DOCSLIB.ORG

Lipid Bilayer Composition Modulates the Unfolding Free Energy of A

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lipid Bilayer Composition Modulates the Unfolding Free Energy of A Lipid bilayer composition modulates the unfolding free PNAS PLUS energy of a knotted α-helical membrane protein M. R. Sandersa, H. E. Findlaya, and P. J. Bootha,1 aDepartment of Chemistry, King’s College London, SE1 1DB London, United Kingdom Edited by David Baker, University of Washington, Seattle, WA, and approved January 12, 2018 (received for review August 18, 2017) α-Helical membrane proteins have eluded investigation of their gregation, most helical proteins are thought to insert directly into thermodynamic stability in lipid bilayers. Reversible denaturation the membrane cotranslationally with the assistance of the curves have enabled some headway in determining unfolding free translocon apparatus. Although the exact mechanism of mem- energies. However, these parameters have been limited to deter- brane protein insertion is unclear, the final stages of protein gent micelles or lipid bicelles, which do not possess the same me- folding are most likely to occur in the lipid bilayer (4, 5). Equally, chanical properties as lipid bilayers that comprise the basis of lipids can induce posttranslational repositioning of helices and natural membranes. We establish reversible unfolding of the protein orientation within the membrane (6, 7). If the unique membrane transporter LeuT in lipid bilayers, enabling the compar- folded state is an equilibrium structure, then it should be possible ison of apparent unfolding free energies in different lipid composi- to achieve the folded structure via other pathways, as has been demonstrated for example from coexpression (8), from reas- tions. LeuT is a bacterial ortholog of neurotransmitter transporters sembly of protein fragments (9), or from cell-free synthesis (10). and contains a knot within its 12-transmembrane helical structure. Moreover, it has proved possible to regain the folded structure of Urea is used as a denaturant for LeuT in proteoliposomes, resulting some membrane proteins from a partly denatured state in urea, in the loss of up to 30% helical structure depending upon the lipid by refolding directly into liposomes (11). Additionally, the sta- bilayer composition. Urea unfolding of LeuT in liposomes is revers- bility of some membrane proteins is such that they can be suc- ible, with refolding in the bilayer recovering the original helical cessfully refolded in detergent micelles or mixed detergent/lipid structure and transport activity. A linear dependence of the unfold- mixtures (11–13). These latter systems have enabled insight into ing free energy on urea concentration enables the free energy to be the thermodynamic stability of membrane proteins by translating extrapolated to zero denaturant. Increasing lipid headgroup charge the classical chemical denaturation approach of water-soluble BIOPHYSICS AND or chain lateral pressure increases the thermodynamic stability of proteins studies. A folded protein is denatured and a reversible COMPUTATIONAL BIOLOGY LeuT. The mechanical and charge properties of the bilayer also af- refolding reaction established such that the free energy of fect the ability of urea to denature the protein. Thus, we not only unfolding can be determined between the folded and chemically gain insight to the long–sought-after thermodynamic stability of an unfolded state. The initial approach for helical membrane pro- α-helical protein in a lipid bilayer but also provide a basis for studies teins used a partially denatured state in SDS and established an of the folding of knotted proteins in a membrane environment. equilibrium with a folded state in renaturing detergent micelles (14). The best-studied case is bacteriorhodopsin (bR) for which protein folding | membrane proteins | protein–lipid interactions folding rates and yields have been shown to be dependent on detergent, lipid dynamics, detergent/lipid concentrations, and lipid bilayer mechanics (3, 15–22). As a result, the unfolded state nowledge of the energetics of protein reactions is necessary actually changes over time and thus is not at equilibrium. A Kto generate physical descriptions of cellular processes. The comprehensive equilibrium and kinetic study overcame this and thermodynamic stability of a protein is a fundamental parameter. established a pseudoequilibrium over a specific time period; A third of all cellular proteins