Bulletin of the American Physical Society
2021 Virtual Conference for Undergraduate Women in Physics
Friday–Sunday, January 22–24, 2021; Virtual
Session U04: BioPhysicsInteractive Live
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Chair: Maham Zia |
Sunday, January 24, 2021 12:00PM - 12:10PM |
U04.00001: Disguising Upconversion Nanoparticle Probes in a Virus Protein Cloak Amberly Xie, Ruben Cadena-Nava, Irina Tsvetkova, Bogdan Dragnea, Xingchen Ye While virus capsid assembly has been extensively studied in environments mimicking \textit{in vivo }conditions, such as with the synthesis of virus-like particles (VLPs), not much is known about virus assembly in buffers containing organic solvents. In this study, Brome Mosaic Virus (BMV) capsid proteins were assembled around both gold nanoparticles (GNP) as well as upconversion nanoparticles (UCNP), which have the unique ability to absorb low energy IR light and emit higher energy visible light. While GNPs can easily be modified to be stable in aqueous buffers, UCNPs are usually only stable in organic solvents. Because of this, assemblies were conducted in different concentrations of DMSO to try and encapsulate the UCNPs. Analysis of assemblies utilized techniques such as transmission electron microscopy, dynamic light scattering, fluorescence measurements, and circular dichroism. It was found that increasing the concentration of DMSO did not affect GNP-VLP assembly nor the BMV capsid proteins themselves. Assembly around UCNPs in buffers with DMSO ultimately proved successful, with the UCNP retaining their optical properties. Not only can these UCNP-VLP be used in medical imaging and cell targeting, but the success of assembly in non-biological conditions opens the door to studying virus assembly in a multitude of environments. [Preview Abstract] |
Sunday, January 24, 2021 12:10PM - 12:20PM |
U04.00002: Properties of Chromatin Extracted by Salt Fractionation from both Cancerous and Non-cancerous Esophageal Cell Lines Emily Luffey, Jiawei Liu, Stuart Lindsay, Robert Ros The National Institute of Health estimates that approximately 38.4{\%} of men and women will be diagnosed with cancer at some point during their lifetimes. While cancer is mostly viewed as a genetic disease characterized by genetic markers and expression of mutant proteins, there is considerable evidence that there is more to cancer than somatic mutations. For example, the first signature looked for by a pathologist is grossly aberrant cell nuclei. It has been shown that the more abnormal a particular cell nucleus is, the more aggressive a particular form of cancer is. A major variable in the overall nuclear structure is chromatin compaction and structure. We compared chromatin compaction and structure for two esophageal cell lines, EPC2 (non-cancerous) and CP-D (cancerous) by using a combination of salt fractionation and atomic force microscopy (AFM) and found significant differences in the chromatin morphology of cancerous and non-cancerous cell lines. We anticipate that our results will help to gain insight into the mechanisms of phenotypic change in cells from normal to cancerous. [Preview Abstract] |
Sunday, January 24, 2021 12:20PM - 12:30PM |
U04.00003: Control of Interlimb Coordination in Drosophila Amber Young Animals and insects adjust how they move through dynamic environments by changing speeds and altering walking patterns. This flexible control over their limbs stems from networks of spinal neurons called central pattern generators. Distinct central pattern generators control the motor output for contralateral and ipsilateral limbs. Yet, the neural mechanisms responsible for producing limb coordination have not been identified due to the overwhelmingly large number of neurons in quadruped mammals. Drosophila has shown itself to be an exemplary subject for neuroscience studies since the fruit fly has relatively fewer neurons while maintaining complex behaviors. The ultimate goal of this project is to determine whether central pattern generators are coupled in Drosophila, and whether this contributes to limb coordination during walking. To experiment, I suspended a fly on a moving treadmill and captured its limb positions with an overhead camera. I then analyzed the limb positions over time using DeepLabCut. Understanding how the limbs are coordinated will also inform the coupling amongst central pattern generators. Characterizing their mechanisms will contribute to neuromechanics and physiological studies in humans, particularly relating to the neural basis of locomotion. [Preview Abstract] |
Sunday, January 24, 2021 12:30PM - 12:40PM |
U04.00004: To biofilm or not to biofilm: the autoinducer-yield parameter for determining biofilm formation Selena Chiu, Jenna Ott, Daniel Amchin, Tapomoy Bhattacharjee, Sujit Datta Bacteria form biofilms in a host of organic environments, from soil to the mammalian gut. While biofilms assist in remediating soil contaminants, they also cause infection, from chronic lung infections in cystic fibrosis patients to industrial biofouling. It is, thus, vital to understand factors regulating the extent of biofilm formation to develop potential treatments for better human and environmental health. Unfortunately, little is known about the transition of free-swimming planktonic bacteria to sedentary biofilms in these environments. Here, we simulate bacterial behavior in heterogenous media to investigate the competition between bacterial dispersal, governed by chemotaxis, and biofilm formation, triggered by autoinducer accumulation. My work in this project focuses on characterizing the competition between bacterial cell yield and autoinducer secretion in determining the extent of biofilm formation. By simulating bacterial activity while varying cell yield and autoinducer secretion, I determined an autoinducer-yield parameter quantitatively predicts the extent of biofilm formation given the rate of cell yield and autoinducer secretion. Simulation results demonstrate a critical value at which biofilm formation transitions from continuum to step-like behavior. [Preview Abstract] |
Sunday, January 24, 2021 12:40PM - 12:50PM |
U04.00005: Unraveling the Complexities of Microtubule Rigidity Regulation. Kendra Kreienbrink Microtubules are a vital cellular component involved in functions such as movement, structure, division and intracellular transport. To maintain their efficacy in these processes, microtubules must adapt their rigidity. Persistence length is the standard measurement of rigidity and is generally used to evaluate microtubules under varying conditions. While modification to microtubule persistence length can lead to neurological disorders, such as Alzheimer's, others can be beneficial, like modifications via the anticancer drug, Taxol. There have been significant advances in our understanding of how microtubule alterations induce persistence length variations. However, the effects of many tuning factors are still eliciting conflicting results for experimentalists. Determining the cause of such discrepancies is crucial for advancing the understanding of microtubule rigidity. Thus, deliberate analysis of the methodology and the results of current literature on the topic is necessary to help illuminate the possible causes of such discrepancies. [Preview Abstract] |
