Harsh Acid Research Articles

Lifetime Estimation for Plastic Optical Fibers in Harsh Acid Environments

The work described in this paper explores the suitability of using plastic optical fibers (POFs) as sensors for the development of fast battery chargers. Lead–acid batteries, widely used in the automotive industry, contain an electrolyte formed by a high concentration of sulfuric acid (35% <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{H}_{2}\hbox{SO}_{4}$</tex></formula> ), an acid environment that can maintain an elevated temperature during the charge and discharge processes. This presents a challenge for the selection of sensors that can withstand such harsh conditions over extended periods of time, in order to monitor the charge cycle and state of health of the battery. POFs can be used as density sensors immersed in the electrolyte at different places within the battery—density varies with location. The accuracy of the density readout must be maintained throughout the useful life of the battery, up to 15 years. In this paper, we present results of over 9000 h of lifetime tests of POFs used as sensing elements for electrolyte density, as well as a procedure to estimate their lifetime for the target application.

Two-Stage Acid-Catalyzed Conversion of Carbohydrates into Levulinic Acid

In this paper, we report on a two-stage acid-catalytic conversion of carbohydrates from hybrid poplar wood chips into levulinic acid (LA), a renewable platform chemical which can be used for fuels and chemicals. It was hypothesized that under the harsh acid conditions utilized during LA production, the pentose fraction in biomass would first form furfurals which would then polymerize with saccharides forming humins. These reactions would both reduce any potential value from the pentose fraction as well as lower the levulinic acid yield. To test this idea, a two-stage conversion process was designed starting with a mild acid extraction to remove the majority of the pentoses while maintaining the hexose sugars in a solid form utilizing previously described optimized conditions. LA was then produced by subjecting the extracted solids to a second more severe step. The temperature, time, acid concentration, and a liquor-to-wood ratio were varied and modeled to find the optimal conditions. The best conditions were high acid concentration, high temperature, and low substrate consistency, which produced a maximum molar yield of 66% based on the hexose content or 17.5 wt % based of the initial biomass. A comparison of this two-stage process to a single-stage process without the pentose extraction was performed both with biomass and model compounds, which indicated no pentose or furfural in the product stream and a marked molar yield decrease in LA yield from the presence of pentose sugars, validating our initial hypothesis.

The use of poly(alkylene oxide)s to achieve fast and controlled photochromic switching in rigid matrices

We report a conjugation system for the enhancement of photochromic dye performance in rigid matrices using widely available, cheap, chemically robust and compatible polymeric starting materials, namely poly(propylene oxide) (PPO) and poly(1,2-butylene oxide). Conjugation of these soft (low Tg) polymers to an indeno-fused naphthopyran photochromic dye, in a telechelic geometry, gives access to a wide range of accelerated and tuned fade speeds (decoloration) via variation in molecular weight. The t1/2 and t3/4 fade speeds for PPO conjugates (polymer molecular weights ranging between ca. 425 and 2000) are accelerated by 35–58 and 51–76%, respectively, compared with the nonconjugated control dye. Longer oligomers provide faster decoloration approaching that obtained in solution. The stability of the polyethers allows functionalization using a wide variety of chemistries, including harsh acid catalyzed transformations, providing an overall facile synthesis of photochromic dye-polymer conjugates in high yield and purity. In addition, these polymers give easy access to conjugates with star-type architectures, which provide an even further improvement in performance compared with their linear counterparts with less conjugated polymer needed per dye to achieve a given fade speed. © 2012 Commonwealth of Australia. J Polym Sci Part A: Polym Chem, 2012

