Biology Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2749

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    VALIDATION OF AGE AND GROWTH USING MICROCONSTITUENT ANALYSIS OF FISH HARDPARTS
    (2022) Frey, Benjamin Alexander; Secor, David H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Without accurate age interpretation or validation, serious errors in the management and understanding of fish populations can occur. This study employs a novel approach to age validation using trace element microconstituent analysis of hardparts. The optical zones of annuli are hypothesized to be the result of seasonal changes in organic content and experienced temperature, either of which can result in cycles of trace elements associated with annulus formation. Using Laser Ablation ICP-MS analysis, we tested for periodicity in hardpart Ca, Cu, P, Sr, Mg, Mn, Zn, and Ba in comparison to the periodicity of annulus zonation (opaque and translucent zones). Initial tests were conducted for black sea bass, a species for which yearly annulus formation has been validated. Periodicities in elemental profiles in otoliths were identified using a Lomb-Scargle periodogram analysis that confirmed that cycles in Mg corresponded to annulus formation in the model species. This same approach was applied to Atlantic monkfish, a species without a valid ageing procedure. Annular chemical oscillations occurred in illicia hardparts that exhibited modest agreement (80.7%) with known-age samples.
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    Structural Basis for Clonal Diversity of the Public T Cell Response to Dominant Epitopes from Cytomegalovirus and Influenza
    (2016) Yang, Xinbo; Mariuzza, Roy A; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A diverse T cell receptor (TCR) repertoire is a prerequisite for effective viral clearance. However, knowledge of human TCR repertoire to defined viral antigens is limited. Recent advances in high-throughput sequencing (HTS) and single-cell sorting have revolutionized the study of human TCR repertoires to different types of viruses. In collaboration with the laboratory of Dr. Nan-ping Weng (National Institute on Aging, NIH), we applied unique molecular identifier (UMI)-labelled HTS, single-cell paired TCR analysis, surface plasmon resonance, and X-ray crystallography to exhaustively interrogate CD8+ TCR repertoires specific for cytomegalovirus (CMV) and influenza A (Flu) in HLA-A2+ humans. Our two CMV-specific TCR-pMHC structures and two Flu-specific TCR-pMHC structures provide a plausible explanation for the much higher diversity of CMV-specific than Flu-specific TCR repertoires in humans. Our comprehensive biochemical and structural portrait of two different anti-viral T cell responses may contribute to the future development of predictors of immunity or disease at the individual level.
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    Identifying Molecular Functions of Heliotropic Motor Tissue Through Proteomic Analysis of Soybean Pulvini
    (2013) Lee, Hakme; Sullivan, Joseph; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Heliotropic and nyctinastic leaf movement are mediated in soybean through turgor changes in the motor cells of the pulvinus, located at the base of the leaves. While some elements of the signaling pathways have been studied, a broad-scale protein identification has not yet been reported. In my research pulvini proteins were extracted in light- and dark-harvested soybean using the TCA/acetone method and identified by LC-MS/MS. Gene ontology analysis revealed proteins involved in proton transport were enriched in the soybean pulvinus proteome compared to a background soybean proteome. Proteins more highly expressed in the light were mostly stress response proteins, while under-expressed proteins were categorized as energy proteins. Further investigations using more sensitive extraction protocols and a multitude of sample times will build on these initial results to provide a thorough examination of heliotropic mechanisms at the molecular level.
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    VISUALIZATION OF CERAMIDE CHANNELS BY TRANSMISSION ELECTRON MICROSCOPY
    (2011) SAMANTA, SOUMYA; COLOMBINI, MARCO; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Functional studies have shown that the sphingolipid ceramide, self-assembles in phospholipid membranes to form large channels capable of allowing proteins to cross the membrane. Here these channels are visualized by negative stain transmission electron microscopy. The images contain features consistent with stain-filled pores having a roughly circular profile. There is no indication of tilt, and the results are consistent with the formation of right cylinders. The sizes of the pores range from 5 to 40 nm in diameter with an asymmetric distribution indicating no apparent upper size limit. The size distribution matches well with the distribution of sizes calculated from electrophysiological measurements.