17 results
The Gating Mechanism of Mechanosensitive Channels in Droplet Interface Bilayers
- Joseph S. Najem, Eric Freeman, Sergei Sukharev, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1722 / 2015
- Published online by Cambridge University Press:
- 16 June 2015, mrsf14-1722-f05-49
- Print publication:
- 2015
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MscL, a large-conductance mechanosensitive channel, is a ubiquitous osmolyte release valve that aids bacteria in surviving abrupt hypo-osmotic shocks. The large scale of its tension-driven opening transition makes it a strong candidate to serve as a transducer in novel stimuli-responsive biomolecular materials. In the previous work, a low-threshold gain-of-function V23T mutant of MscL produced a reliable activation behavior in a droplet interface bilayer (DIB) with applied axial droplet compression. Near the maximal compression, the aqueous droplets deform and the resulting increase in surface area leads to an increase in tension in the water-lipid-oil interface. This increase in tension is the product of the relative change in the droplet surface area and the elastic modulus of the DPhPC lipid monolayer (∼120 mN/m). This paper, presents a study of the physical processes that cause MscL gating in the DIB. Analysis of video during compression and relaxation of the droplets is utilized to estimate the change in the surface area of the droplet and the variation on monolayer surface tension. The monolayer surface tension is proportional to the area change of the droplet normalized to the original surface area. The results demonstrate that the area change in the droplet is negligible at frequencies above 1 Hz, but is approximately 2% at frequencies in the range of 100 mHz. In addition, at low frequencies (∼0.2 Hz) bilayer thinning occurs at maximum compression, proving an increase in bilayer tension. However, this study also shows that gating at frequencies higher than 0.2 Hz could be achieved through the application of high duty cycle oscillation (∼75%). The relative change in monolayer area increases significantly at higher duty cycle oscillations where the compression stroke is much faster than the relaxation stroke.
Mechanosensitive Channels Activity in a Droplet Interface Bilayer System
- Joseph Najem, Myles Dunlap, Sergei Sukharev, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1621 / 2014
- Published online by Cambridge University Press:
- 30 January 2014, pp. 171-176
- Print publication:
- 2014
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This paper presents the first attempts to study the large conductance mechano-sensitive channel (MscL) activity in an artificial droplet interface bilayer (DIB) system. A novel and simple technique is developed to characterize the behavior of an artificial lipid bilayer interface containing mechano-sensitive (MS) channels. The experimental setup is assembled on an inverted microscope and consists of two micropipettes filled with PEG-DMA hydrogel and containing Ag/AgCl wires, a cylindrical oil reservoir glued on top of a thin acrylic sheet, and a piezoelectric oscillator actuator. By using this technique, dynamic tension can be applied by oscillating axial motion of one droplet, producing deformation of both droplets and area changes of the DIB interface. The tension in the artificial membrane will cause the MS channels to gate, resulting in an increase in the conductance levels of the membrane. The results show that the MS channels are able to gate under an applied dynamic tension. Moreover, it can be concluded that the response of channel activity to mechanical stimuli is voltage-dependent and highly related to the frequency and amplitude of oscillations.
List of Contributors
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- By Leisy J. Abrego, Leo R. Chavez, Nicholas De Genova, Joanna Dreby, Marie Friedmann Marquardt, Tanya Golash-Boza, Roberto G. Gonzales, Luisa Laura Heredia, Josiah McC. Heyman, Bill Ong Hing, Pierrette Hondagneu-Sotelo, Daniel Kanstroom, Donald M. Kerwin, Paul G. Lewis, Cecilia Menjívar, Genevieve Negrón-Gonzales, Walter J. Nicholls, Cristian Paredes, Doris Marie Provine, Nestor Rodriguez, Jose Miguel Ruiz, Susanna J. Snyder, Manuel A. Vásquez
- Edited by Cecilia Menjívar, Arizona State University, Daniel Kanstroom, Boston College, Massachusetts
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- Book:
- Constructing Immigrant 'Illegality'
- Published online:
- 05 December 2013
- Print publication:
- 25 November 2013, pp ix-xiv
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Biomolecular material systems with encapsulated interface bilayers
- Stephen A. Sarles, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1301 / 2011
- Published online by Cambridge University Press:
- 28 January 2011, mrsf10-1301-pp10-02
- Print publication:
- 2011
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In this paper we present a novel approach for interface bilayer formation in which the uptake of an aqueous lipid vesicle solution by two polymeric hydrogels contained in a substrate causes the gels to swell so as to come into contact within an internal oil-filled region of the device. An interface bilayer, similar to those formed using the droplet interface bilayer (DIB) method, forms upon contact in oil between the lipid-encased ends of the two gels. Experimental measurements provide initial evidence that gel swelling enables automatic bilayer formation within a few minutes after the addition of lipid solution. The approach presented herein works toward the development of a new portable, easy-to-use screening platform that features tailored interface bilayers for a wide variety of screening applications.
