Cyclosporin A distribution in cholesterol-sphingomyelin artificial membranes modeled as Langmuir monolayers.

Cyclosporin A (CsA), a hydrophobic peptide, mainly known for its immunosuppressant properties, has shown a broad range of biological activities, including antimalarial action. Since CsA was found to be active on membrane level, it was subjected for investigations involving membrane models. Our former studies on interactions between CsA and different membrane lipids using Langmuir monolayer technique indicated its affinity for sphingomyelin (SM).

Kinetic Study on the Formation of Bimetallic Core-Shell Nanoparticles via Microemulsions.

Computer calculations were carried out to determine the reaction rates and the mean structure of bimetallic nanoparticles prepared via a microemulsion route. The rates of reaction of each metal were calculated for a particular microemulsion composition (fixed intermicellar exchange rate) and varying reduction rate ratios between both metal and metal salt concentration inside the micelles. Model predictions show that, even in the case of a very small difference in reduction potential of both metals, the formation of an external shell in a bimetallic nanoparticle is possible if a large reactant concentration is used.

The impact of the confinement of reactants on the metal distribution in bimetallic nanoparticles synthesized in reverse micelles.

A kinetic study on the formation of bimetallic nanoparticles in microemulsions was carried out by computer simulation. A comprehensive analysis of the resulting nanostructures was performed regarding the influence of intermicellar exchange on reactivity. The objects of this study were metals having a difference in standard reduction potential of about 0.

Fluorinated vs hydrogenated surfactants in mixtures with valinomycin--the Langmuir monolayer study.

Selected fluorinated and hydrogenated surfactants, namely a semifluorinated alkane (SFA): 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-henicosafluorononacosane (F10H19), two long chain alcohols: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-ol (F8H10OH) and octadecane-1-ol (C18OH) and with two long chain thiols of the analogous apolar part structure to the above-mentioned alcohols, i.e.: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-thiol (F8H10SH) and octadecane-1-thiol (C18SH) have been tested in mixtures with valinomycin as potential artificial matrixes for its immobilization.

Behaviour of a peptide sequence from the GB virus C/hepatitis G virus E2 protein in Langmuir monolayers: its interaction with phospholipid membrane models.

The GB virus C/hepatitis G virus (GBV C/HGV) is a Flaviviridae member that despite its non pathogenicity, has become of great interest given that it could inhibit the replication of the human immunodeficiency virus (HIV). Therefore, a better knowledge of the virus peptides involved in the cellular membrane fusion mechanism has become our aim. The selected peptide, named E2(347-363), corresponds to the GBV-C/HGV E2 protein and has been synthesized in order to study its interaction with in vitro membrane models.

Interaction of GB virus C/hepatitis G virus synthetic peptides with lipid langmuir monolayers and large unilamellar vesicles.

In this paper, we aimed to continue the previous study undertaken with one segment of E1 protein belonging to the GB virus C/hepatitis G virus (GBV-C/HGV), specifically between the 53-66 amino acids and their palmitoyl derivative peptide. The sequence selection has been made on the basis of different prediction algorithms of hydrophobicity and antigenicity. Their interactions between two different in vitro membrane models, lipid Langmuir monolayers and vesicles of different lipidic composition, have been evaluated.

Study of the collapse mechanism of selected fluorinated surfactants.

Two semifluorinated alkanes (SFAs), differing in their fluorinated segment lengths (F6H18 and F10H19), were compared with typical surfactants (F8H10OH and C18OH) as regards their collapse mechanism. It has been found that analysis of the pi-A isotherms under different experimental conditions is insufficient for a reliable description of the collapse phenomenon, and the importance of the relaxation experiments complemented with Brewster angle microscopy observation has been emphasized in this respect. The applied nucleation-growth-collision model points out differences between typical (alcohols) and nontypical (SFAs) surfactants as regards the collapse mechanism.

Two-dimensional miscibility studies of alamethicin and selected film-forming molecules.

