59 results on '"M. Szklarczyk"'
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2. A polarizable empirical force field for molecular dynamics simulation of liquid hydrocarbons.
- Author
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Oliwia M. Szklarczyk, Stephan J. Bachmann, and Wilfred F. van Gunsteren
- Published
- 2014
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3. Receptor Concentration and Diffusivity Control Multivalent Binding of Sv40 to Membrane Bilayers.
- Author
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Oliwia M. Szklarczyk, Nélido González-Segredo, Philipp Kukura, Ariella Oppenheim, Daniel Choquet, Vahid Sandoghdar, Ari Helenius, Ivo F. Sbalzarini, and Helge Ewers
- Published
- 2013
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4. Flexible Boundaries for Multiresolution Solvation: An Algorithm for Spatial Multiscaling in Molecular Dynamics Simulations
- Author
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Noah S. Bieler, Philippe H. Hünenberger, Wilfred F. van Gunsteren, and Oliwia M. Szklarczyk
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Surface (mathematics) ,Alanine ,Chemistry ,Solvation ,Water ,Boundary (topology) ,Molecular Dynamics Simulation ,Computer Science Applications ,Molecular dynamics ,Solvents ,Thermodynamics ,Molecule ,Surface layer ,Physical and Theoretical Chemistry ,Layering ,Peptides ,Algorithm ,Layer (electronics) ,Algorithms - Abstract
An algorithm is proposed for performing molecular dynamics (MD) simulations of a biomolecular solute represented at atomistic resolution surrounded by a surface layer of atomistic fine-grained (FG) solvent molecules within a bulk represented by coarse-grained (CG) solvent beads. The method, called flexible boundaries for multiresolution solvation (FBMS), is based on: (i) a three-region layering of the solvent around the solute, involving an FG layer surrounded by a mixed FG-CG buffer layer, itself surrounded by a bulk CG region; (ii) a definition of the layer boundary that relies on an effective distance to the solute surface and is thus adapted to the shape of the solute as well as adjusts to its conformational changes. The effective surface distance is defined by inverse-nth power averaging over the distances to all non-hydrogen solute atoms, and the layering is enforced by means of half-harmonic distance restraints, attractive for the FG molecules and repulsive for the CG beads. A restraint-free region at intermediate distances enables the formation of the buffer layer, where the FG and CG solvents can mix freely. The algorithm is tested and validated using the GROMOS force field and the associated FG (SPC) and CG (polarizable CGW) water models. The test systems include pure-water systems, where one FG molecule plays the role of a solute, and a deca-alanine peptide with two widely different solute shapes considered, α-helical and fully extended. In particular, as the peptide unfolds, the number of FG molecules required to fill its close-range solvation layer increases, with the additional molecules being provided by the buffer layer. Further validation involves simulations of four proteins in multiresolution FG/CG mixtures. The resulting structural, energetic, and solvation properties are found to be similar to those observed in corresponding pure FG simulations.
- Published
- 2015
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5. A polarizable empirical force field for molecular dynamics simulation of liquid hydrocarbons
- Author
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Stephan Bachmann, Wilfred F. van Gunsteren, and Oliwia M. Szklarczyk
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Thermodynamics ,Dielectric ,Molecular Dynamics Simulation ,010402 general chemistry ,Models, Biological ,01 natural sciences ,Force field (chemistry) ,Molecular dynamics ,symbols.namesake ,Cyclohexanes ,Polarizability ,Computational chemistry ,0103 physical sciences ,Water model ,Physics::Chemical Physics ,Alkane ,chemistry.chemical_classification ,Quantitative Biology::Biomolecules ,010304 chemical physics ,Proteins ,General Chemistry ,Enthalpy of vaporization ,Lipids ,Hydrocarbons ,0104 chemical sciences ,Gibbs free energy ,Computational Mathematics ,chemistry ,symbols - Abstract
Electronic polarizability is usually treated implicitly in molecular simulations which may lead to imprecise or even erroneous molecular behavior in spatially electronically inhomogeneous regions of systems such as proteins membranes interfaces between compounds or mixtures of solvents. The majority of available molecular force fields and molecular dynamics simulation software packages does not account explicitly for electronic polarization. Even the simplest charge on spring (COS) models have only been developed for few types of molecules. In this work we report a polarizable COS model for cyclohexane as this molecule is a widely used solvent and for linear alkanes which are also used as solvents and are the precursors of lipids amino acid side chains carbohydrates or nucleic acid backbones. The model is an extension of a nonpolarizable united atom model for alkanes that had been calibrated against experimental values of the density the heat of vaporization and the Gibbs free energy of hydration for each alkane. The latter quantity was used to calibrate the parameters governing the interaction of the polarizable alkanes with water. Subsequently the model was tested for other structural thermodynamic dielectric and dynamic properties such as trans/gauche ratios excess free energy static dielectric permittivity and self diffusion. A good agreement with the experimental data for a large set of properties for each considered system was obtained resulting in a transferable set of polarizable force field parameters for CH2 CH3 and CH4 moieties. © 2014 Wiley Periodicals Inc.
- Published
- 2014
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6. Polarizable coarse-grained models for molecular dynamics simulation of liquid cyclohexane
- Author
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Wilfred F. van Gunsteren, Eirini Arvaniti, and Oliwia M. Szklarczyk
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Cyclohexane ,Chemistry ,Thermodynamics ,General Chemistry ,Enthalpy of vaporization ,Dielectric ,Molecular Dynamics Simulation ,7. Clean energy ,Force field (chemistry) ,Massless particle ,Computational Mathematics ,Molecular dynamics ,chemistry.chemical_compound ,Models, Chemical ,Computational chemistry ,Polarizability ,Cyclohexanes ,Solvents ,Granularity ,Physics::Atomic Physics ,Physics::Chemical Physics ,Particle Size - Abstract
Force field parameters for polarizable coarse-grained (CG) supra-atomic models of liquid cyclohexane are proposed. Two different bead sizes were investigated, one representing two fine-grained (FG) CH(2)r united atoms of the cyclohexane ring, and one representing three FG CH(2)r united atoms. Electronic polarizability is represented by a massless charge-on-spring particle connected to each CG bead. The model parameters were calibrated against the experimental density and heat of vaporization of liquid cyclohexane, and the free energy of cyclohexane hydration. Both models show good agreement with thermodynamic properties of cyclohexane, yet overestimate the self-diffusion. The dielectric properties of the polarizable models agree very well with experiment.
- Published
- 2014
7. Ionic adsorption at the solid—solution interphase using three in situ methods
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M. Szklarczyk, M. Gamboa-Aldeco, and J. O'm. Bockris
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Water dimer ,Aqueous solution ,Chemistry ,General Chemical Engineering ,Enthalpy ,Analytical chemistry ,Analytical Chemistry ,Gibbs free energy ,Ion ,symbols.namesake ,Partial charge ,Adsorption ,Electrochemistry ,symbols ,Solid solution - Abstract
The adsorption of HSO4−, Cl− and I− from aqueous solutions of 1 M HClO4 was examined using radiotracer Fourier transform IR spectroscopy and ellipsometry. The dependence of the adsorption was measured as a function of time of equilibrium, concentration at constant potential, and at various potentials at constant concentration. For the HSO4− adsorption, some measurements were made as a function of temperature at constant potential. The dependence on time corresponded neither to the ln Γt-t nor Γt-ln t relations expected from previously deduced theoretical models. Up to ca. τ/4, θt was found to be proportional to the adsorption time. The dependence of adsorption on concentration at constant potential was carried out over an extended region, i.e. from 10−9 to 10−2 M. In the concentration range up to 10−5 M the behaviour followed the Henry isotherm and at concentrations up to 10−3 M the results followed a logarithmic law. (∂θ /∂ log c)E,T was about the same for HSO4− and Cl− but around two times higher for I−. The maximum coverage of HSO4− and Cl− was reached at ca. 0.25 and ca. 1 for I−. The dependence on potential at constant concentration was essentially linear until oxide formation for HSO4− and Cl−. I− results showed little variation with potential before oxide formation. The dependence of (θ)E,c as a function of temperature for HSO4− cannot be expressed as a simple law because of the low number of experiments successfully investigated; nevertheless, some approximate values of ΔG°, ΔH° and ΔS° were derived. An isotherm was derived in such account that the heterogeneity of the surface, ion—ion repulsion through a simple imaging model and ion—ion dispersive forces were considered. In the calculations, electrostriction effects on ion size were computed. Evidence for partial charge transfer was found: 0.2, 0.6 and 0.9 for HSO4−, Cl− and I− respectively. Indications of water displacement from the surface was found to be consistent with one displaced entity represented by a water dimer. The thermodynamic parameters derived for HSO4− were ΔG° = −32 kJ mol−1 (25°C), ΔH° = −57 kJ mol−1 and ΔS° = −78 J K−1 mol−1 at θss = 0.22. from these values, the PtO bond was estimated to be ca. one-quarter of that expected for the isolated PtO bond in the gas phase. The entropy was consistent with immobile adsorbed ions with hindered rotation.
