Chimeric Interaction of Nitrogenase-Like Reductases with the MoFe Protein of Nitrogenase

The engineering of transgenic organisms with the ability to fix nitrogen is an attractive possibility. However, oxygen sensitivity of nitrogenase, mainly conferred by the reductase component (NifH)₂, is an imminent problem. Nitrogenase-like enzymes involved in coenzyme F₄₃₀ and chlorophyll biosynthesis utilize the highly homologous reductases (CfbC)₂ and (ChlL)₂, respectively. Chimeric protein–protein interactions of these reductases with the catalytic component of nitrogenase (MoFe protein) did not support nitrogenase activity. Nucleotide-dependent association and dissociation of these complexes was investigated, but (CfbC)₂ and wild-type (ChlL)₂ showed no modulation of the binding affinity. By contrast, the interaction between the (ChlL)₂ mutant Y127S and the MoFe protein was markedly increased in the presence of ATP (or ATP analogues) and reduced in the ADP state. Upon formation of the octameric (ChlL)₂MoFe(ChlL)₂ complex, the ATPase activity of this variant is triggered, as seen in the homologous nitrogenase system. Thus, the described reductase(s) might be an attractive tool for further elucidation of the diverse functions of (NifH)₂ and the rational design of a more robust reductase.     

Selective recognition in potentiometric transduction of amoxicillin by molecularly imprinted materials

The indiscriminate use of antibiotics in food-producing animals has received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria (Woodward in Pesticide, veterinary and other residues in food, CRC Press, Boca Raton, 2004). Numerous analytical methods for quantifying antibacterial residues in edible animal products have been developed over years (Woodward in Pesticide, veterinary and other residues in food, CRC Press, Boca Raton, 2004; Botsoglou and Fletouris in Handbook of food analysis, residues and other food component analysis, Marcel Dekker, Ghent, 2004). Being Amoxicillin (AMOX) one of those critical veterinary drugs, efforts have been made to develop simple and expeditious methods for its control in food samples. In literature, only one AMOX-selective electrode has been reported so far. In that work, phosphotungstate:amoxycillinium ion exchanger was used as electroactive material (Shoukry et al. in Electroanalysis 6:914–917, 1994). Designing new materials based on molecularly imprinted polymers (MIPs) which are complementary to the size and charge of AMOX could lead to very selective interactions, thus enhancing the selectivity of the sensing unit. AMOX-selective electrodes used imprinted polymers as electroactive materials having AMOX as target molecule to design a biomimetic imprinted cavity. Poly(vinyl chloride), sensors of methacrylic acid displayed Nernstian slopes (60.7 mV/decade) and low detection limits (2.9 × 10⁻⁵ mol/L). The potentiometric responses were not affected by pH within 4–5 and showed good selectivity. The electrodes were applied successfully to the analysis of real samples.     

Essential Oils for Food Application: Natural Substances with Established Biological Activities

Essential oils (EOs) are natural products obtained from aromatic plants. Steam distillation and hydrodistillation are the most commonly used methods for the extraction of EOs at laboratory scale. They have been widely studied due to their potential in the food industry. EO can be used in food in order to prolong the shelf-life, and additionally, they can reduce or replace synthetics additives. Their effectiveness can be confirmed in antimicrobial and antioxidant tests performed, in general, by diffusion test in agar and DPPH^? assay, respectively. Volatile compounds are present in EOs, a role in their biological activities. In this line of thought, chromatography techniques can be applied to identify the main volatile compounds present in EOs. In general, EOs extend food stability during storage, inhibiting the growth of spoilage or pathogenic microorganisms and protecting against oxidation. It is important to evaluate the responsible compounds for the biological activities of EOs and determine their utilization limits, including their safety. Highly variable composition with source species, plant parts, and/or extraction methods appears to play important roles in the variability of EO biological activities. This review provides a concise and critical insight in the use of EOs with emphasis in food applications.     

Different drug incorporation routes in ethylene oxide based copolymers

Coumarin is successfully incorporated in poly(ethylene oxide)‐poly(propylene oxide) block copolymers functionalized with terminal alkynes, PEO‐b‐PPO‐b‐GPE, by click reactions at atmospheric pressure and in CO₂ supercritical conditions (scCO₂). The presence of glycidyl propargyl ether (GPE), an alkynyl‐terminated monomer, in the copolymer chain allows the covalent attachment of the coumarin by click chemistry, obtaining polymer–drug conjugates. First, the most suitable synthesis procedure for the above‐mentioned copolymers was established. Then, the click reactions were carried out confirming the coumarin attachment by Fourier transform IR and ¹H NMR analyses, achieving good yields in both cases with a coumarin content of about 9.3 wt% and avoiding the use of toxic solvents in the case of scCO₂. In addition, thanks to the amphiphilic character of the copolymer due to the presence of hydrophilic (PEO) and hydrophobic (PPO) segments, micelle formation is also possible and was confirmed by dynamic light scattering and high resolution SEM. Finally, coumarin incorporation was achieved by micelle formation using the direct dissolution method in order to compare the polymer–drug system properties. This second route allows a drug entrapment efficiency of 14 wt% to be reached. In both cases, the size of the polymeric micelles obtained is in a suitable range to enable permeability. However, an interesting point is the reduction in the size of the micelles with increase in the GPE percentage and with the covalent attachment of the coumarin to the copolymer, which is supposed to improve their permeability. © 2019 Society of Chemical Industry     

Effects of pluronic F68 micellization on the viability of neuronal cells in culture

Triblock copolymers with surface‐active properties, referred to as Pluronic, have shown potential medical applications such as drug delivery to selective targets in the human body. In particular, the transport of anti‐inflammatory substances to the brain is required for illness treatment, thus the study of delivery agents that cross the blood–brain barrier is relevant. In this article we study the effects of the micelle formation on the morphologic and cytotoxic properties of Pluronic F68. We determinate the critical micellar concentration (CMC) by standard tensiometric and absorbance measurements, and also we analyze the morphology of polymers by atomic force microscopy. Our observations indicate that the morphological properties of F68 are drastically modified in the CMC range, as well as the ability to increase the viability of neuroblastoma cells maintained under culture conditions, as compared with nontreated cells. Our conclusions highlight the close correlation between morphological and physiochemical properties of Pluronic, which must be further understood in order to achieve highly controlled pharmacological uses. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2159–2164, 2013     

Heat inactivation of Listeria innocua in broth and food products under non-isothermal conditions

The objective of this work was to study the effect of three linear temperature profiles (heating rates of 1.5, 1.8 and 2.6 °C/min, from 20 to 65 °C) on Listeria innocua inactivation in liquid medium. The inactivation was also analyzed in artificially contaminated parsley (heating rate of 1.8 °C/min) and throughout a frying process, using a pre-cooked frozen food as case study. Inactivation showed a sigmoidal behaviour and all data was fitted with a Gompertz-inspired model. Results demonstrated that, in liquid media, Listeria inactivation is influenced by the temperature profile used. As heating rate increases, the shoulder decreases and the tail effect disappears. If Listeria was in parsley, its heat resistance increased (for identical experimental conditions in broth). Besides model adequacy was proven in all studied situations, the heating rate affected parameters’ precision.     

DSD: document sparse-based denoising algorithm

Pattern Analysis and Applications - In this paper, we present a sparse-based denoising algorithm for scanned documents. This method can be applied to any kind of scanned documents with satisfactory...