Rising Stars in Analytical Chemistry Spring 2021

Congrats Rising Stars Spring 2021!

Meet the Rising Stars in Analytical Chemistry:

May 12th, 2021 1:00-2:00 pm EST

Dr. Lindsay K. Pino

Harmonizing and calibrating quantitative mass spectrometry experiments

Biography: Lindsay is a postdoctoral researcher with over a decade of experience in developing mass spectrometry proteomics methods for studying human disease. She has trained at the Broad Institute, the University of Washington, and most recently the University of Pennsylvania. Her focus is on developing techniques for quantitative proteomics and in particular she is interested in the challenges associated with scaling-up quantitative proteomics experiments. Lately, she’s been working on expanding these techniques to target dynamic systems including protein turnover, epigenetics, and protein interactions.She is also active and involved in the proteomics community: she is a highly reviewed teacher and coordinator for quantitative proteomics training workshops, sits on several conference organizing and special interest committees, and is a one-on-one mentor to trainees both in her postdoc lab and beyond. The trainees she has worked with have not only been trained in mass spectrometry and computational proteomics skills but have succeeded in applying for fellowships from the NIH and NSF, won awards for their poster presentation at ABRCMS, and most importantly gained confidence in themselves and their abilities.

Abstract: Research into basic biology, as well as translational human research and clinical applications, all benefit from the growing accessibility and versatility of mass spectrometry (MS)-based proteomics. Although once limited in throughput and sensitivity, proteomic studies have quickly grown in scope and scale over the last decade due to significant advances in instrumentation, computational approaches, and biosample preparation. Despite the growing size of quantitative MS proteomics datasets, mass spectrometry is itself not inherently quantitative and requires experimental designs to interpret instrument signal into protein abundances. In this talk, I introduce the need for reference materials in mass spectrometry proteomics, describing a simple strategy to calibrate using a reference sample, which places peptide and protein quantifications on the same scale and harmonizes quantities between different instruments, acquisition methods, and laboratories. Then, I extend my reference material calibration approach to show how not all peptides detected by MS are truly quantitative and show that by assessing the quantitative proteome (limit of detection, LOD; limit of quantitation, LOQ) in yeast lysate, human cerebrospinal fluid, and formalin-fixed paraffin-embedded samples. Finally, I showcase how these techniques can be applied in spatiotemporal proteomics, specifically protein turnover studies. In my methods development, I strive to make sure that my approaches are useful to and used by the community by making them simple to implement, agnostic to mass spectrometer hardware, and broadly generalizable across experimental systems.

Kira L. Rahn

Optimization of paper-based lateral flow assay employing ion concentration polarization for analyte enrichment

Biography: Kira L. Rahn (she/her) is a Ph.D. candidate at Iowa State University in the Department of Chemistry, where she is advised by Asst. Prof. Robbyn K. Anand. Kira is an electrochemist and studies AC voltammetric techniques applied to bipolar electrodes with electrochemiluminescent reporting reactions, as well as the employment of electrokinetic focusing to increase lateral flow assay sensitivity. As a 4th year graduate student in the Anand Group, Kira enjoys mentoring new graduate students to the lab, as well as several undergraduate research assistants. She acted as a graduate peer mentor in her position as a writing consultant for the graduate students in the Chemistry Department, where in addition to helping students improve their communication skills, she initiated a preliminary oral exam preparation group to provide support for third-year chemistry graduate students. Kira is an active member of the planning committee for the Midwest Retreat for Diversity in Chemistry (next Retreat in May 2022!). The goal of the Retreat is to aid in the retention of underrepresented groups in chemistry by teaching skills for a positive approach to a career in chemistry and by fostering professional relationships between members in the field. Kira has been awarded a 2021 ACS Division of Analytical Chemistry Fellowship sponsored by Eli Lilly and several departmental awards, including the Mary K. and Velmer A. Fassel Analytical Chemistry Fellowship, the Witiak Graduate Fellowship, the Women in Chemistry Award, and the Arthur Hellwig Memorial Scholarship.

