Electrochemistry of ethanol and dimethyl ether at a Pt electrode in a protic ionic liquid: the electrode poisoning mechanism.

A protic ionic liquid (PIL), N,N-diethyl-N-methyl ammonium trifluoromethane sulfonate, [dema][TfO] was synthesized and confirmed using 1H-NMR and ion chromatography (IC). The surface electrocatalysis of ethanol (EtOH) and dimethyl ether (DME) was investigated on a polycrystalline Pt electrode in a PIL using a cyclic voltammetry technique. The voltammetry response shows that surface Pt-oxides/hydroxides (PtOH/PtO) are formed due to the oxidation of trace water (240 ppm determined by coulometric Karl-Fischer (FT) titration) in [dema][TfO] which plays a pivotal role during the electrocatalytic oxidation of EtOH and DME in the PIL. Oxidation of EtOH and DME coincides with coverage of the Pt surface by the adsorbed oxide species that helps to activate both processes by oxidizing the adsorbed poisoning CO and CO-like intermediate species via a 'bifunctional' reaction mechanism. The influence of temperature was investigated to obtain quantitative and qualitative information on the kinetics of EtOH oxidation. Higher activation energies are measured for EtOH oxidation in [dema][TfO] than in aqueous electrolytes due to the low water content and high viscosity of the PIL. This study gave a basic insight into the mechanism of EtOH and DME oxidation reactions, and the Pt-electrode poisoning species formation mechanism in the neoteric electrolyte medium is electrochemically investigated and reported.

Discriminative Long-Distance Transport of Selenate and Selenite Triggers Glutathione Oxidation in Specific Subcellular Compartments of Root and Shoot Cells in Arabidopsis.

Selenium is an essential trace element required for seleno-protein synthesis in many eukaryotic cells excluding higher plants. However, a substantial fraction of organically bound selenide in human nutrition is directly or indirectly derived from plants, which assimilate inorganic selenium into organic seleno-compounds. In humans, selenium deficiency is associated with several health disorders Despite its importance for human health, selenium assimilation and metabolism is barely understood in plants. Here, we analyzed the impact of the two dominant forms of soil-available selenium, selenite and selenate, on plant development and selenium partitioning in plants. We found that the reference plant Arabidopsis thaliana discriminated between selenate and selenite application. In contrast to selenite, selenate was predominantly deposited in leaves. This explicit deposition of selenate caused chlorosis and impaired plant morphology, which was not observed upon selenite application. However, only selenate triggered the accumulation of the macronutrient sulfur, the sister element of selenium in the oxygen group. To understand the oxidation state-specific toxicity mechanisms for selenium in plants, we quantified the impact of selenate and selenite on the redox environment in the plastids and the cytosol in a time-resolved manner. Surprisingly, we found that selenite first caused the oxidation of the plastid-localized glutathione pool and had a marginal impact on the redox state of the cytosolic glutathione pool, specifically in roots. In contrast, selenate application caused more vigorous oxidation of the cytosolic glutathione pool but also impaired the plastidic redox environment. In agreement with the predominant deposition in leaves, the selenate-induced oxidation of both glutathione pools was more pronounced in leaves than in roots. Our results demonstrate that Se-species dependent differences in Se partitioning substantially contribute to whole plant Se toxicity and that these Se species have subcellular compartment-specific impacts on the glutathione redox buffer that correlate with toxicity symptoms.

Crosstalk Between Iron and Sulfur Homeostasis Networks in Arabidopsis.

The widespread deficiency of iron (Fe) and sulfur (S) is becoming a global concern. The underlying mechanisms regulating Fe and S sensing and signaling have not been well understood. We investigated the crosstalk between Fe and S using mutants impaired in Fe homeostasis, sulfate assimilation, and glutathione (GSH) biosynthesis. We showed that chlorosis symptoms induced by Fe deficiency were not directly related to the endogenous GSH levels. We found dynamic crosstalk between Fe and S networks and more interestingly observed that the upregulated expression of IRT1 and FRO2 under S deficiency in Col-0 was missing in the cad2-1 mutant background, which suggests that under S deficiency, the expression of IRT1 and FRO2 was directly or indirectly dependent on GSH. Interestingly, the bottleneck in sulfite reduction led to a constitutively higher IRT1 expression in the sir1-1 mutant. While the high-affinity sulfate transporter (Sultr1;2) was upregulated under Fe deficiency in the roots, the low-affinity sulfate transporters (Sultr2;1, and Sultr2;2) were down-regulated in the shoots of Col-0 seedlings. Moreover, the expression analysis of some of the key players in the Fe-S cluster assembly revealed that the expression of the so-called Fe donor in mitochondria (AtFH) and S mobilizer of group II cysteine desulfurase in plastids (AtNFS2) were upregulated under Fe deficiency in Col-0. Our qPCR data and ChIP-qPCR experiments suggested that the expression of AtFH is likely under the transcriptional regulation of the central transcription factor FIT.

