Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session A13: Biomaterials IFocus Live
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Sponsoring Units: DBIO Chair: Pupa Gilbert, University of Wisconsin - Madison |
Monday, March 15, 2021 8:00AM - 8:36AM Live |
A13.00001: Drops: A bio-inspired tool to fabricate granular materials Invited Speaker: Esther Amstad Nature produces soft materials possessing exceptional mechanical properties. These properties are to a large extent related to the well-defined structures and locally varying compositions of these natural materials. Key to the excellent control nature possesses over the structure and local composition of its materials is their fabrication: Many of these materials are formed from compartmentalized reagents that are transported to the desired locations where they are locally released. Inspired by nature, we use emulsion drops as compartments to build macroscopic granular hydrogels. In this talk, I will demonstrate how we convert individually dispersed emulsion drops into selectively permeable viscoelastic capsules that enable controlled localized release of reagents. I will present examples how these viscoelastic capsules and microparticles can be additive manufactured into strong and tough, adaptable macroscopic granular materials. |
Monday, March 15, 2021 8:36AM - 8:48AM Live |
A13.00002: Determining Structure and Action Mechanism of Artificial Peptide LBF14 by Molecular Simulation Florian Solbach, Roland Faller Membrane-active peptides (MAP) interact with biomembranes though binding, deformation, penetration or disruption of membranes, or transport of other molecules through a membrane. Some MAPs are used as an antimicrobial defense mechanism by many organisms. Others may be used to transport drugs across a cell membrane into the target cell. Recently a new membrane-active peptide called LBF14 which contains non-proteinogenic amino acids was discovered. |
Monday, March 15, 2021 8:48AM - 9:00AM Live |
A13.00003: Origin of Viscoelasticity in Protein-RNA Condensates Ibraheem Alshareedah, Priya R Banerjee Biomolecular condensates are biopolymer-rich liquid-like droplets that regulate cellular biochemistry and constitute a prevalent mode for intracellular organization. These condensates are thought to form via liquid-liquid phase separation of cellular proteins and nucleic acids. It has been suggested that many intracellular protein-RNA condensates are complex viscoelastic fluids, albeit the molecular driving forces that control their viscoelasticity remain to be elucidated. Here, we perform quantitative rheological characterization of protein-RNA condensates using active and passive optical tweezer-based microrheology. We find that protein-RNA condensates are viscoelastic fluids with time-dependent viscous and elastic moduli that resemble a typical Maxwell fluid. By mapping the viscoelastic behavior of condensates formed by a series of designed protein sequences, we reveal simple analytics that describe how the amino-acid sequence composition and patterning encode the viscoelastic behavior of protein-RNA condensates. Overall, our findings shed light on the molecular determinants of viscoelasticity in protein-RNA condensates and provide guiding principles for designing artificial protein-RNA condensates with programmable viscoelastic behavior. |
Monday, March 15, 2021 9:00AM - 9:12AM Live |
A13.00004: Diffusion of water through palm leaf materials debapriya pinaki mohanty, Anirudh Udupa, Mysore Dayananda, Srinivasan Chandrasekar Leaf sheath from Areca catechu palm is showing promise as a plant material for manufacture of eco-friendly food packaging, and as a sustainable material substitute for plastics. Here, we report on a study of diffusion of water through the sheath since water penetration affects the structural integrity of the material, controlling product life. We characterize the diffusion using mass gain measurements, and in situ observations of water transport through the sheath. The diffusion coefficient is estimated using a model that incorporates effects of material porosity, and swelling due to water penetration. Parametric effects of water temperature and salt concentration on the diffusion are characterized. The in-situ imaging reveals the role of microstructural features such as matrix and fibers in influencing water penetration. The results are of value for estimating product life, developing strategies to reduce water penetration in plant leaf materials, and for better understanding liquid transport in plant materials. |
Monday, March 15, 2021 9:12AM - 9:24AM Live |
A13.00005: Understanding red blood cell behavior in contracting clot Yueyi Sun, David Myers, Wilbur Lam, Alexander Alexeev Blood clots are active biomaterial in which anucleate cells, called platelets, can extend micrometer-long filopodia to impose contractile forces on the fibrin scaffold that lead to drastic macroscopic changes in clot volume. Blood clots are involved in physiologic and pathologic processes such as wound healing and thrombosis diseases. Blood clots composition and properties depend on their location within blood circulation. Red blood cells (RBCs) affect the structure, mechanical properties and contraction process of blood clots. We use experiments and mesoscale modeling to examine the biophysics of clot contraction. We evaluate the effects of platelets and RBCs on the macroscale biomaterial properties and contraction dynamics of blood clots. We probe how RBCs concentration affects clot contraction. We also examine the effect of clot contraction on RBC shape and ability to remain within a contracting clot. |
