ALBERT

Description: Background: Avocado (Persea americana) is an economically important tropical fruit considered to be a good source of fatty acids. Despite its importance, the molecular and cellular characterization of biochemical and developmental processes in avocado is limited due to the lack of transcriptome and genomic information. Results: The transcriptomes of seeds, roots, stems, leaves, aerial buds and flowers were determined using different sequencing platforms. Additionally, the transcriptomes of three different stages of fruit ripening (pre-climacteric, climacteric and post-climacteric) were also analyzed. The analysis of the RNAseqatlas presented here reveals strong differences in gene expression patterns between different organs, especially between root and flower, but also reveals similarities among the gene expression patterns in other organs, such as stem, leaves and aerial buds (vegetative organs) or seed and fruit (storage organs). Important regulators, functional categories, and differentially expressed genes involved in avocado fruit ripening were identified. Additionally, to demonstrate the utility of the avocado gene expression atlas, we investigated the expression patterns of genes implicated in fatty acid metabolism and fruit ripening. Conclusions: A description of transcriptomic changes occurring during fruit ripening was obtained in Mexican avocado, contributing to a dynamic view of the expression patterns of genes involved in fatty acid biosynthesis and the fruit ripening process.

Description: In aqueous acid (pH 〈4) solutions, in the dark, and in the absence of reductants, arenediazonium ions, ArN 2 + decompose spontaneously through the rate-limiting formation of the extremely unstable aryl cation that reacts with any nucleophile present in its solvation shell (D N  + A N mechanism). However, in weak acidic and alkaline solutions, ArN 2 + react with H 2 O and OH − at the terminal nitrogen to give azo adducts of the type ArN 2 OH that are in equilibrium with the parent ArN 2 + . The diazohydroxide, in this case an acid, is in equilibrium with its conjugate base, and diazoate ArN 2 O − . The equilibrium constant for reaction with OH − has been determined for a limited number of ArN 2 + from kinetic measurements but not with H 2 O ( K R ). Here, we have exploited the electrochemical properties of ArN 2 + to determine, for the first time, the equilibrium constants K R of formation of 4-substituted X–ArN 2 OH (X H, Me, MeO, Br, and NO 2 ), which can decompose in several ways including Z–E isomerization or further reaction with OH − to give diazoate ArN 2 O − . The technique applied was differential pulse polarography, which is very selective and sensitive. The determined p K R values are 5–6, and they are somewhat higher than those obtained for the reaction of ArN 2 + with alcohols ROH (p K DE  = 3–5) under similar acidic conditions. The K R values are not very sensitive to changes in the nature of the substituent in the aromatic ring and a linear Hammett plot with a slope of ρ  = 0.58 was obtained. Copyright © 2013 John Wiley & Sons, Ltd. We determined the equilibrium constants K R for the formation of ArN 2 OH from the reaction of 4-substituted ArN 2 + with H 2 O in aqueous acid solution.

Description: Drug treatments and vaccine designs against the opportunistic human pathogen Pseudomonas aeruginosa have multiple issues, all associated with the diverse genetic traits present in this pathogen, ranging from mult...

Description: Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in inhabitants from low-income countries and in visitors to these countries. The impact of the human intestinal microbiota on the initiation an...

Description: We have investigated the kinetics and mechanism of the reaction between 3-methylbenzenediazonium, 3MBD, ions and catechol (1,2-dihydroxybenzene, [CAT]) in aqueous buffer solution under acidic conditions by employing spectrometric UV/VIS. The variation of the observed rate constant, k obs , with the acidity at a given [CAT] follows an upward curve, with rate enhancements of up to 20-fold on going from pH  = 3.0 up to pH  = 5.0, suggesting that the reaction takes place with the monoanionic form of [CAT]. At relatively high acidities, the variation of k obs with [CAT] is linear with an intercept very close to the value for the thermal decomposition of 3MBD; however, a decrease in the acidity leads to saturation kinetics profiles with non-zero pH-dependent intercepts, prompting us to propose a reaction mechanism comprising two consecutive equilibrium processes involving the bimolecular, reversible, formation of a highly unstable Z -diazo ether, which undergoes isomerization to the E -isomer through a unimolecular step. The results highlight the complexity of the reactions of arenediazonium ions with nucleophilic arenes containing two or more hydroxy groups and are valuable to exploit arenediazonium ions as chemical probes to determine antioxidant distributions. Copyright © 2016 John Wiley & Sons, Ltd. The non-zeron, pH dependent, intercepts of the saturation kinetics suggest a mechanism of the type.

