The Role of Ion Exchange in the Movement of Chemicals Through Periderm and Cuticular Membranes

This thesis is principally an investigation on the factors contributing to the role of ion exchange in the movement of chemicals through the potato periderm and pear fruit cuticular membranes. This was investigated by monitoring the penetration of alkali cations, neutral amino acids and some pesticides through the potato periderm and pear fruit cuticular membranes in terms of physicochemical parameters such as permeability, diffusion, selectivity and adsorption by using the infinite-dose system, finite-dose and sorption process. Isolated cuticles or periderms, which represent the prime barrier to penetration, provide a physical system by which transport studies can be conducted under well defined and highly controlled conditions. Most studies with isolated cuticles have focused on sorption, desorption and infinite-dose cuticular transport of chemical compounds in aqueous systems. Transport systems, using isolated cuticles or periderms, may be used to quantify the effects of permeability, sorption, environmental pollutants, foliar absorption and spray additives on pesticide penetration. The work can be subdivided as follows: A brief discussion was made on the background chemistry, structure and ion exchange properties of potato periderm and pear fruit cuticles with regard to the use of chemicals on isolated membrane samples. The mechanisms of penetration of chemicals, the nature and chemistry of the potato periderm and pear fruit cuticles and some of the interacting factors contributing to variability were considered. The focus was on the use of potato periderm and pear fruit cuticles as model systems. The ion exchange properties and counter ion selectivity of the potato periderm and pear fruit cuticles towards alkali cations were studied. The important role of ion exchange, pretreatment and counter ion selectivity were demonstrated by results on the capacity and selectivity of alkali ions, which generally followed the order; Li+> Na+> K+> Cs+. The ion exchange capacity and selectivity of the potato periderm and pear fruit cuticles depended on the different ionic forms, increasing with increasing pH and counter ion valence and decreasing with decreasing crystal radius. The titration curves obtained with NaOH in the presence of NaC1 depend markedly on pretreatment. Three separate groups can be distinguished over the pH ranges studied. Within these ranges, the first was between pH 3-5.5, the second between pH 5.5-9 and, the endpoint of the third group was estimated between pH 9-11.5. The isolated potato periderm and pear fruit cuticles exhibited a behaviour typical of highly cross-linked, high capacity ion exchange resins of the weak acid cation exchanger type. The adsorption equations obtained from plotting the experimental data gave a fair agreement with the Freundlich equation. Permeability and diffusion coefficients can be calculated from cuticular transport studies. These transport parameters provide a better understanding of the mechanisms of cuticular penetration phenomena. Further, they are useful when comparing both penetration characteristics of selected compounds and permeability studies. The details of penetration rates and the mechanisms of alkali cation uptake through the isolated potato periderm and pear fruit cuticles were determined. and the permeability and diffusion coefficients and, also from these parameters, relative values of permeability and diffusion coefficients were calculated. (Abstract shortened by ProQuest.)

Microphase Seperation Depending on Different Parameters for Nanopatterned Devices

We report a comparative study on microphase separation of a serial of block copolymers (BCPs) de-pending on some parameters such as solvent, annealing time. Toluene-Chlorobenzene mixtures show the best phase separation in comparison with other pristine or mixture of solvents. The results were optimized for large area studies. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3520

Fascin expression in colorectal carcinomas

PURPOSE: The purpose of this study was to investigate the significance of fascin expression in colorectal carcinoma. METHODS: This is a retrospective study of 167 consecutive, well-documented cases of primary colorectal adenocarcinoma for which archival material of surgical specimens from primary tumor resections were available. We chose a representative tissue sample block and examined fascin expression by immunohistochemistry using a primary antibody against "fascin". We calculated the "immunohistochemical score (IHS)" of fascin for each case, which was calculated from the multiplication of scores for the percentage of stained cells and the staining intensity. RESULTS: Fascin immunoreactivity was observed in 59 (35.3%) of all cases with strong reactivity in 24 (14.4%), moderate reactivity in 25 (14.9%) and weak reactivity in 10 (6.0%) cases. Strong/moderate immunoreactivities were mostly observed in invasive fronts of the tumors or in both invasive and other areas. Fascin immunoreactivity scores were significantly higher in tumors with lymph node metastasis (p:0.002) and advanced stage presentation (p:0.007). There was no relation between fascin expression and age, gender, depth of invasion, distant metastasis or histological grade (p>0.05). There was a higher and statistically significant correlation between fascin immunoreactivity in the invasive borders of tumors and lymph node metastasis (r:0.747, p:0.005). In stage III/IV tumors, two-year survival was 92.2% in tumors without fascin immunoreactivity, and only 60.0% in tumors with a fascin IHS>10 (p:0.003). CONCLUSION: These findings suggest that fascin is heterogeneously expressed in approximately one third of colorectal carcinomas with a significant association with lymph node metastasis, tumor stage and location. Moreover, these results indicate that fascin may have a role in the lymph node metastasis of colorectal carcinoma

