- Community and cosmopolitanism in the new Ubud
- MacRae, G. | Annals of tourism research (v.59 / pp.16-29 / 20160160-7383)
- Ubud has, since the 1930s, represented a distinctive model of tourism in Bali-based on ''traditional culture'' but also engagement of foreigners with the local community
초록보기원문보기 >
Ubud has, since the 1930s, represented a distinctive model of tourism in Bali-based on ''traditional culture'' but also engagement of foreigners with the local community in which the line between ''tourists who stay longer'' and an expatriate community has been blurred. From the 1970s tourist and expatriate numbers increased steadily and since 2010 numbers have exploded and new kinds of tourists and expatriates and new relationships with local culture and community have developed. Ubud is no longer a village-with-tourists but a diversifying international town. This article documents this ''new Ubud'' and argues that the categories of tourism studies are inadequate for making sense of it, suggesting instead cosmopolitanism as a potentially more useful tool for understanding this transformation.
- Crystallinity and mechanical effects from annealing Parylene thin films
- Jackson, N., Stam, F., O'Brien, J., Kailas, L., Mathewson, A., O'Murchu, C. | Thin solid films (v.603 / pp.371-376 / 20160040-6090)
- Parylene is commonly used as thin film polymer for MEMS devices and smart materials. This paper investigates the impact on bulk properties due to annealing various types
초록보기원문보기 >
Parylene is commonly used as thin film polymer for MEMS devices and smart materials. This paper investigates the impact on bulk properties due to annealing various types of Parylene films. A thin film of Parylene N, C and a hybrid material consisting of Parylene N and C were deposited using a standard Gorham process. The thin film samples were annealed at varying temperatures from room temperature up to 300 o C. The films were analyzed to determine the mechanical and crystallinity effects due to different annealing temperatures. The results demonstrate that the percentage of crystallinity and the full-width-half-maximum value on the 2 theta; X-ray diffraction scan increases as the annealing temperature increases until the melting temperature of the Parylene films was achieved. Highly crystalline films of 85% and 92% crystallinity were achieved for Parylene C and N respectively. Investigation of the hybrid film showed that the individual Parylene films behave independently to each other, and the crystallinity of one film had no significant impact to the other film. Mechanical testing showed that the elastic modulus and yield strength increase as a function of annealing, whereas the elongation-to-break parameter decreases. The change in elastic modulus was more significant for Parylene C than Parylene N and this is attributed to the larger change in crystallinity that was observed. Parylene C had a 112% increase in crystallinity compared to a 61% increase for Parylene N, because the original Parylene N material was more crystalline than Parylene C so the change of crystallinity was greater for Parylene C.
- Organic reactions for the electrochemical and photochemical production of chemical fuels from CO2 - The reduction chemistry of carboxylic acids and derivatives as bent CO2 surrogates
- Luca, O.R., Fenwick, A.Q. | Journal of photochemistry and photobiology. B, Biology (v.152 / no.1 / pp.26-42 / 20151011-1344)
- The present review covers organic transformations involved in the reduction of CO 2 to chemical fuels. In particular, we focus on reactions of CO 2 with organic molec
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The present review covers organic transformations involved in the reduction of CO 2 to chemical fuels. In particular, we focus on reactions of CO 2 with organic molecules to yield carboxylic acid derivatives as a first step in CO 2 reduction reaction sequences. These biomimetic initial steps create opportunities for tandem electrochemical/chemical reductions. We draw parallels between long-standing knowledge of CO 2 reactivity from organic chemistry, organocatalysis, surface science and electrocatalysis. We point out some possible non-faradaic chemical reactions that may contribute to product distributions in the production of solar fuels from CO 2 . These reactions may be accelerated by thermal effects such as resistive heating and illumination.
