1,333 research outputs found
The free energy of small solute permeation through the E. coli outer membrane has a distinctly asymmetric profile
No full textPermeation of small molecules across cell membranes is aubiquitous process in biology and is dependent on the principles of physicalchemistry at the molecular level. Here we use atomistic molecular dynamicssimulations to calculate the free energy of permeation of a range of smallmolecules through a model of the outer membrane of Escherichia coli, anarchetypical Gram-negative bacterium. The model membrane containslipopolysaccharide (LPS) molecules in the outer leaflet and phospholipids inthe inner leaflet. Our results show that the energetic barriers to permeationthrough the two leaflets of the membrane are distinctly asymmetric; the LPSheadgroups provide a less energetically favorable environment for organiccompounds than do phospholipids. In summary, we provide the firstreported estimates of the relative free energies associated with the differentchemical environments experienced by solutes as they attempt to cross theouter membrane of a Gram-negative bacterium. These results provide keyinsights for the development of novel antibiotics that target these bacteria
Molecular dynamics simulations reveal the conformational flexibility of Lipid II and its loose association with the defensin plectasin in the Staphylococcus aureus membrane
Get PDFLipid II is critical for peptidoglycan synthesis, which is the main component of the bacterial cell wall. Lipid II is a relatively conserved and important part of the cell wall biosynthesis pathway and is targeted by antibiotics such as the lantibiotics, which achieve their function by disrupting the biosynthesis of the cell wall. Given the urgent need for development of novel antibiotics to counter the growing threat of bacterial infection resistance, it is imperative that a thorough molecular-level characterization of the molecules targeted by antibiotics be achieved. To this end, we present a molecular dynamics simulation study of the conformational dynamics of Lipid II within a detailed model of the Staphylococcus aureus cell membrane. We show that Lipid II is able to adopt a range of conformations, even within the packed lipidic environment of the membrane. Our simulations also reveal dimerization of Lipid II mediated by cations. In the presence of the defensin peptide plectasin, the conformational lability of Lipid II allows it to form loose complexes with the protein, via a number of different binding modes
William Morris and Edward Carpenter: back to the land and the simple life, 1880-1910
No full textThis thesis focuses on the influence of William Morris and Edward Carpenter on
aspects of the back-to-the-land and simple-life movements between the years 1880-
1910. Specifically, it seeks to define and explore the convergence and divergence of
both writers' return-to-nature ideology, and considers their influence on the
development of particular groups, who represented some of the multiplicity of backto-
the-land ideas and experiments current during this period. The thesis is divided
into three main parts; the intellectual framework for the study is broad, and takes into
account the historical context, the cultural significance and the character of the
material in each section.
The first part of the thesis undertakes an expository evaluation of key texts
from Morris's and Carpenter's political journalism, lectures and imaginative writing,
examining how both writers developed an appropriate language to convey their
social and political ideals. The critical method employed uses detailed textual
analysis, identifying and discussing the individual qualities of Morris's and
Carpenter's back-to-the-land writing, and reflecting on the differing emphases of
their utopian rhetoric. The second part of the research explores the take-up of
Morris's and Carpenter's ethos in four diverse and little known late-nineteenthcentury
journals, concerned with simple-life issues and a return to the land, namely
Seed-time, The New Order, Land and Labor and Land and People. It employs the
thinking of Pierre Bourdieu and Mikhail Bakhtin to establish an appropriate balance
between critical theory and empirical study. Lastly using a historical and descriptive
method the thesis uses archival material to examine the nature and extent of both
writers' influence on two Cotswold back-to-the-land experiments - the Whiteway
Colony and the Chipping Campden Guild of Handicraft. These provide a particular
opportunity to consider and compare the practical outcomes of return-to-the-land and
simple-life ideologies.
