Over time and with oxygen ingress, the chemical composition of wine evolves through a cascade of reactions comprising many pathways, one of which yields acetaldehyde, an oxidation product which not only directly impacts wine aroma but also facilitates further reactions altering other sensory properties such as color and mouthfeel. Key reactions in this pathway are catalyzed by the redox cycling of iron between two oxidation states, iron(II) and iron(III), thus the majority of the work presented herein focuses on control of iron’s reactivity. A spectrophotometric method of iron speciation was developed as a means of monitoring the reciprocal processes of iron reduction and oxidation in wine. The method relies on the combined use of two opposing chelating agents, ferrozine and ethylenediaminetetraacetic acid (EDTA), iron(II)- and iron(III)-selective respectively, to halt redox reactions, thereby providing a stable measurement of iron(II):iron(III) ratios in wine. This method was used to investigate the redox cycling of iron in model wine as it occurs in the primary reactions of the oxidation pathway: the oxidation of iron(II) by oxygen and the reduction of iron(III) by phenols. The rates of both processes varied with changes to model wine composition, though the former was found to be consistently slower. This suggests that iron(II) oxidation is the rate-determining reaction for the wine oxidation pathway, and wine ages at a rate limited not necessarily by its chemical composition but by oxygen ingress. Despite this, different wines subject to the same oxidative conditions will often vary in their response to oxygen, thus the reactions of hydrogen peroxide, a key branchpoint further down the oxidation pathway, were investigated, specifically as influenced by complexation of iron by major wine acids (tartaric, malic, and citric). The rate of the iron(II)-catalyzed Fenton oxidation of ethanol into acetaldehyde was found to occur more quickly toward the upper limits of typical wine pH, an effect most apparent with citrate complexation of iron. This appeared to affect the efficacy of sulfur dioxide as an antioxidant in competing with iron(II) for hydrogen peroxide. In addition, acetaldehyde formation in wine was found also to depend on oft-overlooked biotic factors post-fermentation. In a series of experiments pertaining to micro-oxygenation, found critical to the process were residual sugar and populations of Saccharomyces cerevisiae, without which acetaldehyde production would not occur. The question of why acetaldehyde does not accumulate with oxygenation alone warrants further investigation.

Proteins are an important class of therapeutics. The have many advantages over small-molecule drugs including high target specificity, low cytotoxicity and low immunogenicity. However, due to their inherent instability during storage, transport and delivery in vitro and in vivo, their therapeutic usefulness has not been maximized. One approach is to conjugate poly(ethylene glycol) to proteins to enhance pharmacokinetics in vivo, and there are eleven FDA approved therapeutic PEG conjugates. However, efforts to stabilize proteins against environmental stressors are still limited. In this dissertation, the development of biomimetic polymers, specifically heparin-mimicking polymers, to stabilize an important unstable therapeutic protein, basic fibroblast growth factor (bFGF), is described.

Chapter 1 reviews the biomedical applications of heparin-based hydrogels and heparin-mimicking polymers. Heparin is a naturally occurring polysaccharide that was first exploited for its antithrombotic activity. It was later realized that heparin-mediated biological functions were wide-ranging and included cell differentiation, angiogenesis, inflammation, host defense and viral infection mechanisms, lipid transport and clearance, and cell adhesion and interaction. Thus, researchers have shifted to investigate other properties of heparin-mimicking polymers besides its use as an anticoagulant. This chapter focuses on the development of heparin-based hydrogels and heparin-mimicking polymers for treatments of skin wounds specifically.

Chapter 2 describes the stabilization of bFGF by covalent conjugation of a heparin-mimicking polymer, a copolymer consisting of styrene sulfonate units and methyl methacrylate units bearing poly(ethylene glycol) side chains. bFGF plays a crucial role in diverse cellular functions from wound healing to bone regeneration. However, a major obstacle in the widespread application of bFGF is its inherent instability during storage and delivery. The bFGF conjugate of this polymer, bFGF-p(SS-co-PEGMA), retained bioactivity after synthesis and was stable to a variety of environmentally and therapeutically relevant stressors, such as heat, mild and harsh acidic conditions, storage, and proteolytic degradation, compared to native bFGF. After applied stress, the conjugate was also significantly more active than the control conjugate system where the styrene sulfonate units were omitted from the polymer structure. This research has important implications for the clinical use of bFGF and for stabilization of heparin-binding growth factors in general.

