The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jacek Lipkowski - One of the best experts on this subject based on the ideXlab platform.
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Spectroelectrochemical Characterization of 1,2-Dipalmitoyl-sn-glycero-3-cytidine Diphosphate Nucleolipid Monolayer Supported on Gold (111) Electrode
2019Co-Authors: Julia Alvarez-malmagro, Jay J. Leitch, Francisco Prieto, Manuela Rueda, Jacek LipkowskiAbstract:The effect of the Electrode potential on the orientation and conformation of the 1,2-dipalmitoyl-sn-glycero-3-cytidine monolayer deposited on a gold (111) Electrode Surface was described. The potential of zero free charge (Epzc) for the monolayer-covered Electrode was determined to be −0.2 V vs SCE. The differential capacitance and charge density data indicated that the monolayer is stable at the Electrode Surface when (E – Epzc) > 0.0 V. At negative rational potentials, a progressive detachment (Electrodewetting) of the monolayer occurs. The monolayer is fully detached from the Electrode Surface at (E – Epzc) < −0.6 V. The conformation and orientation of the acyl chains and the orientation of the cytosine moiety were determined with the help of photon polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). The IR measurements demonstrate that the acyl chains are predominantly in the gel phase in the adsorbed state and tilted at an angle of ∼30° with respect to the Electrode Surface normal. The tilt angle of the acyl chains increases when the film is detached from the gold Surface, indicating that the monolayer becomes more disordered. At (E – Epzc) > 0.0 V, the plane of the cytosine moiety assumes a small angle of ∼20° with respect to the Surface. At negative potentials, the tilt angle of the cytosine fragment increases and rotates. With the help of DFT calculations, these changes were explained by the repulsion of the positive pole of the cytosine permanent dipole moment by the positively charged gold Surface and its attraction to the metal Surface at negative Electrode potentials. This work provides unique information for the future development of sensors based on the molecular recognition of nucleoside targets
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electric field driven conformational changes of gramicidin d in a model membrane supported on a au 111 Electrode Surface
Biophysical Journal, 2009Co-Authors: Jacek Lipkowski, Slawomir Sek, Thamara Laredo, John DutcherAbstract:In this work, we show molecular resolution scanning tunnelling microscopy (STM) images of gramicidin, a model antibacterial peptide, inserted into a phospholipid matrix supported at a gold Electrode Surface. The resolution of the images is superior to that obtained in previous attempts to image gramicidin in a lipid environment using atomic force microscopy (AFM). This breakthrough has allowed visualization of individual peptide molecules surrounded by individual lipid molecules. We have observed several important features: the peptide molecules do not aggregate, the peptide molecules adopt a single conformation corresponding to a specific ion channel form, and the lipid molecules adjacent to the peptide molecules are systematically longer than those in the lipid matrix. These results constitute a new approach to obtain structural characteristics of antibiotic peptides in lipid assemblies that is necessary for the understanding of their biological activity.We then applied the polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) to investigate the effect of the electric field on the conformation and orientation of gramicidin molecules in a bilayer supported at the gold Electrode Surface. We observed potential controlled changes in the orientation and conformation of the gramicidin molecules in the supported bilayer. Careful analysis of the IR data indicated that the potential applied to the Electrode affects the bilayer structure and these changes cause reorientation and conformational transformations of gramicidin molecules.
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afm studies of solid supported lipid bilayers formed at a au 111 Electrode Surface using vesicle fusion and a combination of langmuir blodgett and langmuir schaefer techniques
Langmuir, 2008Co-Authors: Maohui Chen, Erin Sheepwash, Christa L Brosseau, Bruno Pettinger, Hans Gruler, Jacek LipkowskiAbstract:Atomic force microscopy (AFM) has been used to characterize the formation of a phospholipid bilayer composed of 1,2-dimyristyl-sn-glycero-3-phosphocholine (DMPC) at a Au(111) Electrode Surface. The bilayer was formed by one of two methods: fusion of lamellar vesicles or by the combination of Langmuir−Blodgett (LB) and Langmuir−Schaefer (LS) deposition. Results indicate that phospholipid vesicles rapidly adsorb and fuse to form a film at the Electrode Surface. The resulting film undergoes a very slow structural transformation until a characteristic corrugated phase is formed. Force−distance curve measurements reveal that the thickness of the corrugated phase is consistent with the thickness of a bilayer lipid membrane. The formation of the corrugated phase may be explained by considering the elastic properties of the film and taking into account spontaneous curvature induced by the asymmetric environment of the bilayer, in which one side faces the gold substrate and the other side faces the solution. The e...
