Biological and bio-inspired systems using ion transport across a membrane for energy conversion has inspired recent developments in smart materials. The active mechanism in bioderived materials is ion transport across an impermeable membrane that converts electrochemical gradients into electrical and mechanical work. In addition to bioderived materials, ion transport phenomenon in electroactive polymers such as ionomeric and conducting polymers produces electromechanical coupling in these materials. Inspired by the similarity in transduction mechanism, this thesis focuses on integrating the ion transport processes in a bioderived material and a conducting polymer for developing novel actuation systems. The integrated membrane has a bilayer lipid membrane (BLM) formed on a conducting polymer, and the proteins reconstituted in the BLM regulate ion transport into the conducting polymer. The properties of the polymer layer in the integrated device are regulated through a control signal applied to the bioderived layer and hence the hybrid membrane resembles an ionic transistor. Due to the bioderived nature of this device, it is referred to as a ‘bioderived ionic transistor’. The research carried out in this thesis will demonstrate the fabrication, characterization and design limitations for fabricating a chemoelectromechanical actuator using the BIT membrane. The BIT membrane has been fabricated using BLM (DPhPC) reconstituted with protein (alamethicin) to gate Na$^+$ transport into conducting polymer membrane (PPy(DBS)). In this membrane, the bioderived layer is fabricated with proteins by vesicle fusion method and conducting polymer is fabricated by electropolymerization. The bioderived layers, the conducting polymer layers and the hybrid membrane are characterized using electrochemical measurements such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The fabrication, characterization and design effort presented in this thesis focuses on the integration of ion transport through the bioderived membrane into volumetric expansion and bending actuation. The characterization efforts are supported by empirical and physics-based models to represent the input-output relationship for both PPy(DBS) actuator and bioderived membrane, and design rules for the proposed actuation platforms are specified. The electropolymerized PPy(DBS) actuator is anticipated to be used in a bicameral device with the chambers kept separated by the DPhPC-alamethicin bioderived membrane. The relationship between the gradient potential, ionic current through the gate, ion concentration, ion transport coefficient in the conducting polymer layer, and the induced tip displacement in the polymer has been concluded from experiments and fitted to the actuation system model. This thesis will also address future directions for this research and anticipated applications for this hybrid actuation concept, such as artificial muscle, drug delivery.

A leptospirose é uma zoonose de importância mundial, causada por leptospiras patogênicas. Aproximadamente 5 a 10% das infecções humanas cursam com a forma grave. A Doença de Weil é a forma mais comum de doença grave e pode apresentarse com duas formas de evolução, aguda progressiva monofásica ou de curso prolongado. A doença grave se caracteriza por uma combinação de hemorragia, mais comumente pulmonar, icterícia e insuficiência renal, com letalidade de 5 a 15%. O rim é um órgão muito acometido na Leptospirose. Clinicamente o envolvimento renal ocorre de 16 a 40%, com manifestações peculiares como poliúria, hipocalemia, e perda de sódio. A disfunção tubular renal, é característica da leptospirose forma grave, com envolvimento dos transportadores renais de sódio ao longo do néfron, levando às manifestações observadas. A terapêutica antimicrobiana é recomendada na Leptospirose, porém com controvérsias à sua indicação após o quarto dia de doença. Quando da instalação da lesão não haveria benefícios com a utilização de antibióticos. O tratamento pode diminuir a morbidade e letalidade, assim como interferir no envolvimento renal e na expressão dos transportadores renais de sódio. A patogênese pode estar relacionada a efeitos diretos da leptospira ou a resposta inflamatória assim como o estresse oxidativo. A utilização de antioxidantes, pode ser considerada como terapia adjuvante. Nós avaliamos a expressão no túbulo proximal do trocador Na+-H+ (NHE3) e na porção espessa da medula ascendente o cotransportador Na+-K+-2Cl- (NKCC2), no modelo de hamster com as duas formas de evolução de doença grave, mimetizando a doença de humanos realizados em dois experimentos. Os experimentos envolveram animais infectados não tratados e tratados com ampicilina associado ou não ao antioxidante, N-acetilcisteína. A presença de antígenos de Leptospira e a expressão dos transportadores foram avaliadas por imunohistoquímica, e o ácido tiobarbitúrico, marcador de estresse oxidativo, (TBARS) foi quantificado.Hamsters infectados, apresentaram altas quantidades de antígenos nos tecidos-alvo, enquanto que a expressão de ambos os transportadores apresentou-se diminuída. O tratamento com ampicilina esteve associado com mínima detecção ou ausência de antígenos, restabelecimento da expressão dos transportadores nos respectivos locais e redução dos níveis de TBARS. O tratamento precoce e tardio com ampicilina restabeleceu os defeitos tubulares na leptospirose forma grave em ambos experimentos, sem benefícios com a utilização da N-acetilcisteína. / Leptospirosis is a zoonosis of worldwide distribution. About 5-10% of all human infections presents with severe forms. Weil\'s syndrome, the most common presentation of severe forms of leptospirosis, may courses either as a single monophasic disease or as a disease with prolonged course, characterized by a combination of hemorrhage, particularly in the lung, renal failure, and jaundice, with fatality rates ranging from 5 to 15%. The kidney is an important target organ in leptospiral infection. Clinically, renal involvement in leptospirosis occurs in 16% to 40% of cases and is unique because of the atypical presentation of polyuria, hypokalemia, and sodium wasting, suggestive of a special form of tubular dysfunction related to the major renal sodium transporters expressed along the nephron. A wide range of antimicrobial therapy for leptospirosis was described and benefits have been disputed for cases with more than four days of clinical disease, because after a threshold of leptospiremia, the delayed use of antibiotics is unlikely to reduce fatality. Antimicrobial therapy is thought to interfere on fatality, renal involvement, and renal sodium transporters expression during severe disease. The pathogenesis may be related to direct effects of leptospiral compounds or inflammatory response due to oxidative stress. Antioxidant could be considered for adjunctive therapy.We evaluated the expression of proximal tubule type 3 Na+/H+ exchanger (NHE3) and thick ascending limb Na+-K+-2Cl- cotransporter (NKCC2) in infected non treated and treated hamsters reproducing the two forms of clinical human presentations of Weil\'s syndrome divided in two experiments. Animals were treated or not with ampicillin and/or N-acetyl-cysteine (NAC). Leptospiral antigen/s and expression of renal transporters were evaluated by immunohistochemistry, and serum thiobarbituric acid (TBARS) was quantified. Infected hamsters had high amounts of detectable leptospiral antigen/s in target tissues while renal expression of NHE3 and NKCC2 decreased. Ampicillin treatment was associated with minimal or no detection of leptospiral antigens, normal expression of NHE3 and NKCC2 transporters, and reduced levels of TBARS. Early and late ampicillin treatment rescued tubular defects in leptospirosis severe disease in both experiments, and there was no evidence of benefit from antioxidant therapy.