Contributors
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- By Charles E. Argoff, Gerard A. Banez, Samantha Boris-Karpel, Barbara K. Bruce, Alexandra S. Bullough, Annmarie Cano, Victor T. Chang, Elizabeth A. Clark, Daniel J. Clauw, June L. Dahl, Tam K. Dao, Amber M. Davis, Courtney L. Dixon, Michael H. Ebert, Robin M. Gallagher, Gerald W. Grass, Carmen R. Green, Jay Gunkelman, Bradford D. Hare, Jennifer A. Haythornthwaite, Jaclyn Heller Issner, W. Michael Hooten, Mark P. Jensen, Mark E. Jones, Robert D. Kerns, Raphael J. Leo, Morris Maizels, Mary E. Murawski, Brooke Myers-Sorger, Akiko Okifuji, Renata Okonkwo, John D. Otis, Stacy C. Parenteau, Laura E. Pence, Donald B. Penzien, Donna B. Pincus, Ellyn Poltrock Stein, Wendy J. Quinton, Jeanetta C. Rains, M. Carrington Reid, Thomas J. Romano, Jeffrey D. Rome, Robert L. Ruff, Suzanne S. Ruff, Steven H. Sanders, Ingra Schellenberg, John J. Sellinger, Howard S. Smith, Brenda Stoelb, Jon Streltzer, Mark D. Sullivan, Kimberly S. Swanson, Gabriel Tan, Stephen Thielke, Beverly E. Thorn, Cynthia O. Townsend, Dennis C. Turk, Stephanie C. Wallio, Lawrence J. Weinberger, David A. Williams, Hilary Wilson
- Edited by Michael H. Ebert, Yale University, Connecticut, Robert D. Kerns, Yale University, Connecticut
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- Book:
- Behavioral and Psychopharmacologic Pain Management
- Published online:
- 10 January 2011
- Print publication:
- 25 November 2010, pp ix-xii
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- By Rose Teteki Abbey, K. C. Abraham, David Tuesday Adamo, LeRoy H. Aden, Efrain Agosto, Victor Aguilan, Gillian T. W. Ahlgren, Charanjit Kaur AjitSingh, Dorothy B E A Akoto, Giuseppe Alberigo, Daniel E. Albrecht, Ruth Albrecht, Daniel O. Aleshire, Urs Altermatt, Anand Amaladass, Michael Amaladoss, James N. Amanze, Lesley G. Anderson, Thomas C. Anderson, Victor Anderson, Hope S. Antone, María Pilar Aquino, Paula Arai, Victorio Araya Guillén, S. Wesley Ariarajah, Ellen T. Armour, Brett Gregory Armstrong, Atsuhiro Asano, Naim Stifan Ateek, Mahmoud Ayoub, John Alembillah Azumah, Mercedes L. García Bachmann, Irena Backus, J. Wayne Baker, Mieke Bal, Lewis V. Baldwin, William Barbieri, António Barbosa da Silva, David Basinger, Bolaji Olukemi Bateye, Oswald Bayer, Daniel H. Bays, Rosalie Beck, Nancy Elizabeth Bedford, Guy-Thomas Bedouelle, Chorbishop Seely Beggiani, Wolfgang Behringer, Christopher M. Bellitto, Byard Bennett, Harold V. Bennett, Teresa Berger, Miguel A. Bernad, Henley Bernard, Alan E. Bernstein, Jon L. Berquist, Johannes Beutler, Ana María Bidegain, Matthew P. Binkewicz, Jennifer Bird, Joseph Blenkinsopp, Dmytro Bondarenko, Paulo Bonfatti, Riet en Pim Bons-Storm, Jessica A. Boon, Marcus J. Borg, Mark Bosco, Peter C. Bouteneff, François Bovon, William D. Bowman, Paul S. Boyer, David Brakke, Richard E. Brantley, Marcus Braybrooke, Ian Breward, Ênio José da Costa Brito, Jewel Spears Brooker, Johannes Brosseder, Nicholas Canfield Read Brown, Robert F. Brown, Pamela K. Brubaker, Walter Brueggemann, Bishop Colin O. Buchanan, Stanley M. Burgess, Amy Nelson Burnett, J. Patout Burns, David B. Burrell, David Buttrick, James P. Byrd, Lavinia Byrne, Gerado Caetano, Marcos Caldas, Alkiviadis Calivas, William J. Callahan, Salvatore Calomino, Euan K. Cameron, William S. Campbell, Marcelo Ayres Camurça, Daniel F. Caner, Paul E. Capetz, Carlos F. Cardoza-Orlandi, Patrick W. Carey, Barbara Carvill, Hal Cauthron, Subhadra Mitra Channa, Mark D. Chapman, James H. Charlesworth, Kenneth R. Chase, Chen Zemin, Luciano Chianeque, Philip Chia Phin Yin, Francisca H. Chimhanda, Daniel Chiquete, John T. Chirban, Soobin Choi, Robert Choquette, Mita Choudhury, Gerald Christianson, John Chryssavgis, Sejong Chun, Esther Chung-Kim, Charles M. A. Clark, Elizabeth A. Clark, Sathianathan Clarke, Fred Cloud, John B. Cobb, W. Owen Cole, John A Coleman, John J. Collins, Sylvia Collins-Mayo, Paul K. Conkin, Beth A. Conklin, Sean Connolly, Demetrios J. Constantelos, Michael A. Conway, Paula M. Cooey, Austin Cooper, Michael L. Cooper-White, Pamela Cooper-White, L. William Countryman, Sérgio Coutinho, Pamela Couture, Shannon Craigo-Snell, James L. Crenshaw, David Crowner, Humberto Horacio Cucchetti, Lawrence S. Cunningham, Elizabeth Mason