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 S12: Mechanisms of Self-Assembly: Biology and BeyondInvited
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Sponsoring Units: DPOLY Chair: Jonathan Whitmer, University of Notre Dame; Samanvaya Srivastava, UCLA Room: Room 235 |
Thursday, March 9, 2023 8:00AM - 8:36AM |
S12.00001: Assembly of Reduced Graphene Oxide-Conducting Polymer Fibers in the Lyotropic Liquid Crystal Phase as Synthetic Muscle Actuators Invited Speaker: Shu Yang Soft actuators are known for their compliance, adaptivity and dexterity, however, at the cost of load bearing, bit rates and energy efficiency compared with rigid body counterparts. Very few have achieved performance comparable with biological muscles with fast response time, high elastic energy and power density at the same time. Meanwhile, among different stimulation methods, application of electric fields is highly desired for more forceful and faster responses. |
Thursday, March 9, 2023 8:36AM - 9:12AM |
S12.00002: Biophysical cues regulating structural organization of fat in adipocytes upon caloric excess Invited Speaker: Cecilia Leal Obesity is an alarmingly common and serious disease. Adipose tissue stores excess calories as triacylglycerol (TAG) and cholesterol ester in lipid droplets (LDs) and mobilizes them as needed. How adipose tissue regulates fat packing in the different depots—white versus brown—during obesity remains poorly understood. We show that adipose LDs are not simple emulsions as originally thought. TAG distributes among LD rims as solid-like and LD cores as liquid-like. During obesity, the number of TAG lamellae increases in a manner that is adipose depot—specific. Additionally, collagen packs randomly in white fat forming a permissive environment for LD expansion but is highly–oriented in brown fat. |
Thursday, March 9, 2023 9:12AM - 9:48AM |
S12.00003: Entropy-Driven Supramolecular Biomaterials Enabling Innovations in Drug and Cell Delivery Invited Speaker: Eric A Appel Supramolecular biomaterials exploiting rationally-designed non-covalent interactions exhibit many distinct properties that enable innovative approaches to drug delivery. For example, supramolecular interactions can be used to generate dynamically cross-linking polymer networks, yielding shear-thinning and self-healing hydrogels that exhibit viscoelastic mechanical properties similar to biological tissues and flow properties enabling minimally invasive implantation in the body though direct injection or catheter delivery. In this talk we will discuss the preparation, characterization and application of a class of physical hydrogels generated by non-covalent interactions between modified biopolymers (BPs) and nanoparticles (NPs). Owing to the dynamic, non-covalent interactions between the NPs and BPs, the hydrogels flow under applied stress and their mechanical properties recover completely within seconds when the stress is relaxed, demonstrating the shear-thinning and injectable nature of the materials. Moreover, these interactions have been shown to be entropically driven, causing these materials to elicit alternative temperature-dependent mechanical properties than those typically observed in physical hydrogels. Further, the hierarchical construction of these biphasic hydrogels allows for multiple therapeutics ranging form peptides to proteins to cells to be entrapped simultaneously and delivered over user-defined timeframes ranging from days to months. These materials have proven to be particularly promising as controlled delivery technologies in vaccines and cancer immunotherapies - applications where precise release of complex mixtures of compounds over prolonged timeframes is crucial. In particular, the use of these materials for the controlled delivery of CAR-T cells and stimulatory cytokines to improve treatment of solid tumors will be discussed. Overall, this presentation will demonstrate the utility of a supramolecular approach to the design of biomaterials affording unique opportunities in the controlled delivery of therapeutics. |
Thursday, March 9, 2023 9:48AM - 10:24AM |
S12.00004: Self-assembly of the dipole-driven physical polyzwitterions in solutions Invited Speaker: Di Jia Dipolar polymers are capable of forming complex, self-regulating structures which could be employed in various fields from drug-delivery systems to the next-generation polymers. Here in a polycation-negatively charged organic salt complaxation system, we found that dipolar interaction will transform a polycation into a physical polyzwitterion. In dilute solutions we found isolated polycation chain shrinks upon a decrease in ionic strength, exhibiting a “globule-to-coil” conformational transition with increasing ionic strength. Such an “anti-polyelectrolyte effect” , which is a feature of traditional chemical polyzwitterion, is due to the intra-chain dipolar interactions. In concentrated solutions, by tuning the ionic strength, the system exhibits rich phase behavior, including phase separation at low ionic strength and a homogeneous solution at very high ionic strength, with a stable mesomorphic state of monodispersed spherical aggregates with the size around 100-200 nm as an interlude between the two limits. By using light scattering we found that the size of the aggregates depends on the polymer concentration Cp according to the scaling law R~Cp^1/6. Further increasing the polymer concentration will make the mesomorphic aggregates disassemble into single chains by a self-poisoning mechanism. |
Thursday, March 9, 2023 10:24AM - 11:00AM |
S12.00005: Characterizing Protein Hydration to Inform its Interactions Invited Speaker: Amish Patel The extent to which the inherent structure of water is perturbed by complex molecules, such as proteins, peptides, and surfactants, influences the thermodynamics and the kinetics of their assembly. However, accurately characterizing this perturbation is challenging, because the manner in which proteins disrupt the inherent structure of water depends not only on the chemistry of the underlying protein surface, but also on the precise topographical and chemical pattern displayed by the protein. Nevertheless, understanding the role of water in mediating protein interactions is essential to understanding, predicting, and eventually controlling such interactions, which play a crucial role in the development of therapeutic strategies and in protein separations. In this presentation, I will discuss our recent successes in quantitatively characterizing the disruption of water structure in the hydration shell of proteins, and in using this information to predict the interfaces through which proteins interact with one another and self-assemble. Our approach also informs strategies for optimally modulating protein interactions, and facilitates the design of ligands that will bind to proteins of interest with high affinity and specificity. We hope that these advances will pave the way for the discovery of novel therapeutics that specifically target proteins of interest, and the rational design chromatographic ligands for challenging protein separations. |
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