Potential of hydrothermal treatments in lignocellulose biorefineries

AbstractThe aqueous fractionation of native lignocellulosic materials with hot, compressed water (also known as hydrothermal processing or autohydrolysis) has been proposed as a fractionation method for biorefineries, as it enables the simultaneous removal of water‐soluble extractives and the solubilization of hemicelluloses, yielding a solid phase enriched in lignin and cellulose. When the operation is carried out under favorable conditions, the liquid phase from autohydrolysis contains valuable products derived from hemicelluloses, including oligosaccharides that keep the major structural features of the polymer (including substitution by acetyl groups). Post‐hydrolysis of oligosaccharides in media catalyzed by acids or enzymes yields fermentable media containing hemicellulosic sugars; whereas harsh acid hydrolysis conditions result in the production of levulinic acid. Subsequent delignification of autohydrolyzed solids enables the separation of the three major lignocellulose components (hemicelluloses, cellulose, and lignin). As an alternative way for using autohydrolyzed solids, they can be used as substrates for the enzymatic hydrolysis of cellulose, leaving lignin as a solid by‐product. The sustainable manufacture of materials, fuels and chemicals from the biorefinery schemes cited above is discussed. Particular attention is paid to hemicellulose‐derived products. © 2011 Society of Chemical Industry and John Wiley &amp; Sons Ltd

Pre-treatment optimization of Scenedesmus obliquus microalga for bioethanol production

The present work deals with the optimization of cellular disruption and sugar extraction from the microalgae Scenedesmusobliquus (Sc) for bioethanol production.Among the physical and physicochemical methods tested, the best results were obtained with acid hydrolysis by H2SO4 (2N), at 120°C for 30min and using dried biomass. The sugar extraction efficiency level reached was 95.6% when compared to the harsh quantitative acid hydrolysis. The influence of other parameters such as biomass loading and number of extraction cycles were also evaluated. The results obtained in the latter case showed that a unique hydrolysis step is sufficient.

A Comparative Investigation of Hydrolysis Methods to Analyze Natural Organic Dyes by HPLC-PDA - Nine Methods, Twelve Biological Sources, Ten Dye Classes, Dyed Yarns, Pigments and Paints

This paper presents a comparative investigation of recovery procedures for the analysis of natural organic colorants, encompassing ten major natural organic dye chemical classes, several sample types (silk, wool, cotton, pigment, paint), prepared from the extracts of twelve biological sources, and nine different recovery protocols. These protocols are based on the traditional harsh hydrochloric acid method; on mild hydrolysis methods involving formic, oxalic or hydrofluoric acid; and on methods consecutively employing mild and harsh hydrolysis on the same sample. An evaluation system was developed by classifying analytical results in an upper, middle or lower grade with reference to the best result obtained. This classification was used to calculate scores for each hydrolysis method and for either textile (silk and wool or cotton) or pigment/paint. The best overall hydrolysis method for textile samples was a combination of mild oxalic acid with traditional hydrochloric acid hydrolysis. The best overall hydrolysis method for pigment/paint was a combination of a newly modified mild hydrofluoric acid treatment with traditional hydrochloric acid hydrolysis. The application of these methods to historical samples will not necessarily give the optimal result achievable for every biological source, but will definitely reduce the risk of missing essential information for the elucidation of ancient technology in a geographical and historical context. The reduced level of risk will avoid repetitive sampling and reduce the level of invasiveness, hence taking into account good conservation policies. The potential of these selected methods is illustrated with the analysis of some historical Chinese textile and paint samples.

Sensing and Adaptation to Low pH Mediated by Inducible Amino Acid Decarboxylases in Salmonella

During the course of infection, Salmonella enterica serovar Typhimurium must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments. Three low pH inducible amino acid decarboxylases were annotated in the genome of S. Typhimurium, AdiA, CadA and SpeF, which are specific for arginine, lysine and ornithine, respectively. In this study, we characterized and compared the contributions of those enzymes in response to acidic challenges. Individual mutants as well as a strain deleted for the three genes were tested for their ability (i) to survive an extreme acid shock, (ii) to grow at mild acidic pH and (iii) to infect the mouse animal model. We showed that the lysine decarboxylase CadA had the broadest range of activity since it both had the capacity to promote survival at pH 2.3 and growth at pH 4.5. The arginine decarboxylase AdiA was the most performant in protecting S. Typhimurium from a shock at pH 2.3 and the ornithine decarboxylase SpeF conferred the best growth advantage under anaerobiosis conditions at pH 4.5. We developed a GFP-based gene reporter to monitor the pH of the environment as perceived by S. Typhimurium. Results showed that activities of the lysine and ornithine decarboxylases at mild acidic pH did modify the local surrounding of S. Typhimurium both in culture medium and in macrophages. Finally, we tested the contribution of decarboxylases to virulence and found that these enzymes were dispensable for S. Typhimurium virulence during systemic infection. In the light of this result, we examined the genomes of Salmonella spp. normally responsible of systemic infection and observed that the genes encoding these enzymes were not well conserved, supporting the idea that these enzymes may be not required during systemic infection.

