Potassium (K+) is an essential nutrient and the most abundant cation in plant cells. Plants possess two transport systems for K+ acquisition: a high-affinity system (HATS), operating at external K+ concentrations ([K+]ext) below 1 mM, and showing reduced transport activity in the presence of ammonium (NH4+); and, a low-affinity system (LATS), operating at [K+]ext above 1 mM, that is not affected by NH4+. K+ transport and compartmentation were investigated in barley (Hordeum vulgare L.) and rice (Oryza sativa L.) using the non-invasive technique of compartmental analysis by tracer efflux (CATE), to simultaneously determine unidirectional membrane fluxes, ion concentrations, and exchange characteristics in subcellular compartments. These studies revealed striking differences in unidirectional K+ fluxes between HATS and LATS. It was found that flux measurements, using traditional direct influx (DI) protocols, accurately represented HATS influx, but underestimated LATS influx by as much as seven-fold. In both barley and rice, LATS K+ fluxes were found to undergo rapid, futile cycling, with the ratio of efflux:influx 3 to 5 times greater, and the cytosolic exchange rate 2 to 3 times faster than under HATS. Based upon plasma-membrane electrical potential measurements, efflux was found to be active under LATS conditions. LATS-mediated conditions for K+ were found to provide relief from NH4+ toxicity in barley by immediately reducing NH4+ influx by more than 50%, and significantly reducing NH4+ futile cycling. Employing the K+ channel inhibitors cesium, lanthanum, and tetraethylammonium, NH4+ was shown to have both K+-sensitive and –insensitive influx pathways at high [NH4+]ext. Based on current models of flux energetics, the combined uptake of K+ and NH4+ was found to utilize 60% of root oxygen consumption. Barley and rice both showed signs of NH4+ toxicity at low [K+]ext, but rice recovered at much lower [K+]ext, suggesting a crucial role of K+ in the NH4+-tolerance of rice. These experiments address fundamental aspects of K+ fluxes, and help provide a physiological framework for future studies of K+ transport and mineral nutrition.

Potassium (K+) is an essential nutrient and the most abundant cation in plant cells. Plants possess two transport systems for K+ acquisition: a high-affinity system (HATS), operating at external K+ concentrations ([K+]ext) below 1 mM, and showing reduced transport activity in the presence of ammonium (NH4+); and, a low-affinity system (LATS), operating at [K+]ext above 1 mM, that is not affected by NH4+. K+ transport and compartmentation were investigated in barley (Hordeum vulgare L.) and rice (Oryza sativa L.) using the non-invasive technique of compartmental analysis by tracer efflux (CATE), to simultaneously determine unidirectional membrane fluxes, ion concentrations, and exchange characteristics in subcellular compartments. These studies revealed striking differences in unidirectional K+ fluxes between HATS and LATS. It was found that flux measurements, using traditional direct influx (DI) protocols, accurately represented HATS influx, but underestimated LATS influx by as much as seven-fold. In both barley and rice, LATS K+ fluxes were found to undergo rapid, futile cycling, with the ratio of efflux:influx 3 to 5 times greater, and the cytosolic exchange rate 2 to 3 times faster than under HATS. Based upon plasma-membrane electrical potential measurements, efflux was found to be active under LATS conditions. LATS-mediated conditions for K+ were found to provide relief from NH4+ toxicity in barley by immediately reducing NH4+ influx by more than 50%, and significantly reducing NH4+ futile cycling. Employing the K+ channel inhibitors cesium, lanthanum, and tetraethylammonium, NH4+ was shown to have both K+-sensitive and –insensitive influx pathways at high [NH4+]ext. Based on current models of flux energetics, the combined uptake of K+ and NH4+ was found to utilize 60% of root oxygen consumption. Barley and rice both showed signs of NH4+ toxicity at low [K+]ext, but rice recovered at much lower [K+]ext, suggesting a crucial role of K+ in the NH4+-tolerance of rice. These experiments address fundamental aspects of K+ fluxes, and help provide a physiological framework for future studies of K+ transport and mineral nutrition.

