Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session G07: Enzyme Driven Active Matter from Nano to MicroscaleFocus
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Sponsoring Units: DSOFT DBIO Chair: Wylie Ahmed, California State University, Fullerton; Benjamin Rogers Room: Room 130 |
Tuesday, March 7, 2023 11:30AM - 12:06PM |
G07.00001: Explore DNA Nanostructures for Controlling Multienzyme Assembly and Modulating Catalysis Invited Speaker: Jinglin Fu Cellular functions rely on a series of organized and regulated multienzyme cascade reactions. The catalytic efficiency of multienzyme complexes depends on the spatial organization of composite components which are precisely controlled to facilitate substrate transport and regulate activities. If these cellular mechanisms can be mimicked and translated to a non-living artificial system, it can be useful in a broad range of applications that will bring significant scientific and economic impact. Self-assembled DNA nanostructures are promising to organize biomolecular components into prescribed, multi-dimensional patterns. Here, we described a robust strategy for DNA-scaffolded assembly and confinement of biochemical reactions. DNA nanostructures are used to organize spatial arrangements of multienzyme cascades with control over their relative distance, substrate channeling paths, compartmentalization, local confinement of ligands, as well as the construction of smart and biomimetic reactors. The combination of addressable DNA assembly and multienzyme cascades promises to deliver breakthroughs toward the engineering of novel biomimetic nanomaterials, which have great potential for broad applications from chemical synthesis, functional biomaterials and biofuel production to therapeutics and diagnosis. |
Tuesday, March 7, 2023 12:06PM - 12:18PM |
G07.00002: Coupling reactive and diffusive fluxes to predict catalysis-driven chemotaxis at the nanoscale Kathleen T Krist, William Noid
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Tuesday, March 7, 2023 12:18PM - 12:30PM |
G07.00003: Mechanochemical active nematics: how to design topology sensing enzymes Michael M Norton, Piyush Grover Active nematic fluids are an important class of materials whose dynamics are intrinsically chaotic. Towards developing bioinspired signaling pathways that shape these flows into desired configurations, we aim to design feedback loops that spatiotemporally modulate active stress in response to structural cues from the nematic. Here, we focus on the ``sensing'' part of that problem: the conversion of structural (Q-field) information into chemical fields. We show that a curvature-dependent reaction dipole is sufficient for creating a system that dynamically senses topology by producing a concentration field possessing local extrema coinciding with +/- 1/2 defects. We consider two possible physical origins of such dipoles that can inspire experiments: (i) curved molecules that preferentially bind to nematic regions matching their curvature and (ii) nematic molecules that polarize (become reaction dipoles) when deformed. We demonstrate the behavior of this system for stationary defects and in the presence of active hydrodynamic flows. |
Tuesday, March 7, 2023 12:30PM - 12:42PM |
G07.00004: The concept of a chemical temperature from optical tweezers experiments Tian Huang, Jin Tae Park, Hyuk Kyu Pak, Steve Granick It is fundamental to consider that the random forces giving rise to thermal fluctuations generate both diffusion and dissipation. Our optical tweezer experiments suggest that chemical reaction can also generate such random forces. We have measured the fluctuations of optically-trapped beads that are immersed in aqueous solutions within which the classical click CuAAC chemical reaction system (copper-catalyzed azide-alkyne cycloaddition) is performed. These micrometer-sized beads fluctuate less-and-less rapidly as the chemical reacts moves towards its equilibrium. From the perspective that active matter consists of individual agents that consume energy to move or exert mechanical forces, we conclude that chemical reactions can act as instances of active matter. |
Tuesday, March 7, 2023 12:42PM - 12:54PM |
G07.00005: A background enzymatic active bath affects Liquid-Liquid Phase Separation of protein Kevin Ching, Diego A Luna, Anthony Estrada, Sarthak Gupta, J. M Schwarz, Jennifer L Ross The cell interior is an active bath driven by a myriad of enzymes. It is an open problem as to how this background activity can affect physical processes in the cell including liquid-liquid phase separation. We seek to experimentally reconstitute a model system for an active bath of enzymes to determine the effects on the liquid phase separation of a model condensate protein. We will use urease, an exothermic and kinetically fast enzyme that converts urea to carbon dioxide and ammonia, as the background enzyme. We will use ubiquilin-2 (UBQLN2), a protein that phase separates when high salt is added. With the newly developed microfluidic chamber that flushes out carbon dioxide and ammonia while maintaining the concentration of urea, we scanned both the salt concentration to form condensates, and the urea concentration to control urease activity and observed droplets using fluorescence microscopy. In addition, to provide some theoretical interpretation for our experimental results, we implement polymer-based molecular dynamics simulations via a sticker-spacer polymer model that can recapitulate LLPS in the presence of active particles. |
Tuesday, March 7, 2023 12:54PM - 1:06PM |
