Physics ABC Seminar: "Traction Force Microscopy by Using Paramagnetic Particles" by Yuwen Mei, and "Molecular-Scale Understanding of the Changes to Lipid Mobility Induced by Bilayer Curvature" by Susheel Pangeni, Wayne State University

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Date: September 22, 2020
Time: 3:30 p.m. - 4:30 p.m.
Location: Zoom
Category: Seminar

I. Traction Force Microscopy by Using Paramagnetic Particles
Yuwen Mei
Department of Physics and Astronomy, Wayne State University

Mechanical cellular interactions heavily influence major cellular processes such as immune response, embryogenesis, angiogenesis, and metastasis. Most of these physiological processes are in direct relation to cell migration. Such biological function is responsible for positive responses in one’s body in aid of healing of wounds, or infamously, invasion of cancer cells through the connective tissues. To better understand these major physiological phenomena, it is critical to understand how these contractile motions are generated and quantification of traction forces is necessary. To measure these forces, Traction Force Microscopy is often employed, and fluorescent particles are embedded in the substrate as markers to track the forces being applied. However, such a setup has no control over marker positions and often introduces background noise, resulting in loss of spatial resolution. In addition, particle depth variations can result in underestimations in force estimations. Thus, we have improved our method of force detection by employing fluorescent paramagnetic nanoparticles. Under the influence of an external magnetic field, the paramagnetic nanoparticles readily form a single particle layer near the surface of the substrate. The inter-particle distance can be controlled by changing the magnitude of the magnetic field. We employ this method for biomechanical analysis of the pancreatic cancer cell line (PANC-1). With the background noise reduced significantly in the single-layer scheme, the image filtering process is simplified. Since the magnetic particles are in a much closer distance to the cells compared to the conventional methods, therefore reflects a more accurate force measurement.

II. Molecular-Scale Understanding of the Changes to Lipid Mobility Induced by Bilayer Curvature
Susheel Pangeni
Department of Physics and Astronomy, Wayne State University

Biological membranes have evolved tremendous complexity and versatility to perform processes that require the generation of membrane curvature. The interplay of bilayer curvature and mechanical properties are critical for diverse disease treatments and engineering applications. Molecular dynamics simulations provide both means of high-throughput testing of system parameters and revealing molecular-scale details of bilayer behavior. This work is guided by the hypothesis that the mechanical properties of lipids vary with bilayer topography to generates a force for molecular sorting and regulating lipid diffusion. The target is to study how membrane curvature and the molecular interactions between the lipids affect lipid behaviors. We used coarse-grained molecular dynamics (CGMD) models to reveal molecular resolution while enabling larger and longer simulations than all-atom simulations. We are exploring complex and challenging unsolved mechanisms in the cellular physics of trafficking and signaling. The effects of bilayer curvature on diffusion while mimicking of endocytic nano-mechanics is studied with the CGMD Martini model and compared to single-lipid tracking experiments



Zhi-Feng Huang
(313) 577 2791


September 2020