reside in membranes, and those nonetheless, extensive extrapolation to zero denaturant was re- with helical structures are ubiquitous across prokaryotes and eu- quired to attain a free energy of unfolding in the absence of SDS karyotes. The hydrophobic character of these proteins together (23, 24). More recently, a novel steric trapping approach was with their native membrane surroundings can make them experi- mentally challenging to study (1). As a result, there is little in- Significance formation on key properties, including folding from their primary amino sequences to the final functional structure. Several lines of Cells in our bodies sense and communicate with the outside evidence suggest that these functional states of native integral world via proteins embedded in membranes that surround the membrane proteins are equilibrium structures (2). However, to cells. As with all proteins, a fundamental parameter governing date there are no thermodynamic measurements of the helical their biological function is the inherent, thermodynamic stability membrane protein class in lipid bilayers. The few thermodynamic of the folded state. Surprisingly, there is no measure of this stability measurements that exist for helical membrane proteins thermodynamic stability in a lipid membrane for the ubiquitous are in detergent micelles or bicelles, which do not adequately class of membrane proteins with structures based on α-helices. reproduce the properties of the lipid membrane that surrounds We remedy this through the study of a protein related to the the proteins in cells. Evidence has emerged that charge and me- physiologically important membrane proteins that are partly chanical properties of the bilayer play an important role in the responsible for transmitting signals in the nervous system. We folding, stability, and function of helical proteins (3). Such prop- identify key properties of the surrounding lipid membrane that erties cannot be reproduced in micelles and only to a very limited regulate the thermodynamic stability of the protein. extent in bicelles. Studies are therefore needed in lipid bilayers to determine the extent to which the fold of a membrane protein is Author contributions: M.R.S., H.E.F., and P.J.B. designed research; M.R.S. performed re- dictated by the amino acid sequence and the surrounding lipid search; M.R.S. analyzed data; and M.R.S. and P.J.B. wrote the paper. membrane. This not only advances membrane protein folding The authors declare no conflict of interest. studies, by providing boundaries in which natural folding operates, This article is a PNAS Direct Submission. but gives a physical basis for factors that alter membrane protein Published under the PNAS license. stability and misfolding linked to disease. 1To whom correspondence should be addressed. Email: [email protected]. The hydrophobicity of membrane proteins means they have a This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. high propensity to aggregate in aqueous solutions. To avoid ag- 1073/pnas.1714668115/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1714668115 PNAS | Published online February 5, 2018 | E1799–E1808 Downloaded by guest on September 26, 2021 used, which employs different assumptions for equilibrium ther- modynamic determination and avoids denaturants, instead using streptavidin binding to the doubly biotinylated protein and in- ducing partial unfolding (25). Urea has also proven useful in de- naturing helical membrane proteins (11) and has moved the folding field forward to larger, more dynamic proteins; namely the 12-transmembrane (TM) major facilitator superfamily (MFS) (12, 26). These proteins are partially denatured by urea, and although the exact regions of the protein that are denatured are currently unknown, it seems likely that urea accesses aqueous exposed re- gions and those accessible via the substrate translocation site (11, 12, 26). Far-UV CD provides a categorical measure of the partly denatured state in terms of secondary structure loss. To demon- strate correct refolding, we combine regain of function, coupled with recovery of helical structure. Here, we extend chemical denaturation approaches on mem- brane transporter proteins to free-energy measurements in lipid bilayers. At present, there have been no successful measure- ments of the thermodynamic stability of helical membrane pro- teins in bilayers. There have been thermodynamic studies of TM Fig. 1. Crystal structure of LeuT in OG (PDB ID code 3GJD) taken from