Membranes

In the past decades, it has become increasingly apparent that in addition to therapeutic effect, drugs need to exhibit favourable absorption, distribution, metabolism and excretion (ADME) characteristics to produce a desirable response in vivo. As the recent progress in drug discovery technology enables rapid synthesis of vast numbers of potential drug candidates, robust methods are required for the effective screening of compounds synthesized within such programs, so that compounds with poor pharmacokinetic properties can be rejected at an early stage of drug development. Furthermore, a viable in silico method would save resources by enabling virtual screening of drug candidates already prior to synthesis. This review gives a general overview of the approaches aimed at predicting biological permeation, one of the cornerstones behind the ADME behaviour of drugs. The most important experimental and computational models are reviewed. Physicochemical factors underlying the permeation process are discussed.

This paper presents the hypothesis, based on the amino acid sequence of the AChR proteins, that the main body of the channel is in the form of a B-barrel. This is based both on a Chou and Fasman analysis of the reported sequence, which predicts B-sheet for residues %28 to %46, of all four subunits, as well as the amphoteric nature of the B-sheet so formed, in which one side is almost entirely lipophilic and the other is hydrophilic. A means of testing my previous hypothesis, that residues 1-17 of the two a-subunits contain the actual ACh binding site, is also presented.

Membrane distillation is an emerging membrane process based on evaporation of a volatile solvent. One of its often stated advantages is the low flux sensitivity toward concentration of the processed fluid, in contrast to reverse osmosis. In the present paper, we looked at 2 high-solids applications of the dairy industry: skim milk and whey. Performance was assessed under various hydrodynamic conditions to investigate the feasibility of fouling mitigation by changing the operating parameters and to compare performance to widespread membrane filtration processes. Whereas filtration processes are hydraulic pressure driven, membrane distillation uses vapor pressure from heat to drive separation and, therefore, operating parameters have a different bearing on the process. Experimental and calculated results identified factors influencing heat and mass transfer under various operating conditions using polytetrafluoroethylene flat-sheet membranes. Linear velocity was found to influence performance during skim milk processing but not during whey processing. Lower feed and higher permeate temperature was found to reduce fouling in the processing of both dairy solutions. Concentration of skim milk and whey by membrane distillation has potential, as it showed high rejection (>99%) of all dairy components and can operate using low electrical energy and pressures (<10 kPa). At higher cross-flow velocities (around 0.141 m/s), fluxes were comparable to those found with reverse osmosis, achieving a sustainable flux of approximately 12 kg/ h·m 2 for skim milk of 20% dry matter concentration and approximately 20 kg/h·m 2 after 18 h of operation with whey at 20% dry matter concentration.

Orphenadrine has been used as an antiparkinsonian, antispastic and analgesic drug for many years. Here we show that orphenadrine inhibits [3H]MK-801 binding to the phencyclidine (PCP) binding site of the N-methyl-D-aspartate (NMDA)-receptor in homogenates of postmortem human frontal cortex with a Ki-value of 6.0 + 0.7 ~M. The NMDA receptor antagonistic effects of orphenadrine were assessed using concentration-and patch-clamp techniques on cultured superior colliculus neurones. Orphenadrine blocked open NMDA receptor channels with fast kinetics and in a strongly voltagedependent manner. The ICs0-value against steady state currents at-70mV was 16.2 _+ 1.6 ~tM (n = 6). Orphenadrine exhibited relatively fast, concentration-dependent open channel blocking kinetics (Kon 0.013 + 0.002 106M-1S-1) whereas the offset rate was concentration-independent (Kof f 0.230 _+ 0.004S-1). Calculation of the ratio Koff/Kon revealed an apparent Kd-value of 17.2 ~tM which is nearly identical to the ICs0 calculated at equilibrium.

Hollow fiber membranes using Polyethersulfone (PES) were fabricated inhouse using phase inversion technique by modification with synthesized chargedsurface modifying macromolecules (cSMM). The cSMM comprise with end-group component of Hydroxybenzene sulfonate or Hydroxybenzene carboxylate. The electrical properties of the membranes were modeled by utilizing the combination of irreversible thermodynamic model, Steric-Hindrance Pore (SHP) model and Teorell-Meyer-Sievers (TMS) model. The negatively-charged of the modified hollow fiber membranes was calculated based on sodium chloride rejection performance. The analysis of the modeling results revealed that sulfonate induce negative 1.61 electrical properties compared to carboxylate that is negative 1.49 for the modified PES membranes.