Currier, Emmanuel Cutrone, Mary L. Daniel, David D. Daniels, Robert Darden, Rolf Darge, Isaiah Dau, Jeffry C. Davis, Jane Dawson, Valentin Dedji, John W. de Gruchy, Paul DeHart, Wendy J. Deichmann Edwards, Miguel A. De La Torre, George E. Demacopoulos, Thomas de Mayo, Leah DeVun, Beatriz de Vasconcellos Dias, Dennis C. Dickerson, John M. Dillon, Luis Miguel Donatello, Igor Dorfmann-Lazarev, Susanna Drake, Jonathan A. Draper, N. Dreher Martin, Otto Dreydoppel, Angelyn Dries, A. J. Droge, Francis X. D'Sa, Marilyn Dunn, Nicole Wilkinson Duran, Rifaat Ebied, Mark J. Edwards, William H. Edwards, Leonard H. Ehrlich, Nancy L. Eiesland, Martin Elbel, J. Harold Ellens, Stephen Ellingson, Marvin M. Ellison, Robert Ellsberg, Jean Bethke Elshtain, Eldon Jay Epp, Peter C. Erb, Tassilo Erhardt, Maria Erling, Noel Leo Erskine, Gillian R. Evans, Virginia Fabella, Michael A. Fahey, Edward Farley, Margaret A. Farley, Wendy Farley, Robert Fastiggi, Seena Fazel, Duncan S. Ferguson, Helwar Figueroa, Paul Corby Finney, Kyriaki Karidoyanes FitzGerald, Thomas E. FitzGerald, John R. Fitzmier, Marie Therese Flanagan, Sabina Flanagan, Claude Flipo, Ronald B. Flowers, Carole Fontaine, David Ford, Mary Ford, Stephanie A. Ford, Jim Forest, William Franke, Robert M. Franklin, Ruth Franzén, Edward H. Friedman, Samuel Frouisou, Lorelei F. Fuchs, Jojo M. Fung, Inger Furseth, Richard R. Gaillardetz, Brandon Gallaher, China Galland, Mark Galli, Ismael García, Tharscisse Gatwa, Jean-Marie Gaudeul, Luis María Gavilanes del Castillo, Pavel L. Gavrilyuk, Volney P. Gay, Metropolitan Athanasios Geevargis, Kondothra M. George, Mary Gerhart, Simon Gikandi, Maurice Gilbert, Michael J. Gillgannon, Verónica Giménez Beliveau, Terryl Givens, Beth Glazier-McDonald, Philip Gleason, Menghun Goh, Brian Golding, Bishop Hilario M. Gomez, Michelle A. Gonzalez, Donald K. Gorrell, Roy Gottfried, Tamara Grdzelidze, Joel B. Green, Niels Henrik Gregersen, Cristina Grenholm, Herbert Griffiths, Eric W. Gritsch, Erich S. Gruen, Christoffer H. Grundmann, Paul H. Gundani, Jon P. Gunnemann, Petre Guran, Vidar L. Haanes, Jeremiah M. Hackett, Getatchew Haile, Douglas John Hall, Nicholas Hammond, Daphne Hampson, Jehu J. Hanciles, Barry Hankins, Jennifer Haraguchi, Stanley S. Harakas, Anthony John Harding, Conrad L. Harkins, J. William Harmless, Marjory Harper, Amir Harrak, Joel F. Harrington, Mark W. Harris, Susan Ashbrook Harvey, Van A. Harvey, R. Chris Hassel, Jione Havea, Daniel Hawk, Diana L. Hayes, Leslie Hayes, Priscilla Hayner, S. Mark Heim, Simo Heininen, Richard P. Heitzenrater, Eila Helander, David Hempton, Scott H. Hendrix, Jan-Olav Henriksen, Gina Hens-Piazza, Carter Heyward, Nicholas J. Higham, David Hilliard, Norman A. Hjelm, Peter C. Hodgson, Arthur Holder, M. Jan Holton, Dwight N. Hopkins, Ronnie Po-chia Hsia, Po-Ho Huang, James Hudnut-Beumler, Jennifer S. Hughes, Leonard M. Hummel, Mary E. Hunt, Laennec Hurbon, Mark Hutchinson, Susan E. Hylen, Mary Beth Ingham, H. Larry Ingle, Dale T. Irvin, Jon Isaak, Paul John Isaak, Ada María Isasi-Díaz, Hans Raun Iversen, Margaret C. Jacob, Arthur James, Maria Jansdotter-Samuelsson, David Jasper, Werner G. Jeanrond, Renée Jeffery, David Lyle Jeffrey, Theodore W. Jennings, David H. Jensen, Robin Margaret Jensen, David Jobling, Dale A. Johnson, Elizabeth A. Johnson, Maxwell E. Johnson, Sarah Johnson, Mark D. Johnston, F. Stanley Jones, James William Jones, John R. Jones, Alissa Jones Nelson, Inge Jonsson, Jan Joosten, Elizabeth Judd, Mulambya Peggy Kabonde, Robert Kaggwa, Sylvester Kahakwa, Isaac Kalimi, Ogbu U. Kalu, Eunice Kamaara, Wayne C. Kannaday, Musimbi Kanyoro, Veli-Matti Kärkkäinen, Frank Kaufmann, Léon Nguapitshi Kayongo, Richard Kearney, Alice A. Keefe, Ralph Keen, Catherine Keller, Anthony J. Kelly, Karen Kennelly, Kathi Lynn Kern, Fergus Kerr, Edward Kessler, George Kilcourse, Heup Young Kim, Kim Sung-Hae, Kim Yong-Bock, Kim Yung Suk, Richard King, Thomas M. King, Robert M. Kingdon, Ross Kinsler, Hans G. Kippenberg, Cheryl A. Kirk-Duggan, Clifton Kirkpatrick, Leonid Kishkovsky, Nadieszda Kizenko, Jeffrey Klaiber, Hans-Josef Klauck, Sidney Knight, Samuel Kobia, Robert Kolb, Karla Ann Koll, Heikki Kotila, Donald Kraybill, Philip D. W. Krey, Yves Krumenacker, Jeffrey Kah-Jin Kuan, Simanga R. Kumalo, Peter Kuzmic, Simon Shui-Man