Survivability of probiotics encapsulated in alginate gel microbeads using a novel impinging aerosols method

Encapsulation of probiotic bacteria in cross-linked alginate beads is of major interest for improving the survivability in harsh acid and bile environment and also in food matrices. Alginate micro beads (10–40 μm) containing the probiotics Lactobacillus rhamnosus GG and Lactobacillus acidophilus NCFM were produced by a novel technique based on dual aerosols of alginate solution and CaCl 2 cross linking solution. Extruded macro beads (approximately 2 mm diameter) produced by the conventional method and micro beads produced by novel aerosols technique offered comparable protection to L. rhamnosus in high acid and bile environment. Chitosan coating of micro beads resulted in a significant increase in survival time of L. rhamnosus from 40 to 120 min in acid condition and the reduction in cell numbers was confined to 0.94 log over this time. Alginate macro beads are more effective than micro beads in protecting L. acidophilus against high acid and bile. Chitosan coating of micro beads resulted in similar protection to L. acidophilus in macro beads in acid and extended the survival time from 90 to at least 120 min. Viability of this organism in micro beads was 3.5 log after 120 min. The continuous processing capability and scale-up potential of the dual aerosol technique offers potential for an efficient encapsulation of probiotics in very small alginate micro beads below sensorial detection limits while still being able to confer effective protection in acid and bile environment.

Visualization of Mitochondrial DNA Replication in Individual Cells by EdU Signal Amplification

Mitochondria are key regulators of cellular energy and mitochondrial biogenesis is an essential component of regulating mitochondria numbers in healthy cells1-3. One approach for monitoring mitochondrial biogenesis is to measure the rate of mitochondrial DNA (mtDNA) replication4. We developed a sensitive technique to label newly synthesized mtDNA in individual cells in order to study mtDNA biogenesis. The technique combines the incorporation of 5-ethynyl-2'-deoxyuridine (EdU)5-7 with a tyramide signal amplification (TSA)8 protocol to visualize mtDNA replication within subcellular compartments of neurons. EdU is superior to other thymidine analogs, such as 5-bromo-2-deoxyuridine (BrdU), because the initial click reaction to label EdU5-7 does not require the harsh acid treatments or enzyme digests that are required for exposing the BrdU epitope. The milder labeling of EdU allows for direct comparison of its incorporation with other cellular markers9-10. The ability to visualize and quantify mtDNA biogenesis provides an essential tool for investigating the mechanisms used to regulate mitochondrial biogenesis and would provide insight into the pathogenesis associated with drug toxicity, aging, cancer and neurodegenerative diseases. Our technique is applicable to sensory neurons as well as other cell types. The use of this technique to measure mtDNA biogenesis has significant implications in furthering the understanding of both normal cellular physiology as well as impaired disease states.

Visualization of Mitochondrial DNA Replication in Individual Cells by EdU Signal Amplification

Mitochondria are key regulators of cellular energy and mitochondrial biogenesis is an essential component of regulating mitochondria numbers in healthy cells1-3. One approach for monitoring mitochondrial biogenesis is to measure the rate of mitochondrial DNA (mtDNA) replication4. We developed a sensitive technique to label newly synthesized mtDNA in individual cells in order to study mtDNA biogenesis. The technique combines the incorporation of 5-ethynyl-2'-deoxyuridine (EdU)5-7 with a tyramide signal amplification (TSA)8 protocol to visualize mtDNA replication within subcellular compartments of neurons. EdU is superior to other thymidine analogs, such as 5-bromo-2-deoxyuridine (BrdU), because the initial click reaction to label EdU5-7 does not require the harsh acid treatments or enzyme digests that are required for exposing the BrdU epitope. The milder labeling of EdU allows for direct comparison of its incorporation with other cellular markers9-10. The ability to visualize and quantify mtDNA biogenesis provides an essential tool for investigating the mechanisms used to regulate mitochondrial biogenesis and would provide insight into the pathogenesis associated with drug toxicity, aging, cancer and neurodegenerative diseases. Our technique is applicable to sensory neurons as well as other cell types. The use of this technique to measure mtDNA biogenesis has significant implications in furthering the understanding of both normal cellular physiology as well as impaired disease states.

