Bulletin of the American Physical Society
85th Annual Meeting of the APS Southeastern Section
Volume 63, Number 19
Thursday–Saturday, November 8–10, 2018; Holiday Inn at World’s Fair Park, Knoxville, Tennessee
Session F04: Biophysics and Medical Physics |
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Chair: Maxim Lavrentovich, University of Tennessee, Knoxville Room: Holiday Inn Knoxville Downtown Parlor |
Friday, November 9, 2018 11:00AM - 11:12AM |
F04.00001: Investigation of the mechanical vibrations excited by multiple light sources in a protein. Dmytro Wl Obolenskyi, Sanichiro Yoshida Understanding of physical properties of proteins remains a vital area of research. Many experiments show that light can significantly affect protein folding processes. We attempt to IR and Raman spectroscopy to observe the changes in protein structure of egg white brought on by the illumination by a HeNe laser. Raman spectroscopy has previously been used to detect THz mechanical vibration in lysozymes. We may be producing THz vibrations in the ovalbumins (egg white proteins with molecular weight 42.7 kDa which denature at 84 C.) |
Friday, November 9, 2018 11:12AM - 11:24AM |
F04.00002: Fabrication and Characterization of Electrospun Vascular Grafts from Polymer Blends Kiran r Adhikari Mechanical mismatch between the native blood vessels and the implanted graft is the primary reason for the implant failure. In this study, we use the process of electrospinning for the fabrication of the synthetic vascular graft using blend polymers like PET, PU, PHH and PDO. Incorporation of elastomer PU into widely used vascular graft material PET (commercially known as Dacron) in 50/50 ratio enhanced the breaking strain of PET graft by 60%, which is helpful in the pulsating environment of the grafts inside the body. The Young's modulus of the graft is found to be 2.1 MPa at 10 percent elongation. SEM images shows the mesh structure in the nanoscale which is suitable for mimicking the ECM of the native blood vessels. |
Friday, November 9, 2018 11:24AM - 11:36AM |
F04.00003: Dynamic Nuclear Polarization for Neutron Crystallography Anna Dawn Jennings X-ray crystallography has been a widely used technique to study the macromolecular structure of proteins, however x-rays do not diffract well off lighter elements, so determining the precise location of the hydrogens in a molecule isn’t feasible. A solution is to use neutrons instead. Neutrons are much more sensitive to lighter elements and can fill in these hydrogen gaps. The low flux of neutrons leads to a need for large protein crystals, which are technically challenging to grow in a lab. Dynamic Nuclear Polarization (DNP) works to polarize the hydrogen atoms in a protein crystal using high magnetic field (2.5 – 5T), low temperature (≤1K), and microwave irradiation, which greatly increases the coherent scattering cross-section and decreases the S/N ratio. We built a proof-of-concept DNP system at Oak Ridge National Laboratory to study single protein crystals. We tested several T4 lysozyme protein crystals soaked in TEMPO prior to freezing in LN2. This was tested on the IMAGINE beamline, a Laue diffractometer, at the High Flux Isotope Reactor. Preliminary results and a description of the test apparatus will be presented. |
Friday, November 9, 2018 11:36AM - 11:48AM |
F04.00004: The use of Brillouin spectroscopy to study the effects of matrix metalloproteinases on the extracellular matrix during cancer metastasis Britta Gorman, Bailey L Canter, Laurie E McNeil A cancer cell secretes certain matrix metalloproteinases (enzymes) to degrade the surrounding extracellular matrix (ECM), and disrupt the basement membrane. However, the exact mechanism by which the cell affects the surrounding tissue and the cancer begins to metastasize is not well documented. To better understand how the cells affect the ECM, we use Brillouin spectroscopy to study how these enzymes change the bulk modulus of the ECM. Brillouin spectroscopy is a technique used to measure the energy difference between light that is elastically and inelastically scattered by the sample. The energy difference is caused by the annihilation or creation of a phonon in the sample, and can be used to determine the speed of sound in a material. From these values the bulk moduli can be calculated. Our samples are Matrigel, a basement membrane matrix, that has been exposed to type I collagenase such that the proteins in Matrigel are cleaved by the enzyme. The degree of matrix degradation is quantified by the exposure time, and therefore, the percent of the proteins that have been cleaved by the enzyme. The corresponding Brillouin spectra are used to show that there is a nonlinear relationship between the elastic constant of Matrigel and the percent scission of the proteins. |
Friday, November 9, 2018 11:48AM - 12:00PM |
F04.00005: Three-photon imaging using defect-induced photoluminescence in biocompatible ZnO nanoparticles Wren Gregory, Achyut Raghavendra, Ramakrishna Podila Although optical spectroscopy promises improved lateral resolution for cancer imaging, its clinical use is seriously impeded by background fluorescence and photon attenuation even in the so-called two-photon absorption (2PA) imaging modality. An efficient strategy to meet the clinical cancer imaging needs, beyond what two-photon absorption (2PA) offers, is to use longer excitation wavelengths outside the water absorption window (~950-1300 nm) through three-photon absorption (3PA). A variety of fluorescent dyes and nanoparticles (NPs) have been used in 3PA imaging. However, their non-linear 3PA coefficient is often low necessitating high excitation powers, which cause overheating, photodamage, and photo-induced toxicity. To address this demand we designed defected ZnO nanoparticles (ZnO NPs) for enabling a low-power 3PA paradigm at longer excitation and emission wavelengths, lower background noise, and improved spatial resolution (<1 um) at powers below 5 mW.