Alamethicin (ALM), a 20-amino acid antibiotic peptide (peptaibol) from fungal sources, was mixed in Langmuir monolayers with six different surfactants: semifluorinated (F6H18, F10H19, F8H10OH, F6H10SH) and hydrogenated (C18SH and DODAC), aimed at finding appropriate molecules for ALM incorporation for nanodevice construction. Alamethicin-containing mixed monolayers were investigated by means of surface manometry (pi-A isotherms) and Brewster angle microscopy (BAM). Our results show that only semifluorinated alkanes can serve as an appropriate material since they form miscible and homogeneous monolayers with ALM within the whole concentration range.

Per-6-O-(tert-butyldimethylsilyl)cyclodextrins (TBDMS-CDs) in Langmuir monolayers: the importance of a spreading solvent in the preparation of LB layers suitable for sensor application.

Commercially available amphiphilic cyclodextrins, namely per-6-O-(tert-butyldimethylsilyl) alpha, beta and gamma cyclodextrins (TBDMS-alpha-, -beta-, and -gamma-CDs) were subjected to a thorough Langmuir monolayer characterization, using both traditional methods of surface manometry (pi/A isotherms, stability experiments) and modern micrometer/nanometer resolution (BAM, AFM) surface techniques. It has been found that inconsistent behavior regarding the isotherms reproducibility obtained upon compression of TBDMS-beta-CDs is due to the aggregation of the investigated molecules in chloroform and hexane, while good reproducibility ensured a mixed spreading solvent system of hexane/isopropanol 7:3 (v/v). Although the stability of films dropped from chloroform and hexane/isopropanol solvents below the equilibrium surface pressure (ESP) was comparable, pronounced differences were observed at pressures above ESP.

Nucleation and growth in the collapsed langmuir monolayers from semifluorinated alkanes.

The 3D phase formation was monitored in relaxation experiments of the collapsed Langmuir monolayers of selected partially fluorinated tetracosanes, that is, F6H18, F8H16, and F10H14. To carry out these experiments, the classical method of surface manometry, such as pi-A isotherms registration and the molecular area-time dependencies, under quasi-static monitoring conditions were applied. The evolution of 3D structures at the water/air interface was observed with Brewster angle microscopy (BAM).

Mixed Langmuir monolayers of gramicidin A and fluorinated alcohols.

Mixed monolayers of gramicidin A (GA) and three alcohols, differing in the degree of fluorination, namely C18OH, F18OH, and F8H10OH have been investigated by means of: surface manometry (pi-A isotherms) and Brewster angle microscopy (BAM) aiming at finding appropriate molecules for incorporating gramicidin A for a biosensor design. Our results proved that only the semifluorinated alcohol is appropriate material for this purpose since it forms miscible and homogeneous monolayers with GA within the whole concentration range. The experimental results have been supported by the calculations of van der Waals energy profiles using the Insight II program.

Gramicidin A channel in a matrix from a semifluorinated surfactant monolayer.

Gramicidin A, a polypeptide antibiotic forming transmembrane ion channels, has been incorporated into a Langmuir monolayer formed by a semifluorinated alkane (SFA). In this work, partially fluorinated tetracosane, perfluorohexyloctadecane (F6H18), has been applied, aiming at finding a suitable matrix for gramicidin A to be transferred onto solid support for a biosensor design. For this purpose, the physiological conditions were of special interest (mixed monolayers containing low gramicidin proportion and the surface pressure of 30 mN/m).

Two-dimensional miscibility studies--the analysis of interaction between long-chain alcohols and semifluorinated alkanes.

This work presents the results of phase behavior studies of two-dimensional (2D) binary systems involving semifluorinated alkanes (SFAs) and fatty alcohols. Four different SFAs were selected for investigations: (i) with a short and branched perfluorinated moiety (iF3H20), (ii) with a short and normal perfluorinated chain (F4H20), (iii) with a long and branched perfluorinated fragment (iF9H20), and (iv) with a long and normal perfluorinated group (F10H20). Two alcohols were selected to mix with the above-mentioned SFAs: tetradecanol and docosanol.