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Aquaporins are water-permeable membrane-channel proteins found in biological cell membranes that selectively exclude ions and large molecules and have high water permeability, which makes them promising candidates for water desalination systems. To effectively apply the properties of aquaporins in the desalination process, many studies have been conducted on aquaporin-lipid membrane systems using phospholipids, which are the main component of cell membranes. Many parametric studies have evaluated the permeability of such systems with various aquaporin types and lipid compositions. In this study, we performed molecular dynamics simulations for four cases with different protein-lipid molar ratios (1:50, 1:75, 1:100, and 1:150) between aquaporin Z and the phospholipids, and we propose a possibility of the existence of optimal protein-lipid molar ratio to maximize water permeability. Elucidating these simulation results from a structural viewpoint suggests that there is a relationship between the permeability and changes in the hydrophobic thickness of the lipid membrane adjacent to the aquaporin as a structural parameter. The results of this study can help optimize the design of an aquaporin-lipid membrane by considering its molar ratio at an early stage of development. [ABSTRACT FROM AUTHOR]

Background/Aims: Across the mitochondrial membrane an exceptionally intense exchange of O2 and CO2 occurs. We have asked, 1) whether the CO2 permeability, PM,CO2, of this membrane is also exceptionally high, and 2) whether the mitochondrial membrane is sufficiently permeable to HCO3- to make passage of this ion an alternative pathway for exit of metabolically produced CO2. Methods: The two permeabilities were measured using the previously published mass spectrometric 18O exchange technique to study suspensions of mitochondria freshly isolated from rat livers. The mitochondria were functionally and morphologically in excellent condition. Results: The intramitochondrial CA activity was exclusively localized in the matrix. PM,CO2 of the inner mitochondrial membrane was 0.33 (SD ± 0.03) cm/s, which is the highest value reported for any biological membrane, even two times higher than PM,CO2 of the red cell membrane. PM,HCO3- was 2·10-6 (SD ± 2·10-6) cm/s and thus extremely low, almost 3 orders of magnitude lower than PM,HCO3- of the red cell membrane. Conclusion: The inner mitochondrial membrane is almost impermeable to HCO3- but extremely permeable to CO2. Since gas channels are absent, this membrane constitutes a unique example of a membrane of very high gas permeability due to its extremely low content of cholesterol. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) is a potentially non-invasive therapeutic strategy that involves the use of a photosensitizing agent molecule capable to absorb light at a specific wavelength and to transfer the absorbed energy to generate singlet oxygen. This oxidizing agent reacts with double bonds of membrane phospholipids and sterols present in biological membranes causing damages and/or cell permeability. With the aim to analyze and to determine the effectiveness of possible photosensitizing agents, in this work we evaluate the in vitro amoebicidal effect of nine cosmetic dyes, 1 – 9 , belonging to the xanthene, chlorophyll, aminoanthraquinone, and pyrene group of chromophores, against Acanthamoeba castellanii Neff. Red 22 (2, eosin Y) and red 28 (4) were the most effective photosensitizers to inhibit cell growth, with 2 showing the highest growth inhibition when it is activated by white light. The study of their mechanisms of action reveals that red 22 (2) increases membrane permeability and induces chromatin condensation of parasites, and could be used in combined therapies with currently used drugs. Image 1 • An antiparasitic photodynamic therapy (PDT) has been tested against Acanthamoeba castellanii Neff. • The in vitro amoebicidal effectiveness of nine cosmetic dyes, 1 – 9 , was evaluated. • Red 22 (2 , eosin Y) and red 28 (4): the most effective photosensitizers to inhibit cell growth. • Red 22 (2) increases membrane permeability and induces chromatin condensation of parasites. [ABSTRACT FROM AUTHOR]

• p-CoA modulate electrical parameters of biological and model lipid membranes. • p-CoA retains in cell membrane or enters the cytoplasm and membrane-bound organelles. • Microelectrophoretic mobility assay as a tool of studying membranes of living cells. • Altered surface charge of cell membranes as an indicator of drug-membrane interaction. Biological membranes are one of the most important elements of living cells determining their permeability to the active compounds. Still, little is known about the drug-membrane interactions in terms of pharmacological properties of potential drugs. Chemoprevention based on natural compounds is becoming a strong trend in modern oncopharmacology, and p-coumaric acid (p-CoA) is one such compound with tentative anticancer activity. The microelectrophoretic mobility measurements and electrochemical impedance spectroscopy were applied to study the effects of p-CoA on electrical properties of liposomes, spherical bilayers, and human glioblastoma cell membranes. Our results demonstrated that after treatment with p-CoA, the surface charge of LBC3, LN-229 and LN-18 cell lines was significantly changed in alkaline pH solutions, but not in acidic pH solutions. In contrast, no changes in surface charge density values were registered for phosphatidylethanolamine liposomal membranes and A172 cell membranes after p-CoA treatment. The impedance data showed an increase in values of both the electrical capacitance and the electrical resistance, indicating that p-CoA can be partially inserted into the phosphatidylcholine bilayers. The MTT assay showed cell line-dependent cytotoxic effect of p-CoA. Further molecular analyses revealed the ATP depletion and gene transcription modulation, which might indicate organelle membrane-crossing potential of p-CoA. These results suggest, that changes in surface charge of membranes of living cells not only might be potential predictor of membrane permeability, but also indicate differential composition of cell membranes in various cell lines. Thus further multidirectional analyses are required to implement electrochemical methods as standard testing procedures during drug development process. [ABSTRACT FROM AUTHOR]