- Near-infrared spectra of liquid/solid acetylene under Titan relevant conditions and implications for Cassini/VIMS detections
- Singh, S., Cornet, T., Chevrier, V.F., Combe, J.Ph., McCord, T.B., Roe, L.A., Le Mouelic, S., Le Menn, E., Wasiak, F.C. | Icarus (v.270 / pp.429-434 / 20160019-1035)
- Acetylene is thought to be abundant on Titan according to most photochemical models. While detected in the atmosphere, its likely presence at the surface still lacks phys
초록보기원문보기 >
Acetylene is thought to be abundant on Titan according to most photochemical models. While detected in the atmosphere, its likely presence at the surface still lacks physical evidence. It is thought that solid acetylene could be a major component of Titan's lakes shorelines and dry lakebed, detected as the 5 mu;m-bright deposits with the Cassini/VIMS instrument. Acetylene could also be present under its liquid form as dissolved solids in Titan's methane-ethane lakes, as emphasized by thermodynamics studies. This paper is devoted to the near-infrared spectroscopy study of acetylene under solid and liquid phases between 1 and 2.2 mu;m, synthesized in a Titan simulation chamber that is able to reproduce extreme temperature conditions. From experiments, we observed a ~10% albedo increase between liquid acetylene at 193-188K and solid acetylene at 93K. Using the NIR spectroscopy technique we successfully calculated the reflectivity ratio of solid/liquid acetylene as 1.13. The second difference we observed between liquid and solid acetylene is a shift in the major absorption band detected at 1.54 mu;m, the shift of ~0.01 mu;m occurring toward higher wavelength. In order to assess the detectability of acetylene on Titan using the Cassini/VIMS instrument, we adapted our spectra to the VIMS spectral resolution. The spectral band at 1.55 mu;m and a negative slope at 2.0 mu;m falls in the Cassini/VIMS atmospheric windows over several VIMS infrared spectels, thus Cassini/VIMS should be able to detect acetylene.
- Effects of Pressure in Cathodic Deposition of TiO2 and SnO2 with Supercritical CO2 Emulsified Electrolyte
- Lin, W.H., Chen, C.Y., Chang, T.F.M., Hsu, Y.J., Sone, M. | Electrochimica acta (v.208 / pp.244-250 / 20160013-4686)
- This study reports the effect of the high pressure on properties, especially the crystallinity, of the TiO 2 and SnO 2 films cathodically deposited in supercritical C
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This study reports the effect of the high pressure on properties, especially the crystallinity, of the TiO 2 and SnO 2 films cathodically deposited in supercritical CO 2 emulsified electrolyte. The as-deposited metal oxides are usually amorphous when cathodic deposition is applied. An additional heat treatment process is needed to have crystalline metal oxides. In this study, the TiO 2 and SnO 2 thin films cathodically deposited at elevated pressure showed an improvement in the crystallinity with an increase in the pressure using X-ray diffraction analysis. The high-resolution transmission electron microscopy and selected-area electron diffraction confirmed that the TiO 2 deposited at 35MPa had the anatase crystal structure. An enhancement in the charge carrier dynamics at the TiO 2 electrode/electrolyte interface with an increase in the pressure was observed from the electrochemical impedance spectroscopy, which is a result of the improved crystallinity. The effect of the pressure on the crystallinity of the SnO 2 was more obvious than that on the TiO 2 . Grain size of the SnO 2 films estimated by the Scherrer equation was increased from 3.5 to 14.8nm when the pressure was increased from 5 to 25MPa.
- Resolution of international trade disputes in the WTO and other Fora
- Sacerdoti, Giorgio | Journal of international trade law policy (v.14 / no.3 / pp.147-156 / 20151477-0024)
- Purpose ndash; The purpose of this paper is to assess the success of the world trade organisation (WTO) dispute settlement system and its transferability to other fora.
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Purpose ndash; The purpose of this paper is to assess the success of the world trade organisation (WTO) dispute settlement system and its transferability to other fora. Design/methodology/approach ndash; The paper compares the design and case law of trade and investment law, and seeks lessons for the settlement of trade and investment disputes in other fora. Findings ndash; It concludes that despite its shortcomings, the WTO Appellate Body provides vital stability regarding legal interpretations, something notably absent from other fora. Originality/value ndash; The paper offers the perspective of a former Member and Chairman of the WTO Appellate Body on the success of the dispute settlement system.
