@article{todorov_calhoun_mccarty_sombers_2024, title={Electrochemical Quantification of Enkephalin Peptides Using Fast-Scan Cyclic Voltammetry}, volume={8}, ISSN={["1520-6882"]}, DOI={10.1021/acs.analchem.4c02418}, abstractNote={Endogenous opioid neuropeptides serve as important chemical signaling molecules in both the central and peripheral nervous systems, but there are few analytical tools for directly monitoring these molecules in situ. The opioid peptides share the amino acid motif, Tyr-Gly-Gly-Phe-, at the N-terminus. Met-enkephalin is a small opioid peptide comprised of only five amino acids with methionine (Met) incorporated at the C-terminus. Tyrosine (Tyr) and Met are electroactive, and their distinct electrochemical signatures can be utilized for quantitative molecular monitoring. This work encompasses a thorough voltammetric characterization of Tyr and Met redox chemistry as individual amino acids and when incorporated into small peptide fragments containing the shared Tyr-Gly-Gly-Phe- motif. NMR spectroscopy was used to determine the structure and conformation at near-physiological conditions. Voltammetric data demonstrate how the peak oxidation potential and the rate of electron transfer are dependent on the local chemical environment. Both the proximity of the electroactive residue to the C- or N-terminus and the hydrophobicity of the additional nonelectroactive amino acids profoundly affect sensitivity. Finally, the work uses the electrochemical signal for individual amino acids in a "training set", with a combination of principal component analysis and least-squares regression to accurately predict the voltammetric signal for short peptides comprising different combinations of those amino acids. Overall, this study demonstrates how fast-scan cyclic voltammetry can be utilized to discriminate between peptides with small differences in the chemical structure, thus establishing a framework for reliable quantification of small peptides in a complex signal, broadly speaking.}, journal={ANALYTICAL CHEMISTRY}, author={Todorov, Jovica and Calhoun, Sarah E. and Mccarty, Gregory S. and Sombers, Leslie A.}, year={2024}, month={Aug} }
 @article{todorov_mccarty_sombers_2023, title={Exploring Electrochemistry: A Hydrogen Peroxide Sensor Based on a Screen-Printed Carbon Electrode Modified with Prussian Blue}, volume={100}, ISSN={["1938-1328"]}, DOI={10.1021/acs.jchemed.3c00844}, abstractNote={There is an increasing need for fundamental electrochemistry concepts to be taught in the undergraduate curriculum, given the broad applicability of electrochemical technologies in addressing a wide range of global issues from critical energy shortages to real-time medical diagnostics. However, many electrochemical concepts are often taught in disparate laboratory experiments, spread out through the curriculum, which can be intimidating to students (and instructors). This experiment, which has been tested and optimized in the undergraduate classroom over multiple semesters, covers a wide range of electrochemistry topics in realizing the construction of a hydrogen peroxide (H2O2) sensor that is based on Prussian blue electrochemistry. The experiment introduces the fundamentals of cyclic voltammetry by prompting students to distinguish faradaic and capacitive components of voltammograms and to investigate their relationship with scan rate as per electrochemical theory. Students also evaluate electrocatalysis through electrodeposition of a thin film of Prussian blue on the sensor surface and the effects of this modification on electron transfer and sensor performance. Finally, students combine amperometric measurements with the method of standard additions to determine H2O2 concentrations in an unknown sample. Overall, this experiment offers an integrated and cohesive experience that connects many important electroanalytical concepts that are often taught individually into one 3 h, hands-on laboratory experiment that requires minimal resources.}, number={12}, journal={JOURNAL OF CHEMICAL EDUCATION}, author={Todorov, Jovica and McCarty, Gregory S. and Sombers, Leslie A.}, year={2023}, month={Nov}, pages={4853–4859} }