by Vincent, Wai-ip Law. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 128-134). / Abstract also in Chinese. / Chapter Chapter I. --- Literature Review / Chapter I.1. --- "Structure, functions and general physiology of equine sweat gland" / Chapter I.1.1. --- Ultrastructure of equine sweat gland --- p.1 / Chapter I.1.2. --- Functions and physiology of equine sweat gland --- p.3 / Chapter I.1.3. --- Experimental studies on equine sweat gland by functional approaches --- p.4 / Chapter I.1.4. --- Hormonal and neuronal regulation of sweat secretion in equidaes --- p.5 / Chapter I.1.5. --- Possible role(s) of extracellular ATP in equine sweat gland epithelia --- p.6 / Chapter I.1.6. --- Measurement of electrogenic anion secretion by short-circuit current (Isc) technique --- p.8 / Chapter I.2. --- Classification of purinergic receptors and its existence in biological systems / Chapter I.2.1. --- Functional classification of purinergic receptors --- p.13 / Chapter I.2.2. --- Basic structure of G-protein coupled P2Y receptors --- p.17 / Chapter I.2.3. --- Physiological function and significance of purinergic receptors --- p.20 / Chapter I.3. --- Objectives of study --- p.22 / Chapter Chapter II. --- Methods and Materials / Chapter II.l. --- Culture technique of the equine epithelial cells --- p.23 / Chapter II.2. --- Conventional short-circuit current (Isc) measurement technique / Chapter II.2.1. --- Introduction --- p.25 / Chapter II.2.2. --- Preparation of permeable supports and electrodes --- p.25 / Chapter II.2.3. --- Experimental set up and measurement of Isc --- p.28 / Chapter II.2.4. --- Measurement of Isc during experiment --- p.30 / Chapter II.3. --- Measurement of intracellular free calcium ( [Ca2+ ]ii) by microspectrofluorimetry / Chapter II.3.1. --- Preparation of cells --- p.31 / Chapter II.3.2. --- The set up and procedures for experiment --- p.31 / Chapter II.4. --- Simultaneous measurement of changes in [Ca2+ ]i and Isc / Chapter II.4.1. --- Experimental set up and manipulation --- p.35 / Chapter II.4.2. --- Other preparations before experiment --- p.37 / Chapter II.5. --- Material and solutions used for experiment / Chapter II.5.1. --- Culture media and enzyme --- p.40 / Chapter II.5.2. --- Chemicals and Drugs --- p.40 / Chapter II.5.3. --- Preparation of solution for experiments --- p.42 / Chapter II.6. --- Statistical analysis --- p.44 / Chapter Chapter III. --- Results / Chapter III.l. --- Effects of nucleotides on transepithelial ion transport / Chapter III.1.1. --- Basic electrophysiological properties of cultured equine sweat gland epithelia --- p.45 / Chapter III. 1.2. --- Short-circuit current (Isc) induced by nucleotides --- p.45 / Chapter III. 1.3. --- Identification of ion species responsible for the change in Isc --- p.50 / Chapter III. 1.4. --- Effects of chloride channels blockers on the UTP-induced Isc --- p.51 / Chapter III.2. --- Signal transduction mechanisms of P2Y-nucleotide receptors / Chapter III.2.1. --- The involvement of Gi-proteins --- p.56 / Chapter III.2.2. --- Effect of BAPTA on the increases in Isc induced by nucleotides --- p.58 / Chapter III.2.3. --- Study of P2Y-receptor mediated increase in [Ca2+]i --- p.62 / Chapter III.3. --- Characterization of the P2Y subtype(s) by cross desensitization experiments / Chapter III.3.1. --- Autologous desensitization experiments --- p.70 / Chapter III.3.2. --- Classical cross desensitization experiments --- p.70 / Chapter III.3.3. --- Characterization of the ATP-insensitive P2Y-receptor --- p.80 / Chapter III.3.4. --- Interaction between ATP and bradykinin --- p.87 / Chapter III.4. --- Simultaneous measurement of [Ca2+]i and Issc / Chapter III.4.1. --- Effect ofUDP and ADP --- p.89 / Chapter III.4.2. --- Correlation of Isc and [Ca2+]i --- p.92 / Chapter III.4.3. --- Cross desensitization experiments --- p.97 / Chapter III.5. --- Evidence of a [Ca2+]i-independent Isc-component induced by nucleotides / Chapter III.5.1. --- The time course of the ΔRf and ΔISC --- p.102 / Chapter III.5.2. --- Effect of ionomycin on the ΔISC and ΔRf induced by nucleotides --- p.110 / Chapter III.5.3. --- Effect of thapsigargin on the ΔISC and ΔRf induced by nucleotides --- p.110 / Chapter III.5.4. --- Effect of thapsigargin in nominal Ca2+-free solution --- p.115 / Chapter Chapter IV. --- Discussion / Chapter IV. 1. --- Role of extracellular nucleotides in epithelial tissues --- p.119 / Chapter IV.2. --- Characterization of an ATP-insensitive P2Y-nucleotide receptor --- p.120 / Chapter IV.3. --- Expression of the novel ATP-insensitive receptor on a functionally polarized epithelia --- p.122 / Chapter IV.4. --- Involvement of a [Ca2+]i -independent Isc induced by nucleotides --- p.124 / Chapter Chapter V. --- References --- p.128