Simple carbohydrates are associated with the enhanced risk of cardiovascular disease and adverse changes in lipoproteins in the organism. Conversely, sugars are known to exert a stabilizing effect on biological membranes, and this effect is widely exploited in medicine and industry for cryopreservation of tissues and materials. In view of elucidating molecular mechanisms involved in the interaction of mono- and disaccharides with biomimetic lipid systems, we study the alteration of dielectric properties, the degree of hydration, and the rotational order parameter and dipole potential of lipid bilayers in the presence of sugars. Frequency-dependent deformation of cell-size unilamellar lipid vesicles in alternating electric fields and fast Fourier transform electrochemical impedance spectroscopy are applied to measure the specific capacitance of phosphatidylcholine lipid bilayers in sucrose, glucose and fructose aqueous solutions. Alteration of membrane specific capacitance is reporte...

Because of the continuous focusing of thermal and chemical energy, ancient submarine hot springs are contenders as sites for the origin of life. But it is generally assumed that these would be of the acid and high-temperature 'black smoker' variety (Corliss et al., 1981). In fact today the greater part of the ocean circulates through off-ridge springs where it issues after modification at temperatures of around 40 °C or so but with the potential to reach 200 °C. Such offridge or ridge-flank springs remind us that there are other candidate sites for the origin of life. Although there is no firm indication of the pH of these off-ridge springs we have argued that the solutions are likely to be alkaline rather than acid. We test the feasibility of this idea using EQ geochemical water-rock interaction modelling codes (Wolery 1983) and find that for a range of possible initial chemistries of Hadean seawater, the pH of issuing solutions at around 200 °C is around one or more units alkaline. Such pH values hold for interaction with both basaltic and komatiitic crust. The robustness of this result suggests to us that alkaline submarine springs of moderate temperature, carrying many hundreds of ppm HS-to the ocean basins, are also serious contenders as sites for the origin of life, particularly as Hadean seawater was probably slightly acid, with a dissolved iron concentration approaching 100 ppm. On mixing of these solutions, supersaturation, especially of iron sulphide, would lead to the precipitation of colloidal gels. In our view iron sulphide was the likely substance of, or contributor to, the first vesicle membranes which led to life, as the supply of organic molecules would have been limited in the Hadean. Such a membrane would have had catalytic properties, expansivity, and would have maintained the natural chemiosmotic gradient, a consequence of the acid ocean and the alkaline interior to the vesicles.

Human serum albumin (HSA) and immunoglobulin G (IgG) represent over 75% of all proteins present in human plasma. These high-abundance proteins prevent the detection of low-abundance proteins which are potential markers for various diseases. The depletion of HSA and IgG is therefore essential for further proteome analysis. In this paper we describe the optimization of conditions for selective depletion of HSA and IgG using affinity and pseudo-affinity chromatography. A BIA Separations CIM (convective interaction media) Protein G disk was applied for the removal of IgG and the Mimetic Blue SA A6XL stationary phase for the removal of HSA. The binding and the elution buffer for CIM Protein G disk were chosen on the basis of the peak shape. The dynamic binding capacity was determined. It was shown to be dependent on the buffer system used and independent of the flow rate and of the concentration of IgG. Beside the binding capacity for the IgG standard, the binding capacity was also determined for IgG in human plasma. The Mimetic Blue SA A6XL column was characterized using human plasma. The selectivity of the depletion was dependent on the amount of human plasma that was loaded on the column. After the conditions on both supports had been optimized, the Mimetic Blue SA A6XL stationary phase was combined with the CIM Protein G disk in order to simultaneously deplete samples of human plasma. A centrifuge spin column that enables the removal of IgG and HSA from 20 L of human plasma was designed. The results of the depletion were examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis.