- Cross-cultural differences in uses of online experts
- Obal, M., Kunz, W. | Journal of business research (v.69 / no.3 / pp.1148-1156 / 20160148-2963)
- Existing research on how consumers utilize online reviewers to make purchasing decisions has generally taken a Western viewpoint. However, the majority of new online cons
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Existing research on how consumers utilize online reviewers to make purchasing decisions has generally taken a Western viewpoint. However, the majority of new online consumers come from Eastern nations. Therefore, the present article takes a cross-cultural view of how consumers from Eastern nations, such as China and India, respond to expert and non-expert online reviewers, in comparison with consumers from Western nations, such as the United States and Canada. The results from an experimental study of 134 North American respondents and 132 Asian respondents reveal that Asians are more likely to rely on advice from an online reviewer, while North Americans are more skeptical of and less reliant on non-expert reviewers. Asians are more forgiving of non-experts and do not necessarily distinguish between experts and non-experts when deciding on whom to rely. This article thus highlights a clear difference between Asian and North American expectations of online reviewers.
- Determination of chiral pharmaceuticals and illicit drugs in wastewater and sludge using microwave assisted extraction, solid-phase extraction and chiral liquid chromatography coupled with tandem mass spectrometry
- Evans, S.E., Davies, P., Lubben, A., Kasprzyk-Hordern, B. | Analytica chimica acta : an international journal devoted to all branches of analytical chemistry (v.882 / pp.112-126 / 20150003-2670)
- This is the first study presenting a multi-residue method allowing for comprehensive analysis of several chiral pharmacologically active compounds (cPACs) including beta-
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This is the first study presenting a multi-residue method allowing for comprehensive analysis of several chiral pharmacologically active compounds (cPACs) including beta-blockers, antidepressants and amphetamines in wastewater and digested sludge at the enantiomeric level. Analysis of both the liquid and solid matrices within wastewater treatment is crucial to being able to carry out mass balance within these systems. The method developed comprises filtration, microwave assisted extraction and solid phase extraction followed by chiral liquid chromatography coupled with tandem mass spectrometry to analyse the enantiomers of 18 compounds within all three matrices. The method was successfully validated for 10 compounds within all three matrices (amphetamine, methamphetamine, MDMA, MDA, venlafaxine, desmethylvenlafaxine, citalopram, metoprolol, propranolol and sotalol), 7 compounds validated for the liquid matrices only (mirtazapine, salbutamol, fluoxetine, desmethylcitalopram, atenolol, ephedrine and pseudoephedrine) and 1 compound (alprenolol) passing the criteria for solid samples only. The method was then applied to wastewater samples; cPACs were found at concentration ranges in liquid matrices of: 1.7ngL -1 (metoprolol) - 1321ngL -1 (tramadol) in influent, -1 in effluent, and in solid matrix digested sludge: 0.4ngg -1 (metoprolol) - 275ngg -1 (citalopram). Enantiomeric profiling revealed that studied compounds were present in analysed samples in non-racemic composition. Furthermore, enantiomeric composition of studied analytes differed in liquid and solid matrices. This demonstrates that not analysing the solid fraction of wastewater may lead to over-estimation of the removal rates of cPACs as well as possible misrepresentation of the enantiomeric fraction of the compounds as they leave the wastewater treatment plant. Consequently risks from cPACs entering the environment might be higher than anticipated.
- La fluiditE de l'espace montrEalais : Etude sur la diffusion de la diversitE ethnoculturelle A MontrEal entre 2001 et 2006
- Leloup, Xavier | The Canadian geographer. G eacute;ographe canadien (v.59 / no.3 / pp.328-340 / 20150008-3658)
- Abstract The recent increase in ethno #8208;cultural diversity has raised numerous questions in countries of immigration. One of them focuses on the processes and mechan
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Abstract The recent increase in ethno #8208;cultural diversity has raised numerous questions in countries of immigration. One of them focuses on the processes and mechanisms that lead to the creation of integrated or multiethnic neighbourhoods. To address it, various models were elaborated to explain the phenomenon. We will first recall the main features of these various models. Afterward, we test the hypothesis proposed by Germain and Poirier to explain the evolution of ethno #8208;cultural diversity in Montreal. This hypothesis supposes that it has evolved in a context where fluidity was central. Our aim is to propose an empirical test of this hypothesis using several methods (i.e., spatial analysis tools, regression model, and structural equation modeling). The results confirm the ldquo;fluidity rdquo; hypothesis, even if they also stress a stratification process between the various minority groups linked to neighbourhood socio #8208;demographic characteristics.
