Liposomes as tools for elucidating the mechanisms of membrane fusion
; Liposomes as Tools in Basic Research and Industry (1994); 2017; pp. 103-136. Publisher's VersionAbstract
Membrane fusion is a central biophysical and biochemical reaction in numerous biological processes. Exocytosis involves the fusion of the secretory vesicle membrane with the plasma membrane in diverse biological systems, including neurotransmitter release at the neuromuscular junction, histamine release from mast cells, chromaffin granule extrusion from adrenal medullary cells, trichocyst discharge in Paramecium, endotoxin-induced degranulation in Limulus amebocytes, and the cortical reaction in sea urchin eggs.1-4 The first stage in the formation of an endocytotic vesicle is the fusion of apposed regions of the invaginated plasma membrane. Later in the endocytotic pathway, endosomes and phagosomes fuse with lysosomes. Receptor recycling back to the plasma membrane proceeds through pinching off of receptor-containing vesicles from the compartment of uncoupling of receptor and ligand. Transport of newly synthesized membrane or secretory proteins from the endoplasmic reticulum to the Golgi apparatus, within the cis, medial and trans regions of the Golgi is thought to be mediated by transport vesicles that bud off from one compartment and fuse with another.5-7. © 1995 by Taylor & Francis.
Removal of cyanobacteria and cyanotoxins from lake water by composites of bentonite with micelles of the cation octadecyltrimethyl ammonium (ODTMA)
. Water Research 2017
, 165-173. Publisher's VersionAbstract
Cyanobacteria and their toxins present potential hazard to consumers of water from lakes, reservoirs and rivers, thus their removal via water treatment is essential. The capacity of nano-composites of Octadecyltrimethyl-ammonium (ODTMA) complexed with clay to remove cyanobacterial and their toxins from laboratory cultures and from lake water, was evaluated. Column filters packed with micelles of ODTMA complexed with bentonite and granulated were shown to significantly reduce the number of cyanobacteria cells or filaments and their corresponding toxins from laboratory cultures. Fluorescence measurements demonstrated that cyanobacteria cells lost their metabolic activity (photosynthesis) upon exposure to the micelle (ODTMA)–bentonite complex, or ODTMA monomers. The complex efficiently removed cyanobacteria toxins with an exceptional high removal rate of microcystins. The effectiveness of the complex in elimination of cyanobacteria was further demonstrated with lake water containing cyanobacteria and other phytoplankton species. These results and model calculations suggest that filters packed with granulated composites can secure the safety of drinking water in case of a temporary bloom event of toxic cyanobacteria. © 2017 Elsevier Ltd
Removal of Escherichia coli and total bacteria from water by granulated micelle-clay complexes: Filter regeneration and modeling of filtration kinetics
. Applied Clay Science 2017
, 63-68. Publisher's VersionAbstract
Granulated micelle-clay composites (0.3 to 2 mm) formed from Na-bentonite and the organic cations Octadecyltrimethylammonium (ODTMA), or Benzyldimethylhexadecylammonium (BDMHDA) were employed to remove from water by filtration (a) Escherichia coli S-17 and (b) total bacteria count (TBC). In (a) filters included 4 g to 27 g of complex mixed with sand, and bacteria numbers were 6.4·105 to 5·106/mL. A model which considered convection, adsorption, and desorption simulated the filtration results and yielded predictions. Bacteria capture by filtration was independent of the complex used, but BDMHDA complexes were superior in reducing numbers of emerging bacteria, due to a larger biocidal, or biostatic effect of released cations. Placing a layer of activated carbon after the micelle-clay filter reduced the released cations to 1 μg/L. Regeneration was by: (i) passing a solution of 0.1% NaOCl, or 0.01 M of HCl, or (ii) heating in a furnace at 105 °C for 2.5 h. Capacities for removal of bacteria after first and second regenerations by (i) were 86% and 57% of those with fresh granules, respectively. It is suggested that the technology can provide a safe and economical treatment for drinking water contaminated by pathogenic bacteria. In (b) the capacity of filters was smaller than in (a), but the technology enables to avoid using UV lamps in domestic filters. © 2017 Elsevier B.V.
Combined adsorption and degradation of the off-flavor compound 2-methylisoborneol in sludge derived from a recirculating aquaculture system
, 69 - 77. Publisher's VersionAbstract
Off-flavor in fish poses a serious threat for the aquaculture industry. In the present study, removal of 2-methylisoborneol (MIB), an off-flavor causing compound, was found to be mediated by adsorption and bacterial degradation in sludge derived from an aquaculture system. A numerical model was developed which augmented Langmuir equations of kinetics of adsorption/desorption of MIB with first order degradation kinetics. When laboratory-scale reactors, containing sludge from the aquaculture system, were operated in a recirculating mode, MIB in solution was depleted to undetectable levels within 6 days in reactors with untreated sludge, while its depletion was incomplete in reactors with sterilized sludge. When operated in an open flow mode, removal of MIB was significantly faster in reactors with untreated sludge. Efficient MIB removal was evident under various conditions, including ambient MIB levels, flow velocities and sludge loads. When operated in an open flow mode, the model successfully predicted steady MIB removal rates with time. During steady state conditions, most of the MIB removal was found to be due to microbial degradation of the adsorbed MIB. Findings obtained in this study can be used in the design of reactors for removal of off-flavor compounds from recirculating aquaculture systems.
Pairing micropollutants and clay-composite sorbents for efficient water treatment: Filtration and modeling at a pilot scale
. Applied Clay Science 2017
, 225 - 232. Publisher's VersionAbstract
Organically modified clay minerals have been widely developed, tested and employed as sorbents for organic pollutants. However, the process of pollutant-composite pairing is not commonly addressed, which would be valuable for efficient pollutant filtration by such sorbents. This study presents an approach for achieving efficient pollutant removal by large-scale composite filters, based on pairing chemically compatible pollutants and composites and by employing a predictive filtration model. The removal of three organic pollutants, simazine, sulfentrazone and diclofenac by lab-scale filtration columns containing one of three sorbents, a polymer-, micelle- or liposome-clay composite, was measured. Understanding the factors governing pollutant-organic modifier interactions enabled to pair an efficient sorbent to each pollutant. The high removal (80%) of simazine by the polymer composite, was attributed to hydrogen bonds and π-π interactions, compared to less than 20% removal by the surfactant composites. The removal of the anionic diclofenac (pKa=4.1) was mainly governed by electrostatic attraction, explaining its high removal by the most positively charge sorbent, the liposome composite. Sulfentrazone (pKa=6.5) removal was mostly affected by micellar solubilization and upon its removal, the zeta potential of the micelle-composite was not reduced as obtained for diclofenac removal. The filtration of the successful pairs was modelled to determine sorbent capacity and adsorption and desorption rate constants. The pilot filtration experiments were well described by the model and demonstrated efficient removal of paired pollutants and sorbents. Model simulations predicted promising treatment at environmental pollutant concentrations in the μgL−1 range. This pairing approach along with model calculations can be a strong and valid tool for efficient pollutant-sorbent filtration.