The α7 nicotinic acetylcholine receptors (nAChRs) play an important role in the pathophysiology of neuropsychiatric diseases such as schizophrenia and Alzheimer's disease. However, there are currently no suitable small molecule radioligands for imaging α7 nAChRs in the brain. In this study, we synthesized the novel radioligand [ 125 I]4-iodophenyl 1,4diazaicyclo[3.2.2]nonane-4-carboxylate ([ 125 I]CHIBA-1006), a iodine-derivative of the selective α7 nAChR agonist SSR180711, and studied the characterization of [ 125 I]CHIBA-1006 binding to rat brain membranes. The assays of [ 125 I]CHIBA-1006 binding to rat brain membranes were performed at 4°C. The presence of a single saturable high-affinity binding component for [ 125 I] CHIBA-1006 in the rat brain was shown. Scatchard analysis revealed an apparent equilibrium dissociation constant (K d ) of 88.2 ± 21.4 nM and a maximal number of binding sites (B max ) of 65.4 ± 6.8 fmol/mg protein (mean ± SEM, n = 4). The specific binding of [ 125 I]CHIBA-1006 was inhibited by a number of α7 nAChR-selective ligands (e.g., unlabeled CHIBA-1006, SSR180711, CHIBA-1001, MG624 and A844606), suggesting a similarity among α7 nAChR pharmacological profiles. In contrast, α-bungarotoxin, MLA, and nicotine showed very weak affinity for [ 125 I]CHIBA-1006 binding. The regional distribution of [ 125 I]CHIBA-1006 binding to crude membranes from dissected regions of the rat brain was different from that of [ 125 I]α-bungarotoxin binding, suggesting that [ 125 I]CHIBA-1006 binding sites may not be identical to [ 125 I]α-bungarotoxin binding sites in the rat brain. The present findings suggest that [ 125 I]CHIBA-1006 would be a useful new small molecule radioligand for α7 nAChRs in the brain. a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m w w w . e l s e v i e r . c o m / l o c a t e / b r a i n r e s

The effects of fluidized media characteristics on membrane fouling and energy consumption in the anaerobic fluidized membrane bioreactor (AFMBR) were evaluated. Both adsorbing granular activated carbon (GAC) and non-adsorbing silica and polyethylene terephthalate (PET) beads were evaluated. For fresh GAC, the energy requirement for fluidization increased with size, but smaller sizes led to greater reduction in membrane fouling. But when the GAC adsorption capacity was first exhausted, the reverse was noted, the larger particles reduced membrane fouling best. Non-adsorbing silica particles and PET beads demonstrated similar results to pre-adsorbed GAC, lower fouling was accomplished by the larger media that had a higher energy requirement for fluidization. The media packing ratio was also of importance, the higher the packing ratio up to 50%, the greater the reduction in fouling. Fouling reduction was also somewhat better at a given energy expenditure with lower specific gravity PET beads than with denser and smaller pre-adsorbed GAC particles.

In this work, PVDF homopolymer was blended with PVDF-co-HFP copolymer and studied in terms of morphology, porosity, pore size, hydrophobicity, permeability, and mechanical properties. Different solvents, namely N-Methyl-2 pyrrolidone (NMP), Tetrahydrofuran (THF), and Dimethylformamide (DMF) solvents, were used to fabricate blended PVDF flat sheet membranes without the introduction of any pore forming agent, through a non-solvent induced phase separation (NIPS) technique. Furthermore, the performance of the fabricated membranes was investigated for pressure and thermal driven applications. The porosity of the membranes was slightly increased with the increase in the overall content of PVDF and by the inclusion of PVDF copolymer. Total PVDF content, copolymer content, and mixed-solvent have a positive effect on mechanical properties. The addition of copolymer increased the hydrophobicity when the total PVDF content was 20%. At 25% and with the inclusion of mixed-solvent, the hydrophob...

In arid and semi-arid regions, water is a major limited factor to vegetation and environment. To study the influence of membranes on water retention, three homogeneous sand columns with membranes were installed. Keep the height of free water at Scm above the soil surface of those columns for 3 hours. Experiments results showed that membranes have strong influence on water retention in saturated sand columns. The membranes could slower water movements through the columns and reduce water dynamic parameters such as hydraulic conductivity. So it has an important role in water retention in sand soils, especially in arid and semi-arid regions.

