Melittin is one of the most studied α-helical cationic membrane disrupting peptides. It is the main component of bee venom, however it is considered an antimicrobial peptide for its ability to kill bacteria. Melittin is believed to act by opening large toroidal pores in the plasma membrane of the targeted cells/bacteria, although this is questioned by some authors. Little is known, however, about the molecular mechanism leading to this activity. In this study the mechanism of action of melittin was studied by dye leakage and quartz crystal microbalance fingerprinting analysis in biomimetic model membranes. The results revealed the existence of multiple stages in the membrane disrupting action with characteristic differences between different membrane types. In bacterial-mimetic (charged) lipid mixtures the viscoelastic fingerprints suggest a surface-acting mechanism, whereas in mammalian-mimetic (neutral) membranes melittin appears to penetrate the bilayer already at low concentrations. In domain-forming mixed membranes melittin shows a preference for the domain containing predominantly zwitterionic lipids. The results confirm membrane poration but are inconsistent with the insertion-to-toroidal pore pathway. Therefore hypotheses of the two membrane disrupting pathways were developed, describing the membrane disruption as either surface tension modulation leading to toroidal pore formation, or linear aggregation leading to fissure formation in the membrane.

A SBA-15/polyaniline para-toluenesulfonic acid nanocomposite supported micro-solid-phase extraction procedure has been developed for the extraction of parabens (methylparaben, ethylparaben, and propylparaben) from wastewater and cosmetic products. The variables of interest in the extraction process were pH of sample, sample and eluent volumes, sorbent amount, salting-out effect, extraction and desorption time, and stirring rate. A Plackett-Burman design was performed for the screening of variables in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by using a central composite design. The optimum experimental conditions found at 50 mL sample solution, extraction and desorption times of 40 and 20 min, respectively, 500 μL of 3% v/v acetic acid in methanol as eluent, 0.01 M salt addition, and 10 mg of the sorbent. Under the optimum conditions, the developed method provided detection limits in the range of 0.08-0.4 ng/mL with good repeatability (RSD% < 7) and linearity (r(2) = 0.997-0.999) for the three parabens. Finally, this fast and efficient method was employed for the determination of target analytes in cosmetic products and wastewater, and satisfactory results were obtained.

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Antimicrobial peptides (AMPs) are integral components of the innate immune defence system of all complex organisms including plants, insects, and mammals. They have wide range of antibacterial, antifungal, antiviral, and even anticancer activities, therefore AMPs are attractive candidates for developing novel therapeutic approaches. Cationic α-helical membrane disrupting peptides are perhaps the most widely studied subclass of AMPs due to their common fundamental characteristics that allow for detailed structure-function analysis and therefore offer a promising solution to the threat of multidrug resistant strains of bacteria. The majority of the studies of AMP activity focused on the biological and biophysical aspects of membrane disruption; the understanding of the molecular mechanism of action from the physicochemical point of view forms a relatively small subfield. This review will provide an overview of these works, focusing on the empirical and thermodynamic models of AMP action.

This article contains errors in the authors section. In the author list, the name of seventh author was misspelled as "Sara Padidan". The correct name spelling is "Sara Pandidan". Also, in the "Supporting Information", the same author's name is corrected as "Sara Pandidan".