Markers for Identification of Faded Safflower (Carthamus tinctorius L.) Colorants by HPLC-PDA-MS - Ancient Fibres, Pigments, Paints and Cosmetics Derived from Antique Recipes

Safflower red was prepared by extracting safflower petals (carthamus tinctorius L.) at alkaline pH, after the preliminary removal of water-soluble safflower yellow. Alkaline extracts were used to prepare dyed silk, wool, cotton and paper, to precipitate the pigment, to prepare paint and to produce the antique Chinese cosmetic rouge. All reference samples were analyzed with high-performance liquid chromatography–photodiode array–mass spectrometric detection (HPLC-PDA-MS) after colorant was removed from its substrate by both a harsh and mild acid hydrolysis method. In addition to the red colorant carthamin, four colorless components are markers for safflower. These components were characterized by their retention times, ultraviolet–visible (UV-Vis) spectra and mass spectra and were given the codes Ct1, Ct2, Ct3 and Ct4. Experiments on references clearly indicated that these Ct components, unlike carthamin, withstood harsh acid hydrolysis as well as light-induced accelerated ageing, and that they could be found even in a completely faded wool sample. This made them excellent markers to identify safflower red, even in discolored historical samples or in samples that must be treated in a way that destroys carthamin. These findings may contribute to a better understanding of the manufacturing technology and to better conservation of objects that have already undergone considerable light-induced ageing.

Thermally Cross-Linked PNVP Films As Antifouling Coatings for Biomedical Applications

Protein repellent coatings are widely applied to biomedical devices in order to reduce the nonspecific adhesion of plasma proteins, which can lead to failure of the device. Poly(N-vinylpyrrolidone) (PNVP) is a neutral, hydrophilic polymer with outstanding antifouling properties often used in these applications. In this paper, we characterize for the first time a cross-linking mechanism that spontaneously occurs in PNVP films upon thermal annealing. The degree of cross-linking of PNVP films and their solubility in water can be tailored by controlling the annealing, with no need for additional chemical treatment or irradiation. The physicochemical properties of the cross-linked films were investigated by X-ray photoelectron spectroscopy, infrared spectroscopy, neutron and X-ray reflectometry, ellipsometry, and atomic force microscopy, and a mechanism for the thermally induced cross-linking based on radical formation was proposed. The treated films are insoluble in water and robust upon immersion in harsh acid environment, and maintain the excellent protein-repellent properties of unmodified PNVP, as demonstrated by testing fibrinogen and immunoglobulin G adsorption with a quartz crystal microbalance. Thermal cross-linking of PNVP films could be exploited in a wide range of biotechnological applications to give antifouling properties to objects of any size, essentially making this an alternative to high-tech surface modification techniques.

Ionotropically cross-linked pH-sensitive IPN hydrogel matrices as potential carriers for intestine-specific oral delivery of protein drugs