The rapid emergence of multidrug resistant bacterial strains represents a major global healthcare issue. Amongst five known classes of membrane transporters, which play a huge role in multidrug efflux, primary-active ATP-binding cassette (ABC) transporters are ATP powered whilst secondary-active transporters utilize electrochemical ion gradients to drive substrate transport. Mechanistic insights into transport by these proteins can help with the design and development of novel therapeutic agents against multidrug resistance, and can increase our understanding of the physiological functions of these transporters. Although available crystal structures illustrate a common alternate access model for transport by ABC transporters, the mechanisms by which metabolic energy is coupled to the transport cycle is still elusive. This thesis presents a series of functional studies using whole cells as well as artificial phospholipid membranes to study the energetics of transport, and the influence of membrane phospholipids on substrate transport by the homodimeric Escherichia coli lipid A/multidrug ABC exporter MsbA. Current alternating access models for ABC exporters involve cycling between conformations with inward- and outward-facing substrate-binding sites in membrane domains (MDs) in response to engagement and hydrolysis of ATP at the nucleotide-binding domains (NBDs). Here we report that MsbA also utilizes another major energy currency in the cell by coupling substrate transport to a transmembrane electrochemical proton gradient. In this thesis, analogous substrate transport reactions are also studied for two other ABC exporters, the MsbA homologue LmrA and the human multidrug transporter ABCG2. The dependence of ATP-dependent transport on proton coupling, and the stimulation of MsbA-ATPase by the chemical proton gradient highlight the functional integration of both forms of metabolic energy. It also raises questions about the role of NBDs in the transport process. Comparisons of drug transport and resistance in cells expressing MsbA-MD (truncated MsbA lacking the NBD) and full length MsbA (MsbA-WT) demonstrate increased transport efficiency of MsbA-WT compared to MsbA-MD. In addition, growth studies using E. coli WD2 cells, which are conditionally defective in MsbA’s essential activity in lipid A transport, show that lipid A transport can be restored by the expression of MsbA-WT but not MsbA-MD or ATP-hydrolysis impaired Walker A mutant (MsbA- ΔK382). Lastly, we also present biochemical experiments with proteoliposomes with a defined phospholipid composition, which suggest that cardiolipin is essential for the transport activity of MsbA. These techniques open the way to further explore lipid-proteins interactions and examine the physiological role(s) of MsbA. In conclusion, this thesis produces new insights in the mechanisms of transport and energy coupling in ABC exporters.

