Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session J22: Biomaterials II: Paleo and Modern Structure and Function in AnimalsFocus
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Sponsoring Units: DBIO DCP DMP DPOLY Chair: Pupa Gilbert, University of Wisconsin - Madison Room: 303 |
Tuesday, March 3, 2020 2:30PM - 3:06PM |
J22.00001: Building with melanin: Low complexity Glycera jaw protein is master of multitasking Invited Speaker: J Herbert Waite In protein structure-function relationships, there is a widely held view that complex functions require complex structures. Recent studies with a low complexity protein from the jaws of Glycera, a benthic marine polychaete, appear to challenge this. Used for grasping and injecting venom, the jaws are stiff, sharp, durable and wear resistant. Proteins (50 wt %) are one of three jaw components including melanin (40 wt %) and copper (10 wt %) present as a copper mineral (atacamite) and Cu2+ ions. Although jaw stiffness is correlated with melanin not mineral, little was known about the protein contribution until its recent characterization and recombinant expression. The Glycera jaw protein has an extremely low complexity sequence in which GGH repeats represent 80% of the composition. Notwithstanding such monotony, GJP exhibits the following distinct properties: 1) it binds 26 equivalents of Cu per protein, 2) catalyzes oxidation of Dopa to Dopa-quinone en route to melanin, 3) templates a sheet-like assembly (32 nm thick) of melanin at the air-water interface, and 4) forms a structural network with melanin and Cu in the stacked sheets of higher order architecture. |
Tuesday, March 3, 2020 3:06PM - 3:18PM |
J22.00002: Memory and learning in biomolecular soft materials Charles Collier, Joseph Najem, Stan Williams, Graham Taylor, Catherine Schuman, Alex Belianinov, Benjamin Doughty, Ryan Weiss, Md Sakib Hasan, Garrett Rose, Stephen Sarles Neuromorphic elements have been predominantly solid-state devices which simulate the resistive and capacitive behaviors needed for neural networks and brain-inspired computing, but in non-brain-like ways. We are integrating lipid and polymer bilayer membranes with micro- and nanofabrication to develop fundamentally new types of neuromorphic elements that have the composition (biomolecules), structure (biomembranes), and switching mechanism (voltage-sensitive ion channels) of real biological synapses, and operate at lower power than the current state-of-the-art. Our devices consist of insulating, nm-thick lipid or polymer-based bilayer membranes that assemble at the interfaces of two or more aqueous droplets in oil, and that have demonstrated both memristive and memcapacitive behaviors, including memory resistance and capacitance, synaptic functions such as paired-pulse facilitation and depression, spike rate dependent plasticity, voltage-dependent inactivation and recovery, and charging hysteresis. These behaviors are linked to electrostriction, an electromechanical phenomenon that encompasses both electrowetting and electrocompression in the membrane, which are changes in membrane area and thickness due to charging in the presence of electric fields. |
Tuesday, March 3, 2020 3:18PM - 3:54PM |
J22.00003: Formation temperature of biomaterials through geologic time Invited Speaker: Kristin Bergmann The well-known secular increase in δ18O values of both calcitic and phosphatic marine fossils through early Phanerozoic time suggests three end-member hypotheses 1) early Paleozoic surface temperatures were high, in excess of 40C (tropical MAT), 2) the δ18O value of seawater has increased by up to 7–8‰ VSMOW over Paleozoic time, or 3) early Paleozoic samples are more significantly altered than younger materials, with the secular trend reflecting these differences in post-depositional processes. Carbonate clumped isotope analysis, in combination with petrographic and elemental analysis, has the capacity to deconvolve fluid composition from temperature effects and therefore to determine which of these hypotheses is best supported. A sample suite including calcitic, aragonitic and phosphatic marine fossils from the last 500 million years indicate surface temperatures in tropical seas were similar to slightly warmer than today (avg. 26-38C) in the early Paleozoic, while the oxygen isotope budget of seawater appears to be similar to that of today. |
Tuesday, March 3, 2020 3:54PM - 4:06PM |
J22.00004: Nano-optical characterization of photosynthetic bacteria-2D material coupled system Sharad Ambardar, Zachary Frey, Dmitri v Voronine Atomically thin 2D materials especially TMDs grown laterally, on combining with other TMDs form heterostructures with atomically sharp interfaces. We use conventional far-field (FF) photoluminescence (PL) and near-field (NF) tip-enhanced photoluminescence (TEPL) to investigate the bio-sensing applications of TMD materials by depositing photosynthetic cyanobacteria on MoS2-WS2 heterostructure grown on SiO2/Si substrate. The energy transfer between the 2D materials and the photosynthetic bacteria leads to formation of an energy funnel at the pole of the bacteria. Due to this, the photoluminescence at the pole is high and is enhanced due to the cyanobacteria. The coupling between the photosynthetic bacteria and 2D material can be used for production of sustainable energy resources. |