Kwan, Kwok Pui-lan, André LaCocque, Stephen E. Lahey, John Tsz Pang Lai, Emiel Lamberts, Armando Lampe, Craig Lampe, Beverly J. Lanzetta, Eve LaPlante, Lizette Larson-Miller, Ariel Bybee Laughton, Leonard Lawlor, Bentley Layton, Robin A. Leaver, Karen Lebacqz, Archie Chi Chung Lee, Marilyn J. Legge, Hervé LeGrand, D. L. LeMahieu, Raymond Lemieux, Bill J. Leonard, Ellen M. Leonard, Outi Leppä, Jean Lesaulnier, Nantawan Boonprasat Lewis, Henrietta Leyser, Alexei Lidov, Bernard Lightman, Paul Chang-Ha Lim, Carter Lindberg, Mark R. Lindsay, James R. Linville, James C. Livingston, Ann Loades, David Loades, Jean-Claude Loba-Mkole, Lo Lung Kwong, Wati Longchar, Eleazar López, David W. Lotz, Andrew Louth, Robin W. Lovin, William Luis, Frank D. Macchia, Diarmaid N. J. MacCulloch, Kirk R. MacGregor, Marjory A. MacLean, Donald MacLeod, Tomas S. Maddela, Inge Mager, Laurenti Magesa, David G. Maillu, Fortunato Mallimaci, Philip Mamalakis, Kä Mana, Ukachukwu Chris Manus, Herbert Robinson Marbury, Reuel Norman Marigza, Jacqueline Mariña, Antti Marjanen, Luiz C. L. Marques, Madipoane Masenya (ngwan'a Mphahlele), Caleb J. D. Maskell, Steve Mason, Thomas Massaro, Fernando Matamoros Ponce, András Máté-Tóth, Odair Pedroso Mateus, Dinis Matsolo, Fumitaka Matsuoka, John D'Arcy May, Yelena Mazour-Matusevich, Theodore Mbazumutima, John S. McClure, Christian McConnell, Lee Martin McDonald, Gary B. McGee, Thomas McGowan, Alister E. McGrath, Richard J. McGregor, John A. McGuckin, Maud Burnett McInerney, Elsie Anne McKee, Mary B. McKinley, James F. McMillan, Ernan McMullin, Kathleen E. McVey, M. Douglas Meeks, Monica Jyotsna Melanchthon, Ilie Melniciuc-Puica, Everett Mendoza, Raymond A. Mentzer, William W. Menzies, Ina Merdjanova, Franziska Metzger, Constant J. Mews, Marvin Meyer, Carol Meyers, Vasile Mihoc, Gunner Bjerg Mikkelsen, Maria Inêz de Castro Millen, Clyde Lee Miller, Bonnie J. Miller-McLemore, Alexander Mirkovic, Paul Misner, Nozomu Miyahira, R. W. L. Moberly, Gerald Moede, Aloo Osotsi Mojola, Sunanda Mongia, Rebeca Montemayor, James Moore, Roger E. Moore, Craig E. Morrison O.Carm, Jeffry H. Morrison, Keith Morrison, Wilson J. Moses, Tefetso Henry Mothibe, Mokgethi Motlhabi, Fulata Moyo, Henry Mugabe, Jesse Ndwiga Kanyua Mugambi, Peggy Mulambya-Kabonde, Robert Bruce Mullin, Pamela Mullins Reaves, Saskia Murk Jansen, Heleen L. Murre-Van den Berg, Augustine Musopole, Isaac M. T. Mwase, Philomena Mwaura, Cecilia Nahnfeldt, Anne Nasimiyu Wasike, Carmiña Navia Velasco, Thulani Ndlazi, Alexander Negrov, James B. Nelson, David G. Newcombe, Carol Newsom, Helen J. Nicholson, George W. E. Nickelsburg, Tatyana Nikolskaya, Damayanthi M. A. Niles, Bertil Nilsson, Nyambura Njoroge, Fidelis Nkomazana, Mary Beth Norton, Christian Nottmeier, Sonene Nyawo, Anthère Nzabatsinda, Edward T. Oakes, Gerald O'Collins, Daniel O'Connell, David W. Odell-Scott, Mercy Amba Oduyoye, Kathleen O'Grady, Oyeronke Olajubu, Thomas O'Loughlin, Dennis T. Olson, J. Steven O'Malley, Cephas N. Omenyo, Muriel Orevillo-Montenegro, César Augusto Ornellas Ramos, Agbonkhianmeghe E. Orobator, Kenan B. Osborne, Carolyn Osiek, Javier Otaola Montagne, Douglas F. Ottati, Anna May Say Pa, Irina Paert, Jerry G. Pankhurst, Aristotle Papanikolaou, Samuele F. Pardini, Stefano Parenti, Peter Paris, Sung Bae Park, Cristián G. Parker, Raquel Pastor, Joseph Pathrapankal, Daniel Patte, W. Brown Patterson, Clive Pearson, Keith F. Pecklers, Nancy Cardoso Pereira, David Horace Perkins, Pheme Perkins, Edward N. Peters, Rebecca Todd Peters, Bishop Yeznik Petrossian, Raymond Pfister, Peter C. Phan, Isabel Apawo Phiri, William S. F. Pickering, Derrick G. Pitard, William Elvis Plata, Zlatko Plese, John Plummer, James Newton Poling, Ronald Popivchak, Andrew Porter, Ute Possekel, James M. Powell, Enos Das Pradhan, Devadasan Premnath, Jaime Adrían Prieto Valladares, Anne Primavesi, Randall Prior, María Alicia Puente Lutteroth, Eduardo Guzmão Quadros, Albert Rabil, Laurent William Ramambason, Apolonio M. Ranche, Vololona Randriamanantena Andriamitandrina, Lawrence R. Rast, Paul L. Redditt, Adele Reinhartz, Rolf Rendtorff, Pål Repstad, James N. Rhodes, John K. Riches, Joerg Rieger, Sharon H. Ringe, Sandra Rios, Tyler Roberts, David M. Robinson, James M. Robinson, Joanne Maguire Robinson, Richard