- A thermo-mechanical large deformation constitutive model for polymers based on material network description: Application to a semi-crystalline polyamide 66
- Maurel-Pantel, A., Baquet, E., Bikard, J., Bouvard, J.L., Billon, N. | International journal of plasticity (v.67 / pp.102-126 / 20150749-6419)
- A visco-hyperelastic constitutive model, based on an original approach initially developed by (Billon, 2012) and applied to amorphous rubbery polymers for a one-dimension
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A visco-hyperelastic constitutive model, based on an original approach initially developed by (Billon, 2012) and applied to amorphous rubbery polymers for a one-dimensional formalism, was extended in this study to three-dimensional constitutive equations based on a thermodynamic framework. The model was applied to a semi-crystalline polyamide polymer, PA66. The experiments included tension and shear testing coupled with synchronized digital image correlation and infrared measurements device for capturing the time, temperature, and stress state dependence, as well as the complex thermomechanical coupling exhibited by the material under large deformation. A notion of equivalent strain rate (based on the time-temperature principle superposition) was also introduced to show its capability to build master curves and therefore decrease the number of testing needed to build a material database. The model is based on the Edward Vilgis theory (1986) and accounts for chains network reorganization under external loading through the introduction of an evolution equation for the internal state variable, eta;@?, representing the degree of mobility of entanglement points. The model accounting for the equivalent strain rate notion was calibrated using master curves. The thermomechanical model agreed well with the experimental mechanical and temperature measurements under tension and shear conditions. The approach developed in this study may open a different way to model the polymer behavior.
- In Situ Generation of Cellulose Nanocrystals in Polycaprolactone Nanofibers: Effects on Crystallinity, Mechanical Strength, Biocompatibility, and Biomimetic Mineralization
- Joshi, Mahesh Kumar, Tiwari, Arjun Prasad, Pant, Hem Raj, Shrestha, Bishnu Kumar, Kim, Han Joo, Park, Chan Hee, Kim, Cheol Sang | ACS applied materials interfaces (v.7 / no.35 / pp.19672-19683 / 20151944-8244)
- Post-electrospinning treatment is a facile process to improve the properties of electrospun nanofibers for various applications. This technique is commonly used when dire
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Post-electrospinning treatment is a facile process to improve the properties of electrospun nanofibers for various applications. This technique is commonly used when direct electrospinning is not a suitable option to fabricate a nonwoven membrane of the desired polymer in a preferred morphology. In this study, a representative natural-synthetic hybrid of cellulose acetate (CA) and polycaprolactone (PCL) in different ratios was fabricated using an electrospinning process, and CA in the hybrid fiber was transformed into cellulose (CL) by post-electrospinning treatment via alkaline saponification. Scanning electron microscopy was employed to study the effects of polymer composition and subsequent saponification on the morphology of the nanofibers. Increasing the PCL content in the PCL/CA blend solution caused a gradual decrease in viscosity, resulting in smoother and more uniform fibers. The saponification of fibers lead to pronounced changes in the physicochemical properties. The crystallinity of the PCL in the composite fiber was varied according to the composition of the component polymers. The water contact angle was considerably decreased (from 124° to less than 20°), and the mechanical properties were greatly enhanced (Young rsquo;s Modulus was improved by asymp;20 ndash;30 fold, tensile strength by 3 ndash;4 fold, and tensile stress by asymp;2 ndash;4 fold) compared to those of PCL and PCL/CA membranes. Regeneration of cellulose chains in the nanofibers increased the number of hydroxyl groups, which increased the hydrogen bonding, thereby improving the mechanical properties and wettability of the composite nanofibers. The improved wettability and presence of surface functional groups enhanced the ability to nucleate bioactive calcium phosphate crystals throughout the matrix when exposed to a simulated body fluid solution. Experimental results of cell viability assay, confocal microscopy, and scanning electron microscopy imaging showed that the fabricated nanofibrous membranes have excellent ability for MC3T3-E1 cell proliferation and growth. Given the versatility and widespread use of cellulose ndash;synthetic hybrid systems in the construction of tissue-engineered scaffolds, this work provides a novel strategy to fabricate the biopolymer-based materials for applications in tissue engineering and regenerative medicine. Graphic Abstract ACS Electronic Supporting Info
- Chloride-Inducible Expression Vector for Delivery of Antimicrobial Peptides Targeting Antibiotic-Resistant Enterococcus faecium
- Geldart, Kathryn, Borrero, Juan, Kaznessis, Yiannis N. | Applied and environmental microbiology (v.81 / no.11 / pp.3889-3897 / 20150099-2240)
