Chemistry & Biochemistry
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The Department of Chemistry and Biochemistry offers research-oriented programs culminating in the Doctor of Philosophy degree. The faculty in the department have expertise over a broad range of specialty areas including synthesis, structure, spectroscopy, and mechanism. In each of these fields, the strength of the department has been recognized at the international level.
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Item Physical and chemical mechanisms that influence the electrical conductivity of lignin-derived biochar(2021-10) Kane, Seth; Ulrich, Rachel; Harrington, Abigail; Stadie, Nicholas P.; Ryan, Cecily A.Lignin-derived biochar is a promising, sustainable alternative to petroleum-based carbon powders (e.g., carbon black) for polymer composite and energy storage applications. Prior studies of these biochars demonstrate that high electrical conductivity and good capacitive behavior are achievable. However, these studies also show high variability in electrical conductivity between biochars (– S/cm). The underlying mechanisms that lead to desirable electrical properties in these lignin-derived biochars are poorly understood. In this work, we examine the causes of the variation in conductivity of lignin-derived biochar to optimize the electrical conductivity of lignin-derived biochars. To this end, we produced biochar from three different lignins, a whole biomass source (wheat stem), and cellulose at two pyrolysis temperatures (900 °C, 1100 °C). These biochars have a similar range of conductivities (0.002 to 18.51 S/cm) to what has been reported in the literature. Results from examining the relationship between chemical and physical biochar properties and electrical conductivity indicate that decreases in oxygen content and changes in particle size are associated with increases in electrical conductivity. Importantly, high variation in electrical conductivity is seen between biochars produced from lignins isolated with similar processes, demonstrating the importance of the lignin’s properties on biochar electrical conductivity. These findings indicate how lignin composition and processing may be further selected and optimized to target specific applications of lignin-derived biochars.Item Antimicrobial activity of naturally occurring phenols and derivatives against biofilm and planktonic bacteria(2019-10) Walsh, Danica J.; Livinghouse, Tom; Goeres, Darla M.; Mettler, Madelyn; Stewart, Philip S.Biofilm-forming bacteria present formidable challenges across diverse settings, and there is a need for new antimicrobial agents that are both environmentally acceptable and relatively potent against microorganisms in the biofilm state. The antimicrobial activity of three naturally occurring, low molecular weight, phenols, and their derivatives were evaluated against planktonic and biofilm Staphylococcus epidermidis and Pseudomonas aeruginosa. The structure activity relationships of eugenol, thymol, carvacrol, and their corresponding 2- and 4-allyl, 2-methallyl, and 2- and 4-n-propyl derivatives were evaluated. Allyl derivatives showed a consistent increased potency with both killing and inhibiting planktonic cells but they exhibited a decrease in potency against biofilms. This result underscores the importance of using biofilm assays to develop structure-activity relationships when the end target is biofilm.Item Dynamic processing of DOM: Insight from exometabolomics, fluorescence spectroscopy, and mass spectrometry(2018-06) Smith, Heidi J.; Tigges, Michelle M.; D'Andrilli, Juliana; Parker, Albert E.; Bothner, Brian; Foreman, Christine M.Dissolved organic matter (DOM) in freshwater environments is an important source of organic carbon, supporting bacterial respiration. Frozen environments cover vast expanses of our planet, with glaciers and ice-sheets storing upwards of 6 petagrams of organic carbon. It is generally believed that DOM liberated from ice stimulates downstream environments. If true, glacial DOM is an important component of global carbon cycling. However, coupling the release of DOM to microbial activity is challenging due to the molecular complexity of DOM and the metabolic connectivity within microbial communities. Using a single environmentally relevant organism, we demonstrate that processing of compositionally diverse DOM occurs, but, even though glacially derived DOM is chemically labile, it is unable to support sustained respiration. In view of projected changes in glacier DOM export, these findings imply that biogeochemical impacts on downstream environments will depend on the reactivity and heterogeneity of liberated DOM, as well as the timescale.Item Light-Based 3D Printing of Hydrogels with High-Resolution Channels(2019-01) Benjamin, Aaron D.; Abbasi, Reha; Owens, Madison; Olsen, Robert J.; Walsh, Danica J.; LeFevre, Thomas B.; Wilking, James N.Hydrogels are soft, water-based gels with widespread applications in personal care products, medicine and biomedical engineering. Many applications require structuring the hydrogel into complex three-dimensional (3D) shapes. For these applications, light-based 3D printing methods offer exquisite control over material structure. However, the use of these methods for structuring hydrogels is underdeveloped. In particular, the ability to print hydrogel objects containing internal voids and channels is limited by the lack of well-characterized formulations that strongly attenuate light and the lack of a theoretical framework for predicting and mitigating channel occlusion. Here we present a combined experimental and theoretical approach for creating well-defined channels with any orientation in hydrogels using light-based 3D printing. This is achieved by the incorporation of photoblocker and the optimization of print conditions to ensure layer-layer adhesion while minimizing channel occlusion. To demonstrate the value of this approach we print hydrogels containing individual spiral channels with centimeter-scale length and submillimeter-scale cross-section. While the channels presented here are relatively simple, this same approach could be used to achieve more complex channel designs mimicking, for example, the complex vasculature of living organisms. The low cytotoxicity of the gel makes the formulation a promising candidate for biological applications.Item Biochemical association of metabolic profile and microbiome in chronic pressure ulcer wounds(2015-05) Ammons, Mary Cloud B.; Morrissey, Kathryn; Tripet, Brian P.; Van Leuvan, James T.; Han, Anne; Lazarus, Gerald S.; Zenilman, Jonathan M.; Stewart, Philip S.; James, Garth A.; Copie, ValerieChronic, non-healing wounds contribute significantly to the suffering of patients with co-morbidities in the clinical population with mild to severely compromised immune systems. Normal wound healing proceeds through a well-described process. However, in chronic wounds this process seems to become dysregulated at the transition between resolution of inflammation and re-epithelialization. Bioburden in the form of colonizing bacteria is a major contributor to the delayed headlining in chronic wounds such as pressure ulcers. However how the microbiome influences the wound metabolic landscape is unknown. Here, we have used a Systems Biology approach to determine the biochemical associations between the taxonomic and metabolomic profiles of wounds colonized by bacteria. Pressure ulcer biopsies were harvested from primary chronic wounds and bisected into top and bottom sections prior to analysis of microbiome by pyrosequencing and analysis of metabolome using 1H nuclear magnetic resonance (NMR) spectroscopy. Bacterial taxonomy revealed that wounds were colonized predominantly by three main phyla, but differed significantly at the genus level. While taxonomic profiles demonstrated significant variability between wounds, metabolic profiles shared significant similarity based on the depth of the wound biopsy. Biochemical association between taxonomy and metabolic landscape indicated significant wound-to-wound similarity in metabolite enrichment sets and metabolic pathway impacts, especially with regard to amino acid metabolism. To our knowledge, this is the first demonstration of a statistically robust correlation between bacterial colonization and metabolic landscape within the chronic wound environment.