Description: We have analyzed the effects of acidity and emulsifier concentration on the distribution of ascorbic acid or vitamin C (VC) in a model emulsion prepared by mixing octane, acidic (HCl) water and the non-ionic surfactant hexaethyleneglycol monododecyl ether (C 12 E 6 ). VC is oil insoluble, and only the partition constant between the interfacial and aqueous regions ( P W I ) is needed to describe its distribution within the emulsion. The P W I values are calculated from the kinetic analyses of the variation of the observed rate constant ( k obs ) determined electrochemically for the reaction between the hydrophobic 4-hexadecylbenzenediazonium (16-ArN 2 + ) ions and VC with the emulsifier concentration. The determined P W I values ( P W I  = 4–25) are low in comparison with those obtained for more hydrophobic antioxidants like vitamin E, and pH dependent, decreasing upon decreasing the acidity of the medium. These low values are reflected in the distribution of VC so that a large fraction (〉70%) is located in the aqueous region at low emulsifier concentrations. At a given pH, the %VC in the aqueous region decreases upon increasing the emulsifier concentration; meanwhile, at a given emulsifier concentration %VC increases upon lowering the acidity. The intrinsic rate constants in the interfacial region k I for the reaction between 16-ArN 2 + and VC have also been determined at different acidities. Their variation with the pH follows an upward bend curve, suggesting an inverse dependence of k I with the acidity of the medium, in keeping with the proposed mechanism for the reaction. The results may be of some interest to the food and pharmaceutical industries because of the extensive use of VC as antioxidant or preservative and because of the health benefits of VC. Copyright © 2012 John Wiley & Sons, Ltd. The distribution of ascorbic acid (vitamin C [VC]) in an emulsion composed of octane, acidic water and the non-ionic surfactant hexaethyleneglycol monododecyl ether (C 12 E 6 ) has been determined by employing a kinetic method that exploits the reaction between a hydrophobic arenediazonium, 16-ArN 2 + and VC. The fraction of VC in the interfacial region increases upon increasing the surfactant volume fraction and on increasing the acidity of the medium.

Description: Background: Most semiconductor nanoparticles used in biomedical applications are made of heavy metals and involve synthetic methods that require organic solvents and high temperatures. This issue makes the development of water-soluble nanoparticles with lower toxicity a major topic of interest. In a previous work our group described a biomimetic method for the aqueous synthesis of CdTe-GSH Quantum Dots (QDs) using biomolecules present in cells as reducing and stabilizing agents. This protocol produces nanoparticles with good fluorescent properties and less toxicity than those synthesized by regular chemical methods. Nevertheless, biomimetic CdTe-GSH nanoparticles still display some toxicity, so it is important to know in detail the effects of these semiconductor nanoparticles on cells, their levels of toxicity and the strategies that cells develop to overcome it. Results: In this work, the response of E. coli exposed to different sized-CdTe-GSH QDs synthesized by a biomimetic protocol was evaluated through transcriptomic, biochemical, microbiological and genetic approaches. It was determined that: i) red QDs (5 nm) display higher toxicity than green (3 nm), ii) QDs mainly induce expression of genes involved with Cd+2 stress (zntA and znuA) and tellurium does not contribute significantly to QDs-mediated toxicity since cells incorporate low levels of Te, iii) red QDs also induce genes related to oxidative stress response and membrane proteins, iv) Cd2+ release is higher in red QDs, and v) QDs render the cells more sensitive to polymyxin B. Conclusion: Based on the results obtained in this work, a general model of CdTe-GSH QDs toxicity in E. coli is proposed. Results indicate that bacterial toxicity of QDs is mainly associated with cadmium release, oxidative stress and loss of membrane integrity. The higher toxicity of red QDs is most probably due to higher cadmium content and release from the nanoparticle as compared to green QDs. Moreover, QDs-treated cells become more sensitive to polymyxin B making these biomimetic QDs candidates for adjuvant therapies against bacterial infections.