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- 1992
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8. Evaluation of absolute saturation coverages of carbon monoxide on ordered low-index platinum and rhodium electrodes
- Author
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Si-Chung Chang, D. Zurawski, Michael J. Weaver, M. Szklarczyk, Lam-Wing H. Leung, M. Rubel, Andrzej Wieckowski, and X. Jiang
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medicine.diagnostic_test ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,Infrared spectroscopy ,Analytical Chemistry ,Rhodium ,chemistry.chemical_compound ,chemistry ,Spectrophotometry ,Electrochemistry ,medicine ,Perchloric acid ,Cyclic voltammetry ,Platinum ,Voltammetry ,Carbon monoxide - Abstract
The limitations on evaluating surface concentrations, and hence fractional coverages θCOsat, for saturated irreversibly adsorbed CO adlayers on low-index platinum and rhodium electrodes by anodic voltammetry are discussed with particular reference to Pt(111). In agreement with Feliu et al., substantially higher θCOsat estimates (about 0.9) are obtained by this means in aqueous sulfuric acid than in perchloric acid (0.6–0.7). Additional evidence from nonelectrochemical methods, however, indicates that the latter estimate approximates the true θCOsat, values. In particular, thin-layer IR spectrophotometry enables θCOsat values to be extracted from the absorbance of the OCO stretch for the CO2 product. This procedure yields θCOsat values for all six platinum and rhodium low-index faces that are close to (within about 10% of) the values obtained at the corresponding metal-ultrahigh vacuum interfaces at low temperatures. Some likely systematic errors in the conventional voltammetric analysis are discussed in the light of the present results.
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- 1992
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9. In situ STM studies of surface states at the p-Si(111)/propylene carbonate(TBAP) interface
- Author
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M. Szklarczyk, A. González-Martín, and J. O'm. Bockris
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In situ ,Supporting electrolyte ,Chemistry ,Inorganic chemistry ,Analytical chemistry ,Biasing ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,chemistry.chemical_compound ,Adsorption ,law ,Propylene carbonate ,Materials Chemistry ,Cyclic voltammetry ,Scanning tunneling microscope ,Surface states - Abstract
Scanning tunneling microscopy has been used to study p-Si(111) surfaces in propylene carbonate, where tetrabutylammonium perchlorate was the supporting electrolyte. The bias voltage threshold required to observe surface features in the STM images, both in situ and ex situ, allow the detection of surface states. It is found that surface states are introduced after contact with solution by solvent molecules adsorption as well as ClO 4 − ion adsorption. Energy positions of the induced surface states are calculated.
- Published
- 1991
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10. In situ STM studies of polycrystalline platinum electrodes
- Author
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M. Szklarczyk and John O’M. Bockris
- Subjects
Chemistry ,Faradaic current ,Analytical chemistry ,chemistry.chemical_element ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,law ,Chemical physics ,Electrode ,Materials Chemistry ,Crystallite ,Scanning tunneling microscope ,Cyclic voltammetry ,Platinum ,Surface reconstruction ,Electrode potential - Abstract
In situ scanning tunneling microscopy (STM) was applied in a 10−2M NaClO4 solution to study topographical changes of a platinum electrode surface due to its oxidation and reduction. Surface morphology depends on the electrode potential. There are two stages in surface reduction: the fast electrochemical charge transfer and the slow crystallographic reconstruction. Reconstruction during surface reduction tends to proceed in the direction of the topography obtained during the annealing process. Methods of avoiding Faradaic current flowing through the STM tip are discussed in detail.
- Published
- 1991
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11. STM studies of p-Si(111) substrate in air and in electrolytic environment
- Author
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O. Velev, J. O'm. Bockris, A. González-Martín, and M. Szklarczyk
- Subjects
Silicon ,Chemistry ,Analytical chemistry ,chemistry.chemical_element ,Biasing ,Surfaces and Interfaces ,Substrate (electronics) ,Electrolyte ,Condensed Matter Physics ,Electrochemistry ,Surfaces, Coatings and Films ,law.invention ,law ,Materials Chemistry ,Scanning tunneling microscope ,Quantum tunnelling ,Surface states - Abstract
Scanning tunneling microscopy was used to study p-Si(111) surfaces in electrolyte solution and in air as well. The dependence of STM images on the sign and magnitude of tunneling bias voltage, as well as on the surface environment, was detected. This dependence was correlated with the electronic propErtles of p-Si(111) surfaces. It is proposed that electrochemical formation of SiO x and Si-OH surface compounds induces surface states in the band-gap of p-Si(111) at approximately 0.25 eV from the edge of the valence band at the surface.
- Published
- 1990
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12. The detection limit of the in-situ radiotracer technique for the adsorption at the solid-solution interface
- Author
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M. Szklarczyk and M. Gamboa-Aldeco
- Subjects
Detection limit ,In situ ,Adsorption ,Chemistry ,Inorganic chemistry ,Solid solution - Abstract
L'adsorption d'ions sulfate sur une electrode de platine dans une solution d'acide perchlorique est examinee grâce a un marquage isotopique du sulfate de sodium par du soufre 35
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- 1990
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13. STM imaging of Al(111) and poly crystalline Al samples in air
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J. O'm. Bockris, M. Szklarczyk, and Lj. Minevski
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Chemistry ,Analytical chemistry ,Mineralogy ,Poly crystalline - Abstract
La microscopie tunnel a balayage est utilisee pour etudier la surface d'une electrode composee d'un monocristal ou d'un polycristal d'aluminium, a l'air
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- 1990
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14. In Situ STM Studies of Lead Electrodeposition on Graphite Substrate
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M. Szklarczyk and John O’M. Bockris
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In situ ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Materials Chemistry ,Electrochemistry ,Graphite substrate ,Surface structure ,Mineralogy ,Graphite ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Nuclear chemistry - Abstract
Le depot electrolytique de plomb sur une electrode composee d'un monocristal de graphite est etudie in situ par microscopie tunnel a balayage. Le reseau atomique du depot de plomb est observe et compare avec celui obtenu a l'air
- Published
- 1990
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15. ChemInform Abstract: STM Imaging of Al(111) and Polycrystalline Al Samples in Air
- Author
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Lj. Minevski, M. Szklarczyk, and J. O'm. Bockris
- Subjects
Chemistry ,Analytical chemistry ,General Medicine ,Crystallite - Published
- 1990
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16. Photoelectrochemical evolution of hydrogen on p-indium phosphide
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M. Szklarczyk and John O’M. Bockris
- Subjects
chemistry.chemical_compound ,Hydrogen ,Chemistry ,Inorganic chemistry ,General Engineering ,Indium phosphide ,Physical chemistry ,chemistry.chemical_element ,Physical and Theoretical Chemistry - Abstract
Etudes, en solution acide, du degagement photoelectrochimique d'hydrogene sur InP en fonction du potentiel, de la longueur d'onde et de la nature du metal (Pb, Cd, Co, Au, Ni et Pt) formant des ilots sur la surface
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- 1984
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17. Substrate effects on photoelectrochemical kinetics in hydrogen production
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Gene Sparrow, M. Szklarczyk, J. O'm. Bockris, and V. Brusic
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Photocurrent ,Hydrogen ,Electrolysis of water ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Band gap ,Analytical chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Condensed Matter Physics ,Fuel Technology ,Reaction rate constant ,X-ray photoelectron spectroscopy ,Hydrogen production ,Surface states - Abstract
The surface of p-Si has been treated in a number of ways, and the rate of the photoelectrochemical reduction of water to hydrogen measured on each type of surface. Correspondingly, in-situ ellipsometric determinations of thickness and refractive index of the surface films were made; corresponding XPS, ISS and SIMS studies were also carried out. The photoelectrochemical activities of the surfaces, as measured by the positive shift on the potential axis of the mid-current point of the photocurrent/potential curve, differed greatly. In treatments with HF, the chemical structure of the surface remains that of SiO2; in treatments with aquaregia and HF, the surface becomes SiO. After hydrogen evolution, SiOH bonds appear. The degree of dependence of the photoelectrochemical activity on the surface characteristics indicates that a reaction at the semiconductor/solution interface controls the overall (consecutive) photoelectrochemical reaction. The increase in rate with change of surface structure depends on the following factors in increasing order of importance: the presence of band gap surface states, the (established) jump in the order of magnitude of conductance of SiOx at x = 1.8, and the (argued) increasing availability of Si bonds during increasing reduction of the surface, thus causing an increase in the rate constant of a rate-determining proton transfer.