Quick helix oligomerization in bilayers, using a variety of methods et al. (39). A shows the full structure of the protein with the knot core based on steric trapping (27), cross-linking (28), FRET (29), and highlighted in blue, the slipknot loop in yellow, and the slipknot tail in green TOXCAT (based on Tox-R mediated activation of a chloram- from opposite viewpoints (B) taken from sequence data presented by knotprot database. phenicol acetyltransferase gene) (30, 31). The equilibrium chemical denaturation approach we use here, enables us to probe the influ- ence of the mechanical and charge properties of the lipid bilayer that key groundwork for further studies on how knots form at a mo-
Load more

Recommended publications
  • Customized Book List Life Science
    ABCD springer.com Springer Customized Book List Life Science FRANKFURT BOOKFAIR 2007 springer.com/booksellers Life Science 1 M.M. Abdelhaleem, University of Toronto, ON, Canada (Ed.) Transactions on Computational Single Molecules and Systems Biology VIII Nanotechnology Helicases Helicases are enzymes that utilize the energy derived The LNCS journal Transactions on Computation- This book focuses on recent advances in the rapid- from NTP hydrolysis to unwind double standed nu- al Systems Biology is devoted to inter- and multi- ly evolving field of single molecule research. These cleic acids. Significant progress has been achieved in disciplinary research in the fields of computer sci- advances are of importance for the investigation our understanding of the structure and molecular ence and life sciences and supports a paradigmat- of biopolymers and cellular biochemical reactions, mechanisms of helicases. The reader will find proto- ic shift in the techniques from computer and infor- and are essential to the development of quantita- cols utilized by leading experts in the field that span mation science to cope with the new challenges aris- tive biology. Written by leading experts in the field, different species and cover various biological pro- ing from the systems oriented point of view of bio- the articles cover a broad range of topics, including: cesses in which helicases are involved. This volume logical phenomena.  The six papers selected quantum photonics of organic dyes and inorgan- will be useful to students and researchers interested for this special issue are:Bio-inspired Network-Cen- ic nanoparticles their use in detecting properties of in this rapidly expanding filed.
    [Show full text]
  • Shape Dynamics and Lipid Hydrodynamics of Bilayer Membranes: Modeling, Simulation and Experiments
    Universitat Politecnica` de Catalunya Programa de Doctorat en Enginyeria Civil Departament de Matematica` Aplicada III Shape dynamics and lipid hydrodynamics of bilayer membranes: modeling, simulation and experiments by Mohammad Rahimi Doctoral Thesis Advisor: Marino Arroyo Barcelona, December 2012 Abstract Shape dynamics and lipid hydrodynamics of bilayer membranes: modeling, simulation and experiments Mohammad Rahimi Biological membranes are continuously brought out of equilibrium, as they shape organelles, package and transport cargo, or respond to external actions. The dy- namics of lipid membranes are very complex due to the tight interplay between the bilayer architecture, the shape dynamics, the rearrangement of the lipid molecules, and their interactions with adjacent structures. The main goal of the present work is to understand the dynamical shape deformations and reorganizations of lipid bilay- ers, including lipid hydrodynamics, and the mechanical shaping and stabilization of highly curved membrane structures. Towards this goal, we develop theory, simulation methods, and perform experiments. We formulate and numerically implement a continuum model of the shape dynam- ics and lipid hydrodynamics, which describes the bilayer by its mid-surface and by a lipid density field for each monolayer. In this model, the viscoelastic response of bilayers is determined by the stretching and curvature elasticity, and by the inter- monolayer friction and the membrane interfacial shear viscosity. In contrast with previous studies, our numerical approach incorporates the main physics, is fully non- linear, does not assume predefined shapes, and can access a wide range of time and length scales. We apply our model to describe the dynamics of biologically relevant experimental observations, which are insufficiently understood through simpler mod- els introducing geometrical and physical simplifications.
