Study on detoxification and removal mechanisms of hexavalent chromium by microorganisms.

The dynamics of the gel to fluid phase transformation in 100 nm large unilamellar vesicles (LUV) of 1,2-dipalmitoyl(d62)-sn-glycero-3-phosphocholine (d62-DPPC), has been studied by laser-induced temperature-jump initiation coupled with time-resolved infrared spectroscopy and by MD simulations. The infrared transients that characterize the temperature dependent phase transformation are complex, extending from the nanosecond to the millisecond time scales. An initial fast (submicrosecond) component can be modeled by partial melting of the gel domains, initiated at pre-existing defects at the edges of the faceted structure of the gel phase. Molecular dynamics simulations support the model of fast melting from edge defects. The extent of melting during the fast phase is limited by the area expansion on melting, which leads to a surface pressure that raises the effective melting temperature. Subsequent melting is observed to follow highly stretched exponential kinetics, consistent with collective relaxation of the surface pressure through a hierarchy of surface undulations with different relaxation times. The slowest step is water diffusion through the bilayer to allow the vesicle volume to grow along with its expanded surface area. The results demonstrate that the dominant relaxation in the gel to fluid phase transformation in response to a large T-jump perturbation (compared to the transition width) is fast (submicrosecond), which has important practical and fundamental consequences.

Dynamics of the Gel to Fluid Phase Transformation in Unilamellar DPPC Vesicles

Resveratrol, a polyphenolic molecule found in edible fruits and vegetables, shows a wide range of beneficial effects on human health, including anti-microbial, anti-inflammatory, anti-cancer, and anti-aging properties. Due to its poor water solubility and high liposome-water partition coefficient, the biomembrane seems to be the main target of resveratrol, although the mode of interaction with membrane lipids and its location within the cell membrane are still unclear. In this study, using electrophysiological measurements, we study the interaction of resveratrol with planar lipid membranes (PLMs) of different composition. We found that resveratrol incorporates into palmitoyl-oleoyl-phosphatidylcholine (POPC) and POPC:Ch PLMs and forms conductive units unlike those found in dioleoyl-phosphatidylserine (DOPS):dioleoyl-phosphatidylethanolamine (DOPE) PLMs. The variation of the biophysical parameters of PLMs in the presence of resveratrol provides information on its location within a lipid double layer, thus contributing to an understanding of its mechanism of action.

Study of Resveratrol's Interaction with Planar Lipid Models: Insights into Its Location in Lipid Bilayers.

Molecular characterization and environmental impacts of water-soluble organic compounds of bio-oil from the thermochemical treatment of domestic sewage sludge.

Respiratory diseases, including pulmonary fibrosis, silicosis, and allergic pneumonia, can be caused by long-term exposure to dental prosthesis grinding dust. The extent of the toxicity and pathogenicity of exposure to PMMA dust, Vitallium dust, and dentin porcelain dust differs. The dust from grinding dental prosthesis made of these three materials was characterized in terms of morphology, particle size, and elemental composition. The adverse effects of different concentrations of grinding dust (50, 150, 300, 450, and 600 μg ml-l) on RAW264.7 macrophages were evaluated, including changes in cell morphology and the production of lactate dehydrogenase (LDH) and reactive oxygen species (ROS). The dust particles released by grinding dental prosthesis made of these materials had different morphologies, particle sizes, and elemental compositions. They also induced varying degrees of cytotoxicity in RAW264.7 macrophages. A possible cytotoxicity mechanism is the induction of lipid peroxidation and plasma membrane damage as the dust particles penetrate cells. Therefore, clinicians who regularly work with these materials should wear the appropriate personal protection equipment to minimize exposure and reduce the health risks caused by these particulates.

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Cytotoxic effects of dental prosthesis grinding dust on RAW264.7 cells.

An overview of peroxidation reactions using liposomes as model systems and analytical methods as monitoring tools.

Determining the UV absorbances at 234 nm and 280 nm enables a quick determination of the oxidation progress in lipid membranes. Nevertheless, experimental spectral results indicate a significant overlapping of bands arising from different oxidation products. The calculation of theoretical electronic spectra of the plausible oxidation products can provide strong support for spectral interpretation. The goal of this work was to set up a UV-based method to assess the peroxidation products of lecithin liposomes. UV spectra of liposomes exposed to H2O2 and CuSO4 were recorded and peak-fitted to determine the overlapping bands contributing to the experimental features. Time-dependent density functional theory (TD-DFT) calculations were used to optimize the molecular structures and assess the theoretical UV spectra of all possible oxidation products. Two oxidation routes were considered; one of them regarding the formation of conjugated dienes and the other related to the formation of hydroxy fatty acids. The integrated experimental and theoretical analysis of the UV spectra showed the presence of conjugated dienes M and N in the experimental spectra, occurring at λmax ≅ 240 nm and fitting well in the band at λmax ≅ 237 obtained after deconvolution. In turn, compounds A, D, H and I, arising from the hydroxy fatty acid pathway, were those leading to the experimental bands at λmax ≅ 225, 232 and 244 nm, respectively. The integrative computational and experimental approach conducted in this work provides a better understanding of lipid peroxidation processes.

J. M. Faroux

Papers

An overview of peroxidation reactions using liposomes as model systems and analytical methods as monitoring tools.

A combined approach of electronic spectroscopy and quantum chemical calculations to assess model membrane oxidation pathways