Bulletin of the American Physical Society
Joint Fall 2012 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 57, Number 10
Thursday–Saturday, October 25–27, 2012; Lubbock, Texas
Session E1: Invited & Contributed Papers: Chemical & Biological Physics |
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Chair: Harry Swinney, University of Texas at Austin Room: Holiday Inn Towers Petroleum A |
Friday, October 26, 2012 3:30PM - 4:05PM |
E1.00001: DNA in Nanoscale Electronics Invited Speaker: Jason Slinker DNA, the quintessential molecule of life, possesses a number of attractive properties for use in nanoscale circuits. Charge transport (CT) through DNA itself is of both fundamental and practical interest. Fundamentally, DNA has a unique configuration of $\pi $-stacked bases in a well ordered, double helical structure. Given its unparalleled importance to life processes and its arrangement of conjugated subunits, DNA has been a compelling target of conductivity studies. In addition, further understanding of DNA CT will elucidate the biological implications of this process and advance its use in sensing technologies. We have investigated the fundamentals of DNA CT by measuring the electrochemistry of DNA monolayers under biologically-relevant conditions. We have uncovered both fundamental kinetic parameters to distinguish between competing models of operation as well as the practical implications of DNA CT for sensing. Furthermore, we are leveraging our studies of DNA conductivity for the manufacture of nanoscale circuits. We are investigating the electrical properties and self-assembly of DNA nanowires containing artificial base pair surrogates, which can be prepared through low cost and high throughput automated DNA synthesis. This unique and economically viable approach will establish a new paradigm for the scalable manufacture of nanoscale semiconductor devices. [Preview Abstract] |
Friday, October 26, 2012 4:05PM - 4:40PM |
E1.00002: Protein Unfolding and Alzheimer's Invited Speaker: Kelvin Cheng Early interaction events of beta-amyloid (A$\beta )$ proteins with neurons have been associated with the pathogenesis of Alzheimer's disease. Knowledge pertaining to the role of lipid molecules, particularly cholesterol, in modulating the single A$\beta $ interactions with neurons at the atomic length and picosecond time resolutions, remains unclear. In our research, we have used atomistic molecular dynamics simulations to explore early molecular events including protein insertion kinetics, protein unfolding, and protein-induced membrane disruption of A$\beta $ in lipid domains that mimic the nanoscopic raft and non-raft regions of the neural membrane. In this talk, I will summarize our current work on investigating the role of cholesterol in regulating the A$\beta $ interaction events with membranes at the molecular level. I will also explain how our results will provide new insights into understanding the pathogenesis of Alzheimer's disease associated with the A$\beta $ proteins. [Preview Abstract] |
Friday, October 26, 2012 4:40PM - 4:52PM |
E1.00003: Causality, Symmetry, Brain, Evolution, DNA and a new Theory of Physics Sergio Pissanetzky THEORY. Except for black holes, our world is causal. In Physics, causal sets formalize causality. The easiest way to explain the importance of causets is: all finite algorithms and computer programs are causets. Let S be a causet model of a dynamical system. S has a symmetry of the action: set P of legal permutations of S. Hence all causets have conservation laws. Permutations in P represent trajectories in state space. But P is non-conservative. New Physics: an action functional F was observed. When F is minimized over P, conservative subset P* is obtained. In P*, conserved quantities emerge as group-theoretical block systems over S. Block systems are also causets, and iteration leads to a network of blocks. This is a new theory of Physics. PREDICTIONS. (1) Brain's dendritic trees must be optimally short. Cuntz (June 2012) observed a 2/3 optimally short power law. (2) Causal hierarchies. Fuster(2005) observes identical hierarchies in cortex. DNA (Sept 2012) is described as hierarchical networks. (3) Action functional. Lerner (Aug 2012) proposed an action functional and minimum entropy on trajectories of dynamical processes. Friston (2003) proposed an energy functional. (4) Simple computer-brain experiments (Pissanetzky 2011a). REFERENCES: www.SciControls.com. [Preview Abstract] |
Friday, October 26, 2012 4:52PM - 5:04PM |
E1.00004: DFT Studies on Charge Transfer States of a Multi-chromophoric Organic Heptad Antenna Luis Basurto The electronic structure of the ground and the lowest charge transfer excited state of a molecular complex containing BODIPY dye, Zn-porphyrin, bisphenyl anthracene and fullerene are studied using density functional theory. The snowflaked shaped molecule behaves like an antenna capturing photons at different frequencies and transferring the energy to the porphyrin where electron transfer occurs from the porphyrin to the fullerene. We have claculated the energy of the lowest charge transfer state with a hole on prophyrin and an electron on the fullerene using a perturbative delta-SCF method. Our calculated values are in good agreement with the experimental charge transfer energy. [Preview Abstract] |
Friday, October 26, 2012 5:04PM - 5:16PM |
E1.00005: Probing protein conformations at the oil droplet--water interface using single-molecule force spectroscopy Ahmed Touhami, Marcela Alexander, Milena Corredig, John Dutcher We have used atomic force microscopy (AFM) imaging and single molecule force spectroscopy (SMFS) to study $\beta $-lactoglobulin ($\beta $-LG) molecules localized at the interface between oil droplets and water. To immobilize the oil droplets, we have mechanically trapped them in the pores of a filtration membrane. For this sample geometry, we have used SMFS to pull on the $\beta $-LG molecules, revealing changes in their conformation and oligomerization in response to in situ changes in pH. We have compared the present results with those obtained previously for SMFS measurements of b-LG molecules adsorbed onto mica surfaces. At neutral pH, we observe large differences between the results obtained for the two surfaces in the pulling force required to fully extend the molecules, the spacing between sawtooth peaks in the force--distance curves, and the oligomerization of the molecules. The mechanical unfolding of the adsorbed $\beta $-LG molecules at pH 2.5 was very similar for the two surfaces. For pH 9.0, we find that, for both surfaces, there is an irreversible change in the conformation of the $\beta $-LG molecules with a strong repulsion measured between the AFM tip and the $\beta $-LG molecules. This study provides insight into structural changes of this protein when adsorbed onto an oil--water interface, and demonstrates the potential of SMFS as a tool to study the structure of proteins that are important in complex matrices such as food emulsions. [Preview Abstract] |
Friday, October 26, 2012 5:16PM - 5:28PM |
E1.00006: Analytical Comparisons of Tree Ring Data, Greenland Ice Core Temperatures and Temperature Fluctuations of the Sargasso Sea James Otto, Jim Roberts, Jai Dahiya Embedded in various events on Earth are data that allow us to map the temperature of the Earth over many years. In this work we have chosen the temperature fluctuations in the Sargasso sea, the changing patterns in tree ring growth and temperature fluctuations in Greenland ice core samples for comparison with a goal to understanding the patterns in global warming. Signatures have been identified that predate the Industrial Revolution, which had been blamed for much of global warming, that indicate that Earth temperatures have enjoyed numerous intervals of both global warming and global cooling. The intention of this work is not to stir controversy but to make comparisons of scientific data and processes rather than rely on popular opinion or deduction by ``experts'' in climatology to explain global warming. [Preview Abstract] |
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