Bulletin of the American Physical Society
2008 Joint Meeting of the APS Ohio-Region Section, the AAPT Southern Ohio Section, and the ACS Dayton-Section
Volume 53, Number 8
Friday–Saturday, October 10–11, 2008; Dayton, Ohio
Session C7: Biological Physics |
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Chair: Peter Mirau, Air Force Research Laboratory Room: Oelman Hall 30 |
Saturday, October 11, 2008 8:00AM - 8:12AM |
C7.00001: Diffusion dependence of proton NMR relaxation rates in the presence of ferritin Michael Boss, P. Chris Hammel Ferritin is the predominant iron-storage protein in living organisms. In aqueous solutions of ferritin, protons experience a higher transverse relaxation rate, R$_{2}$. This is thought to occur due to a diffusive mechanism, where protons move close enough to the ferritin to pass through a region of elevated magnetic field, and a chemical exchange mechanism, where protons bind to the protein for a period of time, experiencing an even higher magnetic field. These two mechanisms exhibit different dependencies on the self-diffusion coefficient of the protons. By adding glycerol to aqueous solutions, we have been able to control the self-diffusion of protons; this has been confirmed by means of diffusion measurements employing pulsed field gradient techniques. We have measured the relaxation rate of protons in ferritin-containing binary mixtures of water and glycerol using CPMG sequences, and will compare the experimental results to theoretical predictions of diffusion dependence. [Preview Abstract] |
Saturday, October 11, 2008 8:12AM - 8:24AM |
C7.00002: Characterization and Biocompatibility of ``Green'' Synthesized Silver Nanoparticles Michael Moulton, Samantha Kunzelman, Laura Braydich-Stolle, M. Nadagouda, R. Varma, Saber Hussain With ever increasing emphasis on nanotechnology, silver nanoparticle are being considered for many antimicrobial needs ranging from catheter coatings, to burn wound bandages. Current synthesis methods for creating silver nanoparticles typically call for potentially hazardous chemicals, extreme heat, and produce environmentally dangerous byproducts. As a culture intent on reducing our carbon footprint on the earth, societies' focus has turned to ``green'' production capabilities. Therefore, if nanotechnology is to continue to grow at its current rate it is essential that novel ``green'' synthesis of nanoparticles becomes a reality. Furthermore, with the current and near-future applications of silver nanoparticles in biological systems it is imperative to fully analyze the potential toxic effects of these nanoparticles. In this study we have shown that by reducing silver nitrate in solutions of tea extract or epinephrine of varying concentrations spherical silver nanoparticle are formed. Furthermore, evaluation of mitochondrial function (MTS) and membrane integrity (LDH) in alveolar rat macrophages and human keratinocytes showed that these ``green'' synthesized silver nanoparticles were nontoxic. [Preview Abstract] |
Saturday, October 11, 2008 8:24AM - 8:36AM |
C7.00003: Mapping the energy landscape of tubulin under tension with molecular simulations Harshad Joshi, Ruxandra Dima Microtubules (MTs) play major roles in the transport of organelles in the cell and in cell division. MTs are subject to permanent tension [1] and additional forces act on MTs when external mechanical perturbations are applied to cells. To elucidate the microscopic origins of the mechanical response in MTs, we have performed simulations of a self-organized polymer (SOP) model of tubulin, the building block of MTs. The SOP representation is an off-lattice minimalist description of a protein chain which allows us to perform force-induced unfolding simulations of large molecules at the loading rates and time scales of single-molecule experiments [2]. We show that the forced unfolding of tubulin involves a bifurcation in the unfolding pathways and map precise features of the complex energy landscape of tubulin by surveying the structures of the various metastable intermediates [3]. \\[0pt] References: \\[0pt] [1] Schek HT, Gardner MK, Cheng J, Odde DJ, Hunt AJ (2007) Curr Biol 17:1445--1455. \\[0pt] [2] Hyeon C, Dima RI, Thirumalai D (2006) Structure 14:1633--1645. \\[0pt] [3] Dima RI, Joshi H (2008) Proc. Natl. Acad. Sci. USA (accepted). [Preview Abstract] |
Saturday, October 11, 2008 8:36AM - 8:48AM |
