Quantifying Blue Carbon Storage of the Two Dominant Temperate Seagrass Species in the Lower Chesapeake Bay

Seagrass meadows provide key ecosystem services including storing carbon long-term by trapping and burying organic matter in the sediments. Carbon storage likely differs by dominant species within a seagrass meadow, although quantification only exists for a few key species, including those in the Zostera genus. This lack of quantification presents an important issue in the context of changing species distributions due to climate change. One such example is in the Western Mid-Atlantic, where rising summer temperatures in the lower Chesapeake Bay have shifted the dominant seagrass species from Zostera marina to Ruppia maritima, a species more tolerant to heat waves. The carbon storage potential of seagrass meadows dominated by Ruppia is unknown but thought to be lower than those of Zostera due to plant morphology and life history differences. Here, we quantify the carbon stored in Zostera and Ruppia-dominated meadows of the lower Chesapeake Bay. Forty-two sediment cores were collected from seagrass meadows of varying ages for both species and processed for percent organic matter and carbon stocks. We found that Ruppia-dominated meadows had a higher percent carbon content in the top 5 cm of their sediment compared to Zostera-dominated meadows. Aboveground biomass was positively correlated with percent carbon content in Zostera-dominated meadows but not in Ruppia-dominated meadows. Canopy height was positively correlated with percent carbon content in both Zostera and Ruppia meadows. However, aboveground biomass and canopy height were significantly higher in Zostera meadows than in Ruppia meadows despite the lower percent carbon content. Our results suggest that environmental variables may also be responsible for carbon storage in Ruppia and Zostera meadows, along with seagrass morphology. Our study quantifies the carbon stocks of an understudied seagrass species and aids in understanding the implications of species identity on the carbon storage potential of seagrass ecosystems.BiologyBachelors of Science (BS

The Role of Calcium in Early Embryonic Development

Calcium is a ubiquitous, highly conserved universal messenger that mediates an array of functions such as neuronal and neuromuscular synaptic transmission, the stress response, wound healing, cardiac myocyte function, brain homeostasis maintenance, cell proliferation, and the immune response in mature organisms; this highly regular, stereotypical calcium activity in mature organisms has been extensively studied and is well understood (Vig et al., 2009; Fearnley et al., 2011; Patergnani et al., 2020). Calcium activity has also been implicated as a key regulator during the early development of organisms in processes such as neural induction, neuronal fate determination and differentiation, and organogenesis (Paudel et al., 2018). However, despite its universal presence in developing embryos, the spontaneous calcium activity that exists in embryonic systems is less well-characterized. This results from a dearth of studies, lack of consensus on analytical techniques, and contradictory results from literature in this field. Past studies on calcium activity during early embryonic development are also limited in that they are largely correlational rather than causal or functional. This thesis uses several different approaches to explore the role of calcium activity in early embryonic development. Chapter 1 provides a comprehensive review of the tweety gene family—which encodes calcium responsive gated chloride channels—by describing its structure, evolution, expression during development and adulthood, biochemical and cellular functions, and role in human disease. Then, chapter 2 discusses analysis of time-series data collected on embryos that were microinjected with GCaMP mRNA (a genetically-encoded calcium indicator that enables fluorescent visualization of calcium activity) and imaged for calcium activity at cellular resolution over a one hour period using fluorescent confocal microscopy. Importantly, this time-series analysis reveals that there is a lack of standardization in the methodology used to analyze time-series data of embryonic calcium activity imaging. This insight inspired the investigation described in chapter 3, which is a comprehensive review and critique of the existing methodologies used to detect and analyze imaging data of embryonic calcium activity. The review serves as a call to action to standardize the techniques used to analyze imaging data of embryonic calcium activity. Finally, chapter 4 experimentally examines the effects of calcium activity on early embryonic development by perturbing embryonic calcium dynamics using an automated calcium perturbation device that I invented. Ultimately, elucidating the role of calcium activity on early embryonic development through this study helps create the molecular framework necessary for the development of promising therapeutic strategies that target developmental diseases and disorders implicated by dysregulated embryonic calcium dynamics.BiologyBachelors of Science (BS