Graphene-based hybrid for enantioselective sensing applications

Chirality is a major field of research of chemical biology and is essential in pharmacology. Accordingly, approaches for distinguishing between different chiral forms of a compound are of great interest. We report on an efficient and generic enantioselective sensor that is achieved by coupling reduced graphene oxide with γ-cyclodextrin (rGO/γ-CD). The enantioselective sensing capability of the resulting structure was operated in both electrical and optical mode for of tryptophan enantiomers (D-/L-Trp). In this sense, voltammetric and photoluminescence measurements were conducted and the experimental results were compared to molecular docking method. We gain insight into the occurring recognition mechanism with selectivity toward D- and L-Trp as shown in voltammetric, photoluminescence and molecular docking responses. As an enantioselective solid phase on an electrochemical transducer, thanks to the different dimensional interaction of enantiomers with hybrid material, a discrepancy occurs in the Gibbs free energy leading to a difference in oxidation peak potential as observed in electrochemical measurements. The optical sensing principle is based on the energy transfer phenomenon that occurs between photoexcited D-/L-Trp enantiomers and rGO/γ-CD giving rise to an enantioselective photoluminescence quenching due to the tendency of chiral enantiomers to form complexes with γ-CD in different molecular orientations as demonstrated by molecular docking studies. The approach, which is the first demonstration of applicability of molecular docking to show both enantioselective electrochemical and photoluminescence quenching capabilities of a graphene-related hybrid material, is truly new and may have broad interest in combination of experimental and computational methods for enantiosensing of chiral molecules

Oxygen and proton reduction by decamethylferrocene in non-aqueous acidic media

Experimental studies and density functional theory (DFT) computations suggest that oxygen and proton reduction by decamethylferrocene (DMFc) in 1,2-dichloroethane involves protonated DMFc, DMFcH+, as an active intermediate species, producing hydrogen peroxide and hydrogen in aerobic and anaerobic conditions, respectively

Hydrogen Evolution at Liquid–Liquid Interfaces

Blowing bubbles: Hydrogen evolution by proton reduction with [(C5Me5)2Fe] occurs at a soft interface between water and 1,2-dichloroethane (DCE). The reaction proceeds by proton transfer assisted by [(C5Me5)2Fe] across the water–DCE interface with subsequent proton reduction in DCE. The interface essentially acts as a proton pump, allowing hydrogen evolution by directly using the aqueous proton

Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

Molecular oxygen (O2) reduction by decamethylferrocene (DMFc) was investigated at a polarized water/ 1,2-dichloroethane (DCE) interface. Electrochemical results point to a mechanism similar to the EC type reaction at the conventional electrode/solution interface, in which an assisted proton transfer (APT) by DMFc across the water/DCE interface via the formation of DMFcH+ corresponds to the electrochemical step and O2 reduction to hydrogen peroxide (H2O2) represents the chemical step. The proton transfer step can also be driven using lipophilic bases such as 4-dodecylaniline. Finally, voltammetric data shows that lipophilic DMFc can also be extracted to the aqueous acidic phase to react homogeneously with oxygen

Oxygen reduction catalyzed by a fluorinated tetraphenylporphyrin free base at liquid/liquid interfaces

The diprotonated form of a fluorinated free base porphyrin, namely 5-(p-aminophenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (H(2)FAP), can catalyze the reduction of oxygen by a weak electron donor, namely ferrocene (Fc). At a water/1,2-dichloroethane interface, the interfacial formation of H(4)FAP(2+) is observed by UV-vis spectroscopy and ion-transfer voltammetry, due to the double protonation of H(2)FAP at the imino nitrogen atoms in the tetrapyrrole ring. H(4)FAP(2+) is shown to bind oxygen, and the complex in the organic phase can easily be reduced by Fc to produce hydrogen peroxide as studied by two-phase reactions with the Galvani potential difference between the two phases being controlled by the partition of a common ion. Spectrophotometric measurements performed in 1,2-dichloroethane solutions clearly evidence that reduction of oxygen by Fc catalyzed by H(4)FAP(2+) only occurs in the presence of the tetrakis(pentafluorophenyl)borate (TB-) counteranion in the organic phase. Finally, ab initio computations support the catalytic activation of H(4)FAP(2+) on oxygen

Preparation and gas sensing properties of Langmuir-Blodgett thin films of calix[n]arenes: Investigation of cavity effect

WOS: 000332417600022Characterization and organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of calix[n]arene (n=4, 6, 8) derivatives are reported in this work. Surface pressure-area isotherm graph shows that very stable monolayers are formed at the water surface. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Calix[n]arene LB films have been characterized by contact angle measurements, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). LB film of calix[8]arene which has the largest cavity yields a gradient with a mass value of 773 ng per layer according to the QCM results. AFM and SEM images showed a dense surface morphology obtained for all samples. QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. These LB film samples yield a response to all vapors with a large, fast, and reproducible due to the adsorption of vapors into the LB film structures. Among them, calix[8]arene LB film has higher sensitivity toward the organic vapors because of a large cavity size. This study can be concluded that the cavity size of calix[n]arene molecule could have an important role in the research area of room temperature vapor sensing devices. (C) 2014 Elsevier B.V. All rights reserved.Research Foundation of Selcuk University (BAP)Financial support for this work is provided by the Research Foundation of Selcuk University (BAP) and is gratefully acknowledged

Fabrication of novel anisotropic magnetic microparticles

We report a novel technique for fabrication of magnetically anisotropic microparticles based on “arresting” of the alignment of oleic acid coated magnetite nanoparticles (OCMNs) dispersed within the oil drops of a polymerisable oil-in-water emulsion. This was achieved by polymerising the oil drops after gelling the continuous aqueous phase in the presence of an external magnetic field. This approach allowed us to produce magnetic Janus particles with anisotropic optical and magnetic properties which form unusual zig-zag chains and structures when exposed to an external magnetic field. We studied the magnetic properties of these novel microparticles and showed that they retained remanence magnetisation with high coercivity values indicative of ferromagnetic behaviour. This indicates that the composite polymeric Janus microparticles posses a net magnetic dipole and behave like micromagnets due to the “arrested” orientation of the OCMNs in their polymeric matrix. Utilizing the same technique, magnetic Janus microparticles have been prepared based on emulsions stabilised only by OCMNs without the use of surfactants, and the effect of pH of continuous aqueous phase on the morphology of these microparticles has been investigated