Description: The type of specific intermolecular and interionic interactions that are established when an ionic liquid is dissolved in water was here analysed. The study of the solvatochromic response of dipolarity micro-sensors based on Reichardt E T (30) and Kamlet–Abboud–Taft solvent scales and the application of the solvent exchange model confirmed the formation of different intersolvent complexes in binary mixtures of (water + [C 4 mim] [BF 4 ]/[Br]) type. These complexes provide H-bond or electron pairs to the polar network, respectively. Moreover, for 4-methoxybenzenesulfonyl chloride hydrolysis reaction in the (water + [C 4 mim] [BF 4 ]) system, a higher inhibition (13 times) on the k obs values was observed. Multiple linear regression analysis that allows confirming the solvent effect upon the reactive system is due to the hydrogen-bond donor properties of intersolvent complex formed. Then, the correlation between two different solvent-dependent processes proved to be successful. Copyright © 2014 John Wiley & Sons, Ltd. From the analysis of dipolarity micro-sensors solvatochromic response and the application of solvent exchange model, we determine the tendency of the different components of binary mixtures formed by (W + ILs) to interact with potential solutes. Therefore, the analysis of correlation between the microscopic properties and k obs values for a hydrolysis reaction allows us to understand the chemical behaviour observed.

Description: In this work, we have evaluated the effects of emulsifier concentration on the distribution of catechol (1,2-dihydroxybenzene, CAT) in food-grade emulsions composed of stripped corn oil, acidic water, and Tween 20. Auxiliary experiments in binary stripped corn oil–water mixtures, in the absence of emulsifier, showed that CAT is both oil and water soluble (partition constant  = 0.34). Addition of Tween 20 to prepare kinetically stable emulsions creates an interfacial region, and the distribution of CAT is now described by two partition constants, that between the oil and interfacial region, , and that between the aqueous and interfacial region, . These partition constants were determined in the intact emulsion by employing a kinetic method that exploits the reaction between the hydrophobic 4-hexadecylbenzenediazonium ions, 16-ArN 2 + , and CAT. Results show that CAT distributes between the three regions. At emulsifier volume fractions of Φ I  = 0.005, CAT is predominantly located (~61%) in the aqueous region, about 26% is in the interfacial region, and only a small fraction (~13%) in the oil region. An increase in emulsifier concentration promotes the incorporation of CAT to the interfacial region up to ~70% at Φ I  = 0.037. Results obtained should contribute to a better understanding of the antioxidant efficiency in inhibiting lipid oxidation and to the development of new strategies to prepare healthier and more nutritional foods with longer shelf life. Copyright © 2013 John Wiley & Sons, Ltd. We have evaluated the effects of emulsifier concentration on the distribution of catechol (1,2-dihydroxybenzene, CAT) in food-grade emulsions composed of stripped corn oil, acidic water, and Tween 20.

Description: Background: Chromatin plays a critical role in regulating transcription factors (TFs) binding to their canonical transcription factor binding sites (TFBS). Recent studies in vertebrates show that many TFs preferentially bind to genomic regions that are well bound by nucleosomes in vitro. Co-occurring secondary motifs sometimes correlated with functional TFBS. Results: We used a logistic regression to evaluate how well the propensity for nucleosome binding and co-occurrence of a secondary motif identify which canonical motifs are bound in vivo. We used ChIP-seq data for three transcription factors binding to their canonical motifs: c-Jun binding the AP-1 motif (TGAC/GTCA), GR (glucocorticoid receptor) binding the GR motif (G-ACA---T/CGT-C), and Hoxa2 (homeobox a2) binding the Pbx (Pre-B-cell leukemia homeobox) motif (TGATTGAT). For all canonical TFBS in the mouse genome, we calculated intrinsic nucleosome occupancy scores (INOS) for its surrounding 150-bps DNA and examined the relationship with in vivo TF binding. In mouse mammary 3134 cells, c-Jun and GR proteins preferentially bound regions calculated to be well-bound by nucleosomes in vitro with the canonical AP-1 and GR motifs themselves contributing to the high INOS. Functional GR motifs are enriched for AP-1 motifs if they are within a nucleosome-sized 150-bps region. GR and Hoxa2 also bind motifs with low INOS, perhaps indicating a different mechanism of action. Conclusion: Our analysis quantified the contribution of INOS and co-occurring sequence to the identification of functional canonical motifs in the genome. This analysis revealed an inherent competition between some TFs and nucleosomes for binding canonical TFBS. GR and c-Jun cooperate if they are within 150-bps. Binding of Hoxa2 and a fraction of GR to motifs with low INOS values suggesting they are not in competition with nucleosomes and may function using different mechanisms.