Abstract: The need for more sensitive, rapid, point-of-care (POC) diagnostic tests has been made emergent by the SARS-CoV-2 pandemic. The goal of our research is to develop a POC diagnostic platform that preconcentrates antigens for their detection at subpicomolar concentrations in biofluids by lateral flow assay. Ion concentration polarization (ICP) is employed to achieve electrokinetic focusing of charged biomolecules along an electric field gradient established in the paper strip of the lateral flow device. The analyte is focused when a balance between the electrophoretic and convective velocities of the analyte is maintained. Prior to studying the ICP-based enrichment of an antigen and its impact on the limit of detection of a lateral flow assay, we used a fluorescent tracer, BODIPY2-, as a model analyte for platform development. We optimized the growth of a stable line of enriched analyte across the paper strip by altering the electrode configuration and the rate at which the applied voltage bias is ramped. The degree of enrichment that is achieved by each configuration is measured. The resulting platform is anticipated to have a broad impact on the ability to sensitively and rapidly diagnose a wide range of diseases, including COVID-19. The authors gratefully acknowledge financial support from the Research Corporation for Science Advancement through an award as part of the COVID-19 Initiative, as well as the Roy J. Carver Charitable Trust.

May 19th, 2021 1:00-2:30 pm EST

Dr. Nadia Leonard

Understanding Electrostatic Effects at Manganese Complexes to Control Reactivity

Biography: Nadia Léonard received her BS in chemistry at Brown University and conducted research on the development of organoiridium complexes for the functionalization of hydrocarbon feedstocks with Professor Wesley Bernskoetter. Following her undergraduate studies, she taught math and science for grades K-4th at a charter school in the Greater Boston area. She then started her doctoral studies and was an NSF Graduate Research Fellow under the guidance of Professor Paul Chirik at Princeton University. Her doctoral research focused on developing earth-abundant transition metal catalysts for site-selective hydrofunctionalization of hindered alkenes. During her studies at Princeton, Nadia served as a Diversity Fellow for the Graduate School, Office of Diversity and Inclusion where she worked with the LGBT Center, Women*s Center, and Carl A. Fields Center for Equality and Cultural Understanding to develop programming to support the graduate student community. Following completion of her PhD in 2019, she moved to southern California to begin a postdoctoral position with Professor Jenny Yang at the University of California, Irvine where she is currently studying electric field effects at transition metal complexes using a combination of synthesis, electrochemistry, and spectroscopy. Nadia was awarded a President’s Postdoctoral Fellowship in 2021 to continue her research in the Yang lab.

Abstract: Reactive transition metals play an important role in catalyzing chemical transformations, and these chemical transformations often require the transfer of both protons and electrons. In nature, metalloenzymes use electrostatics to align the dipoles and net charges of reactants, products, and transition states, leading to enhanced reactivity and greater catalytic efficiency. We are interested in synthesizing transition metal complexes with tunable electrostatic interactions and using these model complexes to better understand how enzymes achieve enhanced reactivity. In this work, we present model manganese complexes that incorporate positively charged ions to install electrostatic effects. We show how electrostatics are responsible for tuning both the redox properties and protonation at these complexes. Incorporating a cation of charge 1+, 2+, or 3+ is found to shift the redox potential of the manganese complexes to more oxidizing potentials while simultaneously decreasing the basicity at the manganese. We relate this trend to the reactivity of the manganese complexes by exploring net hydrogen-atom transfer (HAT) reactions and breaking thermodynamic scaling relationships. Implications of this study suggest that electric fields may modulate pathways for hydrogen atom transfer reactions or facilitate asynchronous proton-coupled electron transfer pathways.

Rebeca S. Rodriguez

Detection of Food Contaminants via Linear Polymer Affinity Agents and Surface-Enhanced Raman Scattering