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stm studies of fusion of cholesterol suspensions and mixed 1 2 dimyristoyl sn glycero 3 phosphocholine dmpc cholesterol vesicles onto a au 111 Electrode Surface
Journal of the American Chemical Society, 2008Co-Authors: Slawomir Sek, Maohui Chen, Grzegorz S Szymanski, Jacek LipkowskiAbstract:Electrochemical scanning tunneling microscopy (EC-STM) has been applied to study the structure of the film formed by fusion of cholesterol suspensions and mixed dimyristoylphosphatidylcholine (DMPC)/cholesterol vesicles on a Au(111) Electrode Surface. It has been demonstrated that cholesterol molecules assemble at the gold support into several structures templated by the crystallography of the metal Surface and involving flat or edge-on adsorbed molecules. Studies of the film formed by fusion of mixed DMPC/cholesterol vesicles revealed that ordered domains of either pure DMPC or pure cholesterol were formed. These results indicate that, at the metal Surface, the molecules released by the rupture of a vesicle initially self-assemble into a well-ordered monolayer. The self-assembly is controlled by the hydrocarbon skeleton−metal Surface interaction. In the case of mixed DMPC/cholesterol vesicles, the molecule−metal interactions induce segregation of the two components into single component domains. However,...
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in situ ir reflectance absorption spectroscopy studies of pyridine adsorption at the au 110 Electrode Surface
Journal of Electroanalytical Chemistry, 2002Co-Authors: Vlad Zamlynny, Jacek Lipkowski, Frank Henglein, Bruno PettingerAbstract:In situ subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) has been employed to study the adsorption of pyridine at the Au(110) Electrode Surface. The IR spectra provide direct spectroscopic evidence that pyridine molecules adsorb, bonded through the nitrogen atom to the Au(110) Surface, in the whole range of Electrode potentials. IR spectroscopy was further used to study the effect of the Electrode potential on the tilt angle (angle between the C2 axis of the molecule and the direction normal to the Surface) of the adsorbed molecules. The IR data consistently show that the tilt angle decreases progressively with increasing Electrode potential (charge on the metal). The change of the tilt angle may be described in terms of the electric field–dipole interaction and is caused by the dielectric saturation phenomenon. At low charge density, where the field is small, the film of N-bonded pyridine molecules is less rigid and the molecules exhibit a waving motion. This motion is restrained significantly in the presence of a large electrostatic field (high charge density at the metal). The monolayer of adsorbed molecules can be considered as being effectively frozen at sufficiently high charge densities. © 2002 Elsevier Science B.V. All rights reserved.
Hanna Radecka - One of the best experts on this subject based on the ideXlab platform.
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Voltammetric Detection of S100B Protein Using His-Tagged Receptor Domains for Advanced Glycation End Products (RAGE) Immobilized onto a Gold Electrode Surface
Sensors, 2014Co-Authors: Edyta Mikuła, Peter Verwilst, Wim Dehaen, Jerzy Radecki, Aleksandra Wysłouch-cieszyńska, Liliya Zhukova, M. Puchalska, Hanna RadeckaAbstract:In this work we report on an electrochemical biosensor for the determination of the S100B protein. The His-tagged VC1 domains of Receptors for Advanced Glycation End (RAGE) products used as analytically active molecules were covalently immobilized on a monolayer of a thiol derivative of pentetic acid (DPTA) complex with Cu(II) deposited on a gold Electrode Surface. The recognition processes between the RAGE VC1 domain and the S100B protein results in changes in the redox activity of the DPTA-Cu(II) centres which were measured by Osteryoung square-wave voltammetry (OSWV). In order to verify whether the observed analytical signal originates from the recognition process between the His6–RAGE VC1 domains and the S100B protein, the Electrode modified with the His6–RAGE C2 and His6–RAGE VC1 deleted domains which have no ability to bind S100B peptides were applied. The proposed biosensor was quite sensitive, with a detection limit of 0.52 pM recorded in the buffer solution. The presence of diluted human plasma and 10 nM Aβ1-40 have no influence on the biosensor performance.