El objetivo principal de este trabajo es desarrollar un modelo sencillo que permita la caracterización hidrodinámica de membranas selectivas integradas en sistemas bi-iónicos, mediante la determinación de coeficientes de difusión y de espesores de las capas límite alrededor de la membrana. A tal fin, se empleó una célula de difusión rotatoria (CDR), que permite el establecimiento de condiciones hidrodinámicas bien definidas para el sistema de membrana, dado que la variación de la frecuencia de giro del cilindro interior (ω), permite disminuir el espesor de la capa límite sobre la membrana, lo que favorece el intercambio iónico a su través. Se puede comprobar éste comportamiento, mediante consideraciones en torno al coeficiente de difusión de los cationes en el sistema de membrana y del cálculo del propio espesor de la capa límite. El mencionado coeficiente se obtendrá a partir del flujo iónico en la membrana, determinado a partir de medidas de pH, junto a medidas de conductividad, en la fase externa (receptora), a diferentes temperaturas y a distintas valores de ω.La medida de los flujos, una vez establecida su dependencia con ω, permite obtener los coeficientes de difusión catiónicos en el sistema de membrana, en función de la temperatura y de ω. Las medidas de la conductividad permiten testar el modelo propuesto, mediante su correlación con los valores de pH obtenidos, proporcionando información adicional acerca de los coeficientes de difusión de los cationes. / From the experimental study of the ionic transport through selective membranes in biionic systems, a simple model which allows the characterising hydrodynamic of the membrane systems through the determination of diffusion coefficients and the thickness of the limit layer has been developed. With this purpose, a rotating diffusion cell that allows the setting of hydrodynamic conditions clearly for the membrane system has been used, studying the variation of the conductivity and the pH in the external phase (receiving) at different temperatures from 20ºC to 50ºC and at different rotating velocities ω. The measurement of the fluxes, once set its dependence with ω, allows obtained the diffusion coefficients cationics in the membrane system in accordance with the temperature and ω. The measurements of the conductivity allow the testing of this model, through its correlation with the values of the pH measured, obtaining additional data about the diffusion coefficient of the cations in the receiving phase.

No description available.

<p>The successful genomic era has resulted in a great demand for efficient production and purification of proteins. The main objective of the work described in this thesis was to develop methods to facilitate recovery of target proteins after recombinant production in Escherichia coli.</p><p>A positively charged purification tag, Z_basic, has previously been constructed by protein design of a compact three-helix bundle domain, Z. The charged domain was investigated for general use as a fusion partner. All target proteins investigated could be selectively captured by ion-exchange chromatography under conditions excluding adsorption of the majority of Escherichia coli host proteins. A single cation-exchange chromatography step at physiological pH was sufficient to provide Z_basic fusion proteins of high purity close to homogeneity. Moreover, efficient isolation directly from unclarified <i>Escherichia coli</i> homogenates could also be accomplished using an expanded bed mode. Since the intended use of a recombinant protein sometimes requires removal of the purification tag, a strategy for efficient release of the Z_basic moiety using an immobilised protease was developed. The protease columns were reusable without any measurable decrease in activity. Moreover, subsequent removal of the released tag, Z_basic, was effected by adsorption to a second cation-exchanger. </p><p>Using a similar strategy, a purification tag with a negatively charged surface, denoted Z_acid, was constructed and thoroughly characterised. Contrary to Z_basic, the negatively charged Z_acid was highly unstructured in a low conductivity environment. Despite this, all Z_acid fusion proteins investigated could be efficiently purified from whole cell lysates using anion-exchange chromatography</p><p>Synthesis of polypeptides occurs readily in Escherichia coli providing large amounts of protein in cells of this type, albeit often one finds the recombinant proteins sequestered in inclusion bodies. Therefore, a high throughput method for screening of protein expression was developed. Levels of both soluble and precipitated protein could simultaneously be assessed <i>in vivo</i> by the use of a flow cytometer. </p><p>The positively charged domain, Z_basic, was shown also to be selective under denaturing conditions, providing the possibility to purify proteins solubilised from inclusion bodies. Finally, a flexible process for solid-phase refolding was developed, using Z_basic as a reversible linker to the cation-exchanger resin.</p>