“Experimental Philosophy, For Gentlemen and Ladies:” A Foundling Hospital Token History, 1741-1756

From 1741-1756, experimental philosopher, Mr. Erasmus King, advertised scientific lectures from his home in Duke’s Court, London for both ladies and gentlemen. Sometime in those same years an anonymous mother won a place for her child through a lottery system at the London Foundling Hospital. When prompted by the orphanage to leave a token with her child, she produced a small piece of metal inscribed with the words “King’s Experimental Philosophy, Duke’s Court.” What that small material object reveals are connections between women, charity, science, and fashion in London’s social history. These connections point to larger eighteenth-century anxieties and acceptance of women’s place in the quickly changing scientific sphere of society. This project addresses the scientific culture of London by reassessing the events of experimental philosophy lectures from the perspective of female audiences, and the project presents new analysis of material culture and letters associated with the home and experiment room of Erasmus King and his wife Elizabeth. This analysis places the material, emotional, and spatial history of women at the forefront of the project. Scientific ideas inundated the eighteenth-century British urban consciousness, and the manifestations of that culture in London were unavoidable, regardless of gender. Therefore, while society did not often offer women a full and authoritative role in this culture, science could weave its way into crucial parts of women’s lives from mundanity to motherhood.HistoryBachelors of Arts (BA

Examining Factors Affecting Nuclear Retention of the Thyroid Hormone Receptor

The thyroid hormone receptors, TRα1, TRβ1, and TRβ2, are nuclear receptors that regulate many genes involved in development, growth, and homeostasis in response to thyroid hormone (T3). TRs undergo nucleocytoplasmic shuttling and mutations in TR can lead to altered intracellular localization and diseases such as Resistance to Thyroid Hormone (RTH). RTH is caused by mutations in TR leading to a decreased response to T3. Previous studies in our lab have established, using acetylation and non-acetylation mimics, that the acetylation of TR at specific sites leads to a more cytosolic localization and non-acetylation leads to a more nuclear localization, indicating that the deacetylation of TR plays an important role in modulating nucleocytoplasmic shuttling. To determine if histone deacetylases (HDAC) 1 and 3 play a role in altering TR localization by the deacetylation of TR, HeLa cells were transfected with GFP-tagged TRα1, TRβ1, or TRβ2 and an HDAC 1/3 inhibitor was added at 1μM and 10μM concentrations. Analysis of average relative nucleocytoplasmic (N/C) ratios revealed no significant change in localization of any TR variant when compared to the solvent control. These data suggest that the deacetylase activity of HDAC 1 and HDAC 3 is not directly responsible for the localization patterns of TR; as a result, other members of the deacetylase family are now under investigation. While in the nucleus, TR binds to nuclear receptor corepressor 1 (NCoR1), silencing gene expression in the absence of T3. In our investigation of RTHα mutations and NCoR1 binding, it was hypothesized that nuclear retention of RTHα mutants would be increased in the presence of overexpressed NCoR1, since some RTHα mutants have been reported to have increased affinity for NCoR1. RTHα mutants with substitution of arginine for either a cysteine or histidine at position 384 (R384C or R384H) were selected for analysis, because it had previously been shown that these TR variants have a more cytosolic population than wild-type TRα1. HeLa cells were transfected with mCherry-tagged wild type TRα1, R384C, or R384H, as well as GFP-tagged wild type NCoR1 or an NCoR1 mutant that does not bind TR, as a control. N/C ratios for wild-type TRα1 and the RTHα mutants were not significantly different in the presence of overexpressed NCoR1 compared with the non-binding NCoR1. To further investigate the role of NCoR1, HeLa cells were designed with NCoR1 knocked out and transfected with mCherry-tagged wild type TRα1, R384C, or R384H. The N/C ratios for wild-type TRα1 and the RTHα mutants were calculated and compared to those calculated from wild-type HeLa cells. It was determined that the N/C ratios were not significantly different. These experiments suggest that interaction with NCoR1 is not a key factor affecting localization patterns of these RTHα mutants. Overall, these findings provide further insight into TR’s interactions with other proteins and the resulting impacts on nuclear retention. The implications of these findings can be applied to learning more about multiple diseases in the endocrine system including Resistance to Thyroid Hormone syndrome and cancer.BiologyBachelors of Science (BS