Synthesis of Copper Oxide-Based Nanoformulations of Etoricoxib and Montelukast and Their Evaluation through Analgesic, Anti-Inflammatory, Anti-Pyretic, and Acute Toxicity Activities.

Copper oxide nanoparticles (CuO NPs) were synthesized through the coprecipitation method and used as nanocarriers for etoricoxib (selective COX-2 inhibitor drug) and montelukast (leukotriene product inhibitor drug) in combination therapy. The CuO NPs, free drugs, and nanoformulations were investigated through UV/Vis spectroscopy, FTIR spectroscopy, XRD, SEM, and DLS. SEM imaging showed agglomerated nanorods of CuO NPs of about 87 nm size. The CE1, CE2, and CE6 nanoformulations were investigated through DLS, and their particle sizes were 271, 258, and 254 nm, respectively. The nanoformulations were evaluated through in vitro anti-inflammatory activity, in vivo anti-inflammatory activity, in vivo analgesic activity, in vivo anti-pyretic activity, and in vivo acute toxicity activity. In vivo activities were performed on albino mice. BSA denaturation was highly inhibited by CE1, CE2, and CE6 as compared to other nanoformulations in the in vitro anti-inflammatory activity. The in vivo bioactivities showed that low doses (5 mg/kg) of nanoformulations were more potent than high doses (10 and 20 mg/kg) of free drugs in the inhibition of pain, fever, and inflammation. Lastly, CE2 was more potent than that of other nanoformulations.

Synthesis of gemifloxacin conjugated silver nanoparticles, their amplified bacterial efficacy against human pathogen and their morphological study via TEM analysis.

Drug-loaded nanoparticles (NPs) allow specific accumulation and controlled release of drugs to infected tissues with minimal cytotoxicity. In this study, gemifloxacin conjugated silver nanoparticles (Gemi-AgNPs) were synthesized, and the amplification of their antibacterial potential against the human pathogen as well as their stability was monitored under physiological conditions. Fourier transform infrared spectroscopy (FTIR) analysis demonstrated the interaction between -NH2 and -OH functional moiety and the metal surface. The morphological analyses via transmission electron microscopy revealed that Gemi-AgNPs has a round oval shape and average particle size of 22.23 ± 2 nm. The antibacterial and antibiofilm activities of these NPS showed that Gemi-AgNPs exhibit excellent antimicrobial and biofilm inhibition activity against human pathogens, namely, Proteus mirabilis (P. mirabilis) and methicillin-resistant Staphylococcus aureus (MRSA). A significant increase in the antibiofilm activity of Gemi-AgNPs was confirmed by crystal violet, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) staining, and microscopic analysis. Gemi-AgNPs exhibited the ability to inhibit urease with an IC50 value of 57.4 ± 0.72 µg/mL. The changes in the bacterial cell morphology were analyzed via TEM, which revealed that cell membranes disrupted and completely destroyed the cell morphology by the treatment of Gemi-AgNPs.

Sulfur metabolic engineering enhances cadmium stress tolerance and root to shoot iron translocation in Brassica napus L.

Serine acetyltransferase (SAT) (EC 2.3.1.30) is the rate-limiting enzyme of cysteine (Cys) biosynthesis, providing the decisive precursor for the ubiquitous defense thiol glutathione (GSH). Together with O-acetylserine (thiol) lyase (OAS-TL; EC 2.5.1.47) SAT generates Cys in the cytosol, plastids, and mitochondria of vascular plants. The current study aimed to overproduce Cys and GSH for enhanced stress tolerance via overexpression of the feedback-insensitive isoform of serine acetyltransferase from tobacco, i.e., NtSAT4. Constitutive overexpression of NtSAT4 in Brassica napus resulted in the 2.6-fold-4-fold higher SAT activity in different subcellular compartment-specific lines. This higher SAT activity led to a 2.5-fold-3.5-fold higher steady-state level of free Cys and 2.2-fold-5.3-fold elevated level of GSH in leaves compared with nontransformed plants. Among the compartment-specific lines, the mitochondrial targeted NtSAT4 overexpressor line M-182 showed the highest levels of Cys (3.5-fold) and GSH (5.3-fold) compared with wild-type plants. Overexpression of NtSAT4 conferred a physiological advantage in terms of enhanced tolerance against oxidative stress with hydrogen peroxide and the heavy metal cadmium (Cd). The NtSAT4 overexpressor lines showed a significantly higher amount of iron (Fe) translocation from roots to shoots compared with nontransformed plants. Overall, these results suggest that overexpression of NtSAT4 is a promising approach to creating plants with tolerance to heavy metals and oxidative stress and, in addition, may potentially improve plant nutrition in terms of enhanced Fe translocation from roots to shoots.

Viscosine as a Potent and Safe Antipyretic Agent Evaluated by Yeast-Induced Pyrexia Model and Molecular Docking Studies.

