Biomedical subjects

Ewa Rogalska

Publications and source records attributed to Ewa Rogalska.

10 recordsLinked to original sources

PubMed2006

A Langmuir film approach to elucidating interactions in lipid membranes: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine/cholesterol/metal cation systems.

The interactions between two membrane lipids, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and cholesterol (CHOL), were studied in Langmuir films using surface pressure isotherms and Brewster angle microscopy. The DPPE/CHOL interactions were probed for chosen monolayer and subphase (Na(+), Ca(2+)) composition at 20, 25, and 30 degrees C. The results obtained show that DPPE and CHOL are miscible for the cholesterol mol fractions x(CHOL)=0.3-0.5. Cholesterol induces condensation of the DPPE monolayers. The most significant condensation of the DPPE/CHOL monolayers was observed in the presence of Ca(2+) ions in the subphase at x(CHOL)=0.4. The negative deviation of the molecular surface area (MMA) additivity from the ideal behavior together with negative values of excess free enthalpy of mixing in the monolayers were interpreted in terms of attractive interactions between lipid molecules.

Calcium↗

PubMed2006

Interactions of a fungistatic antibiotic, griseofulvin, with phospholipid monolayers used as models of biological membranes.

Griseofulvin (GF) is an oral antibiotic for widely occurring superficial mycosis in man and animals caused by dermaphyte fungi; it is also used in agriculture as a fungicide. The mechanism of the biological activity of GF is poorly understood. Here, the interactions of griseofulvin with lipid membranes were studied using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), and 1,2-myristoyl-sn-glycero-3-phosphoethanolamine (DMPE) monolayers spread at the air/water interface. Surface pressure (Pi), electric surface potential (Delta V), grazing incidence X-ray diffraction (GIXD), and Brewster angle microscopy (BAM) were used for studying pure phospholipid monolayers spread on GF aqueous solutions, as well as mixed phospholipid/GF monolayers spread on pure water subphase. Moreover, phospholipase A2 (PLA2) activity toward DLPC monolayers and molecular modeling of the GF surface and lipophilic properties were used to get more insight into the mechanisms of GF-membrane interactions. The results obtained show that GF has a meaningful impact on the film properties; we propose that nonpolar interactions are by and large responsible for GF retention in the monolayers. The modification of membrane properties can be detected using both physicochemical and enzymatic methods. The results obtained may be relevant for elaborating GF preparations with increased bioavailability.

Air↗

PubMed2006

Analytical investigation of the interactions between SC3 hydrophobin and lipid layers: elaborating of nanostructured matrixes for immobilizing redox systems.

Hydrophobins are highly tensioactive fungal proteins with a pronounced affinity for interfaces and a propensity for self-assembly. Recently, these proteins were shown to be useful in retaining different molecules on solid surfaces. This finding offers a possibility for developing new functional materials, while creating the necessity of further research at a deeper mechanistic level. In this work, the mechanisms governing the surface phenomena were studied using native Schizophyllum commune hydrophobin (SC3) and lipid mono- and bilayers; the soft matter systems were used to get a handle on the interactive protein/interface effects at a molecular level. The results obtained indicated that the SC3/lipid membrane interactions were adjusted by protein conformational adaptation, allowing its incorporation into lipid matrixes; the incorporation of a chelating SC3 hydrophobin (PFA-SC3) in a monoolein cubic phase yielded a biomimetic, cell-like system of Cu(II) cation immobilization. This system, which is suitable for modifying electrode surface and monitoring the Cu(II)/Cu(0) redox process, may be of practical interest in switching and sensing.

Fungal Proteins↗

PubMed2005

Preparing catalytic surfaces for sensing applications by immobilizing enzymes via hydrophobin layers.

Simple and reliable immobilization techniques that preserve the activity of enzymes are of interest in many technologies based on catalysis. Here, two redox enzymes, glucose oxidase from Aspergillus niger and horseradish peroxidase, were immobilized by physisorption on glassy carbon electrodes coated with Schizophyllum commune hydrophobin. Hydrophobins are small, interfacially active proteins that have the remarkable property of adhering to almost any surface. We showed recently that these proteins can be used to immobilize small, electroactive molecules. The results obtained in this work show a way to easily manufacture stable, enzyme-based catalytic surfaces for applications in biosensing.

Biosensing Techniques↗

PubMed2005

Modified electrodes based on lipidic cubic phases.

The lipidic cubic phase can be characterized as a curved bilayer forming a three-dimensional, crystallographical, well-ordered structure that is interwoven by aqueous channels. It provides a stable, well-organized environment in which diffusion of both water-soluble and lipid-soluble compounds can take place. Cubic phases based on monoacylglycerols form readily and attract our interest due to their ability to incorporate and stabilize proteins. Their lyotropic and thermotropic phase behaviour has been thoroughly investigated. At hydration over 20%, lipidic cubic phases Ia3d and Pn3m are formed. The latter is stable in the presence of excess water, which is important when the cubic phase is considered as an electrode-modifying material. Due to high viscosity, the cubic phases can be simply smeared over solid substrates such as electrodes and used to host enzymes and synthetic catalysts, leading to new types of catalytically active modified electrodes as shown for the determination of cholesterol, CO(2), or oxygen. The efficiency of transport of small hydrophilic molecules within the film can be determined by voltametry using two types of electrodes: a normal-size electrode working in the linear diffusion regime, and an ultramicroelectrode working under spherical diffusion conditions. This allows determining both the concentration and diffusion coefficient of the electrochemically active probe in the cubic phase. The monoolein-based cubic phase matrices are useful for immobilizing enzymes on the electrode surface (e.g., laccases from Trametes sp. and Rhus vernicifera were employed for monitoring dioxygen). The electronic contact between the electrode and the enzyme was maintained using suitable electroactive probes.