Background: The oral delivery of proteins and peptide drugs is considered a major challenge. These types of therapeutics are readily degraded, if taken orally, due to the harsh high acidity of stomach and enzymatic attack in the upper small intestinal tract. Methods: Water-soluble copolymers of sodium acrylate (AAs) grafted onto carboxymethyl cellulose (CMC) were prepared and characterized using Fourier transform spectroscopy, differential scanning calorimetry, and X-ray diffraction. The obtained graft copolymers were then used in a combination with sodium alginate to develop a new series of pH-sensitive interpenetrating polymeric network (IPN) hydrogels through ionotropic gelation with divalent ions (Ca2+). Morphology of the developed hydrogels was investigated using SEM. Swelling characteristics, at distinct compositions, were also studied at 37°C in two consecutive buffer solutions of pH 2.1 and 7.4 (similar to that of gastric and intestinal fluids, respectively). The release profiles of bovine serum albumin, as a model protein, from test IPN hydrogel films were studied in simulated gastric and intestinal fluids. In addition, the drug release process was confirmed by means of SEM. Results: Swelling studies of the developed IPN hydrogels at different pH values confirmed their pH-sensitive nature. The equilibrium swelling extents of the hydrogels were found to be dependent on the grafting yield of CMC/AAs graft copolymer. The IPN hydrogels attained equilibrium swelling percentages in the range 445–740%. In addition, the amount of bovine serum albumin released within 2 hours in pH 2.1 was relatively low (less than 18.1%). This amount increased up to 68% after 8 hours in pH 7.4. Conclusions: From the obtained preliminary data, it seems that the IPN hydrogels developed in this contribution can be tailored to act as good potential carriers for oral delivery of protein drugs. These hydrogels showed a promising protection of protein drugs from the harsh acidity of stomach and, at the same time, they conferred sustained drug release in the intestinal fluid.

Synthesis and Studies of Thiacorroles

The first examples of stable 22-thiacorroles containing a direct pyrrole-pyrrole bond were synthesized using thiophene monocarbinols as key precursors. Condensation of 1 equiv of thiophene monocarbinol with 1 equiv of substituted aldehyde and 1.5 equiv of pyrrole under refluxing propionic acid conditions followed by alumina column chromatographic purification yielded the desired 22-thiacorroles. Although the corrole formation had been observed with variety of substituted aldehydes, the stable thiacorroles were isolated in 2-3% yields only with 4- and 3-nitrobenzaldehydes. The stable thiacorroles were obtained only under harsh propionic acid conditions and any other mild reaction conditions did not yield 22-thiacorroles. The structure of thiacorroles were unambiguously established using mass, and 1D and 2D NMR spectroscopy. The NMR study indicated diminished ring current and distortion of 22-thiacorroles. DFT studies also supported the distortion of thiacorroles. The absorption spectra showed reduction in number of absorption bands and fluorescence study indicated that 22-thiacorroles are weakly fluorescent. The electrochemical studies indicated that 22-thiacorroles undergo easier reductions compared to thiaporphyrins.

Evaluating Enzyme Cascades for Methanol/Air Biofuel Cells Based on NAD+‐Dependent Enzymes

AbstractPrevious work by the group has entailed encapsulating enzymes in polymeric micelles at bioelectrode surfaces by utilizing hydrophobically modified Nafion membranes, which are modified in order to eliminate the harsh acidity of Nafion while tailoring the size of the polymer micelles to optimize for the encapsulation of an individual enzyme. This polymer encapsulation has been shown to provide high catalytic activity and enzyme stability. In this study, we employed this encapsulation technique in developing a methanol/air biofuel cell through the combined immobilization of NAD+‐dependent alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AldDH) and formate dehydrogenase (FDH) within a tetrabutylammonium bromide (TBAB) modified Nafion to oxidize methanol to carbon dioxide with poly(methylene green) acting as the NADH electrocatalyst electropolymerized on the surface of the electrode. The methanol biofuel/air cell resulted in a maximum power density of 261±7.6 μW/cm2 and current density of 845±35.5 μA/cm2. This system was characterized for the effects of degree of oxidation, temperature, pH, and concentration of fuel and NAD.

