Combination of off-line solid-phase extraction and on-column sample stacking for sensitive determination of parabens and p-hydroxybenzoic acid in waters by non-aqueous capillary electrophoresis

For the first time, a procedure based on solid-phase extraction (SPE) for the simultaneous extraction of a group of parabens (methyl, ethyl, propyl, butyl and benzyl p-hydroxybenzoates) and p-hydroxybenzoic acid (PHBA), from environmental water samples has been developed. Analysis of the extracts was performed by non-aqueous capillary electrophoresis (NACE) coupled with diode array detection (DAD), using large-volume sample stacking (LVSS) based on the electroosmotic flow pump as on-column preconcentration technique. Several water samples, such as tap, river, and wastewater samples, were analyzed using both SPE-NACE-DAD and SPE-LVSS-NACE-DAD methods. It has been observed that in addition to SPE parameters such as sorbent material, sample pH, breakthrough volume, addition of an organic solvent and elution solvent, also sample characteristics, such as organic matter content, have influence on SPE extraction yields, especially in the case of PHBA. The presence of PHBA and some parabens was detected at trace levels in surface water samples. Concentrations up to 8.4 ng mL⁻¹ were found in raw wastewater, with the highest levels corresponding to methylparaben, propylparaben, and their main degradation product, PHBA.     

Principles of electrostatic interactions and self-assembly in lipid/peptide/DNA systems: Applications to gene delivery

Recently, great progress has been achieved in development of a wide variety of formulations for gene delivery in vitro and in vivo, which include lipids, peptides and DNA (LPD). Additionally, application of natural histone–DNA complexes (chromatin) in combination with transfection lipids has been suggested as a potential route for gene delivery (chromofection). However, the thermodynamic mechanisms responsible for formation of the ternary lipid–peptide–DNA supramolecular structures have rarely been analyzed. Using recent experimental studies on LPD complexes (including mixtures of chromatin with cationic lipids) and general polyelectrolyte theory, we review and analyze the major determinants defining the internal structure, particle composition and size, surface charge and ultimately, transfection properties of the LPD formulations.     

The potential of mass spectrometry to study iron-containing proteins used in clinical diagnosis

Many proteins contain iron as metal ion either within their own structures or bound to their active sites. These iron-containing proteins are involved in numerous biological processes and some of them serve as biomarkers of clinical pathologies, not only related to iron homeostasis but also to other physiological disorders. Thus, a variety of analytical strategies have been developed over the last years in order to conduct studies on Fe-containing proteins. Among them, mass spectrometric (MS) methods still remain as preferred tools since they provide the capabilities of structure elucidation together with quantitative possibilities. Therefore, in this work we have tried to summarize the most recent applications of elemental and molecular mass spectrometric-based methods for the characterization (mostly qualitative but quantitative in some cases) of the high abundant Fe-containing proteins used for clinical diagnosis.