Cholesterol Oxidase↗

PubMed2004

Organization of four thermotropic liquid crystals of different polarities on model liquid and solid surfaces.

The thermodynamic and surface properties of four structurally related thermotropic liquid crystals (LC) were investigated to understand their organization at gas-liquid and gas-solid interfaces. In this study, LC with a benzoyloxy azobenzene mesogenic core substituted with heptyloxy and/or dioxyethylene ether groups were used. The propensity of the LC to form self-assembled multilayers was demonstrated in the films spread at the air/aqueous interface using the Langmuir technique and Brewster angle microscopy and on the solid surfaces of Chromosorb WHP and silica, using differential scanning calorimetry. On the basis of the results obtained, a molecular recognition mechanism underlying separation processes using LC as selectors in gas chromatography is proposed.

Air↗

PubMed2004

Enantiomeric recognition of amino acids by amphiphilic crown ethers in Langmuir monolayers.

Four new chiral, amphiphilic crown ethers differing by the hydrophobic tailgroups were synthesized, and their capacity to recognize enantiomeric amino acids was examined using Langmuir films. Surface pressure and surface potential measurements performed on the subphases containing L or D enantiomers of alanine, valine, phenylglycine, and tryptophane indicate that the crown ethers forming the monolayer interact with the amino acids. The effects observed are ascribed to the formation of host-guest complexes. The differences in the magnitude of the effects measured show that the crown ethers are capable of discriminating between different amino acids as well as the enantiomers. Our results demonstrate that the structure of the monolayer plays a decisive role in the molecular recognition process including chiral recognition.

Amino Acids↗

PubMed2004

Formation of Langmuir layers and surface modification using new upper-rim fully tethered bipyridinyl or bithiazolyl cyclodextrins and their fluorescent metal complexes.

Seven new amphiphilic cyclodextrins bearing bipyridyl or bithiazolyl moieties at the narrow rim and free hydroxyl or methoxyl groups at the wide rim of the cyclooctaamylose crown were synthesized using a one step "phosphine imide" approach. These ligands form metal complexes that have fluorescence properties with potentials for optical applications. Here, the cyclodextrin derivatives were used as probes for evaluating the role of different moieties in the self-assembly process, providing crucial information in creating functional devices. The behavior of these molecules and of complexes with EuIII in some cases was studied in Langmuir films using surface pressure (pi) and surface potential (deltaV) measurements performed as a function of film compression (compression isotherms). For chosen cyclodextrins, Brewster angle microscopy (BAM) in monolayers was performed. Films formed with derivatives 1, 3, 7, and 2compl were transferred on mica using the Langmuir-Blodgett technique. The properties of the films deposited on mica were analyzed with fluorimetry and, in the case of derivative 7, using fringe of equal chromatic order technique (FECO). The monolayer structure and the fluorescence properties of the Langmuir-Blodgett films indicate that the derivatives studied can be used for preparing cyclodextrin-based optical devices.

Cyclodextrins↗

PubMed2004

Electrodes modified with monoolein cubic phases hosting laccases for the catalytic reduction of dioxygen.

An enzyme-catalyzed process has been used for dioxygen monitoring. The enzymes were two different laccases (p-diphenol:dioxygen oxidoreductases), chosen as catalysts for dioxygen reduction. The laccases were immobilized in a liquid crystalline cubic phase formed with monoolein. The structures of the cubic phases, both with and without enzymes, were established using small-angle X-ray scattering. The catalytic reduction of dioxygen was performed using a glassy carbon electrode modified with cubic phases containing the enzymes. The modified electrode was used as a dioxygen sensing system, based on the increasing reduction current of a suitable electrochemical probe in the presence of dioxygen.

Biosensing Techniques↗

PubMed2002

A concept for immobilizing catalytic complexes on electrodes: cubic phase layers for carbon dioxide sensing.

Liquid crystalline cubic phases formed with monoolein and Myverol have been used as matrixes to host a catalytic complex of nickel(II) and 1-hexadecyl-1,4,8,11-tetraazacyclotetradecane for the reduction of carbon dioxide. The structures of the cubic phases, both with and without the catalyst, were established using small-angle X-ray scattering. The catalytic reduction of carbon dioxide was performed using thin mercury film and glassy carbon electrodes modified with cubic phases containing the catalyst. The linear dependence of the catalytic reduction current on the carbon dioxide concentration allowed use of the modified electrodes as sensing devices both in solution and in the gas phase. The high reproducibility of the measurements makes this method of monitoring carbon dioxide levels attractive compared to other methods based on modified electrodes.

Carbon Dioxide↗