Sunday, January 24, 2021 12:50PM - 1:00PM |
U04.00006: How Does the Orientation of Vorticella convallaria change under variable shear rates? Hannah Stockton, Brett Klaassen van Oorschot, Rachel Pepper Vorticella convallaria are a species of microscopic sessile suspension feeders (MSSFs). MSSFs are critical to the survival of aquatic ecosystems; they feed on bacteria and debris, and may play a significant role in the mitigation of environmental disasters like oil spills and heavy metal contamination. In order to elucidate their ecological role, it is important to understand their feeding behaviors. Vorticella and other MSSFs create feeding currents that determine their nutrient uptake rates. These currents, and therefore their feeding rates, depend on both organism orientation and ambient flow speeds, yet the interplay of these in realistic flow conditions has never been studied. For our research, we developed a novel experimental system to investigate the orientation of Vorticella under different shear rates. Using an inexpensive two-camera setup and custom-designed 3D-printed flow chamber, we controlled the flow and examined the orientation of individual Vorticella. The flexible nature of our system allows it to function as a tool for the 3-dimensional visualization of a wide range of microscopic organisms. [Preview Abstract] |
Sunday, January 24, 2021 1:00PM - 1:10PM |
U04.00007: Investigating Gentamicin Mechanism of Action with Fluorescence Microscopy: Relationships between Colony Growth, Antibiotic Accumulation, and Membrane Permeability Jillian Rankin Aminoglycosides constitute a powerful, broad-spectrum class of antibiotics. While aminoglycosides are known to exert their antimicrobial activity through ribosome targeting, the precise mechanism of action through which they produce cell death remains undefined. In particular, there is no clear scientific consensus regarding the role of membrane damage in initiating growth arrest. In this study, we probed aminoglycoside mechanism of action by using fluorescence microscopy to evaluate the relationships between membrane damage, growth arrest, and antibiotic accumulation in \textit{Escherichia coli} microcolonies. A fluorophore-conjugated aminoglycoside, gentamicin-Texas Red, was used to assess antibiotic accumulation, while SYTOX Green, a stain impermeable to live cells, was used to assess membrane permeability. To further evaluate the role of membrane integrity in growth inhibition, treatment groups with variable degrees of induced membrane permeability were compared. We found that, in the context of gentamicin treatment, induced degrees of membrane permeability were associated with increased rates and extents of gentamicin accumulation; however, these outcomes were not reliable predictors of growth rate or the onset of growth inhibition. Furthermore, our analysis of the relationships between changes in membrane permeability, accumulation, and growth inhibition suggests that the onset of significant losses in membrane integrity are not required to initiate growth arrest. [Preview Abstract] |
Sunday, January 24, 2021 1:10PM - 1:20PM |
U04.00008: Development of control in brain networks over temporal and spatial scales using graph models Lindsay Smith, Harang Ju, Danielle Bassett Regions of the human brain vary in their capacity to control whole brain activity, in large part due to their location in the underlying structural network of interconnections crisscrossing the cortex. Recent work suggests that this capacity for control differs across spatial and temporal scales of the brain’s dynamics and can be formally probed using the Laplacian eigenspectrum of the brain’s structural network. Yet how such spatiotemporal control might differ from one human to another, potentially supporting and explaining differences in cognitive function, remains unclear. Here, we address this question by measuring several summary statistics of spatiotemporal control from human brain network architecture, as reflected in diffusion tensor imaging data acquired from 882 youth between the ages of 8 years and 22 years. We found that distinct features of network topology are correlated with a region’s capacity to enact distinct control strategies, and we investigate these relationships as a function of discrete timescales, from markedly slow modes of dynamics to relatively swift modes of dynamics. Our results provide insight into how local variation in connectivity gives rise to distinct processes of global control as a function of timescales over modes of activity. [Preview Abstract] |
Sunday, January 24, 2021 1:20PM - 1:30PM |
U04.00009: Parametric Imaging of Speed of Sound of Fixed Sheep Brain Claudia Chambliss, Will Newman, Cecille Labuda, Brent Hoffmeister Ultrasound provides a useful way to nondestructively investigate the physical properties of materials including biologic tissues. The goal of this study was to measure the speed of sound of ultrasonic pulses propagated through brain tissue. Twelve, 1-cm thick samples of tissue were prepared from the coronal, sagittal and transverse anatomic planes of chemically preserved sheep brains. Ultrasonic measurements were performed using 3.5, 5.0, 7.5 and 10 MHz transducers that were mechanically scanned over the tissue specimens to acquire data from multiple sites. The measurements were imported into image processing software (IMAGE J, NIH) to construct parametric images of the tissue based on the measured values of the speed of sound. A region of interest was determined for each image by selecting all measurements within 1.5 diameters of the ultrasonic beam from the edge of the specimen. The measurements inside the ROI were averaged to determine the mean and standard deviation. The mean speed of sound ranged from 1533 m/s to 1543 m/s and the standard deviation from 8.42 m/s to 13.0 m/s. The parametric images showed features that were consistent with the known anatomic features of the specimens. Statistical analysis of the data showed no evidence of dependence of the speed of sound on anatomic plane, which is consistent with currently published literature. [Preview Abstract] |
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