- Antibiotic-resistant enterococcal infections are a major concern in hospitals where patients with compromised immunity are readily infected. Enterococcus faecium bacter
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Antibiotic-resistant enterococcal infections are a major concern in hospitals where patients with compromised immunity are readily infected. Enterococcus faecium bacteria are of particular interest as these pathogens account for over 80% of vancomycin-resistant enterococcal infections. Antimicrobial peptides (AMPs) produced at the site of infection by engineered bacteria may offer a potential alternative to traditional antibiotics for the treatment of resistant bacteria such as E. faecium . For this mode of delivery to be effective, it is essential to identify a suitable protein expression system that can be used in the desired delivery bacterium. In this study, we describe a promising chloride-inducible promoter and its application in the bacterial delivery of AMPs from Lactococcus lactis to reduce counts of E. faecium bacteria in vitro . Reporter gene studies show that at chloride concentrations found within the human intestines, the chloride-inducible promoter exhibits high levels of protein expression compared to those of the commonly used nisin-inducible promoter. These results indicate that this system is powerful and would not require the exogenous administration of an inducer molecule. In its application for AMP production against E. faecium in vitro , L. lactis producing AMPs under the chloride promoter rapidly decreased E. faecium counts by nearly 10,000-fold. As an extension of this application, we also demonstrate the potential in using this type of delivery system in combination with traditional antibiotics to slow the development of resistance. Collectively, this study shows the promise of using a chloride-inducible promoter for the bacterial delivery of AMPs in the body for the treatment of vancomycin-resistant enterococci (VRE) and other antibiotic-resistant bacteria.
- Chloride migration in structural lightweight aggregate concrete produced with different binders
- Real, S., Bogas, J.A., Pontes, J. | Construction building materials (v.98 / pp.425-436 / 20150950-0618)
- This paper characterizes the chloride penetration resistance of structural lightweight aggregate concrete (SLWAC) produced with different types of aggregates and binders,
초록보기원문보기 >
This paper characterizes the chloride penetration resistance of structural lightweight aggregate concrete (SLWAC) produced with different types of aggregates and binders, for usual compressive strengths of about 20-65MPa. Concrete is characterized by means of capillary absorption, electrical resistivity and accelerated chloride migration tests. In general, it was found that the chloride penetration resistance can be substantially affected by the type of binder. Besides the microstructural refinement effect, the mineral admixtures should also affect the ionic composition of the pore solution. The type of aggregate had a little influence on the chloride penetration resistance. Chloride penetration resistance should not be related to the compression strength of concrete. However, chloride diffusion is exponentially related to the w/c ratio, regardless the type of aggregate. The capillarity and resistivity results did not correlate well with those from the chloride migration test. It is concluded that SLWAC with less porous aggregate can be at least as resistant as normal weight concrete.
- Chloride Ion Mediated Synthesis of Metal/Semiconductor Hybrid Nanocrystals
- Hinrichs, Dominik, Galchenko, Michael, Kodanek, Torben, Naskar, Suraj, Bigall, Nadja C., Dorfs, Dirk | Small (v.12 / no.19 / pp.2588-2594 / 20161613-6810)
- A synthetic route to prepare metal ndash;semiconductor hybrid nanoparticles is presented, along with the possibility to tune the ratio of primary to secondary nucleation
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A synthetic route to prepare metal ndash;semiconductor hybrid nanoparticles is presented, along with the possibility to tune the ratio of primary to secondary nucleation and the morphology of the semiconductor material grown on the metal nanoparticle seeds. Gold and cobalt #8208;platinum nanoparticles are employed as metal seeds, on which CdS or CdSe is grown. Using transmission electron microscopy, absorption spectroscopy (UV ndash;vis), and powder X #8208;ray diffraction as characterization techniques, a significant influence of chloride ions on the type of nucleation (that is, secondary or primary nucleation) as well as on the shape of the resulting heterostructures is observed. Partially replacing the commonly used cadmium precursor CdO by varying amounts of CdCl 2 opens access to rod #8208;like, multiarmed, flower #8208;like, and bullet #8208;like structures. The results suggest that neither pure CdO nor pure CdCl 2 as precursors but only a mixture of both make these structures obtainable. In this article, the influence of the chloride ion concentration during semiconductor growth on metal seeds is investigated in depth. The morphology of the resulting heterostructures is characterized carefully, and a growth mechanism is suggested. Furthermore, it is shown that this synthetic approach can be transferred to seeds of various metals such as platinum, gold, and cobalt platinum.