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- 1984
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18. Eight chemical explanations of the Fleischmann-Pons effect
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G.H. Lin, M. Szklarczyk, O. Velev, J. C. Wass, N.J.C. Packham, R. C. Kainthla, L. Kaba, and J. O'm. Bockris
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Fuel Technology ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Energy Engineering and Power Technology ,Thermodynamics ,Condensed Matter Physics - Abstract
Eight possible explanations for the heat produced in the Fleischmann-Pons effect are examined with the various conservative assumptions concerning the quantities used. No individual explanation is sufficient to explain the heat produced. All of them together can only explain heat as much as 3 W cm −3 .
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- 1989
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19. Photoelectrocatalysis and electrocatalysis on p-silicon
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M. Szklarczyk and J. O'm. Bockris
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Silicon ,chemistry ,Inorganic chemistry ,General Engineering ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Electrocatalyst - Published
- 1984
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20. On photoelectrocatalysis of hydrogen and oxygen evolution
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Shahed U. M. Khan, John O’M. Bockris, A.Q. Contractor, and M. Szklarczyk
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Hydrogen ,Renewable Energy, Sustainability and the Environment ,Photoelectrochemistry ,Oxygen evolution ,Energy Engineering and Power Technology ,Exchange current density ,chemistry.chemical_element ,Condensed Matter Physics ,Alkali metal ,Electrocatalyst ,Metal ,Fuel Technology ,chemistry ,Chemical physics ,visual_art ,visual_art.visual_art_medium ,Atomic physics ,Surface states - Abstract
In most previous treatments of photoelectrochemical kinetics, the focus of attention has been on the hole-electron pair formation by light, transport to the surface and various losses arising from hole-electron recombination. In surfaces of SiO x (2 > x > 0.8), the photoelectrochemical onset potential varies by ca 0.8 V. When the variation of the photoelectrochemical onset potential on metal-decorated p-type semiconductor is plotted against the exchange current density for the dark evolution of hydrogen a slope close to 2RT/F is found. For oxygen evolution on metal decorated n-type semiconductor, there is a dependence of the onset potential on the metal-oxygen bond strength in alkali but zero dependence in acid solution. Work-function dependences are present: there is no correlation with effects of hydrogen on the work-function. The formation of band-gap surface states, recombination and effects of the surface treatment upon work-function are compared with the data but found inconsistent with it. If it is assumed that the surface treatment and metal deposition have a strong effect on the charge-transfer rate constants, several correlations can be rationalized. Implications are drawn regarding the role to be played by electrocatalysis in photoelectrochemistry.
- Published
- 1984
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21. Spectroscopic and microscopic studies of photoelectrode surfaces
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L.A. Bernard, V. Young, M. Szklarczyk, Gene Sparrow, A.Q. Contractor, and J. O'm. Bockris
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Chemistry ,General Engineering ,Physical chemistry ,Mineralogy - Abstract
Etude par differentes techniques spectrometriques et microscopiques de la surface d'electrodes de Si et TiO 2 avec des ilots de differents metaux (Pb, Au, Pt) apres passage dans une cellule photoelectrochimique
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- 1984
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22. Sporadic observation of the Fleischmann-Pons heat effect
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R. C. Kainthla, L. Kaba, J. C. Wass, M. Szklarczyk, O. Velev, G.H. Lin, N.J.C. Packham, and J. O'm. Bockris
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Electrolysis ,Chemistry ,Electrolytic cell ,General Chemical Engineering ,Thermistor ,Analytical chemistry ,Thermodynamics ,Calorimetry ,Overpotential ,law.invention ,Calorimeter ,Anode ,law ,Heat transfer ,Electrochemistry - Abstract
An examination has been made of the heat production at ten palladium electrodes, each prepared in a different way. Seven of these produced heat during D2 evolution in a D2-O2 electrolysis cell (no recombination attempted) which coincided precisely with the prediction of classical electrochemical theory, and thus eliminated the suspicion of heat through unintended D2-O2 recombination. Three electrodes clearly produced an excess heat of ~2-5 watts-cm -3 . The heat was observed for periods of 10-33 hrs. In one electrode the excess heat production "shut off" (after 33 hrs) with no apparent cause: it did not return in five days of further electrolysis. Fleischmann and Pons (1) reported the production of heat during the electrolysis of D2O at a Pd cathode and Pt anode in excess of that predicted by the electrochemical theory for the heat production in cells. Some of the measurements even indicated that the total energy out of the cell as heat was greater than that going in as electricity. The paper attracted attention because it was suggested that the excess heat was due to D-D fusion occurring in Pd at high overpotential. A principal difficulty, since the announcement in March 1989, has been that many electrochemically inexperienced investigators have tried, but failed, to reproduce the alleged heat (however, cf. Huggins (2), Landau (3), McKubre (4), Appleby and Srinivasan (5), Wadsworth (6)). In this note, we report the observation of this excess heat effect in three electrodes out of ten prepared and examined. The calorimeter used in the study was of the heat transfer type. The cell is a glass cylinder 10 cm. high and 5 cm in diameter. The cap is made of 1 cm thick Teflon with holes for the electrodes, the Joule heater and the temperature probe. The cell is placed inside another glass cylinder 12 cm. high and 7 cm. in diameter. For good heat transfer the space between the cylinders is filled with ethylene glycol. The assembly is immersed in a constant temperature bath (0.01°C accuracy) and the temperature difference between the bath and the cell is monitored with thermistor thermometers (Omega 700 series thermistors with 0.01°C resolution). The calorimeter was calibrated by passing different amount of direct current through the electric heater (resistance 275 Ω) in the solution of 0.1 M LiOD (made by dissolution of Li in D2O) and noting the potential drop across it. For each value of the electrical power put in, steady state temperature difference (monitored on a y-t recorder) was noted and plotted to yield a
- Published
- 1989
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23. On the Dielectric Breakdown of Water: An Electrochemical Approach
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M. Szklarczyk, Ramesh C. Kainthla, and John O’M. Bockris
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Condensed matter physics ,Dielectric strength ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Inorganic chemistry ,Fermi level ,Limiting current ,Dielectric ,Condensed Matter Physics ,Cathode ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,symbols.namesake ,law ,Materials Chemistry ,Electrochemistry ,symbols ,Breakdown voltage ,Work function ,Current density - Abstract
The dielectric breakdown of water under static fields has been studied by current‐potential relation for six metals. The relations are quasi‐linear up to a current density of a few A‐cm−2. The limiting current continues for a few volts to a few hundred volts, depending on the metal. A glow develops at the electrode and becomes continuous at the end of the plateau, where the current density increases irregularly (breakdown). The breakdown potential does not depend on the field in the water. It occurs at about the same current density for most of the metals. When electrolytes are added, the cell potential at the breakdown is decreased. Adsorbed layers and organic coatings increase the breakdown potential. Electrical energy storage in water is increased by ~10 times by coatings. The breakdown potential decreases with increase of log of rate constant for hydrogen evolution on the various electrodes and with the corresponding work function. The cell potentials for breakdown correspond to fields in the dielectric below that needed to dissociate it. The limiting current is caused by the formation of a layer at the interface, which causes increase in the electrode potential at constant current. The layer plasmolyzes. When the Fermi level in the cathode reaches the conduction band of water, electrons enter the water and remain stable therein. They interact nonadiabatically with water and are the head of streamers. An analogous model holds for holes in the valence band. "Dielectric breakdown" depends on the Fermi level of the electrons in the condenser plate and the semiconductor characteristics of water. It can be eliminated by modifying the electrode surface.