Monday, March 15, 2021 9:24AM - 9:36AM Live |
A13.00006: E-Cadherin-mediated adhesion in the absence of the cytoskeletal machinery Kartikeya Nagendra, Adrien IZZET, Leah Friedman, Oliver Harrison, Léa-Laetitia Pontani, Larry Shapiro, Barry Honig, Jasna Brujic E-Cadherin-mediated cell-cell adhesion plays a crucial role in biomechanics. We develop a biomimetic emulsion[1] to probe the physical basis of cadherin adhesion and characterize the role of lateral cis interactions in cadherin recruitment. Calcium activates droplet adhesion in Brownian as well as athermal droplets packed under gravity. To achieve a cohesive tissue, we show that compression is necessary to zip up interfaces. Cadherin adhesions in these transparent 3D emulsions, give an equation of state relating the area as a function of the cadherin density. While the MT exhibits a linear relationship, the WT diverges at a lower density, in agreement with the crystal lattice density[2].The free energy of binding on 2D interfaces is on the order of 15kT per molecule. The cadherin density ratio inside and outside adhesions reveals that cis interactions play an important role in recruiting the proteins more efficiently than the MT. Both WT and MT proteins self-assemble into solid adhesions, as shown by their lack of Fluorescence Recovery after Photobleaching (FRAP). These results suggest that active processes inside the cell work to avoid the spontaneous zipping of interfaces by extracellular cadherin proteins. |
Monday, March 15, 2021 9:36AM - 9:48AM Live |
A13.00007: Microfluidics & Algorithm for Comprehensive Small Volume Blood Diagnostics via Rapid Solidification of μL Drops into Homogeneous Thin Film Solid Films and XRF Thilina Balasooriya, Wesley Peng, Nikhil Suresh, Aashi R Gurijala, Mohammed Sahal, Eric Culbertson, Robert J Culbertson, Nicole Herbots Conventional Blood Diagnostics (BD) uses 7- 10 mL of liquid blood and takes hours to days for results. Such blood volumes lead to a 74% rate of ‘Hospital Acquired Anemia’, a condition aggravating chronic illness in the elderly, infants, children, and the critically-ill. |
Monday, March 15, 2021 9:48AM - 10:00AM Live |
A13.00008: Influence of NaCl Concentration on Phospholipid Membranes Sebastian Jaksch, Henrich Frielinghaus, Olaf Holderer, Alexandros Koutsioubas, Piotr Zolnierczuk We previously showed the structure (neutron reflectometry, GISANS) and the dynamic behavior (GINSES) of L-α-phosphatidylcholine (SoyPC) phospholipid membranes, [1,2] and established a multi-lamellar structure as well as a surface mode, attributed to transient waves in the membranes. |
Monday, March 15, 2021 10:00AM - 10:36AM Live |
A13.00009: Evolution and engineering of avian eggs Invited Speaker: Mary Stoddard The eggs laid by modern birds are the products of more than 150 million years of evolution, resulting in a sophisticated package designed to balance a range of competing demands. The egg must be tough enough to prevent external damage but weak enough to permit a chick to hatch. It must resist bacterial contamination but allow gas exchange between the chick and the outside environment. The egg satisfies these requirements, which is remarkable given that it forms in under 24 hours. From an evolutionary perspective, bird eggs are fascinating because they come in a great variety of shapes, sizes, colors, and structures despite the fact that they serve the same essential function: to nourish and protect a chick until it hatches. From an engineering perspective, eggshell is impressive because it is a strong, lightweight material, yet we understand relatively little about eggshell biomechanical properties outside of those from domestic chickens. What is the relationship between the structure and function of eggshell? In addition, how do eggs form in the avian oviduct? Here, we explore these questions through the lenses of evolutionary biology, biophysics and mechanical engineering, which together provide an integrative picture of the form and function of avian eggs. |
Monday, March 15, 2021 10:36AM - 10:48AM Live |
A13.00010: Modeling Kinetoplast Dynamics Edgar Garcia, James Polson, Alexander Klotz
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Monday, March 15, 2021 10:48AM - 11:00AM Live |
A13.00011: Active Elasto-Capillarity Determines the Wetting Dynamics of Living Droplets Sulaiman Yousafzai, Vikrant Yadav, Sorosh Amiri, Michael F Staddon, Alan Tabatabai, Youssef Errami, Gwillherm Jaspard, Sirine Amiri, Shiladitya Banerjee, Michael Murrell At small length-scales, capillary effects are significant, and thus the mechanics of soft material interfaces may be dominated by solid surface stresses and liquid surface tensions. The balance between surface and bulk properties is described by an elasto-capillary length-scale, in which equilibrium interfacial energies are constant. However, at small length-scales in biological materials, including living cells and tissues, interfacial energies are not constant, but are actively regulated and driven far from equilibrium. Here, we model the adhesion and spreading (wetting) of living cell aggregates as ‘active droplets’, with a non-equilibrium surface energy that depends upon internal stress generated by the actomyosin cytoskeleton. Dependent upon the extent of activity, the droplet may exhibit both surface stress and surface tension, and each may adapt to the mechanics of their surroundings. The impact of this activity-dependent adaptation challenges contemporary models of interfacial mechanics, including traditional and extensively used models of contact mechanics and wetting. |
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