- Alkynol natural products target ALDH2 in cancer cells by irreversible binding to the active site
- Heydenreuter, Wolfgang, Kunold, Elena, Sieber, Stephan A. | Chemical communications : Chem comm (v.51 / no.87 / pp.15784-15787 / 20151359-7345)
- Falcarinol and stipudiol are natural products with potent anti-cancer activity found in several vegetables. Here, we use a chemical proteomic strategy to identify ALDH2 a
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Falcarinol and stipudiol are natural products with potent anti-cancer activity found in several vegetables. Here, we use a chemical proteomic strategy to identify ALDH2 as a molecular target of falcarinol in cancer cells and confirm enzyme inhibition via covalent alkylation of the active site. Furthermore, the synthesis of stipudiol led to the observation that ALDH2 exhibits preference for alkynol-based binders. Inhibition of ALDH2 impairs detoxification of reactive aldehydes and limits oxidative stress response, two crucial pathways for cellular viability. Graphic Abstract Chemical proteomic studies reveal ALDH2 as a molecular target of falcarinol in cancer cells.
- Synthesis and Characterization of Semi-crystalline NiCoP Film
- Hemeda, O. M., Tawfik, A., El-Sayed, A. H., Hamad, M. A. | Journal of superconductivity and novel magnetism (v.28 / no.12 / pp.3629-3632 / 20151557-1939)
- Abstract This review treats mainly the initial transformation of the starting unoriented lamellar material into the final oriented microfibrillar structure and its drawi
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- Enhancing Thermomechanical Properties and Heat Distortion Resistance of Poly(l-lactide) with High Crystallinity under High Cooling Rate
- Yin, Hai-Yan, Wei, Xin-Feng, Bao, Rui-Ying, Dong, Quan-Xiao, Liu, Zheng-Ying, Yang, Wei, Xie, Bang-Hu, Yang, Ming-Bo | ACS sustainable chemistry et engineering (v.3 / no.4 / pp.654-661 / 2015)
- In this work, a novel, effective and simple approach to largely improve the thermomechanical properties and heat distortion resistance of biodegradable poly( l -lactide
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In this work, a novel, effective and simple approach to largely improve the thermomechanical properties and heat distortion resistance of biodegradable poly( l -lactide) (PLLA) by using a new nucleating agent (NA), i.e., itself high-melting-point homocrystallites ( h PLLA crystallites) is reported. Specially, h PLLA crystallites with a melting temperature ( T m ) of 187 °C were introduced into the PLLA matrix with a lower T m , i.e., 168 °C via simply melt blending at 170 °C which is between the T m s of the two PLLAs. Nonisothermal and isothermal crystallization results reveal that h PLLA crystallite is an efficient nucleating agent for PLLA. Also, h PLLA crystallites show much more prominently promoting effect on the crystallization rate of PLLA in comparison with two widely reported NAs for PLLA, talc and stereocomplex crystallites. Most importantly, this promoting effect is still efficient at very high cooling rate, leading to a crystallinity of 39.1% at a cooling rate of 100 °C/min, which can help to obtain high-crystallinity PLLA products in conventional manufacturing processes. The optical microscopic observation reveals that the remarkable crystallization promotion can be attributed to the outstanding heterogeneous nucleation effect, as a result of both identical chemical constitution and lattice constitution between h PLLA crystallites and PLLA matrix. Further characterizations indicate that the enhancement of PLLA crystallinity by using such a new efficient NA can enhance the thermomechanical properties and heat distortion resistance of PLLA remarkably. For instance, at 80 °C (above T g of PLLA), the elastic modulus increases by 60 times from 8 to 477 MPa with the incorporation of 5 wt % h PLLA. High-melting-point crystallites of poly( l -lactide) show outstanding nucleation enhancement on low-melting-point poly( l -lactide), achieving high crystallinity under a high cooling rate. Graphic Abstract ACS Electronic Supporting Info
- Membrane interaction of a new synthetic antimicrobial lipopeptide sp-85 with broad spectrum activity
