Bulletin of the American Physical Society
18th Annual Meeting of the APS Northwest Section,
Volume 62, Number 7
Thursday–Saturday, June 1–3, 2017; Forest Grove, Oregon
Session C1: Biology & Physics |
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Room: Price Hall 203 |
Friday, June 2, 2017 1:30PM - 2:05PM |
C1.00001: Engaging Upper-Level Biology Students (Or Everything I need to know about physics I learned in first year). Invited Speaker: Mark Paetkau Thompson Rivers University (TRU) is an open university of about 7000 students located in BC's interior. The university grew out of a community college but retains its strong roots of learning-by-doing and TRU continues to train trades and technology students as well as offer academic degrees. The physics department is small and contributes service courses to many different departments, including biology. Needless to say, many biology majors have an innate fear of physics and often will leave their first year physics requirement until 3$^{\mathrm{rd}}$ or 4$^{\mathrm{th}}$ year. Some of these students embark on honors thesis work or directed studies. As physics/chemistry/ and biology are housed in the same building, I have been able to form collaborations with these biology students whose research is often an application of physics concepts. In this talk I will walk through some of my mentorships of biology students, including measuring the speed of dwarf mistletoe seed discharge (kinematics), dispersal of Artemia franciscana (fluid mechanics), and IR measurements on cattle (heat transport). The projects span the topics of first year physics and make for delightful inclusions into my first year courses as practical applications physics in biology research. [Preview Abstract] |
Friday, June 2, 2017 2:05PM - 2:17PM |
C1.00002: A Study of Internal Friction in Proteins Using a Diffusive, Langevin Formalism Eric Beyerle, Marina Guenza Although internal friction in polymers has been studied since the 1940s, a molecular-level explanation of the phenomenon remains elusive. Proteins, biological heteropolymers, are important testing grounds for theories describing internal friction due to its relevance in biologically significant events such as protein folding. We are studying internal friction using a diffusive, Langevin formalism developed in the Guenza lab, the Langevin Equation for Protein Dynamics (LE4PD), which includes site-specific friction coefficients and hydrodynamic interactions between amino acid residues in its description of protein dynamics. Using the protein ubiquitin as a model system, we have performed molecular dynamics simulations in explicit water to test our theoretical predictions. Preliminary results of our study show an internal viscosity with a contribution dependent on the solvent viscosity and a contribution independent of the solvent viscosity. [Preview Abstract] |
Friday, June 2, 2017 2:17PM - 2:29PM |
C1.00003: Shape Space Dynamics of Migrating MDA-MB-231 Cancer Cells Christopher Eddy, Bo Sun Cancer cell migration is a central step in the metastatic process. Importantly, the plasticity of cancer migration mechanisms have confounded efforts to diminish invasion. Here, we study the morphological dynamics of cancer cells migrating in 3D collagen matrix. We characterize the ensemble distribution in addition to the temporal trajectories of cells in both position as well as shape spaces. We find that more exploratory cells will vary in elongation and protrusion formation during migration, indicating a more invasive phenotype. We also find that increasing matrix rigidity does not change the aspect ratio of the cell, but rather increases surface roughness by promoting protrusions. [Preview Abstract] |
Friday, June 2, 2017 2:29PM - 2:41PM |
C1.00004: Simulating dynein’s powerstroke using Brownian dynamics Elliott Capek, John Waczak, David Roundy Dynein is a motor protein which transports cargo along tracks inside the cell. Like related motor proteins kinesin and myosin, dynein uses cellular energy to take steps with its two foot domains. Unlike kinesin or myosin, dynein's stepping pattern is highly varied: it can take steps between zero and 60nm in both the forwards and backwards directions. It is believed that dynein takes such broad, stochastic steps because its large size and several elastic regions make it more influenced by Brownian motion. To test this, we model the motor as a 2D system of springy hinges, then simulate this model using Brownian dynamics. Preliminary results indicate such a model is capable of taking steps between zero and 25nm. These results give hope that, with further tweaking, the model may be able to generate both larger steps and backwards steps. [Preview Abstract] |
Friday, June 2, 2017 2:41PM - 2:53PM |
C1.00005: OsKCH2 is a novel processive minus end-directed kinesin-14 motor Allison Gicking, Kuo-Fu Tseng, Pan Wang, Yuh-Ru Julie Lee, Joel Bowen, Lijun Guo, Weihong Qiu, Bo Liu In animals and fungi, cytoplasmic dynein contains the ability to generate processive minus end-directed motility on single microtubules without having to form multi-motor ensembles and thus plays a dominant role over kinesin-14 motors. However, land plants do not have cytoplasmic dynein, and no plant kinesin-14 motor is known to be able to move processively on single microtubules as a homodimer. Here, we have analyzed the motility of OsKCH2 -- a plant-specific kinesin-14 that contains an N-terminal actin-binding CH domain and a central microtubule-binding motor domain flanked by a pair of putative coiled coils (CC1 and CC2) -- using TIRF microscopy. We found that OsKCH2 transports actin filaments along the microtubules and exhibits processive minus end-directed motility as a homodimer. We have further revealed that only the upstream CC1 forms a coiled coil to enable the formation of OsKCH2 homodimers. In contrast, the downstream CC2 does not form an authentic coiled-coil and instead plays an indispensable role in OsKCH2 processivity by enhancing its binding to the microtubule. Collectively, this study shows that land plants have evolved unconventional kinesin-14 homodimers with inherent minus end-directed processivity that likely compensate for the loss of cytoplasmic dynein. [Preview Abstract] |
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