- Published
- 1989
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24. Hydrogen production through photoelectrocatalysis on p-type molybdenum sulphide
- Author
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M. Szklarczyk and John O’M. Bockris
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Photocurrent ,endocrine system ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Limiting ,Condensed Matter Physics ,Electrochemistry ,Metal ,Fuel Technology ,Molybdenum ,visual_art ,visual_art.visual_art_medium ,Hydrogen production - Abstract
The effect of depositing islets of metals having widely different work functions has been examined by means of the measurement of the relation of photocurrent to potential on p-MoS 2 , containing, respectively, islets of Pt, Au, Co, Pb and Cd. From the exponential sections of the photocurrent-potential curves, the shift, ΔE , caused at constant photocurrent by the presence of the metal was observed. The limiting photocurrent is unaffected by the metal islets. Four models for such effects are examined. The evidence seems strongest for a model in which the rate-determining step of electrochemical charge transfer occurs at the islet-solution interface.
- Published
- 1984
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25. Influence of metal additions on silicon during hydrogen evolution
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J. O'm. Bockris, A.Q. Contractor, and M. Szklarczyk
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Metal ,Silicon ,Chemistry ,visual_art ,Inorganic chemistry ,visual_art.visual_art_medium ,chemistry.chemical_element ,Hydrogen evolution - Abstract
Le depot d'ilots de metal sur des surfaces de semiconducteurs influe fortement sur le degagement photoelectrochimique d'hydrogene. La presence du metal entraine un deplacement des courbes photocourant-potentiel du cote negatif ou positif, suivant e metal. Explication des phenomenes
- Published
- 1983
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26. ChemInform Abstract: PHOTOELECTROCATALYSIS AND ELECTROCATALYSIS ON P-SILICON
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J. O'm. Bockris and M. Szklarczyk
- Subjects
Silicon ,Chemistry ,chemistry.chemical_element ,Nanotechnology ,General Medicine ,Electrocatalyst - Published
- 1984
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27. ChemInform Abstract: Study of Electrode Processes of Sulphur Dioxide on Platinized Electrode by the Radiochemical Method
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M. SZKLARCZYK, A. CZERWINSKI, and J. SOBKOWSKI
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General Medicine - Published
- 1982
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28. ChemInform Abstract: PHOTOELECTROCHEMICAL EVOLUTION OF HYDROGEN ON P-INDIUM PHOSPHIDE
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M. Szklarczyk and J. O'm. Bockris
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chemistry.chemical_compound ,chemistry ,Hydrogen ,Inorganic chemistry ,Indium phosphide ,chemistry.chemical_element ,General Medicine - Published
- 1985
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29. On models of photoelectrocatalysis
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John O’M. Bockris, M. Szklarczyk, O. J. Murphy, and Shahed U. M. Khan
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Fuel Technology ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,Condensed Matter Physics - Abstract
Presentation de deux modeles de la photoelectrocatalyse par des agregats metalliques revetant des photocathodes de p-Si et de donnees experimentales permettant de choisir l'un de ceux-ci
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- 1984
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30. Photoelectrocatalysis on silicon in solar light
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M. Szklarczyk and John O’M. Bockris
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Photocurrent ,Materials science ,Physics and Astronomy (miscellaneous) ,Silicon ,Hydrogen ,Inorganic chemistry ,Analytical chemistry ,chemistry.chemical_element ,Photoelectrochemical cell ,Rate-determining step ,Nickel ,chemistry ,Electrode ,Current density - Abstract
Photoelectrochemical measurements have been carried out on p‐Si electrodes which contained islands of Pb, Cd, Au, Ni, Co, and Pt. These islands cause the photocurrent density of some of the Si systems to increase greatly (10×) in the middle region of the photocurrent potential curve. A plot of the change in potential observed for this region against log i0 for the dark hydrogen evolution on the metals concerned is linear with a slope close to that expected for a rate determining step at the metal‐solution interface.
- Published
- 1983
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31. Dynamic adaptation of the extremophilic red microalga Cyanidioschyzon merolae to high nickel stress.
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Marchetto F, Santaeufemia S, Lebiedzińska-Arciszewska M, Śliwińska MA, Pich M, Kurek E, Naziębło A, Strawski M, Solymosi D, Szklarczyk M, Bulska E, Szymański J, Wierzbicka M, Allahverdiyeva Y, Więckowski MR, and Kargul J
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- Nickel, Chloroplasts, Extremophiles, Microalgae
- Abstract
The order of Cyanidiales comprises seven acido-thermophilic red microalgal species thriving in hot springs of volcanic origin characterized by extremely low pH, moderately high temperatures and the presence of high concentrations of sulphites and heavy metals that are prohibitive for most other organisms. Little is known about the physiological processes underlying the long-term adaptation of these extremophiles to such hostile environments. Here, we investigated the long-term adaptive responses of a red microalga Cyanidioschyzon merolae, a representative of Cyanidiales, to extremely high nickel concentrations. By the comprehensive physiological, microscopic and elemental analyses we dissected the key physiological processes underlying the long-term adaptation of this model extremophile to high Ni exposure. These include: (i) prevention of significant Ni accumulation inside the cells; (ii) activation of the photoprotective response of non-photochemical quenching; (iii) significant changes of the chloroplast ultrastructure associated with the formation of prolamellar bodies and plastoglobuli together with loosening of the thylakoid membranes; (iv) activation of ROS amelioration machinery; and (v) maintaining the efficient respiratory chain functionality. The dynamically regulated processes identified in this study are discussed in the context of the mechanisms driving the remarkable adaptability of C. merolae to extremely high Ni levels exceeding by several orders of magnitude those found in the natural environment of the microalga. The processes identified in this study provide a solid basis for the future investigation of the specific molecular components and pathways involved in the adaptation of Cyanidiales to the extremely high Ni concentrations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)
- Published
- 2024
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32. Migration of repetitive DNAs during evolution of the permanent translocation heterozygosity in the oyster plant (Tradescantia section Rhoeo).
- Author
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Golczyk H, Hřibová E, Doležel J, Cuadrado Á, Garbsch F, Greiner S, Janeczko M, Szklarczyk M, Masłyk M, and Kubiński K
- Subjects
- Animals, DNA, Ribosomal genetics, Heterochromatin, In Situ Hybridization, Fluorescence, Repetitive Sequences, Nucleic Acid, Translocation, Genetic, Ostreidae genetics, Tradescantia genetics
- Abstract
Due to translocation heterozygosity for all chromosomes in the cell complement, the oyster plant (Tradescantia spathacea) forms a complete meiotic ring. It also shows Rabl-arrangement at interphase, featured by polar centromere clustering. We demonstrate that the pericentromeric regions of the oyster plant are homogenized in concert by three subtelomeric sequences: 45S rDNA, (TTTAGGG)n motif, and TSrepI repeat. The Rabl-based clustering of pericentromeric regions may have been an excellent device to combine the subtelomere-pericentromere sequence migration (via inversions) with the pericentromere-pericentromere DNA movement (via whole arm translocations) that altogether led to the concerted homogenization of all the pericentromeric domains by the subtelomeric sequences. We also show that the repetitive sequence landscape of interstitial chromosome regions contains many loci consisting of Arabidopsis-type telomeric sequence or of TSrepI repeat, and it is extensively heterozygous. However, the sequence arrangement on some chromosomal arms suggest segmental inversions that are fully or partially homozygous, a fact that could be explained if the inversions started to create linkages already in a bivalent-forming ancestor. Remarkably, the subterminal TSrepI loci reside exclusively on the longer arms that could be due to sharing sequences between similarly-sized chromosomal arms in the interphase nucleus. Altogether, our study spotlights the supergene system of the oyster plant as an excellent model to link complex chromosome rearrangements, evolution of repetitive sequences, and nuclear architecture., (© 2022. The Author(s).)
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- 2022
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33. Proteomic Studies of Roots in Hypoxia-Sensitive and -Tolerant Tomato Accessions Reveal Candidate Proteins Associated with Stress Priming.