- Grau-Campistany, A., Pujol, M., Marques, A.M., Manresa, A., Rabanal, F., Cajal, Y. | Colloids and surfaces. A, Physicochemical and engineering aspects (v.480 / pp.307-317 / 20150927-7757)
- Antimicrobial peptides offer a new class of therapeutic agents to which bacteria may not be able to develop genetic resistance, since their main activity is in the lipid
초록보기원문보기 >
Antimicrobial peptides offer a new class of therapeutic agents to which bacteria may not be able to develop genetic resistance, since their main activity is in the lipid component of the bacterial cell membrane. We have developed a series of synthetic cationic cyclic lipopeptides based on natural polymyxin, and in this work we explore the interaction of sp-85, an analog that contains a C12 fatty acid at the N-terminus and two residues of arginine. This analog has been selected from its broad spectrum antibacterial activity in the micromolar range, and it has a disruptive action on the cytoplasmic membrane of bacteria, as demonstrated by TEM. In order to obtain information on the interaction of this analog with membrane lipids, we have obtained thermodynamic parameters from mixed monolayers prepared with POPG and POPE/POPG (molar ratio 6:4), as models of Gram positive and Gram negative bacteria, respectively. Langmuir-Blodgett films have been extracted on glass plates and observed by confocal microscopy, and images are consistent with a strong destabilizing effect on the membrane organization induced by sp-85. The effect of sp-85 on the membrane is confirmed with unilamelar lipid vesicles of the same composition, where biophysical experiments based on fluorescence are indicative of membrane fusion and permeabilization starting at very low concentrations of peptide and only if anionic lipids are present. Overall, results described here provide strong evidence that the mode of action of sp-85 is the alteration of the bacterial membrane permeability barrier.
- Anti-tumor activities of lipids and lipid analogues and their development as potential anticancer drugs
- Murray, M., Hraiki, A., Bebawy, M., Pazderka, C., Rawling, T. | Pharmacology therapeutics (v.150 / pp.109-128 / 20150163-7258)
- Lipids have the potential for development as anticancer agents. Endogenous membrane lipids, such as ceramides and certain saturated fatty acids, have been found to modula
초록보기원문보기 >
Lipids have the potential for development as anticancer agents. Endogenous membrane lipids, such as ceramides and certain saturated fatty acids, have been found to modulate the viability of tumor cells. In addition, many tumors over-express cyclooxygenase, lipoxygenase or cytochrome P450 enzymes that mediate the biotransformation of omega;-6 polyunsaturated fatty acids (PUFAs) to potent eicosanoid regulators of tumor cell proliferation and cell death. In contrast, several analogous products from the biotransformation of omega;-3 PUFAs impair particular tumorigenic pathways. For example, the omega;-3 17,18-epoxide of eicosapentaenoic acid activates anti-proliferative and proapoptotic signaling cascades in tumor cells and the lipoxygenase-derived resolvins are effective inhibitors of inflammatory pathways that may drive tumor expansion. However, the development of potential anti-cancer drugs based on these molecules is complex, with in vivo stability a major issue. Nevertheless, recent successes with the antitumor alkyl phospholipids, which are synthetic analogues of naturally-occurring membrane phospholipid esters, have provided the impetus for development of further molecules. The alkyl phospholipids have been tested against a range of cancers and show considerable activity against skin cancers and certain leukemias. Very recently, it has been shown that combination strategies, in which alkyl phospholipids are used in conjunction with established anticancer agents, are promising new therapeutic approaches. In future, the evaluation of new lipid-based molecules in single-agent and combination treatments may also be assessed. This could provide a range of important treatment options in the management of advanced and metastatic cancer.
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