Contact: Amelie Joffrin, Alexander Sorum, John Thompson, Nitin Pawar

Ismagilov Group

Polymer-Driven Aggregation in the Gut

Polymers abound the gut in the form of host secretions and dietary fibers. These polymers can aggregate particulate matter in the small intestine, which can affect the uptake of food and drugs and the function and behavior of microorganisms. In this poster, we show how particles spontaneously aggregate in the small intestinal lumen fluid ex vivo, and that chemically mediated interactions from mucins and immunoglobulins are not required for this aggregation. Furthermore, we show that aggregation can be controlled with dietary fibers through a mechanism qualitatively consistent with depletion-type interactions, demonstrating a polymer molecular weight and concentration dependence on particle aggregation. Finally, we show that motile E. coli can aggregate via depletion-type interactions, and that their motility enables aggregation in highly viscous environments where nonmotile bacteria and particles cannot aggregate due to lack of collision from hindered Brownian motion.

Contact: Michael Porter

Development of single-cell SPRITE to comprehensively map dynamic organization of DNA in higher-order nuclear structures within single cells

We know that the 3-dimensional genome structure plays a role in regulating gene expression. We know there is heterogeneity in gene expression at the single cell level, which would likely result in heterogeneity in single cell genome structure. However current single cell methods are limited in looking at comprehensive single cell genome organization. As a result, our lab has collaborated with Mitch Guttman's lab at Caltech to develop scSPRITE (single cell split-pool recognition of interactions by tag extension) to look at comprehensive genome organization of DNA at the single cell level.

Contact: Mary Arrastia

Cell envelop damage of Neisseria gonorrhoeae after 15-min beta-lactam exposure enables rapid antimicrobial susceptibility testing

Designing diagnostic tools to detect phenotypic antibiotic resistance at the point-of-care is vital to tackling the global threat of antibiotic resistance. Due to the slow growth rate of N. gonorrhoeaeand the mechanism of action of β-lactams, measuring the effect on the cell wall with nucleic acids can be challenging. By adding specific perturbations in succession with short antibiotic exposures and using nucleic acid accessibility as a readout, we are able to measure these effects. This poster details the development of a rapid, phenotypic antibiotic susceptibility test (AST), which is an active field of research in the Ismagilov lab.

Contact: esavela@caltech.edu; mmcooper@caltech.edu

Lewis Group

Lewis Group Recruitment Poster

Contact: Madeline Meier

Okumura Group

Kinetics and Spectroscopy via Multiplexed Photoionization Mass Spectrometry

The Okumura group uses Multiplexed Photoionization Mass Spectrometry (MPIMS) in collaboration with Sandia National Labs at the Advanced Light Source synchrotron to investigate complex systems of atmospheric reactions. Full mass spectra are taken every 50 microseconds, yielding mass-resolved kinetic traces. Tunable vacuum ultraviolet light provided by the synchrotron allows for separation of same-mass species. The technique is applied to the self-reaction of the beta-hydroxyethylperoxy radical and investigation of chlorine peroxide photolysis cross sections.

Contact: Gregory Jones

High-Resolution Spectroscopy of Stable Atmospheric Molecules

The Okumura group has a variety of projects involving high resolution spectroscopy to answer questions in atmospheric chemistry. One project uses highly sensitive cavity ringdown absorption spectroscopy to measure the kinetic isotope effect of methane isotope substitution in reactions with the atmospheric radicals O(1D) and OH, allowing for the sinks of atmospheric methane to be tracked and quantified. A second project uses the same technique to measure methane to ethane ratios in atmospheric samples, giving another measure how natural or anthropogenic a methane's source is. Another project uses photoacoustic spectroscopy to accurately measure the absorption of atmospheric oxygen, which allows for the accurate quantification of the absorption pathlength of atmospheric CO2, allowing CO2 emissions to be quantitatively measured measured via satellite on a local scale. Last, we use frequency comb spectroscopy to measure the concentration of atmospheric radicals; including the first recorded spectrum of the long-predicted HOCO radical from the reaction of OH + CO.

Contact: Mitchio Okumura, Tzu-Lynn Chen, Ofir Shoshanim, Joey Messinger, Douglas Ober, Greg Jones, Hannah Szentkuti, Wen Chao, Leah Stevenson

Peters Group

Peters Group- Visit Weekend 2020

The Peters Group is interested in small molecule transformations carried out by inorganic and organometallic complexes or materials, especially those with applications in energy and sustainability. Taking cues from the active sites of enzymes, we primarily explore the rich chemistry accessible by mid-to-late first row transition metals. Our group leverages expertise in experimental techniques such as electron paramagnetic resonance spectroscopy, Mossbauer spectroscopy, and electrochemistry in combination with computational methods to fully interrogate mechanism and electronic structure in our systems.