Modification of calmodulin by protein carboxyl methyltransferase requires deamidation of one or more labile asparagine residues (Johnson, B.A., Freitag, N. E., and Aswad, D. W. (1985) J. Biol. Chem. 260, 10913-10916). We now show that deamidation results in the generation of two altered forms of calmodulin, designated A and B, which can be separated by electrophoresis under nondenaturing conditions. The A form is characterized by a larger apparent molecular radius, has only 10% the activity of native calmodulin when assayed for its ability to activate a Ca2+/calmodulin-dependent protein kinase from rat brain, and serves as an excellent substrate for the methyltransferase. The B form more closely resembles native calmodulin: it has an apparent molecular radius more like the native, exhibits about 40% the activity of native calmodulin, and is a relatively poor methyl acceptor. Evidence suggests that the A and B forms probably contain isoaspartate (A) and aspartate (B) in place of Asn-...

The objective of this work is to develop an appropriate technology for environmentally sound membrane-based purification of a tannery effluent assuring, simultaneously, the recovery of chromium, considered as the most hazardous inorganic water pollutant extensively used in leather tanning. A comparison between the permeate fluxes obtained during treatment of a synthetic tannery effluent through nanofiltration (NF270 and NF90 membranes) and reverse osmosis (BW30 and SW30) membranes was first performed. Then, a dedicated polymeric membrane was prepared by coating chitosan (cs) on a polyethersulfone (PES) microfiltration membrane (cs-PES MFO22) support. The resulting membrane was characterized by Fourier Transforms Infrared Spectroscopy Attenuated Total Reflectance (FTIR-ATR), Emission Scanning Electronic Microscopy (SEM) to confirm the process of surface modification and cross-linking of chitosan with glutaraldehyde. This membrane was found to be highly effective for chromium removal ...

Over the last decade DLW employing ultrafast pulsed lasers has become a well-established technique for the creation of custom-made free-form three-dimensional (3D) microscaffolds out of a variety of materials ranging from proteins to biocompatible glasses. Its potential applications for manufacturing a patient&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s specific scaffold seem unlimited in terms of spatial resolution and geometry complexity. However, despite few exceptions in which live cells or primitive organisms were encapsulated into a polymer matrix, no demonstration of an in vivo study case of scaffolds generated with the use of such a method was performed. Here, we report a preclinical study of 3D artificial microstructured scaffolds out of hybrid organic-inorganic (HOI) material SZ2080 fabricated using the DLW technique. The created 2.1 × 2.1 × 0.21 mm(3) membrane constructs are tested both in vitro by growing isolated allogeneic rabbit chondrocytes (Cho) and in vivo by implanting them into rabbit organisms for one, three and six months. An ex vivo histological examination shows that certain pore geometry and the pre-growing of Cho prior to implantation significantly improves the performance of the created 3D scaffolds. The achieved biocompatibility is comparable to the commercially available collagen membranes. The successful outcome of this study supports the idea that hexagonal-pore-shaped HOI microstructured scaffolds in combination with Cho seeding may be successfully implemented for cartilage tissue engineering.

— Textile effluent are abundant source of colored pollutant that present an enhancing the environmental danger. So the color present in textile effluent is that major concern of researcher today. Dyestuff present in textile effluent is mainly xenobiotic in nature and not easily self-biodegradable. Intensive treatment is necessary to degrade the dyestuff and reduces the COD and turbidity of textile effluent. The present work is an attempt to review the all possible treatment methods for remove dyestuff from textile effluent by Advanced Oxidation Processes (AOPs). The proposed studies in this paper summarize the capability and potential of conventional treatment for degradation of dyestuff from textile effluent. Conventional method for treatment of textile effluent has own certain limitations that can be well overcome by advance oxidation processes (AOPs).