Petrochemical and fine chemical industries face a daunting problem in recovering acetic acid from its aqueous solutions. The recovery of acetic acid could be done through esterification reaction. However, esterification is an equilibrium limited reaction. Multi-functional reactors such as chromatographic reactor (CR) and reactive distillation column (RDC) are promising technologies mainly for equilibrium limited reactions wherein reaction and separation of products are carried out in a single equipment that tends to shift the equilibrium towards the desired direction which is not possible in a classical batch reactor. Physical and chemical characterisation of ion exchange resin catalysts such as scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface area measurement, pore size distribution, elemental analysis, true density and particle size distribution were carried out to access the catalysts performance for n-hexyl acetate synthesis. Esterification of acetic acid with n-hexanol was studied with both dilute and concentrated acid in the presence of cation exchange resins (macroporous and gelular) in a jacketed stirred batch reactor to synthesise a value added ester, namely n-hexyl acetate and also to study the recovery of acetic acid from the waste aqueous streams. The effect of various parameters such as speed of agitation, catalyst particle size, feed mole ratio of n-hexanol to acetic acid, reaction temperature, catalyst loading and reusability of catalysts was studied for the optimisation of the reaction condition in a batch reactor. The non-ideality of each component in the reacting mixture was accounted for by using the activity coefficient via the use of the UNIFAC group contribution method. The kinetic data were correlated with both pseudo-homogeneous (PH) and adsorption based heterogeneous reaction rate models, e.g., Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW), and the modified LHHW (ML). Pseudo-homogeneous (PH) model gave the best representation of the kinetic data found experimentally. The feasibility of reactive distillation for the recovery of acetic acid using n-hexanol was evaluated through residue curve map (RCM) determination experiments. RCM provides information to a design engineer of the existence of separation boundaries imposed by the singular points corresponding to the reactive/non-reactive azeotropes, thus provides an insight into the feasibility of reactive distillation for this purpose. A laboratory scale batch chromatographic reactor was designed and constructed. Batch chromatographic reactor experiments were carried out using different parameters such as feed flow rate, feed mole ratio of n-hexanol to acetic acid, desorbent (n-hexanol) flow rate and reaction step to maximise the formation of n-hexyl acetate as well to achieve complete conversion of acetic acid. Continuous chromatographic reactor was designed, constructed and commissioned on the basis of the results obtained from the batch chromatographic reactor experiments. The experiments carried out in continuous chromatographic reactor correlated very well with the results from the batch chromatographic reactor for the optimised condition.

The degradation of wool keratin under conditions relevant to those of wool dyeing was investigated using the techniques of gel permeation chromatography (GPC), ion exchange gel chromatography, and amino acid analysis. Physical testing of the treated and untreated wool was also carried out to determine the physical changes occurring, parameters used being percentage elongation at the break, and the breaking strain of the fibre. Samples of wool keratin were immersed in various aqueous solutions at 1000C for 24 hours and the filtered, aqueous, oxidised extracts were analysed* The solutions used varied only in the dye, or dye intermediate present in the treatment solution. All treatment baths contained 10% owf 1.02 x 10 -2 MSulphuric VI acid; 10%owf 7.04x 10 -3 MSodium sulphate VI ; A 100 :1 liquor ratio was used in each case. Some of the dye intermediates showed a marked catalytic effect, particularly in their effect on breaking strain, a decrease of 40% in some cases. The GPC profiles of the extracted proteins were examined in detail and compared against previous workers' results. An explanation of the behaviour of the dyes and intermediates was proposed. The amino acid composition data of the extracted and fractionated proteins were compared against various morphological components extracted by other workers, as was the total gelatin obtained from each treatment.

Zeolites have been used in agriculture since the 1960s, due to the effectiveness of these crystalline microporous solids as soil amendments for plant growth, their cation exchange capacity (CEC) and slow-release fertilizer properties. Most work on slow-release fertilizers has focused on natural Clinoptilolite, Phillipsite and Chabazite. The aim of this study was to synthesize zeolites, study their effectiveness as soil amendments and their ability to act as controlled release fertilizers to decrease nitrate leaching. Nitrate pollution of groundwater is a major agro-environmental concern. The zeolites Phillipsite and Linde-type F were synthesized from aluminosilicate gels; ion exchanged to introduce ammonium and characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Thermo-gravimetric analysis (TGA) and Scanning electron microscopy (SEM) techniques, both before and after ion exchange. Ammoniumexchanged Phillipsites (natural and synthetic), ammonium-exchanged synthetic Linde-type F (the zeolite having highest affinity towards ammonium) and ammonium exchanged Phillipsites (high crystalline and high aluminium) were compared with conventional NPK fertilizer.Three glasshouse experiments were performed to study the effects of zeolite-amended soils on maize growth. Ion exchanged synthetic and natural Phillipsites were first used as soil amendments (w/w 2, 4, 8% zeolite to soil). Synthetic Phillipsite, at 2% loading, resulted in the most significant improvement in both plant growth and phased ammonium release. The synthetic ammonium-exchanged zeolites Phillipsite and Linde-type F (at w/w 1, 2, 4%) were then compared; synthetic Phillipsite, at 2% loading, again resulted in the most significant plant growth response with an increase (≥15%) in shoot dry weight and a decrease (≥30%) in nitrate leaching. Experiments using unexchanged synthetic Phillipsite (at w/w 2%), but with added NPK fertilizer, showed increased plant growth and decreased nitrate leaching, compared with parallel experiments containing unexchanged synthetic Linde-type F (at w/w 2%) and a conventional fertilizer amended soil. This revealed the beneficial effect of Phillipsite for soil amendment, even without ion exchange to the ammonium form. To study the physico-chemical properties affecting the release of ammonium from the Phillipsite framework; high crystalline/low aluminium and low crystalline/high aluminium forms were synthesized and ion exchanged. Both forms were introduced as soil amendments (at w/w 1 and 2%) and experiments showed that the lower zeolite crystallinity decreased cation exchange and therefore decreased nitrate leaching. Experimental results from the glasshouse experiments and cation exchange capacity (CEC) experiments suggest that synthetic Phillipsite, at lower loadings (1 and 2% w/w zeolite to soil) have most potential as soil amendments for both plant growth and controlled-release applications. This conclusion is supported by soil leachate and shoots dry weight analysis. Furthermore, Phillipsite, synthesized in a low crystalline and low ammonium form, may be an even better soil amendment for controlled release of ammonium, which will thereby further decrease nitrate pollution.