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Czernicka M, Kęska K, Planchon S, Kapusta M, Popielarska-Konieczna M, Wesołowski W, Szklarczyk M, and Renaut J
- Subjects
- Hypoxia metabolism, Oxygen metabolism, Plant Roots metabolism, Proteomics methods, Solanum lycopersicum genetics, Solanum lycopersicum metabolism
- Abstract
Tomato ( Solanum lycopersicum L.) is a vegetable frequently exposed to hypoxia stress induced either by being submerged, flooded or provided with limited oxygen in hydroponic cultivation systems. The purpose of the study was to establish the metabolic mechanisms responsible for overcoming hypoxia in two tomato accessions with different tolerance to this stress, selected based on morphological and physiological parameters. For this purpose, 3-week-old plants (plants at the juvenile stage) of waterlogging-tolerant (WL-T), i.e., POL 7/15, and waterlogging-sensitive (WL-S), i.e., PZ 215, accessions were exposed to hypoxia stress (waterlogging) for 7 days, then the plants were allowed to recover for 14 days, after which another 7 days of hypoxia treatment was applied. Root samples were collected at the end of each time-point and 2D-DIGE with MALDI TOF/TOF, and expression analyses of gene and protein-encoded alcohol dehydrogenase (ADH2) and immunolabelling of ADH were conducted. After collating the obtained results, the different responses to hypoxia stress in the selected tomato accessions were observed. Both the WL-S and WL-T tomato accessions revealed a high amount of ADH2, which indicates an intensive alcohol fermentation pathway during the first exposure to hypoxia. In comparison to the tolerant one, the expression of the adh2 gene was about two times higher for the sensitive tomato. Immunohistochemical analysis confirmed the presence of ADH in the parenchyma cells of the cortex and vascular tissue. During the second hypoxia stress, the sensitive accession showed a decreased accumulation of ADH protein and similar expression of the adh2 gene in comparison to the tolerant accession. Additionally, the proteome showed a greater protein abundance of glyceraldehyde-3-phosphate dehydrogenase in primed WL-S tomato. This could suggest that the sensitive tomato overcomes the oxygen limitation and adapts by reducing alcohol fermentation, which is toxic to plants because of the production of ethanol, and by enhancing glycolysis. Proteins detected in abundance in the sensitive accession are proposed as crucial factors for hypoxia stress priming and their function in hypoxia tolerance is discussed.
- Published
- 2022
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34. Photosynthetic efficiency, growth and secondary metabolism of common buckwheat (Fagopyrum esculentum Moench) in different controlled-environment production systems.
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Hornyák M, Dziurka M, Kula-Maximenko M, Pastuszak J, Szczerba A, Szklarczyk M, and Płażek A
- Subjects
- Biomass, Chlorophyll A metabolism, Crops, Agricultural growth & development, Crops, Agricultural metabolism, Fagopyrum growth & development, Fagopyrum metabolism, Kinetics, Phenols metabolism, Crop Production, Crops, Agricultural radiation effects, Fagopyrum radiation effects, Light, Lighting instrumentation, Photosynthesis radiation effects, Secondary Metabolism radiation effects
- Abstract
Light-emitting diodes (LEDs) and high-pressure sodium lamps (HPS) are among the most commonly used light sources for plant cultivation. The objective of this study was to evaluate the effect of two controlled-environment production systems differing in light sources on growth, photosynthetic activity, and secondary metabolism of common buckwheat. We hypothesized that LED light with the majority of red and blue waves would increase physiological and biochemical parameters compared to sunlight supplemented with HPS lamps. The experiment was performed in a phytotronic chamber (LEDs) and in a greenhouse (solar radiation supplemented with HPS lamps as a control). The effects were analyzed at the flowering phase with biometric measurements, leaf chlorophyll index, the kinetics of chlorophyll a fluorescence, content of soluble carbohydrates and phenolics in the leaves. Applied LED light decreased the biomass but stimulated the production of phenolics compared to control plants. In control plants, a positive correlation between flavonoid content and energy dissipation from photosystem II (DI
o /CSm ) was found, while in plants under LEDs total pool of phenolic content correlated with this parameter and the quantum yield of electron transport (φ Ro and ψ Ro) was lower than that of the control, probably affecting buckwheat biomass., (© 2022. The Author(s).)- Published
- 2022
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35. Physiological and Biochemical Response to Fusarium culmorum Infection in Three Durum Wheat Genotypes at Seedling and Full Anthesis Stage.
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Pastuszak J, Szczerba A, Dziurka M, Hornyák M, Kopeć P, Szklarczyk M, and Płażek A
- Subjects
- Genotype, Seedlings microbiology, Triticum classification, Triticum genetics, Triticum microbiology, Biomarkers metabolism, Fusarium physiology, Plant Diseases microbiology, Seedlings physiology, Trichothecenes metabolism, Triticum physiology
- Abstract
Fusarium culmorum is a worldwide, soil-borne plant pathogen. It causes diseases of cereals, reduces their yield, and fills the grain with toxins. The main direction of modern breeding is to select wheat genotypes the most resistant to Fusarium diseases. This study uses seedlings and plants at the anthesis stage to analyze total soluble carbohydrates, total and cell-wall bound phenolics, chlorophyll content, antioxidant activity, hydrogen peroxide content, mycotoxin accumulation, visual symptoms of the disease, and Fusarium head blight index (FHBi). These results determine the resistance of three durum wheat accessions. We identify physiological or biochemical markers of durum wheat resistance to F. culmorum . Our results confirm correlations between FHBi and mycotoxin accumulation in the grain, which results in grain yield decrease. The degree of spike infection (FHBi) may indicate accumulation mainly of deoxynivalenol and nivalenol in the grain. High catalase activity in the infected leaves could be considered a biochemical marker of durum sensitivity to this fungus. These findings allowed us to formulate a strategy for rapid evaluation of the disease severity and the selection of plants with higher level, or resistance to F. culmorum infection.
- Published
- 2021
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36. VCF2CAPS-A high-throughput CAPS marker design from VCF files and its test-use on a genotyping-by-sequencing (GBS) dataset.
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Wesołowski W, Domnicz B, Augustynowicz J, and Szklarczyk M
- Subjects
- Genetic Markers, Molecular Diagnostic Techniques, Software, Datasets as Topic, Genotype, High-Throughput Nucleotide Sequencing methods
- Abstract
Next-generation sequencing (NGS) is a powerful tool for massive detection of DNA sequence variants such as single nucleotide polymorphisms (SNPs), multi-nucleotide polymorphisms (MNPs) and insertions/deletions (indels). For routine screening of numerous samples, these variants are often converted into cleaved amplified polymorphic sequence (CAPS) markers which are based on the presence versus absence of restriction sites within PCR products. Current computational tools for SNP to CAPS conversion are limited and usually infeasible to use for large datasets as those generated with NGS. Moreover, there is no available tool for massive conversion of MNPs and indels into CAPS markers. Here, we present VCF2CAPS-a new software for identification of restriction endonucleases that recognize SNP/MNP/indel-containing sequences from NGS experiments. Additionally, the program contains filtration utilities not available in other SNP to CAPS converters-selection of markers with a single polymorphic cut site within a user-specified sequence length, and selection of markers that differentiate up to three user-defined groups of individuals from the analyzed population. Performance of VCF2CAPS was tested on a thoroughly analyzed dataset from a genotyping-by-sequencing (GBS) experiment. A selection of CAPS markers picked by the program was subjected to experimental verification. CAPS markers, also referred to as PCR-RFLPs, belong to basic tools exploited in plant, animal and human genetics. Our new software-VCF2CAPS-fills the gap in the current inventory of genetic software by high-throughput CAPS marker design from next-generation sequencing (NGS) data. The program should be of interest to geneticists involved in molecular diagnostics. In this paper we show a successful exemplary application of VCF2CAPS and we believe that its usefulness is guaranteed by the growing availability of NGS services., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2021
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37. Haploid and Doubled Haploid Plant Production in Brassica rapa L. subsp. pekinensis Via Microspore Culture.
