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Advances of in vitro culture models have allowed unprecedented insights into human neurobiology. At the same time genetic screening has matured into a robust and accessible experimental strategy allowing for the simultaneous study of many genes in parallel. The combination of both technologies is a newly emerging tool for neuroscientists, opening the door to identifying causal cell- and tissue-specific developmental and disease mechanisms. However, with complex experimental genetic screening set-ups new challenges in data interpretation and experimental scope arise that require a deep understanding of the benefits and challenges of individual approaches. In this review, we summarize the literature that applies genetic screening to in vitro brain models, compare experimental strengths and weaknesses and point towards future directions of these promising approaches. [ABSTRACT FROM AUTHOR]

Aluminium chlorofluoride (ACF) and high-surface aluminium fluoride (HS-AlF3) were analyzed by a set of characterization methods to assess their acidic properties: NH3-TPD, CO adsorption followed by DRIFTS, CD3CN-PAS-FTIR and MAS NMR spectroscopy after 15N-pyridine adsorption. Both catalysts contain very strong and medium-strong Lewis acid sites as confirmed by CO adsorption, in which small differences arise from the morphological properties of each catalyst, with ACF being microporous and HS-AlF3 mesoporous. Shifts of the CO vibration band of up to 77 cm−1 were observed, which account for very strong Lewis acid sites. In addition, very strong Lewis acid sites could be identified by CD3CN-PAS for both catalysts, exhibiting a shift of 95 cm−1 from free nitrile, the highest ever reported for a solid Lewis acid. [ABSTRACT FROM AUTHOR]

Abstract: H/D‐exchange reactions between methane and deuterated solvents such as [D6]benzene and [D12]cyclohexane were heterogeneously catalyzed by nanoscopic aluminum chlorofluoride (ACF=AlClxF3−x, x≈0.05–0.3) under very mild conditions. 13C NMR spectroscopy experiments at labeled methane revealed the formation of all isotopologues. AlCl3, AlBr3, HS‐AlF3, γ‐Al2O3, and γ‐Al2O3 preheated at 700 °C did not show any H/D‐exchange reaction of methane or [D6]benzene. Mechanistically, electrophilic activation of methane was suggested at the ACF surface. [ABSTRACT FROM AUTHOR]

Enones in which the carbon-carbon double bond is part of the pharmacologically important 2H-chromene (2H-1-benzopyran) nucleus undergo asymmetric copper-catalyzed 1,2-addition of Grignard reagents. High yields and enantiomeric excesses up to 84% are obtained and access to these novel enantio-enriched tertiary alcohols is provided. [ABSTRACT FROM AUTHOR]

Nitro-fatty acids (NO 2 -FAs), which are the result of the interaction between reactive nitrogen species (RNS) and non-saturated fatty acids, constitute a new research area in plant systems, and their study has significantly increased. Very recently, the endogenous presence of nitro-linolenic acid (NO 2 -Ln) has been reported in the model plant Arabidopsis thaliana . In this regard, the signaling role of this molecule has been shown to be key in setting up a defense mechanism by inducing the chaperone network in plants. Here, we report on the ability of NO 2 -Ln to release nitric oxide (NO) in an aqueous medium with several approaches, such as by a spectrofluorometric probe with DAF-2, the oxyhemoglobin oxidation method, ozone chemiluminescence, and also by confocal laser scanning microscopy in Arabidopsis cell cultures. Jointly, this ability gives NO 2 -Ln the potential to act as a signaling molecule by the direct release of NO, due to its capacity to induce different changes mediated by NO or NO-related molecules such as nitration and S -nitrosylation or by the electrophilic capacity of these molecules through a nitroalkylation mechanism. [ABSTRACT FROM AUTHOR]

We report on hydroarylation reactions of arenes with olefins under very mild conditions catalyzed heterogeneously by aluminum chlorofluoride (ACF; AlCl xF3− x, x≈0.05-0.25). The reactions of benzene and toluene with ethylene or propylene proceed with high conversions to afford various alkylated arenes. For cyclohexene and 1-hexene, the reactions require higher temperatures and the conversions are lower. ACF also catalyzes the hydroarylation of 1,3,5-trifluorobenzene and pentafluorobenzene with ethylene and propylene. The alkylations of arenes with non-fluorinated olefins resemble typical Friedel-Crafts chemistry to give rise to Markovnikov regioselectivity. The reaction of CF3CH=CH2 with benzene proceeds with anti-Markovnikov regioselectivity to give the fluorinated olefin PhCHCH=CF2 and the alkylation product PhCH2CH2CF3 as products of C−F and C−H activation. [ABSTRACT FROM AUTHOR]