The study extends scholarship in this area by significantly re-appraising the
relationship between Morris's and Carpenter's back-to-the-land writing, and reinstating
Carpenter as a germinal influence. It also increases our understanding of the
values and function of the journals in the study, and establishes an insight into the
wider cultural assimilation of both writers' ideals
A multidomain outer membrane protein from Pasteurella multocida: Modelling and simulation studies of PmOmpA
No full textPmOmpA is a two-domain outer membrane protein from Pasteurella multocida. The N-terminal domain of PmOmpA is a homologue of the transmembrane ?-barrel domain of OmpA from Escherichia coli, whilst the C-terminal domain of PmOmpA is a homologue of the extra-membrane Neisseria meningitidis RmpM C-terminal domain. This enables a model of a complete two domain PmOmpA to be constructed and its conformational dynamics explored via MD simulations of the protein embedded within two different phospholipid bilayers (DMPC and DMPE). The conformational stability of the transmembrane ?-barrel is similar to that of a homology model of OprF from Pseudomonas aeruginosa in bilayer simulations. There is a degree of water penetration into the interior of the ?-barrel, suggestive of a possible transmembrane pore. Although the PmOmpA model is stable over 20 ns simulations, retaining its secondary structure and fold integrity throughout, substantial flexibility is observed in a short linker region between the N- and the C-terminal domains. At low ionic strength, the C-terminal domain moves to interact electrostatically with the lipid bilayer headgroups. This study demonstrates that computational approaches may be applied to more complex, multi-domain outer membrane proteins, rather than just to transmembrane ?-barrels, opening the possibility of in silico proteomics approaches to such proteins
Delph Carpenter, father of Colorado River treaties: text of Governor Ralph L. Carr's 1943 salute to Delph Carpenter
Get PDFSeptember 1991.Includes introductory material, text of Colorado River Compact.The rulebook for the Colorado River is the 1922 Colorado River Compact, a document now nearly 70 years old. Time said, "This critical document facilitated both the astonishing development of the West and the problems that followed as a result." The centerpiece of Delph Carpenter's career was the Colorado River Compact and the acknowledgement of his role came from no less a person than President Herbert Hoover. Hoover's admiration for the work of Carpenter is evident from the two letters included in the booklet. Not only was Delph Carpenter an institution in the field of western water law; he left a legacy through his son Donald, who became an attorney and accompanied his father to many water meetings including trips to see President Hoover. When Delph Carpenter became disabled with Parkinson's Disease but struggled to continue his work, his son Donald took care of his father's personal needs while he continued to work on the interstate water treaties. At the time that Governor Ralph Carr delivered the speech which is reprinted here, Donald was on the East Coast awaiting shipment to Europe in World War II. Ex-President Hoover arranged for Donald to attend the banquet. Donald Carpenter went on to a distinguished career as a district judge in Greeley, including presiding over the water court. Today's students of water resources management will benefit from the study of this speech and the vision held by Delph Carpenter and his peers about Western water management
OmpA: Gating and dynamics via molecular dynamics simulations
No full textOuter membrane proteins (OMPs) of Gram-negative bacteria have a variety of functions including passive transport, active transport, catalysis, pathogenesis and signal transduction. Whilst the structures of 25 OMPs are currently known, there is relatively little known about their dynamics in different environments. The outer membrane protein, OmpA from Escherichia coli has been studied extensively in different environments both experimentally and computationally, and thus provides an ideal test case for the study of the dynamics and environmental interactions of outer membrane proteins. We review molecular dynamics simulations of OmpA and its homologues in a variety of different environments and discuss possible mechanisms of pore gating. The transmembrane domain of E. coli OmpA shows subtle differences in dynamics and interactions between a detergent micelle and a lipid bilayer environment. Simulations of the crystallographic unit cell reveal a micelle-like network of detergent molecules interacting with the protein monomers. Simulation and modelling studies emphasise the role of an electrostatic-switch mechanism in the pore-gating mechanism. Simulation studies have been extended to comparative models of OmpA homologues from Pseudomonas aeruginosa (OprF) and Pasteurella multocida (PmOmpA), the latter model including the periplasmic C-terminal domain