Contact: eboyd@caltech.edu, tfolsom@caltech.edu, aibrahim@caltech.edu, cjohanse@caltech.edu, djschild@caltech.edu, nwatkins@caltech.edu, mzott@caltech.edu

Reisman Lab

16 StepsTotal Synthesis of the Isoryanoid Diterpene (+)-Perseanol

(+)-Perseanol is an isoryanodane diterpene that is isolated from the tropical shrub Persea indica and has potent antifeedant and insecticidal properties. Here we report a chemical synthesis of (+)-perseanol, which proceeds in 16 steps from commercially available (R)-pulegone. The synthesis involves a two-step annulation process that rapidly assembles the tetracyclic core from readily accessible cyclopentyl building blocks. This work demonstrates how convergent fragment coupling, when combined with strategic oxidation tactics, can enable the concise synthesis of complex and highly oxidized diterpene natural products.

Contact: Yujia Tao

Robb Group

Research at the Intersection of Synthetic Organic, Physical Organic and Polymer Chemistry

The Robb group performs research at the intersection of synthetic organic, physical organic, and polymer chemistry. Research in the Robb group is focused on the emerging area of polymer mechanochemistry, where mechanical force is used to activate productive chemical transformations in stress-responsive molecules known as mechanophores. We use computationally guided experimental methods to develop new mechanophores and strategies that enable access to innovative stimuli-responsive polymers. Ultimately, we seek to develop chemistry that provides new insight into structure-mechanochemical activity relationships and apply these advancements in fundamental understanding to create force-responsive polymers that address a wide variety of materials challenges.

Contact: Anna Overholts , Brooke Versaw, Corey C. Husic, May Zeng, Molly McFadden

Ross Barber, Xiaoran Hu

See Group

Multielectron and Multivalent Chemistry for Energy Storage

The See Group studies multivalent and multielectron chemistry for next-generation energy storage with a focus on Earth-abundant, inexpensive materials. Their research spans the disciplines of solid-state chemistry, inorganic chemistry, materials chemistry, electrochemistry, and analytical chemistry to gain a mechanistic picture of new redox processes and dynamic interfaces.

Contact: anjoma@caltech.edu, fall@caltech.edu, jzak@caltech.edu, sware@caltech.edu, skim@caltech.edu, ziton@caltech.edu,

chansol@caltech.edu, epatheria@caltech.edu, khpham@caltech.edu, mdqian@caltech.edu, sstradle@caltech.edu

Shan Group

Timing and specificity of co-translational nascent protein modification in bacteria

In this work, we use N-terminal methionine excision as an example to demonstrate how correct selection of nascent protein biogenesis pathways are achieved in the cell.

Contact: Chien-I Yang

Interplay with a co-translational chaperone enhances specificity of mammalian SRP pathway

Protein biogenesis is essential in all cells and begins when a nascent polypeptide emerges from the ribosome exit tunnel, where multiple ribosome-associated protein biogenesis factors (RPBs) could direct nascent proteins to distinct fates. How distinct RPBs spatiotemporally coordinate with one another to effect accurate substrate selection is an emerging question. To address this question, we investigated the molecular interplay between signal recognition particle (SRP), a universally conserved protein targeting machine, and nascent polypeptide-associated complex (NAC), a cotranslational chaperone. We demonstrate that NAC co-binds with and alters the conformation of SRP on the ribosome, thus selectively reducing SRP-SRP receptor assembly on ribosomes without an exposed signal sequence. A mathematical model demonstrates that the NAC-induced regulations of SRP activity is essential for the fidelity of cotranslational protein targeting. Our work establishes a new molecular model for how NAC acts as a triage factor to prevent protein mislocalization, and provides valuable concepts and tools to understand nascent protein selection and triage on the ribosome.

Contact: hhsieh@caltech.edu

Stoltz Group

The Stoltz Group: Total Synthesis Projects

The general research paradigm within the Stoltz laboratory is to utilize architecturally complex target molecules as the driving force behind the development of new reactions. Naturally, these endeavors continuously push the boundaries of known chemical reactivity, highlighting the limitations of current technologies. The ensuing synthetic efforts represent not only a feat of synthetic strategy, but one of creativity and ingenuity.

Contact: nhafeman@caltech.edu, angamnit@caltech.edu, creimann@caltech.edu, tfulton@caltech.edu

The Stoltz Group: Methodology and Fundamental Research

In synergy with the synthesis of inspirational targets possessing interesting structural and biological properties, the development of new methodologies is a consistent driving force in our lab. We pride in discovering unique reactivity harnessing transition-metal catalysis that could ultimately be applicable for the synthesis of complex natural products.

Contact: acusuman@caltech.edu, tfulton@caltech.edu, ealexy@caltech.edu, akim2@caltech.edu, cjette@caltech.edu, zsercel@caltech.edu