Tuesday, March 3, 2020 4:06PM - 4:18PM |
J22.00005: African Elephant Sensing Capabilities through Skin and Hair Andrew Schulz, Colin J Boyle, Claire A Higgins, David Hu The mouse and the elephant share a common sensing mechanism, vibrissae, or whiskers. In this study, we dissect an African elephant trunk and perform histology and measurement of the mechanical properties of the skin. We observe both long and short vibrissal hairs, ranging from 1 cm at the base of the trunk to 8 cm at the base. The length of hairs is likely associated with the different requirements at each position. Skin surrounding the vibrissae is stiffer, which may help the vibrissae better receive information. The dorsal part of the trunk is also stiffer than the ventral side, which may help the trunk grasp objects using the ventral portion. Through experiments conducted with histological and tensile test we report the different characteristics of the dermis. Heterogeneous properties of the skin in the elephant may give inspiration to designing of new flexible surfaces for biologically inspired soft robotic manipulators. |
Tuesday, March 3, 2020 4:18PM - 4:54PM |
J22.00006: The role of residual stresses in biomineral morphogenesis revealed by 3D dark-field x-ray microscopy Invited Speaker: Vanessa Schöppler Residual stresses occur in numerous synthetic, geological and biogenic crystals having desirable or undesirable effects on materials performance. Recent studies have shown the significance of residual stresses in the mechanical functionality of a number of biomineralized tissues. However, the role of these forces in biomineral morphogenesis was never previously examined, mainly due to the lack of an appropriate multiscale characterization approach. Most of the state-of-the-art methods are either surface techniques yielding 2D information or allow limited 3D analysis of very small sample volumes. |
Tuesday, March 3, 2020 4:54PM - 5:06PM |
J22.00007: Effect of Sea Water pH on the Maturation of Marine Mussel Plaques Justin Bernstein, Emmanouela Filippidi, J Herbert Waite, Megan Valentine Marine mussel plaques are an exceptional model for wet adhesives. Despite understanding their protein composition, we do not know how soluble proteins are rapidly processed into load-bearing structures. Here, we examine the effects of seawater pH on the time evolution of the internal microstructures in Mytilus californianus plaques. Experimentally, plaques deposited by mussels on glass surfaces are immediately collected, placed into pH-controlled artificial seawater for varying times, and characterized using scanning electron microscopy and tensile testing. We found a pH dependent transition from a liquid-like state to a porous solid within 30 minutes for pH ≥ 6.7; these plaques are load-bearing. By contrast, samples maintained at pH 3.0 showed no porosity and no measurable strength. Interestingly, we found no differences in cuticle thickness, suggesting that cuticle mechanics may be compromised at low pH. Our results suggest that sea water infusion after deposition is critical to the rapid formation of internal structures, which in turn plays an important role in the plaques’ mechanical performance. |
Tuesday, March 3, 2020 5:06PM - 5:18PM |
J22.00008: Mechanics and Adhesive Performance of Mussels on Roughness- and Geometry- controlled 3D printed Substrates Younghoon Kwon, Justin Bernstein, Megan Valentine, Noy Cohen Marine mussels have the remarkable ability to adhere to a variety of natural and artificial surfaces under hostile environmental conditions. Although the molecular composition of mussel adhesives has been well studied, a mechanistic understanding the physical origins of mussels’ impressive adhesive strength remains elusive. Here, we investigated the role of substrate roughness and geometry in the adhesive performance of mussels. Using 3D printing, sandblasting, and laser texturing we created substrates with differing surface treatments and introduced these to mussels, which in turn adhered to the engineered surfaces via plaque-thread byssal structures. Tensile testing with in situ imaging was used to determine the adhesion strength and mechanical properties of the mussel adhesive plaques under various conditions. Our results inform the relationships between adhesive performance and substrate properties, give insight into the physical governing factors of mussel adhesion, and provide design criteria for development of synthetic adhesives for use on complex, textured surfaces. |
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