    [Show full text]
  • Influence of Global and Local Membrane
    membranes Article Influence of Global and Local Membrane Curvature on Mechanosensitive Ion Channels: A Finite Element Approach Omid Bavi 1,2, Charles D. Cox 2, Manouchehr Vossoughi 1,3, Reza Naghdabadi 1,4, Yousef Jamali 5,6 and Boris Martinac 2,7,* 1 Institute for Nanoscience and Nanotechnology, Sharif University of Technology, 89694-14588 Tehran, Iran; [email protected] (O.B.); [email protected] (M.V.); [email protected] (R.N.) 2 Molecular Cardiology and Biophysics Division/Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; [email protected] (O.B.); [email protected] (C.D.C.) 3 Biochemical & Bioenvironmental Research Center (BBRC), 89694-14588 Tehran, Iran 4 Department of Mechanical Engineering, Sharif University of Technology, 89694-14588 Tehran, Iran 5 Department of Mathematics and Bioscience, Tarbiat Modares University, Jalal Ale Ahmad Highway, 14115-111 Tehran, Iran; [email protected] 6 Computational physical Sciences Research Laboratory, School of Nano-Science, Institute for Research in Fundamental Sciences (IPM), 19395-5531 Tehran, Iran; [email protected] 7 St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW 2010, Australia * Correspondence: [email protected]; Tel.: +61-2-9295-8743; Fax: +61-2-9295-8770 Academic Editor: Serdar Kuyucak Received: 1 January 2016; Accepted: 25 January 2016; Published: 5 February 2016 Abstract: Mechanosensitive (MS) channels are ubiquitous molecular force sensors that respond to a number of different mechanical stimuli including tensile, compressive and shear stress. MS channels are also proposed to be molecular curvature sensors gating in response to bending in their local environment.
    [Show full text]
  • Atomic Force Microscopy Study on the Mechanics of Influenza Viruses and Liposomes
    Atomic force microscopy study on the mechanics of influenza viruses and liposomes Dissertation for the award of the degree “Doctor rerum naturalium” In the program of Physics of Biological and Complex Systems Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences of the Georg-August-Universität Göttingen submitted by Sai Li from Hubei, China Göttingen, 2012 Members of the Thesis Committee Dr. Iwan A.T. Schaap (Reviewer, Examination board) Atomic Force Microscopy group at the III. Physikalisches Institut Faculty of Physics Prof. Dr. Andreas Janshoff (Reviewer, Examination board) Institute for Physical Chemistry Faculty of Chemistry Prof. Dr. Christoph F. Schmidt (Examination board) III. Physikalisches Institut Faculty of Physics Prof. Dr. Jörg Enderlein (Examination board) III. Physikalisches Institut Faculty of Physics Prof. Dr. Sarah Köster (Examination board) Institute for X-Ray Physics Faculty of Physics Prof. Dr. Bert de Groot (Examination board) Computational Biomolecular Dynamics Group Max Planck Institute for Biophysical Chemistry Date of oral examination: November, 2012 II I, Sai Li, hereby certify that my doctoral thesis entitled “Atomic force microscopy study on the mechanics of influenza viruses and liposomes” has been written independently and with no other sources and aids than quoted. Signature: III IV Table of contents Abbreviations ........................................................................................................ 1 Abstract ................................................................................................................
    [Show full text]
  • Biophysical Implications of Lipid Bilayer Rheometry for Mechanosensitive Channels
    Biophysical implications of lipid bilayer rheometry for mechanosensitive channels Navid Bavia,b, Yoshitaka Nakayamab, Omid Bavic, Charles D. Coxb, Qing-Hua Qind, and Boris Martinaca,b,1 aSt. Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW 2010, Australia; bMolecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; cInstitute for Nanoscience and Nanotechnology, Sharif University of Technology, 8969414588 Tehran, Iran; and dResearch School of Engineering, Australian National University, Canberra, ACT 0200, Australia Edited by Ching Kung, University of Wisconsin–Madison, Madison, WI, and approved August 14, 2014 (received for review May 15, 2014) The lipid bilayer plays a crucial role in gating of mechanosensitive model, of including in the calculations the boundary conditions (MS) channels. Hence it is imperative to elucidate the rheological caused by a rigid cylindrical pipette and no assumption for volume properties of lipid membranes. Herein we introduce a framework conservation during MA. The material properties resulting from to characterize the mechanical properties of lipid bilayers by these models were imported separately into a continuum FE model combining micropipette aspiration (MA) with theoretical model- (Fig. S1 A–C). This permitted comparisons between the FE model ing. Our results reveal that excised liposome patch fluorometry is parameters and experimentally derived results to define the best superior to traditional cell-attached MA for measuring the intrinsic description of the continuum behavior of azolectin bilayers. Using our alternative models, we compare the membrane tension in an mechanical properties of lipid bilayers. The computational results ’ also indicate that unlike the uniform bilayer tension estimated by azolectin liposome patch estimated using Laplace slawwiththe ’ membrane tension obtained from our computations.