Recent developments in converting biomass to bio-chemicals and liquid fuels provide a promising sight to an emerging biofuels industry. Biomass can be converted to energy via thermochemical and biochemical pathways. Thermal degradation processes include liquefaction, gasification, and pyrolysis. Among these biomass technologies, pyrolysis (i.e. a thermochemical conversion process of any organic material in the absence of oxygen) has gained more attention because of its simplicity in design, construction and operation. This research study focuses on comparative assessment of two types of pyrolysis processes and catalytic upgrading of bio-oil for production of transportation fuel intermediates. Slow and fast pyrolysis processes were compared for their respective product yields and properties. Slow pyrolysis bio-oil displayed fossil fuel-like properties, although low yields limit the process making it uneconomically feasible. Fast pyrolysis, on the other hand, show high yields but produces relatively less quality bio-oil. Catalytic transformation of the high-boiling fraction (HBF) of the crude bio-oil from fast pyrolysis was therefore evaluated by performing liquid-phase reactions at moderate temperatures using Pt/HZSM-5 catalyst. High yields of upgraded bio-oils along with improved heating values and reduced oxygen contents were obtained at a reaction temperature of 200°C and ethanol/HBF ratio of 3:1. Better quality, however, was observed at 240 °C even though reaction temperature has no significant effect on coke deposition. The addition of ethanol in the feed has greatly attenuated coke deposition in the catalyst. Major reactions observed are esterification, catalytic cracking, and reforming. Overall mass and energy balances in the conversion of energy sorghum biomass to produce a liquid fuel intermediate obtained sixteen percent (16 wt.%) of the biomass ending up as liquid fuel intermediate, while containing 26% of its initial energy.

Mechanisms of adsorption of alkaline copper quat (ACQ) components in wood were investigated with emphasis on: copper chemisorption, copper physisorption, and quat adsorption. Various factors were investigated that could affect the adsorption of individual ACQ components in red pine wood. Copper chemisorption in wood was affected by ligand types coordinating with Cu and the stability of the Cu-ligand complexes in solution. For Cu-monoethanolamine (Cu-Mea) system, the prevailing active solvent species at the solution pH, [Cu(Mea)2-H]+ complexes with wood acid sites and loses one Mea molecule through a ligand exchange reaction. The amount of adsorbed Cu was closely related to the cation exchange capacity of wood. An increase in Mea/Cu ratio increased the proportion of the uncharged Cu-Mea complex and resulted in decreased Cu chemisorption in wood. Copper precipitation is also an important Cu fixation mechanisms of Cu-amine treated wood. X-ray diffraction analysis revealed that in vitro precipitated Cu was a mixture of copper carbonates (azurite and malachite) and possibly Cu2O. Higher concentration Cu-amine solutions retarded the Cu precipitation to a lower pH because of higher free amine in the preservative-wood system. The changes in zeta potential of wood in relationship to the quaternary ammonium (alkyldimethylbenzylammonium chloride: ADBAC) adsorption isotherm showed two different adsorption mechanisms for quat in wood: ion exchange reaction at low concentration and additional aggregation form of adsorption by hydrophobic interaction at high concentration. Because of the aggregation effect, when wood was treated with ACQ, high amounts of ADBAC were concentrated near the surface creating a steep gradient with depth. This aggregated ADBAC was easily leached out while the ion exchanged ADBAC had high leaching resistance. Free Mea and Cu of ACQ components appeared to compete with ADBAC for the same bonding sites in wood.