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Friday, November 9, 2018 12:00PM - 12:12PM |
F04.00006: Bacterial deactivation by using graphene quantum dot as an effective photodynamic therapy agent Ermek Belekov, Lauren Cooper, Koushik Devarakonda, Khomidkhodza Kholikov, Saidjafarzoda Ilhom, Michael Smith, Jerry Monroe, Omer San, Ali Er Antibiotics are commonly used in bacterial infection. However, the widespread use of antibiotics has resulted in the emergence of multidrug-resistant or pathogenic bacterial strains. Consequently, the need for developing new bactericidal materials and techniques arose. Photodynamic therapy (PDT) is proposed as an alternative approach. In PDT, light interacts with certain materials and chemicals to induce damage to bacteria. Graphene quantum dots (GQD) are one of the most promising antimicrobial agents since they possess high germicidal activity against a broad range of microbes. In our project, we aim to investigate an effective, inexpensive and available compound which will hold even higher antimicrobial activity and lower toxicity toward human blood. For this purposes, we used GQD and methylene blue (MB). GQDs were grown by focusing nanosecond laser pulses into benzene and were later combined with MB. The Gram-negative bacteria, Escherichia coli, and Gram-positive bacteria, Micrococcus luteus, were deactivated by GQD/MB. Detailed characterization was performed with transmission electron microscopy (TEM), scanning electron microscopy (SEM),UV-Visible (UV-Vis), and photoluminescence (PL) spectra. |
Friday, November 9, 2018 12:12PM - 12:24PM |
F04.00007: Survival Probabilities in a Simple Model of Branching Populations Adam S Bryant, Maxim Olegovich Lavrentovich Cells growing in branching structures are observed in many biological contexts, ranging from |
Friday, November 9, 2018 12:24PM - 12:36PM |
F04.00008: High Local Curvature Reduces Migration Rate of Multi-Layer Tissues Holley E Lynch, Shirley X. Yancey, Lance A. Davidson Development involves the migration of tissues composed of multiple cell layers. The mechanics of these motions remains largely unknown despite significant progress in understanding the migration of confluent monolayers. Thus, we investigate differences in spreading rate in multi-layer, X. laevis tissue explants, ranging in area from 0.12mm2 to 2.63mm2. The average spreading rate increases with initial size, from 22±5µm/hr to 45±5µm/hr. Since size affects both edge curvature and the number of cells, either could increase the spreading rate. Changes in curvature could affect the distribution of forces along the explant’s edge. However, since larger explants have more cells, the difference can also be explained by active tissue rearrangements, such as cell intercalation and programmed cell height changes. To distinguish between these models, we investigate the local spreading rate in explants with multiple curvatures, e.g. triangles. In these explants, spreading rate is lowest for regions of high curvature, even when the distance, and thus number of cells, is greater between the edge and the center of the explant. Our results indicate that the local rate of tissue migration depends on the initial curvature. |
Friday, November 9, 2018 12:36PM - 12:48PM |
F04.00009: Modeling the DNA Molecule as a Quantum Mechanical Turing Machine Fabian Matthew Mihelic The DNA molecule can be modeled as a quantum mechanical Turing machine in the manner that was described by Benioff in 1982. Electron spin ½ qubits are coherently conducted longitudinally along the finite lattice of the DNA “tape” via pi-stacking interactions of the aromatic nucleotide bases, and selectively read into logically and thermodynamically interactive situations in the deoxyribose moiety of each nucleotide via a spin-filtering effect of the helicity of the DNA molecule. The time-independent subsystem of coherent qubit conduction is separated from the time-dependent subsystem of deterministic expression by the mediation of an enantiomeric shift in the deoxyribose moiety of the nucleotide that functions at an energy level appropriate to the quantum limit (i.e. the Landauer limit). The system is topologically insulated from the environment through the precise design of the crystalline nanostructure, as was predicted in Schrödinger’s concept of the genetic “aperiodic crystal”. |
Friday, November 9, 2018 12:48PM - 1:00PM |
F04.00010: Disease Progression on Social Networks Noah A Rosenbalm, Charles Fay The deterministic SIR and SIS models are generally accepted as an efficient way to represent the theoretical number of people in a population infected by a disease over a certain period of time. The goal of this study was to find another method of representing these outbreaks, specifically a stochastic model. To find a stochastic alternative to the SIR and SIS models, graph population and node states were observed as simulators of disease on four different graph types; random, scale-free, configuration model, and hierarchical configuration model. Each node on the graph represented a person and each edge between two nodes represented an interaction between two people. A disease was then introduced into the population and the spread simulated. Once completed, a plot of data was constructed comparing the evolution of the number of susceptible, infected and recovered or dead nodes versus time. This stochastic model was then compared to the deterministic SIR and SIS models, and was found to be a viable alternative on each of the four graph types. Data for an outbreak of Dengue in Puerto Rico was then compared the the stochastic SIR model that had been tested. This data was also used to compare how each of the four graph types compared to real world disease spread data. |
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