The cardiac activity of a series of analogues of the positive inotropic bipyridines amrinone (5amino-[3,4'-bipyridin]-6(1H)-one) and milrinone (2-methyl-5-cyano-[3,4'-bipyridinl-6(1H)-one) was evaluated in vitro in a rabbit myocardial membrane Mg2+-dependent, Ca2+-stimulable adenosine triphosphatase (Ca2+-ATPase) model, and structure-activity relationships were compared for nine closely related derivatives. In the present studies, a 5-bromo analogue of milrinone stimulated myocardial membrane Ca2+-ATPase significantly (lo-' M; P < 0.001 vs control, with 67% of the activity of milrinone), whereas a 2'-methyl-W-milrinone derivative was inactive. Although amrinone was inactive in this assay, its 2-methyl analogue was stimulatory. However, analogues lacking a 2-substituent (with or without a 5-cyano group) or with the 3-N position blocked by a methyl group did not stimulate myocardial membrane Ca2+-ATPase activity. Structural data for these bipyridines show that those with either a 2-or 2'-methyl substituent have a twist conformation, whereas those without are nearly planar. Activity data reveal that those bipyridines with a nonplanar conformation are more active in the Ca2+-ATPase assay. Further study of milrinone analogues with a 2'-methyl substituent shows that even though the effect on the twist angle is equivalent to that of 2-methyl substitution, these analogues are less potent. Data for this series reveal that the prerequisites for Ca2+-ATPase stimulation include not only a 2-methyl to maintain a twist conformation but also a free 3-N position and a 5-substituent. This model for optimal activity in the myocardial membrane Ca2+-ATPase system differs from those proposed for phosphodiesterase enzyme receptor recognition only in the requirement for a nonplanar molecule. We have previously shown that milrinone, but not amrinone, shares structural homology with thyroxine and was able to stimulate myocardial membrane Ca2+-ATPase activity in a manner similar to the thyroid hormone. Additionally, milrinone, but not amrinone, was an effective competitor for thyroxine binding to the serum transport protein transthyretin. Analysis of the milrinone-transthyretin crystal complex confirms the structural homology between milrinone and thyroid hormone which is not shared by amrinone. Modeling studies of the binding interactions of milrinone analogues indicate that the 2-desmethylmilrinone analogue, the most inhibitory analogue, lacks the hydrophobic contacts present in milrinone in its transthyretin-bound complex. These findings correlate with their structure-activity relationships in the Ca2+-ATPase assay. On the basis of these data, it is predicted that increased inhibition of Ca2+-ATPase activity could be achieved by the addition of a 2'-methyl to the 2-desmethylmilrinone analogue, the most inhibitory in this series. However, such an analogue would be a weaker competitor for the binding of thyroxine to transthyretin. * Corresponding author: Vivian Cody, Ph.D. TEL: (716) 856-9600. Of the structure Of FAX: (716) 852-4846. versity, Gagarina 7, 87-100 Torun, Poland. homology with t h y r~x i n e ,~ and a model of the interaction of milrinone in the transthyretin hormone binding site was proposed from computer modeling studies." This model was validated by crystallographic determination of the milrinone-bound complex of human transthyretin.12 In skeletal muscle sarcoplasmic reticulum ? Hauptman-Woodward Medical Research Institute.

The use of membranes in blood processing range from the use of large-pore structures for filtration of blood for the removal of large particles (>20 m transfusion filters) to membranes for the dialysis of blood for the removal of low molecular weight solutes in the treatment of renal failure. Within the past 20 years, membranes have been applied in the separation of plasma from whole blood. Compared to centrifugal plasma separation membrane, plasma separation is preferred when used with online plasma fractionation since the plasma is free of cells. In addition, membranes have also been applied in the on-line treatment of plasma for the selective removal of macromolecules in selected disease states obviating the need for plasma replacement products. The membranes used for plasma separation and fractionation may be distinguished from conventional dialysis membranes and highflux membranes used in hemofiltration by their very high or select passage of plasma proteins. Membrane techniques are simple and safe to apply and can be competitive to other plasma separation and treatment technologies.

The single-layered microporous polyethylene
separator is prepared by dry process and has been
stretched in uni-axial direction to two different ratios
namely 180 and 300 % in order to create highperformance
and cost-effective separator for practical application
in lithium-ion batteries. In this study, the structures
of the microporous polyethylene separator prepared
by dry process and uni-axially stretched to two different
ratios of 180 and 300 % were characterized. The physical
structure of the stretched separator is characterized by key
factors such as thickness, mean pore size, porosity, Gurley
value, ionic resistivity, MacMullin number and tortuosity.
The thermal behavior of the stretched separator is
explained by using differential scanning calorimeter
(DSC). DSC explains the melting and shutdown behavior
of the separator. Electrochemical property is studied by
linear sweep voltammetry, electrochemical impedance
spectroscopy (EIS) and cyclic performance. EIS is performed
to explain, in elaborate, the resistance of separator
and the specific discharge capacity is observed using the
cyclic performance. Three hundred percent stretched separator is observed to have comparatively less resistance
and higher discharge capacity than the 180 % stretched
separator.