G07.00006: Active boundary layers in confined active nematics Jordi Ignés-Mullol, Jérôme Hardoüin, Claire Doré, Justine Laurent, Teresa Lopez-Leon, Francesc Sagués Boundary layers play a central role in fluid dynamics and in soft material science. They are regions whose extent is much smaller than any typical system size, yet, the interfacial transport processes associated with localized profiles of scalar fields, such as pressure or ionic charge density control the distant dynamics. In conventional liquid crystals, molecular interactions in this region determine the equilibrium orientational field of the passive material. However, the role of boundaries in active liquid crystals has just begun to be studied. |
Tuesday, March 7, 2023 1:06PM - 1:18PM |
G07.00007: Onset of Homochirality in Cell Monolayers Ludwig A Hoffmann, Luca Giomi Chirality is a feature of many biological systems and much research has been focused on understanding the origin and implications of this property. Most famously, sugars and amino acids that are found in nature are homochiral, meaning that chiral symmetry is broken and only one of the two possible chiral states is ever observed. Perhaps less well-know, something similar is the case for certain types of cells too. They show chiral behavior and only one of the two possible chiral states is observed in nature. Understanding the origin of cellular chirality and what, if any, use or function it has in tissues and cellular dynamics is still an open problem and subject to much (recent) research. For example, cell chirality has already been shown to play an important role in drosophila morphogenesis. |
Tuesday, March 7, 2023 1:18PM - 1:30PM |
G07.00008: Enhanced Swimming Behavior of Active Hematite Microparticles Sarah N Schyck, Silvana Caipa Cure, Laura Rossi, stefano sacanna The emergence of autonomous, self-propelled active particles has been of interest for cargo delivery, environmental remediation, and as models for biological systems. However, designing highly active and cost effective microparticles is a remaining challenge. Hematite microparticles can be readily synthesized in a variety of shapes and exhibit photocatalytic behavior necessary for light-driven active motion, but they are limited due to the short lifetime of excited states. To mitigate this, we calcined the micro-particles and measured their activity by tracking the particle motion with optical microscopy. We calculated the mean-squared displacement (MSD) and found that increasing the calcination time results in a higher ensemble MSD for the hematite micro-particles. Calcined particles have an average 28-fold rise in MSD at 1-minute lag times. This simple approach makes hematite more accessible to key areas of soft matter and photocatalysis research. |
Tuesday, March 7, 2023 1:30PM - 1:42PM |
G07.00009: Dynamics, scaling behavior, and control of nuclear wrinkling Nicolas Romeo, Jonathan A Jackson, Alexander Mietke, Keaton J Burns, Jan F Totz, Adam C Martin, Jorn Dunkel, Jasmin Imran Alsous The cell nucleus is enveloped by a complex membrane, whose wrinkling has been implicated in disease and cellular aging. The biophysical dynamics and spectral evolution of nuclear wrinkling during multicellular development remain poorly understood due to a lack of direct quantitative measurements. Here, we combine live-imaging experiments, theory, and simulations to characterize the onset and dynamics of nuclear wrinkling during egg development in the fruit fly, Drosophila melanogaster, when nurse cell nuclei increase in size and display stereotypical wrinkling behavior. A spectral analysis of three-dimensional high-resolution data from several hundred nuclei reveals a robust asymptotic power-law scaling of angular fluctuations consistent with renormalization and scaling predictions from a non-linear elastic shell model. We further demonstrate that nuclear wrinkling can be reversed through osmotic shock and suppressed by microtubule disruption, providing tunable physical and biological control parameters for probing mechanical properties of the nuclear envelope. Our findings advance the biophysical understanding of nuclear membrane fluctuations during early multicellular development. |
Tuesday, March 7, 2023 1:42PM - 1:54PM |
G07.00010: Synthesis and Hydrogelation of Bioinspired Block Copolymers Fahed Albreiki, Samanvaya Srivastava Marine organisms such as mussels and sandcastle worms secrete glue proteins that enables robust wet adhesion and curing properties. The adhesive attributes of these proteins have been ascribed to the presence of catecholic 3,4-dihydroxy-l-phenylalanine (DOPA) moieties. We draw inspiration from these marine adhesives to create block polymers with catechol functionalities to seek strong, tunable adhesion in wet environments. Here, we report the preparation of symmetric polyethylene glycol (PEG) block copolymers containing well-defined number and location of unprotected catechol groups. Tunable oxidation of the catechol end blocks into quinones and subsequent catechol-quinone crosslinking resulted in three-dimensional polymer network formation. Using dynamic oscillatory shear rheometry and small angle X-ray scattering we monitor and study the hydrogelation as a function of oxidation strength and time. This approach allows for investigating the effects of molar concentrations of adhesive groups, polymer molecular weight, and concentration and aid in enhancing the adhesive capabilities of PEG-based hydrogels. |
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