Edyta Mikuła - One of the best experts on this subject based on the ideXlab platform.
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Voltammetric Detection of S100B Protein Using His-Tagged Receptor Domains for Advanced Glycation End Products (RAGE) Immobilized onto a Gold Electrode Surface
Sensors, 2014Co-Authors: Edyta Mikuła, Peter Verwilst, Wim Dehaen, Jerzy Radecki, Aleksandra Wysłouch-cieszyńska, Liliya Zhukova, M. Puchalska, Hanna RadeckaAbstract:In this work we report on an electrochemical biosensor for the determination of the S100B protein. The His-tagged VC1 domains of Receptors for Advanced Glycation End (RAGE) products used as analytically active molecules were covalently immobilized on a monolayer of a thiol derivative of pentetic acid (DPTA) complex with Cu(II) deposited on a gold Electrode Surface. The recognition processes between the RAGE VC1 domain and the S100B protein results in changes in the redox activity of the DPTA-Cu(II) centres which were measured by Osteryoung square-wave voltammetry (OSWV). In order to verify whether the observed analytical signal originates from the recognition process between the His6–RAGE VC1 domains and the S100B protein, the Electrode modified with the His6–RAGE C2 and His6–RAGE VC1 deleted domains which have no ability to bind S100B peptides were applied. The proposed biosensor was quite sensitive, with a detection limit of 0.52 pM recorded in the buffer solution. The presence of diluted human plasma and 10 nM Aβ1-40 have no influence on the biosensor performance.
Maohui Chen - One of the best experts on this subject based on the ideXlab platform.
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afm studies of solid supported lipid bilayers formed at a au 111 Electrode Surface using vesicle fusion and a combination of langmuir blodgett and langmuir schaefer techniques
Langmuir, 2008Co-Authors: Maohui Chen, Erin Sheepwash, Christa L Brosseau, Bruno Pettinger, Hans Gruler, Jacek LipkowskiAbstract:Atomic force microscopy (AFM) has been used to characterize the formation of a phospholipid bilayer composed of 1,2-dimyristyl-sn-glycero-3-phosphocholine (DMPC) at a Au(111) Electrode Surface. The bilayer was formed by one of two methods: fusion of lamellar vesicles or by the combination of Langmuir−Blodgett (LB) and Langmuir−Schaefer (LS) deposition. Results indicate that phospholipid vesicles rapidly adsorb and fuse to form a film at the Electrode Surface. The resulting film undergoes a very slow structural transformation until a characteristic corrugated phase is formed. Force−distance curve measurements reveal that the thickness of the corrugated phase is consistent with the thickness of a bilayer lipid membrane. The formation of the corrugated phase may be explained by considering the elastic properties of the film and taking into account spontaneous curvature induced by the asymmetric environment of the bilayer, in which one side faces the gold substrate and the other side faces the solution. The e...
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stm studies of fusion of cholesterol suspensions and mixed 1 2 dimyristoyl sn glycero 3 phosphocholine dmpc cholesterol vesicles onto a au 111 Electrode Surface
Journal of the American Chemical Society, 2008Co-Authors: Slawomir Sek, Maohui Chen, Grzegorz S Szymanski, Jacek LipkowskiAbstract:Electrochemical scanning tunneling microscopy (EC-STM) has been applied to study the structure of the film formed by fusion of cholesterol suspensions and mixed dimyristoylphosphatidylcholine (DMPC)/cholesterol vesicles on a Au(111) Electrode Surface. It has been demonstrated that cholesterol molecules assemble at the gold support into several structures templated by the crystallography of the metal Surface and involving flat or edge-on adsorbed molecules. Studies of the film formed by fusion of mixed DMPC/cholesterol vesicles revealed that ordered domains of either pure DMPC or pure cholesterol were formed. These results indicate that, at the metal Surface, the molecules released by the rupture of a vesicle initially self-assemble into a well-ordered monolayer. The self-assembly is controlled by the hydrocarbon skeleton−metal Surface interaction. In the case of mixed DMPC/cholesterol vesicles, the molecule−metal interactions induce segregation of the two components into single component domains. However,...