    [Show full text]
  • Lipid Bilayer Composition Modulates the Unfolding Free Energy of a Knotted Α-Helical Membrane Protein
    Lipid bilayer composition modulates the unfolding free PNAS PLUS energy of a knotted α-helical membrane protein M. R. Sandersa, H. E. Findlaya, and P. J. Bootha,1 aDepartment of Chemistry, King’s College London, SE1 1DB London, United Kingdom Edited by David Baker, University of Washington, Seattle, WA, and approved January 12, 2018 (received for review August 18, 2017) α-Helical membrane proteins have eluded investigation of their gregation, most helical proteins are thought to insert directly into thermodynamic stability in lipid bilayers. Reversible denaturation the membrane cotranslationally with the assistance of the curves have enabled some headway in determining unfolding free translocon apparatus. Although the exact mechanism of mem- energies. However, these parameters have been limited to deter- brane protein insertion is unclear, the final stages of protein gent micelles or lipid bicelles, which do not possess the same me- folding are most likely to occur in the lipid bilayer (4, 5). Equally, chanical properties as lipid bilayers that comprise the basis of lipids can induce posttranslational repositioning of helices and natural membranes. We establish reversible unfolding of the protein orientation within the membrane (6, 7). If the unique membrane transporter LeuT in lipid bilayers, enabling the compar- folded state is an equilibrium structure, then it should be possible ison of apparent unfolding free energies in different lipid composi- to achieve the folded structure via other pathways, as has been demonstrated for example from coexpression (8), from reas- tions. LeuT is a bacterial ortholog of neurotransmitter transporters sembly of protein fragments (9), or from cell-free synthesis (10).
    [Show full text]
  • Inclusion-Induced Bilayer Deformations: Effects of Monolayer Equilibrium Curvature
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Biophysical Journal Volume 79 November 2000 2583–2604 2583 Inclusion-Induced Bilayer Deformations: Effects of Monolayer Equilibrium Curvature Claus Nielsen*† and Olaf S. Andersen* *Department of Physiology and Biophysics, Cornell University, Weill Medical College, New York, New York 10021 USA, and †August Krogh Institute, University of Copenhagen, Copenhagen DK-2100, Denmark ABSTRACT The energetics of protein-induced bilayer deformation in systems with finite monolayer equilibrium curvature ⌬ were investigated using an elastic membrane model. In this model the bilayer deformation energy Gdef has two major components: a compression-expansion component and a splay-distortion component, which includes the consequences of a bilayer curvature frustration due to a monolayer equilibrium curvature, c0, that is different from zero. For any choice of bilayer ⌬ material constants, the value of Gdef depends on global bilayer properties, as described by the bilayer material constants, as well as the energetics of local lipid packing adjacent to the protein. We introduce this dependence on lipid packing through ϭ ⌬ the contact slope, s, at the protein-bilayer boundary. When c0 0, Gdef can be approximated as a biquadratic function of ⌬ ϭ 2 ϩ ϩ 2 s and the monolayer deformation at the protein/bilayer boundary, u0: Gdef a1u0 a2u0s a3s , where a1, a2, and a3 are functions of the bilayer thickness, the bilayer compression-expansion and splay-distortion moduli, and the inclusion radius ⌬ (this expression becomes exact when the Gaussian curvature component of Gdef is negligible). When c0 0, the curvature frustration contribution is determined by the choice of boundary conditions at the protein-lipid boundary (by the value of s), ⌬ ϭ and Gdef is the sum of the energy for c0 0 plus the curvature frustration-dependent contribution.