A. H. Robinson, Roy R. Robson, Jack B. Rogers, Maria Roginska, Sidney Rooy, Rev. Garnett Roper, Maria José Fontelas Rosado-Nunes, Andrew C. Ross, Stefan Rossbach, François Rossier, John D. Roth, John K. Roth, Phillip Rothwell, Richard E. Rubenstein, Rosemary Radford Ruether, Markku Ruotsila, John E. Rybolt, Risto Saarinen, John Saillant, Juan Sanchez, Wagner Lopes Sanchez, Hugo N. Santos, Gerhard Sauter, Gloria L. Schaab, Sandra M. Schneiders, Quentin J. Schultze, Fernando F. Segovia, Turid Karlsen Seim, Carsten Selch Jensen, Alan P. F. Sell, Frank C. Senn, Kent Davis Sensenig, Damían Setton, Bal Krishna Sharma, Carolyn J. Sharp, Thomas Sheehan, N. Gerald Shenk, Christian Sheppard, Charles Sherlock, Tabona Shoko, Walter B. Shurden, Marguerite Shuster, B. Mark Sietsema, Batara Sihombing, Neil Silberman, Clodomiro Siller, Samuel Silva-Gotay, Heikki Silvet, John K. Simmons, Hagith Sivan, James C. Skedros, Abraham Smith, Ashley A. Smith, Ted A. Smith, Daud Soesilo, Pia Søltoft, Choan-Seng (C. S.) Song, Kathryn Spink, Bryan Spinks, Eric O. Springsted, Nicolas Standaert, Brian Stanley, Glen H. Stassen, Karel Steenbrink, Stephen J. Stein, Andrea Sterk, Gregory E. Sterling, Columba Stewart, Jacques Stewart, Robert B. Stewart, Cynthia Stokes Brown, Ken Stone, Anne Stott, Elizabeth Stuart, Monya Stubbs, Marjorie Hewitt Suchocki, David Kwang-sun Suh, Scott W. Sunquist, Keith Suter, Douglas Sweeney, Charles H. Talbert, Shawqi N. Talia, Elsa Tamez, Joseph B. Tamney, Jonathan Y. Tan, Yak-Hwee Tan, Kathryn Tanner, Feiya Tao, Elizabeth S. Tapia, Aquiline Tarimo, Claire Taylor, Mark Lewis Taylor, Bishop Abba Samuel Wolde Tekestebirhan, Eugene TeSelle, M. Thomas Thangaraj, David R. Thomas, Andrew Thornley, Scott Thumma, Marcelo Timotheo da Costa, George E. “Tink” Tinker, Ola Tjørhom, Karen Jo Torjesen, Iain R. Torrance, Fernando Torres-Londoño, Archbishop Demetrios [Trakatellis], Marit Trelstad, Christine Trevett, Phyllis Trible, Johannes Tromp, Paul Turner, Robert G. Tuttle, Archbishop Desmond Tutu, Peter Tyler, Anders Tyrberg, Justin Ukpong, Javier Ulloa, Camillus Umoh, Kristi Upson-Saia, Martina Urban, Monica Uribe, Elochukwu Eugene Uzukwu, Richard Vaggione, Gabriel Vahanian, Paul Valliere, T. J. Van Bavel, Steven Vanderputten, Peter Van der Veer, Huub Van de Sandt, Louis Van Tongeren, Luke A. Veronis, Noel Villalba, Ramón Vinke, Tim Vivian, David Voas, Elena Volkova, Katharina von Kellenbach, Elina Vuola, Timothy Wadkins, Elaine M. Wainwright, Randi Jones Walker, Dewey D. Wallace, Jerry Walls, Michael J. Walsh, Philip Walters, Janet Walton, Jonathan L. Walton, Wang Xiaochao, Patricia A. Ward, David Harrington Watt, Herold D. Weiss, Laurence L. Welborn, Sharon D. Welch, Timothy Wengert, Traci C. West, Merold Westphal, David Wetherell, Barbara Wheeler, Carolinne White, Jean-Paul Wiest, Frans Wijsen, Terry L. Wilder, Felix Wilfred, Rebecca Wilkin, Daniel H. Williams, D. Newell Williams, Michael A. Williams, Vincent L. Wimbush, Gabriele Winkler, Anders Winroth, Lauri Emílio Wirth, James A. Wiseman, Ebba Witt-Brattström, Teofil Wojciechowski, John Wolffe, Kenman L. Wong, Wong Wai Ching, Linda Woodhead, Wendy M. Wright, Rose Wu, Keith E. Yandell, Gale A. Yee, Viktor Yelensky, Yeo Khiok-Khng, Gustav K. K. Yeung, Angela Yiu, Amos Yong, Yong Ting Jin, You Bin, Youhanna Nessim Youssef, Eliana Yunes, Robert Michael Zaller, Valarie H. Ziegler, Barbara Brown Zikmund, Joyce Ann Zimmerman, Aurora Zlotnik, Zhuo Xinping
- Edited by Daniel Patte, Vanderbilt University, Tennessee
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- Book:
- The Cambridge Dictionary of Christianity
- Published online:
- 05 August 2012
- Print publication:
- 20 September 2010, pp xi-xliv
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Electrical Impedance Analysis of Phospholipid Bilayer Membranes for Enabling Engineering Design of Bio-based Devices
- Stephen A. Sarles, Vishnu B. Sundaresan, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1061 / 2007
- Published online by Cambridge University Press:
- 01 February 2011, 1061-MM03-18
- Print publication:
- 2007