The performance of an inductively coupled plasma mass spectrometer, ICP-MS, depends on the instrument's ability to transport sample ions through the vacuum interface and focus the ions into a well-defined beam that will eventually reach the mass analyzer. In this study two main experiments were performed on the Perkin Elmer NexION 300S, a commercial ICP-MS. First, planar laser-induced fluorescence images were taken of the ion beam in a working instrument downstream from a unique quadrupole ion deflector. The images showed the ability of the instrument design to focus the ions in the ion beam. Second, laser-induced fluorescence was used to characterize ion flow through the vacuum interface. The interface is unique to the NexION ICP-MS in that there are three extraction cones. The effect of a three-cone interface on ideal skimming is discussed.

The organic electronic ion pump (OEIP) is an electrically controlled polymer-based device that has the capability to interact with biological systems down to a single cell level by mimicking neural signalling. This is accomplished by translation of an electrical signal into a chemical output, such as ions and neurotransmitters. Because of the combined spatial and temporal precision, this is a technology with a promising future as an advanced therapeutic device. Depending on the application, the OEIP requires different geometries. Implants that will be used to control on a single cell level require very small dimensions, while for example extracorporeal mounted OIEPs, with only the delivery channel penetrating the skin, require much longer channels. Despite the application, it is necessary to have a good knowledge about the transport and delivery properties and how they change due to the geometry. These properties have been observed as very varying and unstable in early unpublished results, and these findings motivate this project. This project includes photolithographic fabrication and investigation of transport and delivery properties such as effective resistance, efficiency and stability of OEIPs with varying delivery channel lengths and widths. Shorter delivery channels show a consistent but relatively low efficiency. Delamination between different layers of the device is suspected as the cause. Initially, the longer delivery channels show a low functionality, most probably due to poor encapsulation. It is suggested that a soft, water-permeable plastic best encapsulates OEIPs that will be used as a medical implant, while a material impermeable to water, for example a metal, could successfully encapsulate OEIPs operating in air.

This thesis describes the development of an ion channel system exhibiting dissipative assembly characteristics. In this system an active transporter based on an oligoester fragment terminated in a thioester of 6-aminohexanoic acid (HO2C-Hex-Adip-OctS-Hex-NH2) undergoes thioester cleavage to form a thiol terminated oligoester (HO2C-Hex-ADip-Oct-SH). This fragment was expected to be inactive for ion transport but previous work showed high activity in planar bilayer experiments. In this work, the high activity was shown to be due to the oxidized form of the thiol, the disulfide HO2C-ADip-Oct-SS-Oct-ADip-Hex-CO2H. Air oxidation was found to be quite rapid for the thiol based on ESI-MS (negative ion) and HPLC analysis. Under anaerobic conditions, the thiol fragment was an inactive species for ion transport. In situ air oxidation initiated transport activity associated with the disulfide. The transporter HO2C-Hex-Adip-Oct-Hex-NH2 was active in planar bilayer experiments and was compared to the disulfide via activity grids. The activity of these two compounds was shown to be distinct from each other by conductance and channel duration differences. The activity of HO2C-Hex-Adip-Oct-Hex-NH2 was shown to die off in a period of 30 minutes at pH 8.2. Techniques were developed to stimulate and monitor activity and bilayer quality so that an inactive condition could be confirmed. The addition of Pr-S-Hex-NH3+-Cl as a fuel was shown to extend the activity of HO2C-Hex-Adip-Oct-Hex-NH2 by eight-fold in 1M CsCl electrolyte. Previous work had established the capability of thioester exchange reactions by a reaction between Pr-S-Hex-NH3+-Cl and benzyl thiol in a homogenous solution. The extended activity indicated that the same process may occur in a heterogeneous bilayer system. An inactive system created by the die-off in activity of HO2C-Hex-Adip-Oct-S-Hex-NH2 was treated with Pr-S-Hex-NH3+-Cl to regenerate activity. This cycle could be repeated once the activity died off again. All these findings are consistent with the dissipative assembly of a membrane transport system. / Graduate / 0490

Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / "December 1998" Typescript. Vita. Includes bibliographical references (l. 152-155). Also available on the Internet.

Thesis (Ph. D.)--Cornell University, January, 2009. / Vita. Includes bibliographical references (leaves 192-205).

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