Enhanced pH-responsive carrier system based on alginate and chemically modified carboxymethyl chitosan for oral delivery of protein drugs: Preparation and in-vitro assessment

In this investigation a new series of biodegradable pH-responsive hydrogel microspheres were prepared, characterized and in-vitro evaluated as potential carriers for oral delivery of protein drugs. The microspheres are based on ionotropically-crosslinked mixture of sodium alginate and chemically modified carboxymethyl chitosan and coated through polyelectrolyte complexation with chitosan grafted with poly(ethylene glycol). The main objective of the developed microspheres is to survive the harsh acidity of stomach and preferably release peptide and protein drugs in intestine. Both ionotropic gelation and coating process were carried out under mild aqueous conditions, which should be appropriate for retention of biological activity of protein drugs. Swelling studies were carried out for the microspheres at 37 °C in simulated gastric and intestinal fluids. Morphology, size and in-vitro biodegradation of the microspheres were also investigated. A model protein drug was entrapped and the in-vitro drug release profiles were established. The preliminary investigation of the microspheres developed in this study showed a consistent swelling pattern, high entrapment efficiency and promising sustained release profiles of the model protein drug.

Mitochondrial DNA (mtDNA) Biogenesis: Visualization and Duel Incorporation of BrdU and EdU Into Newly Synthesized mtDNA In Vitro

Mitochondria are key regulators of cellular energy and are the focus of a large number of studies examining the regulation of mitochondrial dynamics and biogenesis in healthy and diseased conditions. One approach to monitoring mitochondrial biogenesis is to measure the rate of mitochondrial DNA (mtDNA) replication. We developed a sensitive technique to visualize newly synthesized mtDNA in individual cells to study mtDNA replication within subcellular compartments of neurons. The technique combines the incorporation of 5-bromo-2-deoxyuridine (BrdU) and/or 5-ethynyl-2'-deoxyuridine (EdU) into mtDNA, together with a tyramide signal amplification protocol. Employing this technique, we visualized and measured mtDNA biogenesis in individual cells. The labeling procedure for EdU allows for more comprehensive results by allowing the comparison of its incorporation with other intracellular markers, because it does not require the harsh acid or enzyme digests necessary to recover the BrdU epitope. In addition, the utilization of both BrdU and EdU permits sequential pulse-chase experiments to follow the intracellular localization of mtDNA replication. The ability to quantify mitochondrial biogenesis provides an essential tool for investigating the alterations in mitochondrial dynamics involved in the pathogenesis of multiple cellular disorders, including neuropathies and neurodegenerative diseases.

C60Cl6, C60Br8 and C60(NO2)6 as Selective Tools in Organic Synthesis

Reactions of C60Cl6, C60Br8 and C60(NO2)6 with arene substrates under mild conditions afford primarily monochlorinated, monobrominated or mononitrated organic products in high yield, often with greater selectivity and reactivity than with traditional halogenation or nitration methods. The reactions have the advantages of high stereoselectivity and facile removal and recovery of [60]fullerene. No metal catalysts, gases or harsh acids are required. These results demonstrate the versatility of the functionalized fullerenes as new synthetic tools for organic synthesis.

Comparison of the Suitability of Different Hydrolytic Strategies To Predict Aroma Potential of Different Grape Varieties

Precursor extracts obtained from different grape varieties were submitted to harsh acid hydrolysis (pH 2.5, 100 degrees C, 1 h) and enzymatic hydrolysis (AR2000, pH 5, 40 degrees C, 16 h) and were also added to a synthetic must (200 g L(-1) glucose), which was fermented (yeast strain Stellevin NT 116), to compare the "natural hydrolysis" carried by yeast with alternative "fast" hydrolytic strategies. In all cases, released volatile compounds were extracted by SPE and determined by GC-MS. Leaving aside Muscat, differences between varieties were not relevant, although Grenache and Chardonnay presented some key peculiarities. In general, alcoholic fermentation showed the lowest potential to release volatile compounds from aromatic precursors, whereas enzymatic hydrolysis was the most efficient but also the most different. Practically, this implies that the predictive ability of this hydrolytic strategy is rather poor. In contrast, harsh acid hydrolysis can be considered to much more adequately measure the aroma potential of grapes for winemaking, which suggests that transformations taking place during fermentation include relevant chemical rearrangements in acid media that are better predicted by acid hydrolysis.

Sequential Therapy for Helicobacter Pylori: A Two for One Deal That's Worth the Extra Effort?

Sequential Therapy for Helicobacter Pylori: A Two for One Deal That's Worth the Extra Effort?