Interactions of a fluoroaryl surfactant with hydrogenated, partially fluorinated, and perfluorinated surfactants at the air/water interface

A novel surfactant containing pentafluorophenyl moiety attached at the terminal position of undecanol (11,11-difluoro-11-(pentafluorophenyl)undecan-1-ol, abbr. PBD) was synthesized and employed for the Langmuir monolayer characterization and miscibility studies with a semifluorinated alkane (perfluorodecyleicosane, abbr. F10H20) and four alcohols differing in the degree of fluorination in their hydrophobic chains: octadecanol (C18OH), perfluorooctyldecanol (F8H10OH), perfluoroisononyldecanol (iF9H10OH) and 1H,1H-perfluorooctadecanol (F18OH). Pure monolayers of all of the investigated surfactants as well as their mixtures were investigated with surface pressure-area isotherms complemented by Brewster angle microscopy (BAM) images. PBD was found to form stable Langmuir monolayers of liquid-expanded character. Characteristic dendritic structures were formed at the very early stage of compression and remained up to the vicinity of collapse, where 3D crystallites appeared. 2D miscibility studies revealed that PBD forms mixed monolayers with the investigated semifluorinated alkane (F10H20) as well as with perfluorinated alcohol (F18OH) within the whole composition range, do not mix with octadecanol to the fully hydrogenated alcohol, whereas it is partially miscible (up to a certain surface pressure value) with the studied semifluorinated alcohols. The analysis of the miscibility derived from the surface pressure-area isotherms (collapse pressure vs composition dependencies) agrees well with BAM images. Molecular interactions in the investigated systems have been quantified with interaction parameter, alpha.     

Interactions between phosphatidylcholines and cholesterol in monolayers at the air/water interface

Mixtures of cholesterol and synthetic phospholipids, differing in saturation of phosphatidylcholine (PC) acyl chains, such as distearoyl phosphatidylcholine (DSPC), stearoyl-oleoyl phosphatidylcholine (SOPC) and dioleoyl phosphatidylcholine (DOPC) have been studied as floating Langmuir monolayers at the air/water interface. In order to examine the influence of a polar group, distearoyl phosphatidylethanolamine (DSPE) was chosen. The films were spread at room temperature on aqueous subphases and characterized by the surface pressure-area (pi-A) isotherms and compression modulus (C(s)(-1)) values. The interactions were examined by analyzing the mean molecular areas and quantified by the excess free energy of mixing values. The obtained results indicate that the affinity of cholesterol to saturated/unsaturated phosphatidylcholines does not differ significantly, and revealed strong influence of the kind of a polar group on the cholesterol-phospholipid interactions. On the other hand, the apolar group structure was found to modify the stoichiometry of sterol-PC complexes.     

Potential of Carvacrol and Thymol in Reducing Biofilm Formation on Technical Surfaces

Polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and stainless steel (SS) are commonly used in medicine and food production technologies. During contact with microorganisms on the surface of these materials, a microbial biofilm is formed. The biofilm structure is difficult to remove and promotes the development of pathogenic bacteria. For this reason, the inhibition of biofilm formation in medical and food production environments is very important. For this purpose, five naturally occurring compounds were used for antimicrobial screening tests. The two with the best antimicrobial properties were chosen to inhibit the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. After 3 days of exposure, thymol reduced the amount of biofilm of Pseudomonas aeruginosa within the range of 70–77% and 52–75% for Staphylococcus aureus. Carvacrol inhibited the formation of biofilms by up to 74–88% for Pseudomonas aeruginosa and up to 86–100% for Staphylococcus aureus. Those phenols decreased the enzyme activity of the biofilm by up to 40–100%. After 10 days of exposure to thymol, biofilm formation was reduced by 80–100% for Pseudomonas aeruginosa and by about 79–100% for Staphylococcus aureus. Carvacrol reduced the amount of biofilm by up to 91–100% for Pseudomonas aeruginosa and up to 95–100% for Staphylococcus aureus.     

Conducting materials prepared by the oxidation of <Emphasis Type="Italic">p</Emphasis>-phenylenediamine with <Emphasis Type="Italic">p</Emphasis>-benzoquinone

p-Phenylenediamine was oxidized with p-benzoquinone in the aqueous solutions of methanesulfonic acid (MSA). The conductivity of the products increased with increasing concentration of MSA from 1.5?×?10^?12 S cm^?1 in 0.1 M MSA up to 3.4?×?10^?4 S cm^?1 in 5 M MSA. The low-molecular-weight products are basically composed of one p-benzoquinone and two p-phenylenediamine molecules. Their molecular structure is discussed on the basis of mass, Fourier-transform infrared, Raman, NMR and electron paramagnetic resonance (EPR) spectroscopies. The formation of 2,5-di(p-phenylenediamine)-p-benzoquinone protonated with methanesulfonic acid best complies with the information provided by spectroscopic techniques. Its conversion to hydroquinone tautomer explains the formation of unpaired spins observed by EPR and their potential contribution to the conduction.     

