Biophysics Commons^™

Evaluating Bmx-001 As A Selective Radioprotector For Healthy Tissue In Pelvic Cancers, Molly Myers

Theses & Dissertations

Pelvic cancers, including rectal, anal, and prostate cancer, are relatively survivable cancers with high five-year survival rates, partially due to the addition of radiation to treatment regimens. Radiation confers excellent tumor control, but also causes damage to surrounding tissue, resulting in both short-term and long-term side effects. In a patient population that is surviving longer after treatment, limiting the impact of side effects is instrumental to improving patient quality of life. Radiation-induced ROS is instrumental in causing these side effects and provides a unique opportunity to protect healthy tissue from damage while sensitizing cancer tissue to treatment, as cancer cells …

Advanced Interactions Of Directed Energy With Retinal Pigment Epithelial Cells And Their Photochemical And Photothermal Responses, Jin B. Ha

Theses & Dissertations

Excess optical radiation can injure the retina through either rapid heat deposition (photothermal damage) or cumulative photo‑oxidative stress (photochemical damage), yet current laser‑safety limits treat these mechanisms as independent. To test that assumption, this dissertation integrated systematic wavelength, duration and temperature‑controlled laser exposures with live/dead fluorescence imaging in a melanin‑loaded hTERT‑RPE1 monolayer model. First, concurrent 447 nm (blue) and 2 µm (infra‑red) beams delivered for 200 s demonstrated a strong thermal–photochemical synergy: each beam alone was sub‑threshold (≤25 % lethality) but together produced 100 % RPE death without exceeding 50 °C, proving that modest heating markedly lowers the photon dose …

Cholestasis And Fluid Flow Are Biomechanic Regulators Of Cholangiocarcinoma Progression, Andrew Oleksijew

Theses & Dissertations

Cholestasis, altered or absent bile flow, is associated with poor survival in patients with cholangiocarcinoma, an aggressive cancer of the biliary epithelium. Changes in bile flow often result in stricture or obstruction. Experimental cholestasis promoted tumor growth and progression. However, studies are needed that directly assess the mechanical interaction between bile flow, or bile shear stress, and cholangiocarcinoma signaling. We hypothesized that cholestasis and absent bile shear stress activated cancer signaling and increased aggressive cellular behaviors such as proliferation and migration. Fluid shear stress approximating bile flow was applied by orbital culture plate method and compared to identical static culture …

The Interactions Of Centromeric Nucleosomes Elucidated By Atomic Force Microscopy, Shaun Filliaux

Theses & Dissertations

Nucleosomes are the fundamental unit of compaction for DNA in the genome. These positively charged proteins have two main types of nucleosomes: canonical (H3 containing) and centromere (CENP-A containing). The compacting of DNA allows for DNA to fit into the nucleus of cells, but creates a barrier for DNA accessibility for operations such as replication or transcription. Centromeric chromatin is a subset of chromatin structure and governs chromosome segregation. Compared to the bulk chromosome, centromeres are composed of H3 and CENP-A nucleosomes in which H3 histones is replaced by its homolog CENP-A histone. This results in nucleosomes with different structures, …

Dynamics Of Nucleosome Assembly Characterized By Atomic Force Microscopy, Tommy Stormberg

Theses & Dissertations

Nucleosomes are the basic repeating unit defining the assembly and function of chromatin. Understanding the fundamental mechanisms of nucleosome structure and dynamics is critical to elucidating the chromatin assembly process. This dissertation describes my work in elucidating the role of different factors that drive the nucleosome dynamics.

In my first study, we characterized, for the first time, the effect of sequence on nucleosome assembly. We then characterized the role of internucleosomal interactions, discovering a critical role internucleosomal interactions in the assembly of higher order structures.

Based on the previous study and literature regarding histone tails, we hypothesized the histone H4 …

Structural And Biochemical Studies Of Three Enzymes Involved In Amino Acid Metabolism To Develop Novel Drugs, Yahani Pankaja Jayasinghe Arachchige

Theses & Dissertations

Intrinsic drug resistance in bacteria predates the clinical use of antibiotics. Additionally, heterogeneous metabolic states and the ability of many bacteria to form biofilms further enhances bacterial survival during infection and exacerbates treatment challenges. This necessitates the identification of novel drugs against new drug targets. These studies focus on the development of compounds targeting enzymes in Mycobacterium tuberculosis (Mtb) and Staphylococcus aureus that avoid intrinsic antibiotic defenses. The Mtb-encoded homoserine transacetylase enzyme (HTA) catalyzes the first step of the methionine biosynthesis pathway that produces methionine and S-adenosyl methionine. These compounds are shown to be essential for both dormant …

Extracellular Mechanotransduction In Marfan Syndrome: An Equivalence Principle, Stephen Haller

