Study on liposomes by capillary electrophoresis

Liposomes made of mixtures of zwitterionic and anionic lipids were investigated by means of capillary electrophoresis and dynamic light scattering. The influence of the molar lipid ratio and of the buffers, used in the running electrolyte solution, on the physical characteristics of the liposomes were investigated. Data on effective electrophoretic mobilities, total charges as well as sizes of the liposomes are given. In addition, examples on the use of liposomes as carriers in electrokinetic capillary electrophoresis for the separation of benzene derivatives, steroids, and phenols are shown.     

Extraction of iridoid glycosides and their determination by micellar electrokinetic capillary chromatography

Several methods for the extraction of two iridoid glycosides, catalpol and aucubin, from the plant matrix (Veronica longifolia leaves) were compared. Pressurized hot water extraction and hot water extraction were the most efficient isolation techniques for both. Pressurized liquid extraction and maceration with various organic solvents were also tested. Relative to the amounts extracted with hot water, ethanol extracted only 22% of catalpol and 25% of aucubin and pressurized hot water extracted 83% of catalpol and 92% of aucubin. The lowest relative standard deviations, 22% for catalpol and 8% for aucubin, were achieved with hot water extraction (13 repetitions), and the highest relative standard deviations, 76% for catalpol and 73% for aucubin, with pressurized liquid extraction (five repetitions). A fast capillary electrophoretic method was developed for the quantitative determination of catalpol and aucubin.     

Analysis of phenols in pyrolysis oils by gel permeation chromatography and multidimensional liquid chromatography

A simple method with minimal manual sample preparation was developed for the analysis of phenols in pyrolysis oils. Sample pre-treatment was done by gel permeation chromatography (GPC), where the high-molecular-mass lignins were separated from the phenols. Multidimensional liquid chromatography (LC-LC) was used in the analysis of the phenolic fraction. The pre-column was used for sample clean-up and pre-fractionation before introduction of the phenolic fraction to the analytical column. The repeatability and linearity of the total GPC and LC-LC methods were excellent. The results were in accordance with the reference method in which the sample pre-treatment was done by precipitating the lignins with water, and the phenols were extracted with toluene and analysed by GC-MS.     

Kindergartners’ performance in length measurement and the effect of picture book reading

This paper addresses: firstly, kindergartners’ performance in length measurement, the components of their performance and its growth over time; secondly, the possibility to develop kindergartners’ performance in length measurement by reading to them from picture books. To answer the research questions, an experiment with a pretest–posttest experimental control group design was carried out involving nine experimental classes and nine control classes. The children in the experimental group participated in a 3-month picture book program that, among other things, spotlighted the measurement of length situated in meaningful contexts. Before and after the intervention, the children’s performance in length measurement was assessed in both groups. The responses of 308 kindergartners (4- to 6-year-olds) from two kindergarten years (K1 and K2) were analyzed. Analysis of the pretest data showed that the measurement tasks included in the test were not easy to solve. However, the children belonging to K2 did better than the younger children belonging to K1. Within children’s performance, three components could be identified: holistic visual recognition, ordering and unitizing. Finally, the effect of the intervention was investigated by comparing the performances of the experimental and control group in the pretest and the posttest. We found a weak but significant effect of reading picture books to children on their general measurement performance. However, this effect was only found for K1 children on the component of holistic visual recognition.     

Identification strategy for unknown pollutants using high-resolution mass spectrometry: Androgen-disrupting compounds identified through effect-directed analysis

Effect-directed analysis has been applied to a river sediment sample of concern to identify the compounds responsible for the observed effects in an in vitro (anti-)androgenicity assay. For identification after non-target analysis performed on a high-resolution LTQ-Orbitrap, we developed a de novo identification strategy including physico-chemical parameters derived from the effect-directed analysis approach. With this identification strategy, we were able to handle the immense amount of data produced by non-target accurate mass analysis. The effect-directed analysis approach, together with the identification strategy, led to the successful identification of eight androgen-disrupting compounds belonging to very diverse compound classes: an oxygenated polyaromatic hydrocarbon, organophosphates, musks, and steroids. This is one of the first studies in the field of environmental analysis dealing with the difficult task of handling the large amount of data produced from non-target analysis. The combination of bioassay activity assessment, accurate mass measurement, and the identification and confirmation strategy is a promising approach for future identification of environmental key toxicants that are not included as priority pollutants in monitoring programs.     