The antipyretic potential of viscosine, a natural product isolated from the medicinal plant Dodonaea viscosa, was investigated using yeast-induced pyrexia rat model, and its structure-activity relationship was investigated through molecular docking analyses with the target enzymes cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and microsomal prostaglandin E synthase-1 (mPGES-1). The in vivo antipyretic experiments showed a progressive dose-dependent reduction in body temperatures of the hyperthermic test animals when injected with viscosine. Comparison of docking analyses with target enzymes showed strongest bonding interactions (binding energy -17.34 kcal/mol) of viscosine with the active-site pocket of mPGES-1. These findings suggest that viscosine shows antipyretic properties by reducing the concentration of prostaglandin E2 in brain through its mPGES-1 inhibitory action and make it a potential lead compound for developing effective and safer antipyretic drugs for treating fever and related pathological conditions.

Sulfate-Induced Stomata Closure Requires the Canonical ABA Signal Transduction Machinery.

Phytohormone abscisic acid (ABA) is the canonical trigger for stomatal closure upon abiotic stresses like drought. Soil-drying is known to facilitate root-to-shoot transport of sulfate. Remarkably, sulfate and sulfide-a downstream product of sulfate assimilation-have been independently shown to promote stomatal closure. For induction of stomatal closure, sulfate must be incorporated into cysteine, which triggers ABA biosynthesis by transcriptional activation of NCED3. Here, we apply reverse genetics to unravel if the canonical ABA signal transduction machinery is required for sulfate-induced stomata closure, and if cysteine biosynthesis is also mandatory for the induction of stomatal closure by the gasotransmitter sulfide. We provide genetic evidence for the importance of reactive oxygen species (ROS) production by the plasma membrane-localized NADPH oxidases, RBOHD, and RBOHF, during the sulfate-induced stomatal closure. In agreement with the established role of ROS as the second messenger of ABA-signaling, the SnRK2-type kinase OST1 and the protein phosphatase ABI1 are essential for sulfate-induced stomata closure. Finally, we show that sulfide fails to close stomata in a cysteine-biosynthesis depleted mutant. Our data support the hypothesis that the two mobile signals, sulfate and sulfide, induce stomatal closure by stimulating cysteine synthesis to trigger ABA production.

Generation of Se-fortified broccoli as functional food: impact of Se fertilization on S metabolism.

Selenium (Se)-fortified broccoli (Brassica oleracea var. italica) has been proposed as a functional food for cancer prevention, based on its high glucosinolate (GSL) content and capacity for Se accumulation. However, as selenate and sulphate share the initial assimilation route, Se fertilization could interfere with sulphur metabolism and plant growth. Consequently, GSL accumulation could be compromised. To evaluate these potentially adverse effects of Se fertilization, we performed a comprehensive study on sand-grown young broccoli plants (weekly selenate applications of 0.8 µmol plant(-1) via the root) and field-grown adult broccoli plants during head formation (single foliar selenate application: 25.3 or 253 µmol plant(-1) ). The results show that under these conditions, Se application does not affect plant growth, contents of cysteine, glutathione, total GSL, glucoraphanin (major aliphatic GSL) or the expression of BoMYB28 (encoding a functionally confirmed master regulator for aliphatic GSL biosynthesis). Conversely, due to the changed expression of sulphate transporters (BoSULTR1;1, 1;2, 2;1, and 2;2), sulphate and total S contents increased in the shoot of young plants while decreasing in the root. We conclude that broccoli can be fertilized with Se without reduction in GSL content, even with Se accumulation exceeding the level recommended for human consumption.

Sulfite reductase defines a newly discovered bottleneck for assimilatory sulfate reduction and is essential for growth and development in Arabidopsis thaliana.

The role of sulfite reductase (SiR) in assimilatory reduction of inorganic sulfate to sulfide has long been regarded as insignificant for control of flux in this pathway. Two independent Arabidopsis thaliana T-DNA insertion lines (sir1-1 and sir1-2), each with an insertion in the promoter region of SiR, were isolated. sir1-2 seedlings had 14% SiR transcript levels compared with the wild type and were early seedling lethal. sir1-1 seedlings had 44% SiR transcript levels and were viable but strongly retarded in growth. In mature leaves of sir1-1 plants, the levels of SiR transcript, protein, and enzymatic activity ranged between 17 and 28% compared with the wild type. The 28-fold decrease of incorporation of (35)S label into Cys, glutathione, and protein in sir1-1 showed that the decreased activity of SiR generated a severe bottleneck in the assimilatory sulfate reduction pathway. Root sulfate uptake was strongly enhanced, and steady state levels of most of the sulfur-related metabolites, as well as the expression of many primary metabolism genes, were changed in leaves of sir1-1. Hexose and starch contents were decreased, while free amino acids increased. Inorganic carbon, nitrogen, and sulfur composition was also severely altered, demonstrating strong perturbations in metabolism that differed markedly from known sulfate deficiency responses. The results support that SiR is the only gene with this function in the Arabidopsis genome, that optimal activity of SiR is essential for normal growth, and that its downregulation causes severe adaptive reactions of primary and secondary metabolism.