- Author
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Adamus A, Szklarczyk M, and Kiełkowska A
- Subjects
- Acclimatization genetics, Brassica rapa physiology, Crops, Agricultural genetics, Crops, Agricultural growth & development, Crops, Agricultural physiology, Culture Media chemistry, DNA, Plant genetics, Diploidy, Glucose-6-Phosphate Isomerase genetics, Haploidy, Homozygote, Molecular Biology methods, Pollen genetics, Pollen growth & development, Polymerase Chain Reaction, Regeneration genetics, Tissue Culture Techniques, Brassica rapa genetics, Brassica rapa growth & development, Plant Breeding methods
- Abstract
The production of haploid and doubled haploid plants is a biotechnological tool that shortens the breeding process of new cultivars in many species. Doubled haploid plants are homozygous at every locus and they can be utilized as parents to produce F1 hybrids. In this chapter, we describe a protocol for the production of doubled haploid plants in Brassica rapa L. subsp. pekinensis using androgenesis induced by isolated microspore cultures., (© 2021. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)
- Published
- 2021
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38. The use of Callitriche cophocarpa Sendtn. for the reclamation of Cr-contaminated freshwater habitat: benefits and limitations.
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Augustynowicz J, Sitek E, Bryniarski T, Baran A, Ostachowicz B, Urbańska-Stopa M, and Szklarczyk M
- Subjects
- Ecosystem, Fresh Water, Geologic Sediments, Plant Leaves, Plants, Chromium, Water Pollutants, Chemical
- Abstract
This work is the first attempt to evaluate suitability of Callitriche cophocarpa Sendtn. (water-starwort) to remove Cr under real-world conditions. Our earlier laboratory-scale studies demonstrated outstanding hyperaccumulation properties of this aquatic higher plant (macrophyte) toward chromium in solution. We introduced C. cophocarpa plants into the watershed with sediments heavily polluted (on average 1400 mg/kg d.w. of Cr) by a tannery. The plants grew vigorously and exhibited no physiological or anatomical disorders. Based on chemical fractionations of bottom sediments, we found low Cr bioavailability. The element was strongly associated with the sediments and could be classified into the following fractions (%): oxidizable III (68.2) > residual IV (28.8) > reducible II (1.6) > exchangeable I (1.4). Despite this, Cr content in plant organs at the contaminated sites was 33 up to 83 times greater than in the control leaf/stem and roots, respectively. Altering redox potential during, i.e., sediment deposition on land may change chemical forms of bound metals in a solid phase, and thus further increase Cr phytoextraction by plants. With this in mind, we concluded that the species, being an outstanding Cr accumulator under laboratory conditions, can be useful in the reclamation of Cr-polluted sediments under controlled, oxidizing conditions.
- Published
- 2020
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39. Polyelectrolyte membrane scaffold sustains growth of neuronal cells.
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Grzeczkowicz A, Gruszczynska-Biegala J, Czeredys M, Kwiatkowska A, Strawski M, Szklarczyk M, Koźbiał M, Kuźnicki J, and Granicka LH
- Subjects
- Animals, Neuroglia cytology, Neurons cytology, Rats, Rats, Wistar, Membranes, Artificial, Neuroglia metabolism, Neurons metabolism, Polyelectrolytes chemistry, Tissue Scaffolds chemistry
- Abstract
Cell immobilization within nano-thin polymeric shells can provide an optimal concentration of biological material in a defined space and facilitate its directional growth. Herein, polyelectrolyte membrane scaffolds were constructed using a layer-by-layer approach to determine the possibility of promoting improved growth of rat cortical neuronal cells. Membrane presence was confirmed by Fourier transform infrared spectroscopy, Zeta potential, and atomic force and scanning electron microscopy. Scaffold performance toward neuronal cell growth was assessed in vitro during a 14-day culture. Cell conditions were analyzed immunocytochemically. Furthermore, western blot and real-time PCR analyses were used to validate the presence of neuronal and glial cells on the scaffolds. We observed that alginate/chitosan, alginate/polylysine, and polyethyleneimine/chitosan scaffolds promote neuronal growth similarly to the control, poly-d-lysine/laminin. We conclude that membranes maintaining cell viability, integrity and immobilization in systems supporting neuronal regeneration can be applied in neurological disease or wound healing treatment. © 2018 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 839-850, 2019., (© 2018 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals, Inc.)
- Published
- 2019
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40. Stabilized nanosystem of nanocarriers with an immobilized biological factor for anti-tumor therapy.
- Author
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Kwiatkowska A, Granicka LH, Grzeczkowicz A, Stachowiak R, Kamiński M, Grubek Z, Bielecki J, Strawski M, and Szklarczyk M
- Subjects
- Animals, Antineoplastic Agents chemistry, Biological Factors chemistry, Cell Line, Cell Survival drug effects, Coated Materials, Biocompatible, Drug Design, Drug Stability, Humans, Ligands, Mice, Particle Size, Spectroscopy, Fourier Transform Infrared, Spectrum Analysis, Antineoplastic Agents administration & dosage, Biological Factors administration & dosage, Drug Carriers chemistry, Drug Delivery Systems, Nanomedicine, Nanoparticles chemistry
- Abstract
Objective: The inadequate efficiency of existing therapeutic anti-cancer regiments and the increase in the multidrug resistance of cancer cells underscore the need to investigate novel anticancer strategies. The induction of apoptosis in tumors by cytotoxic agents produced by pathogenic microorganisms is an example of such an approach. Nevertheless, even the most effective drug should be delivered directly to targeted sites to reduce any negative impact on other cells. Accordingly, the stabilized nanosystem (SNS) for active agent delivery to cancer cells was designed for further application in local anti-tumor therapy. A product of genetically modified Escherichia coli, listeriolysin O (LLO), was immobilized within the polyelectrolyte membrane (poly(ethylenimine)|hyaluronic acid) shells of 'LLO nanocarriers' coupled with the stabilizing element of natural origin., Methods and Results: The impact of LLO was evaluated in human leukemia cell lines in vitro. Correspondingly, the influence of the SNS and its elements was assessed in vitro. The viability of targeted cells was evaluated by flow cytometry. Visualization of the system structure was performed using confocal microscopy. The membrane shell applied to the nanocarriers was analyzed using atomic force microscopy and Fourier transform infrared spectroscopy techniques. Furthermore, the presence of a polyelectrolyte layer on the nanocarrier surface and/or in the cell was confirmed by flow cytometry. Finally, the structural integrity of the SNS and the corresponding release of the fluorescent solute listeriolysin were investigated., Conclusion: The construction of a stabilized system offers LLO release with a lethal impact on model eukaryotic cells. The applied platform design may be recommended for local anti-tumor treatment purposes., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2017
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41. The Experimental Study of the Performance of Nano-Thin Polyelectrolyte Shell for Dental Pulp Stem Cells Immobilization.
- Author
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Grzeczkowicz A, Granicka LH, Maciejewska I, Strawski M, Szklarczyk M, and Borkowska M
- Subjects
- Cell Adhesion, Cell Culture Techniques, Cells, Immobilized cytology, Cells, Immobilized drug effects, Humans, Regeneration, Stem Cells drug effects, Dental Pulp cytology, Polyelectrolytes pharmacology, Stem Cells cytology
- Abstract
Carious is the most frequent disease of mineralized dental tissues which might result in dental pulp inflammation and mortality. In such cases an endodontic treatment is the only option to prolong tooth functioning in the oral cavity; however, in the cases of severe pulpitis, especially when complicated with periodontal tissue inflammation, the endodontic treatment might not be enough to protect against tooth loss. Thus, keeping the dental pulp viable and/or possibility of the reconstruction of a viable dental pulp complex, appears to become a critical factor for carious and/or pulp inflammation treatment. The nowadays technologies, which allow handling dental pulp stem cells (DPSC), seem to bring us closer to the usage of dental stem cells for tooth tissues reconstruction. Thus, DPSC immobilized within nano-thin polymeric shells, allowing for a diffusion of produced factors and separation from bacteria, may be considered as a cover system supporting technology of dental pulp reconstruction. The DPSC were immobilized using a layer-by-layer technique within nano-thin polymeric shells constructed and modified by nanostructure involvement to ensure the layers stability and integrity as well as separation from bacterial cells. The cytotoxity of the material used for membrane production was assessed on the model of adherent cells. The performance of DPSC nano-coating was assessed in vitro. Membrane coatings showed no cytotoxicity on the immobilized cells. The presence of coating shell was confirmed with flow cytometry, atomic force microscopy and visualized with fluorescent microscopy. The transfer of immobilized DPSC within the membrane system ensuring cells integrity, viability and protection from bacteria should be considered as an alternative method for dental tissues transportation and regeneration.