Sensor arrays for liquid sensing--electronic tongue systems

Electronic tongue systems are multisensor devices dedicated to automatic analysis of complicated composition samples and to the recognition of their characteristic properties. Recently, the number of publications covering this topic has significantly increased. Many possible architectures of such devices were proposed: potentiometric, voltammetric, as well as approaches embracing mass- and optical-sensors. For the analysis of sensor array data, various pattern recognition systems were proposed. All of these topics are summarized in this review. Moreover, additional problems are considered: miniaturization of electronic tongues and hybrid systems for liquid sensing.     

Hydrogen-induced stress relaxation in thin Pd films: influence of carbon implementation

The influence of carbon impurities on mechanical properties of thin Pd film in the process of hydride formation and its disintegration has been investigated "in situ" by means of atomic force microscopy (AFM). Pd interaction with hydrogen leads to the formation of hydride PdHx, if critical conditions of pressure and temperature are reached (equilibrium hydrogen pressure over PdHx at 298 K is approximately 1 kPa). The lattice constant of PdHx is larger than that of the original metal, and the hydride formation generates high stress within the film. As a consequence, the reversible formation of well organized mesoscopic protrusions on the film surface is observed. In this paper, we focus our investigation on the mechanical response which occurs when, prior to hydride generation, carbon atoms are incorporated into the bulk of the film. The systems characterized by carbon incorporation from the two opposite sides of thin palladium film (HOPG substrate and hydrocarbon fragments deposit from a gas-phase reached by preadsorption of ethylene) are compared. For both cases the mechanism of mechanical response is the same, but very different from that registered for pure thin palladium film. Carbon impurities induce, during PdHx decomposition, creation of an organized network of cracks which divides the continuous film into separated domains. The mechanisms of carbon introduction occurring in both cases have been proposed.     

Efficient Extraction of Fermentation Inhibitors by Means of Green Hydrophobic Deep Eutectic Solvents

The methods for hydrogen yield efficiency improvements, the gaseous stream purification in gaseous biofuels generation, and the biomass pretreatment are considered as the main trends in research devoted to gaseous biofuel production. The environmental aspect related to the liquid stream purification arises. Moreover, the management of post-fermentation broth with the application of various biorefining techniques gains importance. Chemical compounds occurring in the exhausted liquid phase after biomass pretreatment and subsequent dark and photo fermentation processes are considered as value-added by products. The most valuable are furfural (FF), 5-hydroxymethylfurfural (HMF), and levulinic acid (LA). Enriching their solutions can be carried with the application of liquid–liquid extraction with the use of a suitable solvent. In these studies, hydrophobic deep eutectic solvents (DESs) were tested as extractants. The screening of 56 DESs was carried out using the Conductor-like Screening Model for Real Solvents (COSMO-RS). DESs which exposed the highest inhibitory effect on fermentation and negligible water solubility were prepared. The LA, FF, and HMF were analyzed using FT-IR and NMR spectroscopy. In addition, the basic physicochemical properties of DES were carefully studied. In the second part of the paper, deep eutectic solvents were used for the extraction of FF, LA, and HMF from post-fermentation broth (PFB). The main extraction parameters, i.e., temperature, pH, and DES: PFB volume ratio (V_DES:V_PFB), were optimized by means of a Box–Behnken design model. Two approaches have been proposed for extraction process. In the first approach, DES was used as a solvent. In the second, one of the DES components was added to the sample, and DES was generated in situ. To enhance the post-fermentation broth management, optimization of the parameters promoting HMF, FF, and LA extraction was carried under real conditions. Moreover, the antimicrobial effect of the extraction of FF, HMF, and LA was investigated to define the possibility of simultaneous separation of microbial parts and denatured peptides via precipitation.     

Spectroscopic Characterization of i-motif Forming c-myc Derived Sequences Double-Labeled with Pyrene

In current studies we use the oligonucleotides based on c-myc sequence: CCC CAC CCT CCC CAC CCT CCC C (cmyc22) and CCC CAC CCT CCC CAC CCT CCC CA (cmyc22A) functionalized by pyrene moieties at both termini. Results of the circular dichroism (CD), UV absorption melting experiments, and steady-state fluorescence measurements of pyrene-modified i-motifs as well as their unlabeled precursors are presented and discussed here. The pyrene labels have a remarkable influence on i-motif stability which was deduced from CD spectra and confirmed by UV melting experiments. Both probes emit fluorescence band of pyrene monomer with intensity decreasing upon pH lowering.     

Synthesis of Some Quaternary N-(1,4-anhydro-5-deoxy-D,L-ribitol-5-yl)ammonium Salts

The successful removal of the isopropylidene-protecting group from 1,4-anhydro-2,3-O-isopropylidene-5-O-tosyl-D,L-ribitol and from quaternary N-(1,4-anhydro-5-deoxy-2,3-O-isopropylidene-D,L-ribitol-5-yl)ammonium salts is reported. The structures of all isolates were determined by spectral analysis, including extensive 2-D NMR analyses. Single-crystal x-ray diffractions of 1,4-anhydro-5-O-tosyl-D,L-ribitol and its 2,3-O-isopropylidene derivatives are reported.