Phase separation dynamics of SynGAP & PSD-95 in post-synaptic densities

The intricate interplay between SynGAP, PSD-95, and AMPA receptors within the post-synaptic density underpins synaptic plasticity and signal transmission. This study investigates several models of the interactions of these proteins, beginning with a minimal model of the kinetics of the exchange of SynGAP and AMPA receptors in the post- synaptic density after induction of long-term potentiation (LTP). Subsequently, we model the phenomenon of liquid-liquid phase separation (LLPS) mediated by the association of SynGAP and PSD-95. Our model of phase separation utilizes a three-component Flory-Huggins theory type (SynGAP, PSD-95, and solvent), and assumes energetically favorable interactions between SynGAP and PSD-95, as well as PSD-95 with itself. The model reproduces the phenomena of phase-separation-mediated formation of the post- synaptic density. We stimulate the dispersal of SynGAP from the post-synaptic density that follows an induction of LTP, which is modeled by a change in the Flory-Huggins interaction parameter representing the decreased favorability of SynGAP and PSD-95 interactions.NeuroscienceBachelors of Science (BS

Development of Dynamic Nuclear Polarization for Single-sided Nuclear Magnetic Resonance

Nuclear magnetic resonance (NMR) is a tool used to determine molecular structure and chemical dynamics within a magnetic field. This magnetic field creates different energy levels that nuclear spins can occupy. The difference in the number of spins at each energy level determines the amount of polarization, which is proportional to the detected signal. Typically, NMR instruments are expensive, require regular upkeep, restrict sample sizes to small tubes, and give low measurement signal. Single-sided NMR combats some limitations by allowing for larger sample sizes, at the expense of a larger magnetic field gradient which lowers measurement resolution. We aim to circumvent limitations by applying dynamic nuclear polarization (DNP) techniques to single-sided NMR. DNP transfers the polarization from unpaired electrons to hydrogen nuclei, increasing the detected signal and sensitivity. DNP is dependent on factors related to microwave power, radical concentration, and inherent molecular characteristics. This work demonstrates successful construction of a DNP system that maintains the open geometry of single-sided NMR using alternative hardware to excite electron spins. Various experiments reveal a large dependency on power to adequately hyperpolarize samples, leading to further developments in probing thin, interfacial regions within a large field gradient. Future work involves optimizing the DNP system in order to investigate material and biological applications using single-sided NMR.ChemistryBachelors of Science (BS

Eastern Oysters and Ocean Acidification: Does Family Impact Tolerance?

Eastern oysters (Crassostrea virginica) are a bivalve species in Virginia and the Chesapeake Bay that play an important role in their aquatic ecosystems and are an important species in aquaculture. Rising problems caused by climate change, such as ocean acidification (OA), could threaten natural populations and the success of the aquaculture industry. One solution to the threat of OA may be selective breeding of Eastern oysters for increased tolerance of OA, but there is currently limited research to inform the potential of this strategy. The first step towards evaluating the potential of this solution involves determining if oysters with different genetics respond differently to OA. This project looked at two genetically different families of Eastern oysters produced from broodstock bred for high performance in either high salinity or low salinity conditions to see if their tolerance of OA conditions differed. Juvenile oysters from each family were exposed to either acidified or control pH conditions (pH 7.3 and 7.8, respectively) for two weeks after which physiological responses were measured. The individual and interactive impacts of treatment and family on respiration rates, calcification rates, energy stores, oxidative stress, and total protein content were assessed. Family had an impact on response to OA for just total protein content out of the parameters measured, with oyster seed from the low salinity family having higher total protein content at acidified conditions than oysters from the high salinity family, but similar total protein between families at control conditions. Therefore, some traits related to OA tolerance may be influenced by family and thus could be selected for if they are heritable. However, we generally observed negative impacts of OA on oyster seed regardless of family, such as lower calcification rates and evidence of oxidative stress. Further research should examine if traits related to OA tolerance are heritable and whether there are families with more robust physiological tolerance of OA impacts.BiologyBachelors of Science (BS