    [Show full text]
  • King's Research Portal
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by King's Research Portal King’s Research Portal DOI: 10.1088/0957-4484/27/49/494004 Document Version Peer reviewed version Link to publication record in King's Research Portal Citation for published version (APA): Miller, D. M., Findlay, H. E., Ces, O., Templer, R. H., & Booth, P. J. (2016). Light-activated control of protein channel assembly mediated by membrane mechanics. NANOTECHNOLOGY, 27(49), [494004]. DOI: 10.1088/0957-4484/27/49/494004 Citing this paper Please note that where the full-text provided on King's Research Portal is the Author Accepted Manuscript or Post-Print version this may differ from the final Published version. If citing, it is advised that you check and use the publisher's definitive version for pagination, volume/issue, and date of publication details. And where the final published version is provided on the Research Portal, if citing you are again advised to check the publisher's website for any subsequent corrections. General rights Copyright and moral rights for the publications made accessible in the Research Portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognize and abide by the legal requirements associated with these rights. •Users may download and print one copy of any publication from the Research Portal for the purpose of private study or research. •You may not further distribute the material or use it for any profit-making activity or commercial gain •You may freely distribute the URL identifying the publication in the Research Portal Take down policy If you believe that this document breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim.
    [Show full text]
  • Mechanics of Nuclear Membranes Ashutosh Agrawal1,* and Tanmay P
    © 2019. Published by The Company of Biologists Ltd | Journal of Cell Science (2019) 132, jcs229245. doi:10.1242/jcs.229245 REVIEW SUBJECT COLLECTION: EXPLORING THE NUCLEUS Mechanics of nuclear membranes Ashutosh Agrawal1,* and Tanmay P. Lele2,* ABSTRACT domain and INM Sad1/UNC-84 (SUN) proteins (Fig. 2). The SUN– Cellular nuclei are bound by two uniformly separated lipid membranes KASH complex is called the linker of nucleoskeleton and that are fused with each other at numerous donut-shaped pores. cytoskeleton (LINC) complex (Crisp et al., 2006; Majumder et al., These membranes are structurally supported by an array of distinct 2019; Starr and Fridolfsson, 2010). The nuclear lamina underlies the proteins with distinct mechanical functions. As a result, the nuclear nuclear membrane in most mammalian cell types and is composed of envelope possesses unique mechanical properties, which enables the nuclear lamins. In these cell types, the nuclear lamina may balance it to resist cytoskeletal forces. Here, we review studies that are a portion of forces transmitted by the LINC complex and mediate the beginning to provide quantitative insights into nuclear membrane mechanical response of the nucleus to these forces (Dahl et al., 2004; mechanics. We discuss how the mechanical properties of the fused Davidson and Lammerding, 2014). In addition, differences in the nuclear membranes mediate their response to mechanical forces hydrostatic pressure between the nucleoplasm and the perinuclear exerted on the nucleus and how structural reinforcement by different space can act on the INM, and the pressure difference between the nuclear proteins protects the nuclear membranes against rupture. We perinuclear space and the cytoplasm can act on the ONM.
    [Show full text]
  • Continuum and Atomistic Modeling of Lipid Membranes
    CONTINUUM AND ATOMISTIC MODELING OF LIPID MEMBRANES: BIOPHYSICS OF HAIR CELL MECHANOTRANSDUCTION A DISSERTATION SUBMITTED TO THE DEPARTMENT OF MECHANICAL ENGINEERING AND THE COMMITTEE ON GRADUATE STUDIES OF STANFORD UNIVERISTY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Jichul Kim December 2013 © 2013 by Jichul Kim. All Rights Reserved. Re-distributed by Stanford University under license with the author. This dissertation is online at: http://purl.stanford.edu/yn722bf7253 ii I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Peter Pinsky, Primary Adviser I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Charles Steele, Co-Adviser I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Wei Cai Approved for the Stanford University Committee on Graduate Studies. Patricia J. Gumport, Vice Provost for Graduate Education This signature page was generated electronically upon submission of this dissertation in electronic format. An original signed hard copy of the signature page is on file in University Archives. iii ABSTRACT A lipid bilayer membrane is not just a simple inert barrier of cells, but a dynamic structure which plays a crucial role in cell functioning. A force conveying role of the lipid membrane for mechanosensitive ion channels is now an accepted phenomenon across various mechanoreceptors.