- Published
- 2015
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42. Analysis of the mitochondrial proteome in cytoplasmic male-sterile and male-fertile beets.
- Author
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Wesołowski W, Szklarczyk M, Szalonek M, and Słowińska J
- Subjects
- Beta vulgaris genetics, Mitochondrial Proteins genetics, Plant Proteins genetics, Proteome genetics, Beta vulgaris metabolism, Mitochondrial Proteins metabolism, Plant Infertility physiology, Plant Proteins metabolism, Proteome metabolism
- Abstract
The reported analyses were aimed at identification of the mitochondrial proteome features which were associated with cytoplasmic male sterility (CMS) in beets. The set of analyzed accessions included CMS, maintainer and restored lines. Mitochondrial preparations were subjected to blue-native electrophoresis followed either by in-gel activity assays or separation in denaturing conditions. The CMS condition was associated with decreased activity of complex V and enhancement of additional complexes with the ATPase activity. This was accompanied by accumulation of heptamer HSP60, preSATP6 and an increase in the fraction of the free ATP9 oligomer (not bound to complex V). The ATP9 effect was reversed upon fertility restoration., Biological Significance: The reported work provides one of very few comprehensive comparisons of the mitochondrial proteomes from cytoplasmic male-sterile (CMS) and male-fertile plants. It shows that in beets the CMS trait is associated with altered functioning of the mitochondrial ATP synthase complex. The presence of CMS-specific ATP synthase subcomplexes resembles deficiencies of this enzyme reported for mammalian cells., (Copyright © 2015 Elsevier B.V. All rights reserved.)
- Published
- 2015
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43. Mitochondrial atp9 genes from petaloid male-sterile and male-fertile carrots differ in their status of heteroplasmy, recombination involvement, post-transcriptional processing as well as accumulation of RNA and protein product.
- Author
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Szklarczyk M, Szymański M, Wójcik-Jagła M, Simon PW, Weihe A, and Börner T
- Subjects
- Base Sequence, Blotting, Western, DNA, Complementary genetics, Flowers genetics, Genetic Loci, Hydrophobic and Hydrophilic Interactions, Molecular Sequence Data, Open Reading Frames genetics, Plant Infertility genetics, Plant Proteins metabolism, Polymerase Chain Reaction, RNA Editing genetics, RNA, Messenger genetics, RNA, Plant metabolism, Daucus carota genetics, Genes, Mitochondrial, Genes, Plant, Plant Proteins genetics, RNA Processing, Post-Transcriptional genetics, RNA, Plant genetics, Recombination, Genetic
- Abstract
Key Message: Petaloid cytoplasmic male-sterile carrots exhibit overexpression of the mitochondrial atp9 genes which is associated with specific features in organization and expression of these sequences. In carrots, the Sp-cytoplasm causes transformation of stamens into petal-like organs, while plants carrying normal N-cytoplasm exhibit normal flower morphology. Our work was aimed at characterization of distinct features both cytoplasms display with respect to organization and expression of the mitochondrial atp9 genes. We show that two carrot atp9 genes, previously reported as cytoplasm-specific, in fact occur in heteroplasmic condition. In the Sp-cytoplasm the atp9-1 version dominates over atp9-3, while in N-cytoplasmic plants this proportion is reversed. Herein, we also indicate the presence and recombination activity of a 130-/172-bp sequence repeat which likely shaped the present organization of carrot atp9 loci. Furthermore, cDNA sequence examination revealed that the atp9 open reading frames (ORFs) were C to U edited in 4 nucleotide positions. One of the editing events turns a glutamine triplet into the stop codon, thereby equalizing ORFs of atp9-1 and atp9-3. A certain fraction of partially edited molecules was identified-they all represented the atp9-3 sequence. In either Sp- or N-cytoplasmic plants multiple 5' transcript termini were observed. Of these, the ones mapping more distantly from the atp9 ORF were more pronounced in case of petaloid accessions. It was also shown that despite comparable copy number of the genomic atp9 sequences, the level of the respective mRNAs was approximately 3 times higher in case of petaloid carrots. The latter fact corresponded to the elevated content of the ATP9 protein in plants carrying Sp-cytoplasm. The semi-fertile phenotype of such plants is associated with a drop in ATP9 accumulation.
- Published
- 2014
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44. The targeting nanothin polyelectrolyte shells in system with immobilized bacterial cells for antitumor factor production.
- Author
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Granicka LH, Borkowska M, Grzeczkowicz A, Stachowiak R, Szklarczyk M, Bielecki J, and Strawski M
- Subjects
- Antineoplastic Agents pharmacology, Bacillus subtilis drug effects, Cell Survival drug effects, Cells, Immobilized drug effects, Cells, Immobilized metabolism, Flow Cytometry, Humans, Jurkat Cells, Microscopy, Fluorescence, Polyethyleneimine chemistry, Polylysine chemistry, Antineoplastic Agents metabolism, Bacillus subtilis cytology, Bacillus subtilis metabolism, Electrolytes chemistry, Nanoparticles chemistry
- Abstract
Development of anticancer treatment strategies is ongoing considering still inadequate efficiency of existing anticancer therapeutics. Moreover, the lack of therapeutic agents selectivity against the tumor cells requires further investigations into novel anticancer strategies. The use of pathogenic microorganisms producing an oncolytic agent may be an approach for apoptotic therapy in cancer treatment. The purpose of this study was to investigate the targeting efficiency of Bacillus subtilis bacterial cells coated with modified polyelectrolyte shells applied to protect the bacterial cells from potential host immune response as well as to enhance the tumor-targeting efficiency. The shells were modified with transferrin to increase affinity toward the target tumor cells. The impact of bacterial cells coated with unmodified or modified nanothin shells on human leukemia cells was evaluated in vitro. It was observed that the bacterial cells coated with modified shells with incorporated transferrin exhibited stronger lethal impact on leukemia cells as compared to bacterial cells with unmodified shell coating. Applied modified membrane conformation allowing for functioning of encapsulated microorganisms may find potential use in local antitumor treatment purposes., (© 2013 Wiley Periodicals, Inc.)
- Published
- 2014
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45. Suitability of polyelectrolyte shells modified with fullerene derivate for immunoisolation of cells. Experimental study.
- Author
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Borkowska M, Godlewska E, Antosiak-Iwańska M, Kinasiewicz J, Strawski M, Szklarczyk M, and Granicka LH
- Subjects
- Animals, Cell Culture Techniques, Electrolytes chemistry, Glucose metabolism, Humans, Islets of Langerhans cytology, Islets of Langerhans Transplantation immunology, Jurkat Cells, Materials Testing, Mice, Polyethyleneimine chemistry, Polylysine chemistry, Polymers chemistry, Rats, Transplantation, Heterologous, Fullerenes chemistry, Islets of Langerhans Transplantation methods
- Abstract
The polymeric permiselective membranes application for immunoisolation of cells separating the transplanted cells from the host immunological system may eliminate immunosuppressive therapy during transplantation. The suitability of polyelectrolyte modified nanocoatings for immunoisolation of cells was assessed. The polymeric shells modified with incorporated fullerene derivate were applied for encapsulation of human T-lymphocyte cell line Jurkat or rat pancreatic islets of Langerhans using layer-by-layer technique. Hydroxylated fullerene was incorporated to the polyelectrolyte shell for hydrophility increase as well as for layer stability improvement. Evaluation with AFM, FTIR, fluorescence microscopy confirmed the nanocoating presence on the encapsulated cells. It was observed that polylysine-polyethyleneimine membrane with incorporated fullerenol allowed for encapsulated cells functioning in vitro. Membrane conformation applied for encapsulation of pancreatic rat islets allowed for glucose level decline during xenotransplantation into mice. The elaborated nanocoating may be recommended as the possible alternative to the space consuming microencapsulation for biomedical purposes.
- Published
- 2012
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46. Against the traffic: The first evidence for mitochondrial DNA transfer into the plastid genome.