A Gebert - One of the best experts on this subject based on the ideXlab platform.
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desorption of hydrogen from an Electrode Surface under influence of an external magnetic field in situ microscopic observations
Electrochemistry Communications, 2009Co-Authors: Jakub Adam Koza, A Gebert, Sascha Muhlenhoff, Margitta Uhlemann, Kerstin Eckert, L SchultzAbstract:The effect of a magnetic field in the perpendicular-to-Electrode configuration on the hydrogen evolution reaction (HER) was investigated during the deposition of Co. An enhanced desorption of hydrogen in the form of numerous small bubbles was found by combining potentiostatic investigations, coupled with an electrochemical quartz crystal microbalance (EQCM), and simultaneous microscopic observations of the Electrode Surface. The results are consistent with the recently proposed qualitative model [J.A. Koza, M. Uhlemann, A. Gebert, L. Schultz, Electrochem. Commun. 10 (2008) 1330].
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the effect of a magnetic field on the ph value in front of the Electrode Surface during the Electrodeposition of co fe and cofe alloys
Journal of Electroanalytical Chemistry, 2008Co-Authors: Jakub Adam Koza, M Uhlemann, A Gebert, L SchultzAbstract:Abstract The effect of an uniform magnetic field applied parallel to the Electrode Surface, with flux density up to 1 T on the pH value close to the Electrode Surface during the Electrodeposition of Co, Fe, CoFe alloys as well as for the pure hydrogen evolution reaction (HER) has been investigated. Voltammetric and chronoamperometric experiments have been carried out with the in situ pH measurements at the Electrode Surface. Results show that the limiting current for all the investigated systems is increased due to the magnetohydrodynamic (MHD) effect. The hydroxides formation in the metal containing electrolytes buffers the cathodic layer and the interfacial pH value increases to a lesser extent compared to the case of HER electrolyte. The increase of the pH value at the Electrode Surface is lower in the applied magnetic field compared to the case without a magnetic field. It was found that the interfacial pH value is a power function of the magnetic flux density. This effect is attributed to enhanced convection induced by the Lorentz force. The depletion of H + concentration at the Electrode Surface is compensated by the MHD effect and the hydroxide formation is suppressed, moreover the hydroxyl products are removed faster from the Electrode Surface in the magnetic field resulting in better quality of the deposited layers. The pH value close to the Electrode Surface during CoFe alloys deposition is high enough for the precipitation of the iron hydroxide, what satisfies the model proposed by Dahms and Croll.
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effect of a magnetic field on the local ph value in front of the Electrode Surface during Electrodeposition of co
Journal of Electroanalytical Chemistry, 2005Co-Authors: M Uhlemann, A Krause, A GebertAbstract:Abstract The change of the pH value, the hydrogen evolution reaction, and their effect on the Electrodeposition of Co were investigated directly at the Surface of a gold mesh with and without superimposition of a magnetic field of 1 T by cyclic voltammetry and chronoamperometry in 0.1 M Na 2 SO 4 with and without addition of 0.01 CoSO 4 . The reduction of hydrogen ions is increased by superimposition of a magnetic field oriented parallel to the Electrode Surface. The increase of the pH value directly at the Surface is lower in an applied magnetic field compared to the case without a magnetic field. This is likely to be due to the enhanced convection generated by the Lorentz force. The discharged hydrogen ions are rapidly compensated. The effect of a magnetic field on the limited current density as well as on the change of pH value is more significant at lower initial pH value. For initial pH values of 3 and 3.5 the deposition of Co under a superimposed magnetic field is improved and the increase of the pH value is low in front of the Electrode. This leads to a suppression of the spontaneous formation of hydroxides.