Biography: Rebeca (Becky) Rodriguez received her undergraduate degree in Chemistry from American University (2016). She will graduate with her Ph.D. in Chemistry from the University of Minnesota in 2021 under the advisement of Dr. Christy Haynes. Her research is at the interface of analytical, polymer, and materials chemistry, with a focus on the detection of food contaminants with linear polymer affinity agents and surface-enhanced Raman scattering. She completed an internship at the Naval Surface Warfare Center in Dahlgren, VA (2019) in the Chemical, Biological, and Radiological Defense Division. She has served as UMN SACNAS president for two years, where she has planned many outreach events in the Twin Cities at the Science Museum of MN, a K-8 school, and an REU workshop day for local BIPOC undergraduates. She is a co-lead of the College of Science and Engineering D&I Alliance Student Action Committee, a WISE representative for the Department of Chemistry’s D&I Committee, and is spearheading a local Twin Cities research symposium for BIPOC undergraduates in the area (Underrepresented Students in STEM – Twin Cities). She is a 2020-2021 ACS Division of Analytical Chemistry Graduate Fellow, a 2020 Women’s Chemist Committee Merck Research Award recipient, a 2020-2021 UMN Doctoral Dissertation Fellow, and was recently awarded the 2021 UMN President’s Student Leadership and Service Award and the 2021 Josie R. Johnson Human Rights and Social Justice Award.

Abstract: There are a variety of small molecule toxins found in crops that can be extremely carcinogenic to humans, posing dangerous hazards in food production and consumption. This work exploits polymers, with commercially available monomers, as capture agents for various toxin targets such as mycotoxins. Mycotoxins are small molecule toxins produced from fungi, that contaminate crops such as corn and wheat. Detecting mycotoxins traditionally employs the use of specific affinity agents, but they are expensive and do not allow the detection of multiple targets with one affinity agent. For this reason, we propose the use of a less specific affinity agent, like a linear polymer, to detect classes of mycotoxin molecules. The capture agents can be immobilized on plasmonic substrates, and when paired with surface-enhanced Raman spectroscopy (SERS), can provide fingerprint spectra for various targets. Pairing experimental SERS with computational modeling helps confirm hypotheses on binding and target/polymer interaction. Modeling the target mycotoxins and affinity agents with density function theory (DFT) allows one to attribute changes in vibrational spectra to particular interactions between the target and polymer. This work demonstrates optimization of SERS sensing to achieve limits of detection comparable to current detection methods with a simpler and more flexible signal transduction mechanism, providing an opportunity for future applications in complex matrices where these toxins are traditionally found.

Dr. Marcelino Varona

Selective Analysis of Nucleic Acids from Complex Biological Samples with Molecular-Beacon Loop-Mediated Isothermal Amplification and Solid-Phase Microextraction

Biography: Marcelino Varona obtained his B.S. in chemistry and biology from Concordia University Nebraska in 2016. At Concordia, he was a involved with the international student community and assisted incoming students with adapting to campus and academic life. He recently obtained his Ph.D. from Iowa State University under the direction of Professor Jared Anderson. In Professor Anderson’s lab, he mentored and trained several undergraduate and graduate students. His research involved the development of nucleic acid extraction and detection methods for point-of-care applications. A particular emphasis of the research was the advancement of sequence-specific detection of loop-mediated isothermal amplification using molecular beacons. He has received various awards including the International Symposium on Advances in Extraction Technologies (ExTech) Poster Award, Chinese American Chromatography Association Student Excellence Award, and the Iowa State University Research Excellence Award. He is currently working as an Associate Scientist in the Small Molecule Analytical Chemistry division at Genentech.

Abstract: Nucleic acids are essential biopolymers that serve as diagnostic biomarkers in many applications including SARS-CoV-2 and tuberculosis detection, and cancer identification.  Popular detection methods, such as polymerase chain reaction (PCR), suffer from long analysis times and require complex thermal cycling equipment. These drawbacks limit the utility of traditional detection methods for rapid in-field testing and point-of-care applications. Isothermal amplification techniques circumvent many of the limitations posed by traditional methods and are ideally suited for rapid analysis. However, a significant hinderance to isothermal methods is the lack of robust sequence-specific detection schemes. In this talk, molecular beacon loop-mediated isothermal amplification (MB-LAMP) is shown to be a promising alternative to PCR for sequence-specific detection of DNA sequences. Three different assay formats are shown, highlighting the versatility of the MB-LAMP approach. High specificity of each assay is demonstrated through the detection of single-nucleotide polymorphisms. In addition, solid-phase microextraction (SPME) is shown as an alternative sample preparation technique for nucleic acid isolation for MB-LAMP detection. Several complex biological samples were analyzed including plasma, artificial sputum, and artificial saliva.

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