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Recent research at Virginia Tech have shown that active transporter proteins reconstituted into suspended bilayer lipid membranes (BLMs) formed across an array of pores in synthetic substrates can convert chemical energy available in adenosine triphosphate (ATP) into electricity. Experimental results from this work show that this system—called BioCell—is capable of 1.7μW of electrical power per square centimeter of BLM area and per 15μL of ATPase enzyme. In support of such a system, the lipid membrane, as host to active biological proteins and channels, must be formed evenly across a porous substrate, remain stable and yet fluid-like for protein folding and activation, and provide sufficient electrical insulation. We report on the formation and characterization using electrical impedance spectroscopy (EIS) of BLMs formed across two types of porous substrates: polycarbonate filters and single-aperture silicon substrates. Equivalent electrical circuits describing the lipid membranes and their supporting substrates are approximated to fit the measured responses. The results show that BLMs formed in some but not all of the 400nm pores of the filters, while the formation of BLMs on the single-aperture silicon substrates was much more consistent.
Failure Characteristics of Bilayer Lipid Membranes (BLMs) Formed over a Single Pore
- David Hopkinson, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1061 / 2007
- Published online by Cambridge University Press:
- 01 February 2011, 1061-MM03-19
- Print publication:
- 2007
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A new methodology has been developed to measure the maximum pressure that can be withstood by a bilayer lipid membrane (BLM) formed over porous substrates. A custom test fixture was fabricated to pressurize BLMs in very fine increasing increments until they fail. This experiment was performed on 1-Stearoyl-2-Oleoyl-sn-Glycero-3-Phosphatidylocholine (SOPC) BLMs formed over polycarbonate substrates with a single pore ranging from 5 to 20 microns in diameter. Failure pressure was found to be inversely proportional to pore diameter. The same set of experiments was repeated for BLMs that were formed from a mixture of SOPC and 50 mol% cholesterol (CHOL). The presence of cholesterol was found to increase the failure pressure of the BLMs by 56% on average. A model of the characteristic pressure curve from this experiment was developed based on the pressurization and flow of fluid through a porous substrate. The model was found to accurately fit the experimental pressure curves.
Bioenergetics and mechanical actuation analysis with membrane transport experiments for use in biomimetic nastic structures
- Luke Matthews, Vishnu Baba Sundaresan, Victor Giurgiutiu, Donald J. Leo
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- Journal:
- Journal of Materials Research / Volume 21 / Issue 8 / August 2006
- Published online by Cambridge University Press:
- 01 August 2006, pp. 2058-2067
- Print publication:
- August 2006
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Nastic structures are synthetic constructs capable of controllable deformation and shape change similar to plant motility, designed to imitate the biological process of nastic movement found in plants. This paper considers the mechanics and bioenergetics of a prototype nastic structure system consisting of an array of cylindrical microhydraulic actuators embedded in a polymeric plate. Non-uniform expansion/contraction of the actuators in the array may yield an overall shape change resulting in structural morphing. Actuator expansion/contraction is achieved through pressure changes produced by active transport across a bilayer membrane. The active transport process relies on ion-channel proteins that pump sucrose and water molecules across a plasma membrane against the pressure gradient. The energy required by this process is supplied by the hydrolysis of adenosine triphosphate. After reviewing the biochemistry and bioenergetics of the active transport process, the paper presents an analysis of the microhydraulic actuator mechanics predicting the resulting displacement and output energy. Experimental demonstration of fluid transport through a protein transporter follows this discussion. The bilayer membrane is formed from 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine lipids to support the AtSUT4 H+-sucrose cotransporter.