- Author
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Iorizzo M, Grzebelus D, Senalik D, Szklarczyk M, Spooner D, and Simon P
- Abstract
Transfer of DNA between different compartments of the plant cell, i.e., plastid, mitochondrion and nucleus, is a well-known phenomenon in plant evolution. Six directions of inter-compartmental DNA migration are possible in theory, however only four of them have been previously reported. These include frequent cases of mitochondrion and plastid to nucleus transfer, plastid to mitochondrion transfer, and rare nucleus to mitochondrion migrations. The connection between the plastid and mitochondrial genomes in flowering plants has been viewed as a one way road. Contrary to these observations we found that a sequence widespread in the carrot mitochondrial genome, designated as Dc MP, was transferred to the plastid genome of a carrot ancestor. Interestingly, Dc MP was integrated into a tRNA promoter of the plastid trnV gene, replacing the original promoter sequence. The rearrangement of the plastid genome is specific for carrot and closely related species belonging Scandiceae clade. The structure of the sequence and the presence of a 6 nt target site duplication led us to speculate that the transfer was a result of a transposition event of a non-LTR retrotransposon. These findings open interesting questions about the evolution of organellar genomes and mobile genetic elements and provide a useful plastid marker to phylogenetically delineate species relationships within the Scandiceae clade.
- Published
- 2012
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47. De novo assembly of the carrot mitochondrial genome using next generation sequencing of whole genomic DNA provides first evidence of DNA transfer into an angiosperm plastid genome.
- Author
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Iorizzo M, Senalik D, Szklarczyk M, Grzebelus D, Spooner D, and Simon P
- Subjects
- Magnoliopsida genetics, Molecular Sequence Annotation, Molecular Sequence Data, DNA, Plant genetics, Daucus carota genetics, Gene Transfer, Horizontal, Genome, Mitochondrial, Genome, Plant, High-Throughput Nucleotide Sequencing methods
- Abstract
Background: Sequence analysis of organelle genomes has revealed important aspects of plant cell evolution. The scope of this study was to develop an approach for de novo assembly of the carrot mitochondrial genome using next generation sequence data from total genomic DNA., Results: Sequencing data from a carrot 454 whole genome library were used to develop a de novo assembly of the mitochondrial genome. Development of a new bioinformatic tool allowed visualizing contig connections and elucidation of the de novo assembly. Southern hybridization demonstrated recombination across two large repeats. Genome annotation allowed identification of 44 protein coding genes, three rRNA and 17 tRNA. Identification of the plastid genome sequence allowed organelle genome comparison. Mitochondrial intergenic sequence analysis allowed detection of a fragment of DNA specific to the carrot plastid genome. PCR amplification and sequence analysis across different Apiaceae species revealed consistent conservation of this fragment in the mitochondrial genomes and an insertion in Daucus plastid genomes, giving evidence of a mitochondrial to plastid transfer of DNA. Sequence similarity with a retrotransposon element suggests a possibility that a transposon-like event transferred this sequence into the plastid genome., Conclusions: This study confirmed that whole genome sequencing is a practical approach for de novo assembly of higher plant mitochondrial genomes. In addition, a new aspect of intercompartmental genome interaction was reported providing the first evidence for DNA transfer into an angiosperm plastid genome. The approach used here could be used more broadly to sequence and assemble mitochondrial genomes of diverse species. This information will allow us to better understand intercompartmental interactions and cell evolution.
- Published
- 2012
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48. Conformal nano-thin modified polyelectrolyte coatings for encapsulation of cells.
- Author
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Granicka LH, Antosiak-Iwańska M, Godlewska E, Strawski M, Szklarczyk M, Maranowski B, Kowalewski C, and Wiśniewsk J
- Subjects
- Animals, Avidin chemistry, Avidin metabolism, Biotin chemistry, Biotin metabolism, Cell Survival drug effects, Cells, Immobilized cytology, Coated Materials, Biocompatible chemistry, Coated Materials, Biocompatible pharmacology, Fluorescence, Humans, Islets of Langerhans cytology, Jurkat Cells cytology, Microscopy, Confocal, Nanostructures chemistry, Polyethyleneimine chemistry, Polylysine chemistry, Rats, Biotechnology methods, Cells, Immobilized metabolism, Islets of Langerhans metabolism, Jurkat Cells metabolism
- Abstract
Encapsulation of cells in polymeric shells allows for separation of biological material from produced factors, which may find biotechnological and biomedical applications. Human T-lymphocyte cell line Jurkat as well as rat pancreatic islets were encapsulated using LbL technique within shells of polyelectrolyte modified by incorporation of biotin complexed with avidin to improve cell coating and to create the potential ability to elicit specific biochemical responses. The coating with nano-thin modified shells allowed for maintenance of the evaluated cells' integrity and viability during the 8-day culture. The different PE impact may be observed on different biological materials. The islets exhibited lower mitochondrial activity than the Jurkat cells. Nevertheless, coating of cells with polyelectrolyte modified membrane allowed for functioning of both model cell types: 10 μm leukemia cells or 150 μm islets during the culture. Applied membranes maintained the molecular structure during the culture period. The conclusion is that applied modified membrane conformation may be recommended for coating shells for biomedical purposes.
- Published
- 2011
- Full Text
- View/download PDF
49. Dynamics of Vulmar/VulMITE group of transposable elements in Chenopodiaceae subfamily Betoideae.
- Author
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Grzebelus D, Stawujak K, Mitoraj J, and Szklarczyk M
- Subjects
- Genetic Markers, Molecular Sequence Data, Polymorphism, Genetic, Amaranthaceae genetics, DNA Transposable Elements genetics, DNA, Plant chemistry
- Abstract
Transposable elements are important factors driving plant genome evolution. Upon their mobilization, novel insertion polymorphisms are being created. We investigated differences in copy number and insertion polymorphism of a group of Mariner-like transposable elements Vulmar and related VulMITE miniature inverted-repeat transposable elements (MITEs) in species representing subfamily Betoideae. Insertion sites of these elements were identified using a modified transposon display protocol, allowing amplification of longer fragments representing regions flanking insertion sites. Subsequently, a subset of TD fragments was converted into insertion site-based polymorphism (ISBP) markers. The investigated group of transposable elements was the most abundant in accessions representing the section Beta, showing intraspecific insertion polymorphisms likely resulting from their recent activity. In contrast, no unique insertions were observed for species of the genus Beta section Corollinae, while a set of section-specific insertions was observed in the genus Patellifolia, however, only two of them were polymorphic between P. procumbens and P. webbiana. We hypothesize that Vulmar and VulMITE elements were inactivated in the section Corollinae, while they remained active in the section Beta and the genus Patellifolia. The ISBP markers generally confirmed the insertion patterns observed with TD markers, including presence of distinct subsets of TE insertions specific to Beta and Patellifolia., (© The Author(s) 2011. This article is published with open access at Springerlink.com)
- Published
- 2011
- Full Text
- View/download PDF
50. Ribosomal DNA, tri- and bi-partite pericentromeres in the permanent translocation heterozygote Rhoeo spathacea.
- Author
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Golczyk H, Hasterok R, and Szklarczyk M
- Subjects
- Chromosomes, Plant, In Situ Hybridization, Fluorescence, Karyotyping, Centromere genetics, DNA, Plant genetics, DNA, Ribosomal genetics, Tradescantia genetics, Translocation, Genetic
- Abstract
High- and low-stringency FISH and base-specific fluorescence were performed on the permanent translocation heterozygote Rhoeo spathacea (2n = 12). Our results indicate that 45S rDNA arrays, rDNA-related sequences and other GC-rich DNA fraction(s) are located within the pericentromeric regions of all twelve chromosomes, usually colocalizing with the chromomycin A(3)-positive bands. Homogenization of the pericentromeric regions appears to result from the concerted spread of GC-rich sequences, with differential amplification likely. We found new 5S rDNA patterns, which suggest a variability in the breakpoints and in the consequent chromosome reorganizations. It was found that the large 5S rDNA locus residing on each of the 8E and 9E arms consisted of two smaller loci. On each of the two chromosome arms 3b and 4b, in addition to the major subtelomeric 5S rDNA locus, a new minor locus was found interstitially about 40% along the arm length. The arrangement of cytotogenetic landmarks and chromosome arm measurements are discussed with regard to genome repatterning in Rhoeo.
- Published
- 2010
- Full Text
- View/download PDF
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