C7.00004: Computational modeling of protein folding assistance by the eukaryotic chaperonin CCT Manori Jayasinghe, George Stan Chaperonins are biological nanomachines that promote protein folding using energy derived from ATP hydrolysis. They are found in all the three domains of life and are grouped into two distinct classes based on their lineage. Group I chaperonins represented by GroEL of \textit{E. coli.} bind substrate proteins through hydrophobic interactions. By contrast, group II chaperonins are suggested to use both hydrophobic and hydrophilic interactions to recruit substrate proteins. We focus on the substrate binding mechanisms of eukaryotic (Group II) chaperonin CCT. To this end, we study the interaction of CCT with Tubulin, one of the major substrates. Using molecular docking and molecular dynamics simulations, we probe binding of the $\beta$tubulin peptide (205-274) to the CCT$\gamma$ apical domain. We identify two binding mechanisms, one involving mostly hydrophobic interactions with a helical region, which is structurally equivalent to the binding site of the bacterial chaperonin and a second one involving hydrophilic interactions with a helical protrusion region. Our results suggest that the substrate binding in CCT is highly specific, involving both electrostatic and hydrophobic interactions. These mechanisms likely to be optimized for specific substrate protein-CCT subunit pairs. [Preview Abstract] |
Saturday, October 11, 2008 8:48AM - 9:00AM |
C7.00005: Studies of solid DNA-CTMA films using Raman microprobe spectroscopy Faizan Ahmad, Perry Yaney Extensive research has been conducted on the development of deoxyribonucleic acid (DNA) - based electrical and electro-optical devices using purified DNA originally derived from salmon waste. However, the molecular weight of the virgin, as received DNA is greater than 8000 kDa, whereas the electrical and electro-optical properties are optimum at lower molecular weights. High power sonication is used to reduce the molecular weight of the obtained DNA to levels as low as 200 kDa, in which higher power and longer exposure produces lower mean molecular weight. The DNA is then complexed with cetyltrimethl-ammonium chloride (CTMA) to make it water insoluble. To support the various measurements that have been made to confirm that the sonicated material is still double strand DNA and to look for other effects of sonication, Raman studies were carried out to compare the spectra over a wide range of molecular weights and to develop baseline data that can be used in correlation studies when various dopants are added to change the electrical, mechanical or optical properties. Raman microprobe spectra from solid, dry thin films of DNA with molecular weights ranging from 200 kDa to $>$8 MDa complexed with cetyltrimethyl-ammonium chloride (CTMA) are presented and correlated with the as-received spectrum, the CTMA spectrum and with published DNA spectra in aqueous solutions. [Preview Abstract] |
Saturday, October 11, 2008 9:00AM - 9:12AM |
C7.00006: The Bioaccumulation and Toxicity of Platinum Group Metals in Developing Chick Embryos Ioana Pavel, Jennifer Monahan, Marjorie Markopoulos, Zofia Gagnon, Britney NeJame, Jacob Cawley, David Reens Recent studies showed that platinum group metals (PGMs) such as Pt, Pd, and Rh from automobile catalytic converters, can accumulate in the soft tissues of a variety of living organisms. However, the effects of PGMs on bone and organs development of animals are not clearly understood. To examine these aspects, developing chick embryos were injected with 0.1, 1.0, 5, or 10 ppm solutions of Pt, Rh, Pd, or with a PGMs mixture. 1) Pathological Changes: were observed for all PGM treatments above 1 ppm. Bone Cells Assesment: Chondrocyte cells in thibiotarsus showed decreased diameter and length. 2) PGMs Accumulation in Tissues: was quantified by GFAAS spectrometry on finely ground tissue powder. 3) Bone Demineralization: was detected by micro-Raman spectroscopy imaging on paraffin embedded bone sections. 4) DNA Damage in Cells: was determined by using a Comet assay and fluorescence spectroscopy. Oxidative Damage in Tissues: was analyzed using a glutathione peroxidase assay. The overall results indicated that PGMs presence in our environment raises concerns about their long-term health effects on all organisms. [Preview Abstract] |
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