Chapter 3 describes a study of the preclinical value of the bFGF-p(SS-co-PEGMA) conjugate as a potential therapy for active wound healing. The cellular uptake and trafficking of the bFGF-heparin-mimcking polymer conjugate, bFGF-p(SS-co-PEGMA), was studied to better understand the cellular fate of the conjugate. The long-term storage stability of the conjugate was examined at 4 �C and 23 �C to evaluate the usefulness of the conjugate as a widely available therapeutic to patients, including at-home patients and patients in the remote areas. In addition, we report for the first time the superagonist characteristic of the heparin-mimicking polymer conjugate when used in the presence of exogenous heparin.

Chapter 4 describes the development of a 2nd-generation and a 3rd-generation heparin-mimicking polymer. Since the 1st-generation heparin-mimicking polymer described in Chapters 2 and 3, p(SS-co-PEGMA), stabilizes bFGF but is unable to activate FGF receptors (FGFRs) as is heparin, we looked for other heparin-mimicking polymers that could do both. Activation of FGFRs by two bFGF molecules and a heparin molecule leads to the dimerization and phosphorylation of the receptors, and subsequently results in cell responses such as proliferation or migration. Thus, 2nd and 3rd-generation sulfonated polymers were prepared. The 2nd-generation polymer was found to be a strong activator of FGFRs but its conjugate to bFGF had reduced bioactivity. The 3rd-generation polymer was a block copolymer of the 1st- and the 2nd-generation polymers. Although it was not as strong an activator as the 2nd-generation polymer, its conjugate to bFGF exhibited enhanced mitogenic activity compared to other conjugates and native bFGF in heparan sulfate-deficient cells and in human umbilical vein endothelial cells (HUVECs). The 3rd-generation conjugate also stimulated HUVEC migration better than the native protein. Taken together, the 3rd-genration conjugate is promising for applications where promoting angiogenesis is desired, such as in tissue engineering.

In Chapter 1, an overview of the literature of palladium-catalyzed carbenylative coupling reaction was reviewed. Palladium alkylidene intermeditates derived from N-tosylhydrazones and diazo compounds were used in the carbenylative reactions with facile β-hydride elimination, which erased the stereogenic center formed during carbene insertion. The review also covered palladium-catalyzed carbenylative coupling reaction without β-hydride elimination.

In Chapter 2, a palladium-catalyzed three-component intermolecular carbenylative amination and alkylation reaction of vinyl iodides, N-tosylhydrazones and nucleophiles were successfully carried out to yield products resulting from nucleophilic attack on the least hindered side of the η3-allylpalladium complexes. With the optimized reaction conditions, a variety of N-tosylhydrazones and nucleophiles were explored. The reaction works well with cyclic secondary amines and stabilized enolates and moderately with primary amines. A variety of alkyl N-tosylhydrazones have been demonstrated to work with the reaction conditions as well. Good yields were obtained under conditions that minimized the palladium-catalyzed ionization of allylic amines and addition of metalated hydrazones to η3-allylpalladium complexes.

In Chapter 3, vinyl iodides, carbon or nitrogen based nucleophiles and trimethylsilyldiazomethane (TMSD) were utilized to form vinylsilanes via palladium-catalyzed carbenylative cross-coupling reactions. These vinylsilanes were then subjected to iododesilylation conditions to generate new vinyl iodides capable of undergoing a second palladium-catalyzed cross-coupling reaction. This two-step process could be used iteratively to form new C-C and C-N bonds that quickly increased molecular complexity.

This dissertation consists of four studies that explore how high school students interact with and learn from two designs of a text-based conversational agent (chatbot) during small-group science discussions with peers and the agents. The agents utilize natural language processing to send prompts to promote students’ understanding of ecosystems concepts and collaboration. The two agent designs differ in appearances and linguistic styles to resemble a less knowledgeable peer and an expert. The first two studies explore how students interacted with the agents as social partners. In Study 1, I found that interactions with the less-knowledgeable-peer agent generally contained more sequences of questioning and transactive exchange, which provided opportunities for reflection and reasoning. In Study 2, I examined how student groups attempted to remedy interactions with the agents in case the agents failed to interpret students’ intent, similar to how students would repair conversations with human partners. Student groups more often reframed and explained their reasoning to the less-knowledgeable-peer than the expert agent. Furthermore, such interactions were positively correlated with higher counts of systems thinking statements, which indicated an enhanced understanding of interconnections between human and natural systems. Study 3 presents a case study to illustrate how interactions with the agents varied with group compositions: emergent, mixed, and expanding prior science knowledge. In Study 4, I built on studies 1-3 to examine how students learned from the agents, using interaction patterns with the agents as mediators. Results confirm the affordances of certain interaction dynamics, such as transactive exchange, to deepen systems understanding. Overall, the studies provide converging evidence on the utility of agent designs to support interactions that are enriching for learning. I discuss implications for designing conversational agents as social partners to promote collaboration and systems thinking, with applications to other learning contexts.