Aqueous dispersions of lipids isolated from spinach chloroplast membranes were studied by electron microscopy after negative staining with phosphotungstic acid. Influence of low temperature (5°C for 24 h) was also investigated. It was observed that when contacted with water, these lipids, as such, formed multilamellar structures. Upon sonication, these multilamellar structures gave rise to a clear suspension of unilamellar vesicles varying in size (diameter) between 250 and 750 Å. When samples of sonicated unilamellar vesicles were stored at 5°C for 24 h or more, they revealed a variety of lipid aggregates including liposomes, cylindrical rods (about 100 Å wide and up to 3600 Å long), and spherical micellar structures (100-200 Å in diameter)-thus indicating phase separation of lipids.

There is an enormous need in the health welfare sector to manufacture inexpensive dialyzer membranes with minimum dialysis duration. In order to optimize the dialysis cost and time, an in-depth analysis of the effect of dialyzer design and process parameters on toxins (ranging from tiny to large size molecules) clearance rate is required. Mathematical analysis and enhanced computational power of computers can translate the transport phenomena occurring inside the dialyzer while minimizing the development cost. In this paper, the steady-state mass transport in blood and dialysate compartment and across the membrane is investigated with convection-diffusion equations and tortuous pore diffusion model (TPDM), respectively. The two-dimensional, axisymmetric CFD model was simulated by using a solver based on the finite element method (COMSOL Multiphysics 5.4). The effect of design and process parameters is analyzed by solving model equations for varying values of design and process param...

Repeated washing of rat liver mitochondria with sucrose medium removes all of the cytochrome P-450 while low but significant amounts of glucose 6-phosphatase and NADPH cytochrome c reductase are still retained. A t the same time monoamine oxidase and succinate cytochrome c reductase activities increase slightly. Cytochrome P-450 and glucose 6-phosphatase are completely retained by the microsomes even after five waahings with sucrose medium.

Membrane based medical therapies have increased considerably in recent years. At the same time, awareness of the side-effects caused by blood material incompatibility has grown. The necessity of mass production at low cost has also contributed to the formation of demands placed on any membrane used in medical applications today. These demands are application specific transport characteristics, high clearance, blood compatibility and a design enabling cost efficient ways of production. A theoretical approach relating membrane structure to transport properties suggests that the deciding factors are pore radius, porosity, tortuosity, diffusion coefficients, pore shape and protein adsorption potential. A hollow fiber structure, which fits these demands for hemodialysis, hemodialfiltration and hemofiltration, is a three-layer structure consisting of an inner blood facing skin layer, followed by a sponge structure and a macroporous finger structure. The influence of the membrane surface on protein adsorption, leading to a change in permeability, has also been investigated. Two concepts for limiting protein and cell interaction with artificial surfaces are introduced. Copolymerization and blending of hydrophobic and hydrophilic polymers have been successful approaches. To limit blood-membrane interactions, an optimized microdomain surface structure formed by hydrophilic patches in a hydrophobic matrix has evolved. In vitro test methods for measuring activation levels of coagulation, kallikrein-kinin pathways, cell stimulation and complement activation were necessary for the development of highly optimized artificial membranes made for hemodialysis, hemodiafiltration and hemofiltration. The Polyflux S membranes, consisting of the hydrophobic polymers polyamide and polyarylethersulfone as well as hydrophilic poylvinylpyrrolidone, with their integral three-layer microdomain structures performed well in all of the mentioned in vitro tests.

Environmental Context. The fate and behaviour of trace pollutants are very strongly modified, and usually dominated, by their physical and chemical interactions with naturally occurring aquatic colloids (defined as solid phase material with one dimension between 1 nm and 1 µm). This review summarises the area and key advances in the field of natural aquatic colloids, including technique development and quantification of colloidal structure and interactions with pollutants.The review also discusses areas in which significant advances are likely to be made or are needed and, as such, provides a framework for further work in the next few years.