Ultrafast excitation transfer and charge stabilization in a newly assembled photosynthetic antenna-reaction center mimic composed of boron dipyrrin, zinc porphyrin and fullerene

A self-assembled supramolecular triad as a model to mimic the light-induced events of the photosynthetic antenna-reaction center, that is, ultrafast excitation transfer followed by electron transfer ultimately generating a long-lived charge-separated state, has been accomplished. Boron dipyrrin (BDP), zinc porphyrin (ZnP) and fullerene (C(60)), respectively, constitute the energy donor, electron donor and electron acceptor segments of the antenna-reaction center imitation. Unlike in the previous models, the BDP entity was placed between the electron donor, ZnP and electron acceptor, C(60) entities. For the construction, benzo-18-crown-6 functionalized BDP was synthesized and subsequently reacted with 3,4-dihydroxyphenyl functionalized ZnP through the central boron atom to form the crown-BDP-ZnP dyad. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity of the dyad via ion-dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational and electrochemical methods. Steady-state fluorescence and excitation studies revealed the occurrence of energy transfer upon selective excitation of the BDP in the dyad. Further studies involving the pump-probe technique revealed excitation transfer from the (1)BDP* to ZnP to occur in about 7 ps, much faster than that reported for other systems in this series of triads, as a consequence of shorter distance between the entities. Upon forming the supramolecular triad by self-assembling fullerene, the (1)ZnP(*) produced by direct excitation or by energy transfer mechanism resulted in an initial electron transfer to the BDP entity. The charge recombination resulted in the population of the triplet excited state of C(60), from where additional electron transfer occurred to produce C(60)(?-):crown-BDP-ZnP(?+) ion pair as the final charge-separated species. Nanosecond transient absorption studies revealed the lifetime of the charge-separated state to be ~100 μs, the longest ever reported for this type of antenna-reaction center mimics, indicating better charge stabilization as a result of the different disposition of the entities of the supramolecular triad.     

Effect of anion ligation on electron transfer of double-linked zinc porphyrin-fullerene dyad

The interaction between metalloporphyrins and their axial ligands plays an important role in the electron transfer (ET) processes in which the excited porphyrin participates. An efficient photoinduced ET reaction of a double-linked zinc(II) porphyrin-fullerene dyad was demonstrated in ionic environment. The chloride ion of tetrabutylammonium chloride (TBACl) electrolyte solution ligates the zinc porphyrin moiety in the dyad which results in a red shift of the absorption bands and lowers the energy of the charge-separated state by about 0.26 eV as compared to the nonligated dyad. Excitation of the porphyrin chromophore results in ET from porphyrin to fullerene in a moderately polar solvent, anisole. In nonionic and nonligating ionic environments, the ET reaction occurs through an intermediate state, an intramolecular exciplex, which has emission in the near-infrared region of the spectrum. This emission is not observed directly for the dyad in TBACl/anisole solution, but evidence of the exciplex intermediate was seen in the time-resolved measurements. The lower energy of the charge-separated state in the ligated environment explains the different ET reaction rates determined in the spectroscopic studies: the charge recombination process of the ligated dyad is about 5 times faster than that of the nonligated one.     

Surface initiated polymerization of a cationic monomer on inner surfaces of silica capillaries: Analyte separation by capillary electrophoresis versus polyelectrolyte behavior

[2‐(Methacryloyl)oxyethyl]trimethylammonium chloride was successfully polymerized by surface‐initiated atom transfer radical polymerization method on the inner surface of fused‐silica capillaries resulting in a covalently bound poly([2‐(methacryloyl)oxyethyl]trimethylammonium chloride) coating. The coated capillaries provided in capillary electrophoresis an excellent run‐to‐run repeatability, capillary‐to‐capillary and day‐to‐day reproducibility. The capillaries worked reliably over 1 month with EOF repeatability below 0.5%. The positively charged coated capillaries were successfully applied to the capillary electrophoretic separation of three standard proteins and five β‐blockers with the separation efficiencies ranging from 132 000 to 303 000 plates/m, and from 82 000 to 189 000 plates/m, respectively. In addition, challenging high‐ and low‐density lipoprotein particles could be separated. The hydrodynamic sizes of free polymer chains in buffers used in the capillary electrophoretic experiments were measured for the characterization of the coatings.     

Polyethylenimine-modified metal oxides for fabrication of packed capillary columns for capillary electrochromatography and capillary liquid chromatography

The need for novel packing materials in both capillary electrochromatography (CEC) and capillary liquid chromatography (CLC) is apparent and the development towards more selective, application-oriented chromatographic phases is under progress world-wide. In this study we have synthesized new polyethyleneimine (PEI) functionalized Mn(2)O(3), SiO(2), SnO(2), and ZrO(2) particles for the fabrication of packed capillary columns for CEC and CLC. The nanocasting approach was successful for the preparation of functionalized metal oxide materials with a controlled porosity and morphology. PEI functionalization was done using ethyleneimine monomers to create particles which are positively charged in aqueous solution below pH 9. This functionalization allowed the possibility to have both hydrophobic (due to its alkyl chain) and ionic interactions (due to positively charged amino groups) with selected compounds. For comparison aminopropyl-functionalized silica was also synthesized and tested. Both slurry pressure and electrokinetic packing procedures used gave similar results, but fast sedimentation of the material caused some problems during the packing. The high stability and wide pH range of PEI-functionalized SiO(2) material, with potential for hydrophobic and electrostatic interactions, proved to be useful for the CEC and CLC separation of some model acidic and neutral compounds.