Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session A39: Focus Session: Energy Future: Biological and Biometric Systems |
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Sponsoring Units: DBP Chair: Marilyn Gunner, City College of New York Room: A124/127 |
Monday, March 21, 2011 8:00AM - 8:36AM |
A39.00001: Energy conversion in photosynthesis Invited Speaker: Photosystem II (PSII) uses light energy to split water into protons, electrons and O$_{2}$ [1]. In this reaction, Nature has solved the difficult chemical problem of efficient four-electron oxidation of water to yield O$_{2}$ without significant side reactions. In order to use Nature's solution for the design of materials that split water for solar fuel production, it is important to understand the mechanism of the reaction. The X ray crystal structures of cyanobacterial PSII provide information on the structure of the Mn and Ca ions, the redox-active tyrosine called Y$_{Z}$, and the surrounding amino acids that comprise the O$_{2}$ evolving complex (OEC) [2,3]. We have used computational studies used to refine the structure of the OEC to obtain a complete structural model of the OEC that is in agreement with spectroscopic data [4,5]. The structure of the OEC and the mechanism of water oxidation by PSII will be discussed in the light of biophysical and computational studies, inorganic chemistry and X-ray crystallographic information. \\[4pt] [1] J.P. McEvoy and G.W. Brudvig, Chem. Rev. (2006) 106, 4455-4483. \\[0pt] [2] K.N. Ferreira et al., Science (2004) 303, 1831-1838. \\[0pt] [3] B. Loll et al., Nature (2006) 438, 1040-1044. \\[0pt] [4] E.M. Sproviero et al., J. Am. Chem. Soc. (2008) 130, 6728-6730. \\[0pt] [5] E.M. Sproviero et al., J. Am. Chem. Soc. (2008) 130, 3428-3442. [Preview Abstract] |
Monday, March 21, 2011 8:36AM - 9:12AM |
A39.00002: Engineered and Artificial Photosynthesis Invited Speaker: This abstract not available. [Preview Abstract] |
Monday, March 21, 2011 9:12AM - 9:24AM |
A39.00003: QM/MM and MD study on a light-harvesting molecular triad Guoxiong Su, Arkadiusz Czader, Margaret Cheung We investigated the hydrophobic interactions of an artificial photosynthetic molecular triad in nanoconfinement in various sizes using a combined approach of QM/MM method and all-atomistic molecular dynamics simulations with explicit water models. We use the Replica Exchange Method Dynamics (REMD) to investigate the effect of solvation and confinement on the distribution of the ensemble structures and the energy landscape of triad. The relationship of the charge distribution computed from QM/MM and the radial distribution function of water molecules at the proximity of triad will be discussed. The work presented here has profound implications for future studies of the photosynthetic function of triad that provides the opportunity for the insight into the molecular device of green energy. [Preview Abstract] |
Monday, March 21, 2011 9:24AM - 9:36AM |
A39.00004: Nanophotonics of Chloroplasts for Bio-Inspired Solar Energy Materials Paul L. Gourley, Cheryl R. Gourley In the search for new energy sources, lessons can be learned from chloroplast photonics. The nano-architecture of chloroplasts is remarkably well-adapted to mediate sunlight interactions for efficient energy conversion. We carried out experiments with chloroplasts isolated from spinach and leaf lettuce to elucidate the relationship between nano-architecture, biomolecular composition and photonic properties. We obtained high-resolution microscopic images of single chloroplasts to identify geometries of chloroplasts and interior grana. We performed micro-spectroscopy to identify strengths of absorption and fluorescence transitions and related them to broadband reflectance and transmittance spectra of whole leaf structures. Finally, the nonlinear optical properties were investigated with nanolaser spectroscopy by placing chloroplasts into micro-resonators and optically pumping. These spectra reveal chloroplast photonic modes and allow measurement of single chloroplast light scattering cross section, polarizability, and refractive index. The nanolaser spectra recorded at increasing pump powers enabled us to observe non-linear optics, photon dynamics, and stimulated emission from single chloroplasts. All of these experiments provide insight into plant photonics and inspiration of paradigms for synthetic biomaterials to harness sunlight in new ways. [Preview Abstract] |
Monday, March 21, 2011 9:36AM - 9:48AM |
A39.00005: Direct Enzymatic Oxidation of Glucose with a Poly(Ionic Liquid) - Gold-Nanoparticle Composite Millicent Firestone, Sungwon Lee, Soenke Seifert In this work we describe the synthesis, fabrication and characterization of a gold nanoparticle - ionic liquid-derived polymer composite for conversion of biofuels into electricity. Glucose oxidase (GOx) electrostatically adsorbed on an ionic liquid-derived polymer containing internally organized columns of Au nanoparticles exhibits bioelectrocatalytic properties in the oxidation of glucose. The cationic poly(ionic liquid) provides an ideal substrate for the immobilization of GOx. The encapsulated Au nanoparticles serve two roles: promoting direct electron transfer with the recessed enzyme redox centers, and imparting electronic conduction to the composite, thereby allowing it to function as an electrode for electrochemical detection. [Preview Abstract] |
Monday, March 21, 2011 9:48AM - 10:00AM |
A39.00006: Photosystem I assembly on chemically tailored SAM/ Au substrates for bio-hybrid device fabrication Dibyendu Mukherjee, Bamin Khomami Photosystem I (PS I), a supra-molecular protein complex and a biological photodiode responsible for driving natural photosynthesis mechanism, charge separates upon exposure to light. Effective use of the photo-electrochemical activities of PS I for future bio-hybrid electronic devices requires controlled attachment of these proteins onto organic/ inorganic substrates. Our results indicate that various experimental parameters alter the surface topography of PS I deposited from colloidal aqueous buffer suspensions onto OH-terminated alkanethiolate SAM /Au substrates, thereby resulting in complex columnar structures that affect the electron capture pathway of PS I. Specifically, solution phase characterizations indicate that specific detergents used for PS I stabilization in buffer solutions drive the unique colloidal chemistry to tune protein-protein interactions and prevent aggregation, thereby allowing us to tailor the morphology of surface immobilized PS I. We present surface topographical, adsorption, and electrochemical characterizations of PSI /SAM/Au substrates to elucidate protein-surface attachment dynamics and its effect on the photo-activated electronic activities of surface immobilized PS I. [Preview Abstract] |
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