Nitrobenzoxadiazole (NBD)-labeled lipids are popular fluorescent membrane probes.However, the understanding of important aspects of the photophysics of NBD remains incomplete, including the observed shift in the emission spectrum of NBD-lipids to longer wavelengths following excitation at the red edge of the absorption spectrum (REES).REES of NBD-lipids in membrane environments has been previously interpreted as reflecting restricted mobility of solvent surrounding the fluorophore.However, this requires a large change in the dipole moment (Δμ) of NBD upon excitation.Previous calculations of the value of Δμ of NBD in the literature have been carried out using outdated semi-empirical methods, leading to conflicting values.Using up-to-date density functional theory methods, we recalculated the value of Δμ and verified that it is rather small (∼2D). Fluorescence measurements confirmed that the value of REES is ∼16nm for 1,2-dioleoyl-sn-glycero-3-phospho-l-serine-N-(NBD) (NBD-PS) in dioleoylphosphatidylcholine vesicles.However, the observed shift is independent of both the temperature and the presence of cholesterol and is therefore insensitive to the mobility and hydration of the membrane.Moreover, red-edge excitation leads to an increased contribution of the decay component with a shorter lifetime, whereas time-resolved emission spectra of NBD-PS displayed an atypical blue shift following excitation.This excludes restrictions to solvent relaxation as the cause of the measured REES and TRES of NBD, pointing instead to the heterogeneous transverse location of probes as the origin of these effects.The latter hypothesis was confirmed by molecular dynamics simulations, from which the calculated heterogeneity of the hydration and location of NBD correlated with the measured fluorescence lifetimes/REES.Globally, our combination of theoretical and experiment-based techniques has led to a considerably improved understanding of the photophysics of NBD...

"The purpose of this checklist is to identify the stages and potential problems associated with the scale up of fixed bed reactors from the drawing board to the full scale plant, and to determine how they should be checked.

The checking can be done using various methods. These are:

•  Literature data.

•  Lab testing.

•  Calculation.

•  Modeling.

•  Semi-tech testing.

•  Piloting or Side-stream testing.


Identifying the stages that need to be addressed for a particular catalyst/reactor development will help in estimating the time needed for the development of the reactor.
"
#Fundamentals; #New Preparations and New Active Materials; #Synthesis and Characterization of Catalysts; #Characterization of Catalyst in its Working State; #Catalyst Deactivation; #Reaction Kinetics; #Reactor Modeling; #Reactor Design, Control and Optimization; #Novel Reactors and Process Developments;

Membrane technology has been investigated for removing CO 2 from mixtures with light gases such as CH 4 , N 2 and H 2 , and optimal membranes with high CO 2 permeability and high CO 2 /light gas selectivity are of great interest. This overview describes the material science approaches to achieve high CO 2 solubility and CO 2 /light gas solubility selectivity by introducing polar groups in polymers. CO 2 solubility and CO 2 /N 2 solubility selectivity in both liquid solvents and solid polymers containing a variety of polar groups are discussed. Optimum materials appear to have a solubility parameter of about 21.8 MPa 0.5 to achieve both high solubility and high solubility selectivity. However, the introduction of polar groups can decrease CO 2 diffusion coefficients and can make a material more size-selective, which is detrimental to, for example, CO 2 /H 2 separation properties. So far, ether oxygens in ethylene oxide (EO) units appear to provide a good balance of CO 2 separation and permeation properties. One drawback of using pure poly(ethylene oxide) (PEO) is its strong tendency to crystallize. This report reviews strategies for incorporating high concentrations of EO units into polymers while suppressing crystallization. A simple model, based on free volume theory, is used to correlate a wide range of CO 2 permeability coefficients in PEO containing materials, and the results are satisfactory, particularly given the simplicity of the model. Crosslinked poly(ethylene glycol) acrylate (XLPEO) containing branches with methoxy end groups exhibit the highest CO 2 permeability (i.e. 570 Barrers) and highest CO 2 /H 2 selectivity (i.e. 12) at 35 8C and infinite dilution among all PEO containing materials reported to date. Because such materials do not crystallize at typically accessible temperatures, CO 2 /H 2 selectivity can be further improved by decreasing temperature. For example, at an upstream pressure of 4.4 atm, CO 2 /H 2 pure gas selectivity reaches a value of 40 at K20 8C while maintaining a CO 2 permeability of 52 Barrers. q

The ing and integration water ultrafiltration treatment construction of low-pressure (UF) facilities membranes has been and microfiltration new into water both treatexist(MF) and ultrafiltration (UF) membranes into both existing water treatment facilities and new water treatment plant construction has been rapidly gaining favor worldwide (AWWA, 2005). Contributing factors include the efficacy of these membranes in removing cysts and their consistent ability to produce low-turbidity product water despite variations in source water quality. One example of a decision to incorporate MF/UF technology into existing water treatment facilities is in Minnesota, where the Minneapolis Water Works has replaced aging granular media filters with UF at its 70mgd (265-ML/d) Columbia Heights Filtration Plant. Another example is in California, where the Modesto Irrigation District is doubling capacity from 36 to 72 mgd (136 to 273 ML/d) by adding membranes in parallel with existing granular media fil...