Investigation into Amine Polyynes for Antibacterial Properties

Antibiotic resistance is a growing problem in today’s society. Many new antibiotics are derived versions of pre-existing antibiotics, which allows for antibiotic resistance to arise. To combat this issue, it is crucial to elucidate novel antibiotics with unique core structures and mechanisms of action. Asymmetric polyacetylenes have been isolated from natural products, and they have previously been demonstrated to exhibit antimicrobial and antibacterial activity. Solid-supported chemistry was utilized to efficiently synthesize a library of polyynes in a chemoselective fashion. Specifically, amine derivatives of the previously discovered biologically active polyynes were prepared and assessed for biological activity. Many of these compounds displayed improved activity in bacterial viability assays and may be a promising avenue for the development of novel antibiotics. Further investigation is needed to pinpoint the specific structural components that elicit biological activity.ChemistryBachelors of Science (BS

Modulation of Protein Function and Synthesis of Bioconjugates using Unnatural Amino Acids

Nature has evolved 20 amino acids that comprise all the proteins that compose living things. The limited lexicon of building blocks available to accomplish such a vast number of tasks is remarkable. My research aimed to augment protein chemistry by employing unnatural amino acids to modify proteins and introduce novel functionality. This was accomplished in three ways. First, we enabled modulation of Protein Methyltransferase function by incorporating a photocaged unnatural amino acid. A SAM510 Methyltransferase Assay revealed that the unnatural amino acid hindered methyltransferase activity in PRMT1 until irradiation with UV light, following which the photocaging group was removed, and protein activity was restored. Second, we achieved the dimerization of two proteins using a terminal alkyne-containing unnatural amino acid and a bioorthogonal Glaser-Hay reaction. We increased coupling efficiency by using a linker for this reaction. Finally, we synthesized a multivalent bioconjugate using a bromoalkyne unnatural amino acid and a reaction sequence including a bioorthogonal CuAAC followed by a Sonogashira. We demonstrated the use of an unnatural amino acid to confer spatiotemporal control over protein function. Additionally, we developed new pathways toward synthesizing bioconjugates, which have applications in targeted therapeutics, protein monitoring, and assays. Furthermore, a multivalent bioconjugate would expand the operational capacity of protein function by allowing the conjugation of multiple moieties, with each introducing a new function.ChemistryBachelors of Science (BS

A Combination of Environmental and Landscape Variables Drives Movement and Habitat use in Two Anaxyrus spp. in the Eastern Coastal Plain

Amphibians are among the most endangered taxa and are largely threatened by habitat loss. Little work has been conducted on the movement and habitat use of amphibians outside of their breeding season. In this study, we examined the movement patterns of two species of toads inhabiting the Eastern Coastal Plain of Virginia: the Eastern American Toad (Anaxyrus americanus americanus) and the Fowler’s Toad (Anaxyrus fowleri). Based on three years of movement data, we estimated the median migration distance of toads from their breeding locations and the propensity for site fidelity, related variation in distance traveled to environmental (e.g., rain, temperature, humidity) and landscape variables (e.g., coniferous forests, distance to trails, terrain ruggedness index), and compared microhabitat selection for daytime refugia between the two species. We found similar median distances from breeding grounds for the two species, 63 m for the Eastern American Toad and 64 m for the Fowler’s Toad, but Eastern American Toads had a greater range of moved distances (3rd quartiles were 122 m for Eastern American and 73 m for Fowler’s Toads). We also found that both species exhibited site fidelity. Distance to trails and minimum temperature related positively with increased movements. Compared to Fowler’s Toads, Eastern American Toads favored woody structures and leaf litter for daytime refugia. Our research provides crucial information for two toad species about the extent of their movements and habitat use during the nonbreeding season. To lessen the decline of amphibians, habitats occupied during the nonbreeding season need to be included in conservation strategies at biologically relevant distances around breeding areas.BiologyBachelors of Science (BS