Theses & Dissertations

Biological tissues continuously experience mechanical stress and have evolved sophisticated mechanisms to sense mechanical stimuli. While traditional viewpoints regard cells as the ultimate sensors and processors of mechanical information, compounding evidence demonstrates that extracellular matrix, the structural component of tissues, also exhibits evolved molecular responses to force. This led us to propose a new paradigm termed extracellular mechanotransduction, in which matrix orchestrates a complementary form of force integration distinct from traditional cellular and extracellular viewpoints. We thus propose that force-sensitive signaling mechanisms evolved within the extracellular space to help cells maintain mechanical homeostasis in tissues. In this dissertation, we apply …

Dynamics Of Protein-Dna Interactions Characterized By Atomic Force Microscopy, Yaqing Wang

Theses & Dissertations

This thesis describes the nanoscale studies of protein-DNA interactions with different complexities using atomic force microscopy (AFM). One of the systems deals with DNA replication rescue. To maintain the genetic integrity, replication machinery needs to minimize the error rate, repair the damages, and restart the stalled replication caused by the attacks from the environment and inside the cell. The stalled replication rescue is orchestrated by a series of proteins, for example, the DNA helicases PriA and RecG and the ssDNA binding protein (SSB).

We demonstrated that SSB stimulates the restart process in two aspects. First, SSB facilitates the binding of …

Deciphering The Catalytic Mechanism Of Human Manganese Superoxide Dismutase, Jahaun Azadmanesh

Theses & Dissertations

The livelihood of human cells is heavily dependent on the ability to modulate the presence of highly reactive oxygen-based molecules termed reactive oxygen species (ROS). In excess, ROS facilitate oxidative damage to the macromolecules of cellular life. SODs are the major family of antioxidant proteins that prevent the buildup of overwhelming amounts of ROS within cells. Sometimes dubbed the “first line of defense” against oxidative damage, SODs defend against the harmful accumulation of ROS by eliminating superoxide. Superoxide is a ROS itself that is also a precursor to much more harmful ROS molecules. MnSOD is the manganese containing form of …

Engineering Hyaluronic Acid For Biomedical Applications, Deep S. Bhattacharya

Theses & Dissertations

This work presents research using the naturally available non- sulfated carbohydrate glycosaminoglycan hyaluronic acid (HA) for the synthesis of different chemical derivatives of HA for evaluation of binding kinetics with CD44 and P- selectin proteins for applications in fluorescence image-guided surgery. Chemical derivatives of HA such as deacetylated HA (deHA), sulfated HA (sHA), and deacetylated and sulfated HA (s-deHA) were synthesized by modulating sulfating and deacetylating reagents to alter binding specificities to CD44. Modified HA derivatives and CD44 biophysical interactions were assessed by fluorescence polarization. In silico techniques were also used to determine binding using molecular docking and MM-PBSA approaches. …

Molecular Mechanism Of Early Amyloid Self-Assembly Revealed By Computational Modeling, Mohtadin Hashemi

Theses & Dissertations

Protein misfolding followed by the formation of aggregates, is an early step in the cascade of conformational changes in a protein that underlie the development of several neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases. Efforts aimed at understanding this process have produced little clarity and the mechanism remains elusive.

Here, we demonstrate that the hairpin fold, a structure found in the early folding intermediates of amyloid b, induces morphological and stability changes in the aggregates of Aβ(14-23) peptide. We structurally characterized the interactions of monomer and hairpin using extended molecular dynamics (MD) simulations, which revealed a novel intercalated type complex. …

The Beta-Catenin/Muc1.Ct Interaction In Pancreatic Cancer, Edwin Wiest

Theses & Dissertations

MUC1 is overexpressed in over 90% of pancreatic cancer cases, and its interaction with beta-catenin promotes progression of the disease. Various in vitro and in vivo methods show that beta-catenin and MUC1 interact by way of the cytoplasmic tail of MUC1 (MUC1.CT). This interaction occurs in the membrane of pancreatic cancer cells but is found to a smaller extent in the nucleus as well. Biophysical methods suggest that MUC1 interacts with beta-catenin through a sequence of amino acids in the tail of MUC1 that sit very near the transmembrane domain of MUC1. In pancreatic ductal adenocarcinoma cells, it appears that …

Defining The Role Of Phosphorylation And Dephosphorylation In The Regulation Of Gap Junction Proteins, Hanjun Li

Theses & Dissertations

Gap junctions are intercellular channels that permit the free passage of ions, small metabolites, and signaling molecules between neighboring cells. In the diseased human heart, altered ventricular gap junction organization and connexin expression (i.e., remodeling) are key contributors to rhythm disturbances and contractile dysfunction. Connexin43 (Cx43) is the dominant gap junction protein isoform in the ventricle which is under tight regulation by serine/tyrosine phosphorylation. Phosphorylation and dephosphorylation regulate many aspects of Cx43 function including trafficking, assembly and disassembly, electrical and metabolic coupling at the plaque, as well as to modulate the interaction with other proteins.

Serine phosphorylation has long been …