Membrane bioreactors (MBRs) represent an emerging technology for the advanced secondary treatment of municipal wastewater around the world. In this line, seven municipal MBRs facilities recently built, with capacities ranging from 1,100 m3·day-1 to 35,000 m3·day-1 (up to 100,000 m3·day-1 in total) have been diagnosed. The evaluation of the design and operational issues revealed significant improvements from the oldest to the newest MBR installed. The main operational issues surveyed have been classified and described in three different categories: i) design limitations, (ii) membranes and equipment failure and (iii) operational problems, with inter-relationships between them. The two oldest MBRs showed broken membranes after six and seven years of operation, respectively, being required its replacement. While foaming has been determined as the most common operational problem, other troubles such as clogging, reduction of denitrification process efficiency or the air in the permeate line were of more concern for the practitioners. Moreover, fouling has not been mentioned by any of the practitioners and energy consumption has been determined as the main limitation of this technology.

This guide covers the reaction kinetics and diffusional aspects of solid catalyzed reactions. It does not deal with either the fluid dynamics or the mechanical design of reactors for solid Catalyzed reactions.

#Fundamentals; #New Preparations and New Active Materials; #Synthesis and Characterization of Catalysts; #Characterization of Catalyst in its Working State; #Catalyst Deactivation; #Reaction Kinetics; #Reactor Modeling; #Reactor Design, Control and Optimization; #Novel Reactors and Process Developments;

the microporous material is deposited as a thin layer on the Aqueous sodium silicate solutions and hydrochloric acid were top of a porous support which consists generally of a similar used to prepare silica gels without any additives. In order to estabmaterial with a coarser pore structure.

Gravity drainage systems occur frequently on chemical plants. Typical examples are:

(a) the condensate off-take from a condenser;

(b) the liquid off-take from the base of an absorption column;

(c) the emergency overflow from an atmospheric pressure storage tank.

Gas entrained in a liquid flowing by gravity from a vessel will reduce the volume of liquid flowing through the pipe and could cause surging flows.

Environmental context. On a global scale, soils store more carbon than plants or the atmosphere. The cycling of this vast reservoir of reduced carbon is closely tied to variations in environmental conditions, but robust predictions of climate-carbon cycle feedbacks are hampered by a lack of mechanistic knowledge regarding the sensitivity of organic matter decomposition to rising temperatures. This text provides a critical discussion of the practice to conceptualise parts of soil organic matter as intrinsically resistant to decomposition or 'recalcitrant'.

Antimicrobial peptides (AMPs) are showing increasing promise as potential candidate antibacterial drugs in the face of the rapidly emerging bacterial resistance to conventional antibiotics in recent years. The target of these peptides is the microbial membrane and there are numerous models to explain their mechanism of action ranging from pore formation to general membrane disruption. The interaction between the AMP and the target membrane is critical to the specificity and activity of these peptides. However, a precise understanding of the relationship between antimicrobial peptide structure and their cytolytic function in a range of organisms is still lacking. This is a result of the complex nature of the interactions of AMPs with the cell membrane, the mechanism of which can vary considerably between different classes of antimicrobia peptides. A wide range of biophysical techniques have been used to study the influence of a number of peptide and membrane properties on the cytolytic activity of these peptides in model membrane systems. Central to characterisation of this interaction is a quantitative analysis of the binding of peptide to the membrane and the coherent dynamic changes in membrane structure. Recently, dual polarization interferometry has been used to perform an in depth analysis of antimicrobial peptide induced membrane perturbation and with new mass-structure co-fitting kinetic analysis have allowed a real-time label free analysis of binding affinity and kinetics. We review these studies which describe multi-step mechanisms which are adopted by various AMPs in nature and may advance our approach to the development of a new generation of effective antimicrobial therapeutics.