    [Show full text]
  • Development of in Vitro Screening Approaches to Optimise Formulation Performance
    DEVELOPMENT OF IN VITRO SCREENING APPROACHES TO OPTIMISE FORMULATION PERFORMANCE. ANDRZEJ GALLAS, mgr farm. Thesis submitted to the University of Nottingham for the degree of Doctor of Philosophy. September 2013 Abstract. The pharmaceutical industry has been criticised for a lack of innovation associated with the drug discovery and development process, for example when compared with the computer or music industries. In fact, bringing a new medicine to the market requires, on average, the screening of up to 10 000 molecules, an expense in the range of $500 million-$2 billion and roughly 10-15 years of research. Such a situation not only has a direct impact on the health and life expectancy of every single human being on the planet, but also indicates that alternative strategies for drug development should be investigated. In this thesis, studies of direct formulation-membrane interactions, both in a high throughput (HT) manner and at a nanometre scale, were initially identified as an important approach that could offer advantages for in vitro-in vivo correlations of in-man drug behaviours. Subsequently, supported lipid bilayers (SLBs) of physiologically-relevant lipid compositions were indicated as experimental models of preference for pre-clinical drug development. For that reason, the characterisation and assessment of physicochemical and behavioural properties of the model SLBs at a nanometre scale, as well as development of an SLB microarray for HT applications were the focus of this research. Here, the optimisation and characterisation of model lipid films was performed using atomic force microscopy (AFM), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS).
    [Show full text]
  • Springer Handbook of Acoustics Thomas D
    AB2007 PRSRT-STD ABCD springer.com ABCD U.S. POSTAGE PAID SPRINGER 233 Spring Street New York, NY 10013 Springer NEWS Apress AIP Press American Institute of Physics Birkhäuser New York Copernicus Heidelberg Current Medicine Dordrecht Friends of ED London Want this by e-mail? Humana Press Tokyo Subscribe now to the monthly Lars Müller Library Books E-Newsletter: Boston Lavoisier-Intercept Basel springer.com/librarybooks Physica Verlag Get all the content of this catalog in PDF, Excel, and HTML. Berlin Springer-Praxis Hong Kong 10 The Royal Society of Chemistry Milan OCTOBER Springer Wien NewYork New Delhi Steinkopff Verlag 2007 Paris M1324 Vieweg springer.com Please visit springer.com/ebooks Springer News 10/2007 General Information Returns: Discount Key Returns must be in resaleable condition. Please include a copy of the original invoice P = Professional or packing slip along with your shipment. For your protection, we recommend all Springer eBook MC = Medicine/Clinical returns be sent via a traceable method. Damaged books must be reported within two MR = Medicine/Reference months of billing date. Springer reserves the right to reject any return that does not T = Trade follow the procedures detailed above. C = Computer Trade Collection gives Access to all L = Landolt-Bornstein Handbook Returns in the Americas (excluding Canada): S = Special Software Springer c/o Mercedes/ABC Distribution Center Springer Book Content Brooklyn Navy Yard; Bldg. 3 Sales and Service Brooklyn, NY 11205 Returns in Canada: Bookstore and Library Sales: Available directly from Springer or through a participating Springer Matt Conmy, National Sales Director c/o Georgetown Terminal Warehouse book wholesaler or journal agent.
    [Show full text]