Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 59, Number 11
Friday–Saturday, October 17–18, 2014; Orem, Utah
Session D7: Biophysics II: Experimental |
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Chair: Jim Thomas, University of New Mexico Room: Science Building 60 |
Friday, October 17, 2014 1:50PM - 2:14PM |
D7.00001: Experimental Investigations of Single Vesicle to Supported Lipid Bilayer Residence Times Invited Speaker: Kathrin Spendier One of the primary ways in which cells interact with their environments is by release of extracellular vesicles that are formed either from the cell plasma membrane (microvesicles) or secreted from multivesicular bodies (exosomes). These vesicles contain nucleic acids and proteins that have been suggested to play an important role in intercellular signaling and molecular communication between cells. In microvesicle (MV)-mediated intercellular communication, vesicles released by a donor cell must bind to the plasma membrane of a recipient cell in order to deliver their cargo to the target. Despite the important physiological role of vesicle-plasma membrane fusion and vesicle endocytosis, the details of the physical interactions between MVs and the plasma membrane are still poorly understood. To better understand the forces which occur between MVs and cells, TIRF microscopy was employed to experimentally investigate single liposome and exosome binding events with a supported lipid bilayer. Binding lifetimes were determined using a least-squares fitting or a maximum likelihood estimation technique. Comparison of these two techniques shows that a maximum likelihood technique should be used to estimate binding lifetimes. Comments about differences in observed binding lifetimes due supported lipid bilayer composition, liposome composition, and exosome isolation techniques will be made. [Preview Abstract] |
Friday, October 17, 2014 2:14PM - 2:38PM |
D7.00002: High-Speed Hyperspectral Nanoscopy for Studying Dynamic Protein Interactions Invited Speaker: Keith Lidke Many cellular signaling processes are initiated by dimerization or oligomerization of membrane proteins. However, since the spatial scale of these interactions is below the diffraction limit of the light microscope, the dynamics of these interactions have been difficult to study on living cells. We have developed a novel high-speed hyperspectral microscope (HSM) to perform single particle tracking of up to 8 spectrally distinct species of quantum dots (QDs) at 30 frames per second. The distinct emission spectra of the QDs allows localization with $\sim$ 10 nm precision even when the probes are clustered at spatial scales below the diffraction limit. The capabilities of the HSM are demonstrated by application of multi-color single particle tracking to observe membrane protein behavior, including: 1) resolving antigen induced aggregation of the high affinity IgE receptor, Fc$\epsilon$R1; 2) dynamic formation and dissociation of Epidermal Growth Factor Receptor dimers; 3) four color QD tracking while simultaneously visualizing GFP-actin; and 4) high-density tracking for fast viscosity mapping of the cell membrane. [Preview Abstract] |
Friday, October 17, 2014 2:38PM - 3:02PM |
D7.00003: Polyelectrolyte Multilayer: pH-responsive lipid bilayers and beyond Invited Speaker: Ann Junghans Creating large-scale fluid lipid bilayer that are independent from a supporting substrate, stable and durable would be advantageous to multiple applications. A robust and simple method for the preparation of pH-responsive membranes is reported. Structural characterization using Neutron Reflectivity (NR), further supported by Fluorescent Microscopy and Electrochemical Impedance Spectroscopy measurements, revealed that the separation distance between a polymeric cushion and a lipid bilayer can be reversibly adjusted by varying the pH of the aqueous environment. We believe that this novel system offers great potential for fundamental biophysical studies of membrane properties decoupled from the underlying solid support. Additionally, creating large-scale fluid lipid bilayers would be advantageous to multiple applications. Such include membranes for biosensing arrays or cell culturing with easy detachment in one sheet. With regard to the last objective, various live cells have been investigated by NR under different environmental conditions. These measurements represent the first successful visualization and quantization of the interface between live cells and a substrate with sub-nanometer resolution, and are key in the understanding of physiology and disease.\\[4pt] In collaboration with Jarek Majewski, Los Alamos National Laboratory; Luka Pocivavsek, University of Pittsburgh; and Mariano Viapiano, Harvard Medical School. [Preview Abstract] |
Friday, October 17, 2014 3:02PM - 3:14PM |
D7.00004: HemoClear\texttrademark: A Thin Fluid Film Device (TFFD\texttrademark ) and Model to Eliminate both Fogging and Blood on Surgical Lenses Saloni Sinha, Ajjya Acharya, Nicole Herbots, Clarizza Watson, Eric Culbertson, Mark Matiski, Adam Orr, Ross Bennet-Kennet, Ashlee Murphy, Eric Morgan, Alex Brimhall, Robert Culbertson In closed body cavity surgery, blood and water condensation can obstruct surgeons' view through scopes lenses. This forces surgeons to repeatedly remove scopes to wipe lenses during surgery, and increases surgery duration, infection risk and scarring by 10- 40{\%}. HemoClear\texttrademark , a Thin Fluid Film Device (TFFD\texttrademark ), is a layered emulsion combining VitreOx\texttrademark and fibrinogen. [1,2] VitreOx\texttrademark is an anti-fog TFFD\texttrademark , free of optical aberration, optically transparent, and super-hydrophilic, stable for up to 48 hours in closed body-cavity surgery. We find that fibrinogen can evacuated blood without interfering with anti-fog properties VitreOx\texttrademark via he hemo-affinity of fibrinogen and ~hydro-affinity of VitreOx\texttrademark . The mixing and layering of the components of HemoClear\texttrademark are tested via~\textit{in vitro}~clinical trials to optimize our TFFD\texttrademark with the smallest effective dose of fibrinogen. ~A model for 2-D versus 3-D condensation and hemo-affinity will be discussed. ~ [1]~N. Herbots, et al. ~Prov. Pat. filed 11/10/09, 11/3/11 [2] N. Herbots, et al. PCT/US12/62196 Internat. Pat. filed ~11/10/10, 10/26/12 [Preview Abstract] |
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