Microhydraulic Actuation Using Biological Ion Transporters Reconstituted on Artificial BLM
- Vishnu Baba Sundaresan, Donald J Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 944 / 2006
- Published online by Cambridge University Press:
- 01 February 2011, 0944-AA02-02
- Print publication:
- 2006
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Plants and animals have the natural ability to exhibit force through controlled pressurization of cellular compartments. The mechanism through which force is generated is powered by biological fuels. The process involves moving ions against an established concentration gradient expending free energy from bio-fuels like Adenosine-tri-phosphate (ATP), kinesin etc., Materials exhibiting deformation using biological processes are called Nastic materials. The functional component in mass transfer across the cell boundary is the ion transporter embedded in cell membranes. The ion transporters which are complex protein molecules, move ions and water molecules for an applied chemical or electrical stimulus. The bio-inspired microhydraulic actuator uses the same functional component in plant cells reconstituted on a planar bilayer lipid membrane (BLM) formed from purified lipids. The protein transporters pump ions and fluid into an enclosed cavity to cause deformation. The controlled fluid transport through AtSUT4(proton-sucrose co-transporter extracted from Arabidopsis thaliana) reconstituted on a 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) BLM on porous lead silicate glass plate driven by a proton gradient demonstrated the ability to move fluid across the membrane. This article discusses a prototype microhydraulic actuator that increases in thickness for an applied pH and sucrose concentration gradient.
Stack of BioCells Converting ATP to Electrical Power and Possible Applications
- Vishnu Baba Sundaresan, Stephen Andrew Sarles, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 950 / 2006
- Published online by Cambridge University Press:
- 01 February 2011, 0950-D01-03
- Print publication:
- 2006
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Plant and animals convert absorbed nutrients into the most readily available form of biochemical energy in cells - Adenosine triphosphate (ATP). Ion transporter proteins in the cell membranes hydrolyze ATP and use the energy from the reaction for ion transport across cell membranes. The BioCell is an energy conversion device inspired by ion transport through cell membranes that uses a proton-sucrose cotransporter (SUT4) to convert the chemical energy in ATP into electrical energy. Experiments on a single cell demonstrated that the BioCell behaves like a constant current power source with 10 - 22 kΩ internal resistance. The single cell developed a peak power of 0.7 μW per cm2 of bilayer lipid membrane (BLM) area reconstituted with 1 mg of SUT4 and 1 μl of ATP-ase at 10 kΩ load in the external circuit. The actual peak power output from the cell was 160 nW for a BLM area of 0.079 cm2 carrying 0.2 mg of SUT4 and 15 μl of ATP-ase. The 160 nW of electrical power that could be sourced from the cell with a 10 kΩ load (41 mV and 4 μA) is not sufficient to run a low power electronic device and needs to be scaled up to few microwatts. This article discusses our experimental results from stacking a BioCell in series and parallel to develop higher stack voltage and current. We observe that the cell voltage adds linearly by connecting the BioCells in series and a 10-cell stack developed a peak power of 750 nW (500 mV @ 2.5 μA observed at 265 kΩ. The peak power from the stack by connecting the cells in parallel was 1.4 μW (125 mV and 11.2 μA) at 1kΩ. The experimental results demonstrate that the power from a single cell can be scaled by connecting them in series and in parallel without appreciable losses. A survey of electronic devices indicated that a minimum of 20 μW will be required to run a demonstration application from a stack and also gives us the direction to scale the power output from a single cell.
Continuum Modeling of Bilayer Lipid Membranes
- Raffaella De Vita, David Hopkinson, Vishnu B. Sundaresan, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 924 / 2006
- Published online by Cambridge University Press:
- 01 February 2011, 0924-Z08-03
- Print publication:
- 2006
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A continuum model is used for the description of the mechanical response of bilayer lipid membranes (BLMs) subjected to hydrostatic pressure. The model is formulated under the assumption that the BLMs are Smectic A liquid crystals. The mean orientation of the amphiphilic molecules is postulated to be perpendicular to the lipid layers and each layer is idealized as a two dimensional liquid. The permeation process governs the motion of the molecules through the smectic layers. The approach taken in this study is based on the seminal works of Helfrich [1] and de Gennes [2] on Smectic A liquid crystals. The failure process of the BLMs, which is observed in the experimental studies, is considered to be due to extrusion of the BLMs through the pores of the polycarbonate filters.
Chemo-electrical energy conversion of Adenosine triphosphate in a Biological Ion Transporter
- Vishnu Baba Sundaresan, Stephen Andrew Sarles, Brian J Goode, Donald J Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 949 / 2006
- Published online by Cambridge University Press:
- 01 February 2011, 0949-C02-02
- Print publication:
- 2006
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Ion transport across cell membranes happens through protein channels and pumps expending concentration gradients, electrical gradients and energy from chemical reactions. Ion exchange in cell membranes is responsible for nutrient transport from production sites to where they are broken down to release energy. Sucrose transport is vital for growth in higher plants and recent research has led to the discovery of a class of sugar carriers called SUT4. The SUT4 transporter is a low affinity, high capacity proton-sucrose transporter that participates in long distance sucrose transport in higher plants. We demonstrated the possibility to use purified SUT4 transporter proteins — with the genetic code from Arabidopsis thaliana expressed on yeast cells — for fluid transport driven by pH gradient and from exergonic ATP hydrolysis reaction in the presence of ATP-ase enzyme. The SUT4 proteins were reconstituted on a planar bilayer lipid membrane formed from 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) phospholipids on a porous substrate. This article builds upon our previous work to harness energy from the ATP-ase reaction using SUT4 to produce a proton current through SUT4 and demonstrates the technical feasibility to generate electrical current in an external circuit. The results from our characterization experiments on a single cell demonstrate that the power source behaves like a constant current power source with an internal resistance of 10-22 kΩ and produces a peak power of 150 nW.