Restricted use pesticides registered in Idaho
No full textBulletin no. 767 Moscow, Idaho :University of Idaho, College of Agriculture, Cooperative Extension System, 1994-08-01. Author(s): Carpenter, Gene P
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Elizabeth R. Carpenter
Get PDFA native of Hoboken, New Jersey, Emily S. McCain was already forty years old when she started publishing short stories in newspapers and magazines under the pen name Elizabeth R. Carpenter. Shortly afterward, she ventured into the field of screenwriting, where she established herself as a successful independent freelancer. By the mid-1910s, “Elizabeth R. Carpenter” was a prominent author at the peak of her career, and a celebrated figure in the burgeoning film industry. Sometimes also credited as E. R. Carpenter, she sold scenarios to major studios like Vitagraph, Edison, Kalem, and Lubin, and left behind a trail of praise in the early film press. But, despite her literary achievements, McCain kept her real identity well concealed, to the point that specialized film trade outlets, as well as film historians in the following decades, never referred to Carpenter by any other name or seemed aware that this was a pseudonym. Carpenter disappeared suddenly from the industry and press around 1919, leaving behind few clues about her life and identity. Putting a name to the person behind Carpenter has been possible only after the extensive research undertaken for this profile, which represents the first effort to shed light on the screenwriter’s real identity
IUTAM Symposium
No full textThe IUTAM Symposium on Flow in Collapsible Tubes and Past Other Highly Compliant Boundaries was held on 26-30 March, 2001, at the University of Warwick. As this was the first scientific meeting of its kind we considered it important to mark the occasion by producing a book. Accordingly, at the end of the Symposium the Scientific Committee met to discuss the most appropriate format for the book. We wished to avoid the format of the conventional conference book consisting of a large number of short articles of varying quality. It was agreed that instead we should produce a limited number of rigorously refereed and edited articles by selected participants who would aim to sum up the state of the art in their particular research area. The outcome is the present book. Peter W. Ca rpenter, Warwick Timothy J. Pedley, Cambridge May, 2002. VB SCIENTIFIC COMMITTEE Co-Chair: P.W. Carpenter, Engineering, Warwiek, UK Co-Chair: TJ. Pedley, DAMTP, Cambridge, UK V.V. Babenko, Hydromechanics, Kiev, Ukraine R. Bannasch, Bionik & Evolutionstechnik, TU Berlin, Germany C.D. Bertram, Biomedical Engineering, New South Wales, Australia M. Gad-el-Hak, Aerospace & Mechanical Engineering, Notre Dame, USA J.B. Grotberg, Biomedical Engineering, Michigan, USA. R.D. Kamm, Mechanical Engineering, MIT, USA Y. Matsuzaki, Aerospace Engineering, N agoya, Japan P.K. Sen, Applied Mechanics, IIT Delhi, India L. van Wijngaarden, Twente, Netherlands K-S. Yeo, Mechanical Engineering, NU Singapore
Self-assembly of a simple membrane protein: coarse-grained molecular dynamics simulations of the influenza M2 channel
No full textThe transmembrane (TM) domain of the M2 channel protein from influenza A is a homotetrameric bundle of ?-helices and provides a model system for computational approaches to self-assembly of membrane proteins. Coarse-grained molecular dynamics (CG-MD) simulations have been used to explore partitioning into a membrane of M2 TM helices during bilayer self-assembly from lipids. CG-MD is also used to explore tetramerization of preinserted M2 TM helices. The M2 helix monomer adopts a membrane spanning orientation in a lipid (DPPC) bilayer. Multiple extended CG-MD simulations (5 × 5 ?s) were used to study the tetramerization of inserted M2 helices. The resultant tetramers were evaluated in terms of the most populated conformations and the dynamics of their interconversion. This analysis reveals that the M2 tetramer has 2× rotationally symmetrical packing of the helices. The helices form a left-handed bundle, with a helix tilt angle of 16°. The M2 helix bundle generated by CG-MD was converted to an atomistic model. Simulations of this model reveal that the bundle's stability depends on the assumed protonation state of the H37 side chains. These simulations alongside comparison with recent x-ray (3BKD) and NMR (2RLF) structures of the M2 bundle suggest that the model yielded by CG-MD may correspond to a closed state of the channe
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