Application of Rotational Isomeric State Theory to Ionic Polymer Stiffness Predictions
- Lisa Mauck Weiland, Emily K. Lada, Ralph C. Smith, Donald J. Leo
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- Journal:
- Journal of Materials Research / Volume 20 / Issue 9 / September 2005
- Published online by Cambridge University Press:
- 03 March 2011, pp. 2443-2455
- Print publication:
- September 2005
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Presently, rotational isomeric state (RIS) theory directly addresses polymer chain conformation as it relates to mechanical response trends. The primary goal of this work is to explore the adaptation of this methodology to the prediction of material stiffness. This multiscale modeling approach relies on ionomer chain conformation and polymer morphology and thus has potential as both a predictive modeling tool and a synthesis guide. The Mark–Curro Monte Carlo methodology is applied to generate a statistically valid number of end-to-end chain lengths via RIS theory for four solvated Nafion® cases. For each case, a probability density function for chain length is estimated using various statistical techniques, including the classically applied cubic spline approach. It is found that the stiffness prediction is sensitive to the fitting strategy. The significance of various fitting strategies, as they relate to the physical structure of the polymer, are explored so that a method suitable for stiffness prediction may be identified.
High Conductivity Ionic Liquid- Nafion Mat Composites for High Speed Ionic Polymer Transducers
- Barbar Akle, Donald J. Leo, Changwoon Nah, Abdul M. Kader
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- Journal:
- MRS Online Proceedings Library Archive / Volume 889 / 2005
- Published online by Cambridge University Press:
- 01 February 2011, 0889-W07-06
- Print publication:
- 2005
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Ionomeric polymer transducers consist of an ion-exchange membrane plated with conductive metal layers on the outer surfaces. Such materials are known to generate large bending strain (> 9% is possible) at low applied voltages (typically less than 5 V). The main disadvantage of ionomer–ionic liquid transducers is the slow speed of response. The speed of response in such actuators has been correlated to the ionic liquid content and the conductivity of the membrane. To increase the conductivity of the transducers a Nafion™ mat is hydrated with 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf) ionic liquids and high surface area RuO2 electrodes are attached using the Direct Assembly Process (DAP). The Nafion™ mat is prepared from homogenous solution electrospinning. The solution is prepared by mixing 1 wt % of polyethylene oxide solution in methanol (PEO, Mol. wt 3×106) to 5 wt % Nafion 1100 solution.. The syringe needle is connected to a 15kV power supply and is placed 15cm away from the collecting drum. The measured conductivities of water hydrated Nafion electro-spun fibers are 16.8 mS/cm, which are lower than the nominal 110 mS/cm that of H+ Nafion membranes. The uptake is measured to be around 250 %wt compared to 58 %wt obtained in Nafion films. The ionic conductivity of 110 %wt swollen ionic liquids-Nafion mat composite is computed to be 0.9 mS/cm compared to 0.3 mS/cm in ionic liquid-Nafion membrane composite. The speed of response in actuators with an ionic liquid- Nafion™ mat is 1.34 %/s compared to 0.88 %/s for that in ionic liquid Nafion™ film transducers.
on the relationship between the electric double layer and actuation in ionomeric polymer transducers
- Barbar J. Akle, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 855 / 2004
- Published online by Cambridge University Press:
- 01 February 2011, W3.23
- Print publication:
- 2004
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Ionic polymer transducers are soft actuators that perform large bending deflections when voltages on the order of 1–5 V are applied across their thickness. Previous work showed that actuation performance of ionic polymer transducers is strongly correlated with the capacitance due to surface charge accumulation. Increasing the capacitance of the actuator increases the motion of the charges and increases the strain produced under the application of an electric field. Ionomeric transducers consist of an ionomer, such as Nafion (a product of DuPont), sandwiched between two high surface area electrodes. An electric double layer is formed on the interface between the cathode and the adsorbed positive ions. A novel plating technique which was previously developed is used to vary the morphology of the polymer-electrode interface to investigate the parameters of importance to the formation of the electric double layer. Electromechanical transducer tests are performed as a function of electrode morphology to correlate surface charge accumulation with the deflection generated by the transducer.
Hybrid Actuation in Coupled Ionic / Conducting Polymer Devices
- Matthew D. Bennett, Dr, Donald J. Leo
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- Journal:
- MRS Online Proceedings Library Archive / Volume 785 / 2003
- Published online by Cambridge University Press:
- 01 February 2011, D8.2
- Print publication:
- 2003
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Ionic polymer membrane actuators represent a relatively new and exciting entry into the field of smart materials. Several key limitations of these transducers have prevented them from experiencing widespread use, however. For example, the bandwidth of these devices is limited at very low frequencies by characteristic relaxation and at high frequencies by the low elastic modulus of the polymer. In this paper, an overview of the initial results of work with hybrid ionic / conducting polymer actuators is presented. These hybrid actuators are devices that combine the electromechanical coupling of ionic polymer actuators and conducting polymer actuators into one coupled device. Initial results show that these hybrid devices have the potential to offer marked advantages over traditional ionic polymer membrane transducers, including increased stress and strain generation and higher actuation bandwidth. Details of the preparation of these devices and performance metrics are presented and comparisons to baseline materials are made.