Nitro-arachidonic acid (NO2-AA) is a cell signaling nitroalkene that exerts anti-inflammatory activities during macrophage activation. While angiotensin II (ANG II) produces an increase in reactive oxygen species (ROS) production and mitochondrial dysfunction in renal tubular cells, little is known regarding the potential protective effects of NO2-AA in ANG II-mediated kidney injury. As such, this study examines the impact of NO2-AA on ANG II-induced mitochondrial dysfunction in an immortalized renal proximal tubule cell line (HK-2 cells). Treatment of HK-2 cells with ANG II increases the production of superoxide (O2●-), nitric oxide (●NO), inducible nitric oxide synthase (NOS2) expression, peroxynitrite (ONOO-) and mitochondrial dysfunction. Using high-resolution respirometry, it was observed that the presence of NO2-AA prevented ANG II-mediated mitochondrial dysfunction. Attempting to address mechanism, we treated isolated rat kidney mitochondria with ONOO-, a key mediator of ANG II-induced mitochondrial damage, in the presence or absence of NO2-AA. Whereas the activity of succinate dehydrogenase (SDH) and ATP synthase (ATPase) were diminished upon exposure to ONOO-, they were restored by pre-incubating the mitochondria with NO2-AA. Moreover, NO2-AA prevents oxidation and nitration of mitochondrial proteins. Combined, these data demonstrate that ANG II-mediated oxidative damage and mitochondrial dysfunction is abrogated by NO2-AA, identifying this compound as a promising pharmacological tool to prevent ANG II–induced renal disease. [ABSTRACT FROM AUTHOR]

Nitro-fatty acids (NO2-FAs) are the product of the reaction between reactive nitrogen species derived of nitric oxide (NO) and unsaturated fatty acids. In animal systems, NO2-FAs are considered novel signaling mediators of cell function based on a proven antiinflammatory response. Nevertheless, the interaction of NO with fatty acids in plant systems has scarcely been studied. Here, we examine the endogenous occurrence of nitro-linolenic acid (NO2-Ln) in Arabidopsis and the modulation of NO2-Ln levels throughout this plant's development by mass spectrometry. The observed levels of this NO2-FA at picomolar concentrations suggested its role as a signaling effector of cell function. In fact, a transcriptomic analysis by RNA-seq technology established a clear signaling role for this molecule, demonstrating that NO2-Ln was involved in plant defense response against different abiotic-stress conditions, mainly by inducing heat shock proteins and supporting a conserved mechanism of action in both animal and plant defense processes. Bioinformatics analysis revealed that NO2-Ln was also involved in the response to oxidative stress conditions, mainly depicted by H2O2, reactive oxygen species, and oxygen-containing compound responses, with a high induction of ascorbate peroxidase expression. Closely related to these results, NO2-Ln levels significantly rose under several abiotic-stress conditions such as wounding or exposure to salinity, cadmium, and low temperature, thus validating the outcomes found by RNA-seq technology. Jointly, to our knowledge, these are the first results showing the endogenous presence of NO2-Ln in Arabidopsis (Arabidopsis thaliana) and supporting the strong signaling role of these molecules in the defense mechanism against different abiotic-stress situations. [ABSTRACT FROM AUTHOR]

The ascorbate-glutathione cycle is a metabolic pathway that detoxifies hydrogen peroxide and involves enzymatic and non-enzymatic antioxidants. Proteomic studies have shown that some enzymes in this cycle such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR) are potential targets for post-translational modifications (PMTs) mediated by nitric oxide-derived molecules. Using purified recombinant pea peroxisomal MDAR and cytosolic and chloroplastic GR enzymes produced in Escherichia coli, the effects of peroxynitrite (ONOO-) and S-nitrosoglutathione (GSNO) which are known to mediate protein nitration and S-nitrosylation processes, respectively, were analysed. Although ONOO- and GSNO inhibit peroxisomal MDAR activity, chloroplastic and cytosolic GR were not affected by these molecules. Mass spectrometric analysis of the nitrated MDAR revealed that Tyr21, Try29, and Tyr345 were exclusively nitrated to 3-nitrotyrosine by ONOO-. The location of these residues in the structure of pea peroxisomal MDAR reveals that Tyr345 is found at 3.3 Å of His313 which is involved in the NADPbinding site. Site-directed mutagenesis confirmed Tyr345 as the primary site of nitration responsible for the inhibition of MDAR activity by ONOO-. These results provide new insights into the molecular regulation of MDAR which is deactivated by nitration and S-nitrosylation. However, GR was not affected by ONOO- or GSNO, suggesting the existence of a mechanism to conserve redox status by maintaining the level of reduced GSH. Under a nitro-oxidative stress induced by salinity (150 mM NaCl), MDAR expression (mRNA, protein, and enzyme activity levels) was increased, probably to compensate the inhibitory effects of S-nitrosylation and nitration on the enzyme. The present data show the modulation of the antioxidative response of key enzymes in the ascorbate-glutathione cycle by nitric oxide (NO)-PTMs, thus indicating the close involvement of NO and reactive oxygen species metabolism in antioxidant defence against nitro-oxidative stress situations in plants. [ABSTRACT FROM AUTHOR]

Metallaheteroboranes are versatile compounds that can be conveniently modified and eventually tailored by ligand modification at either the metal centre or the boron vertices. Recently, we have discovered that protonation of some rhodathiaboranes affords cationic clusters with interesting reaction chemistry. In order to tune the reactivity of some of these polyhedral boron-based compounds, we have prepared air-stable orange [1,1-(η2-dppe)-3-(NC5H5)-closo-1,2-RhSB9H8] (2) by the treatment of the known hydridorhodathiaborane [8,8,8-(H)(PPh3)2-9-(NC5H5)-nido-8,7-RhSB9H9] (1) with dppe. The new 11-vertex rhodathiaborane, 2, reacts readily with triflic acid (TfOH) in CH2Cl2 to give orange cationic [8,8-(η2-dppe)-9-(NC5H5)-nido-8,7-RhSB9H9]+ (3). VT NMR experiments have allowed the characterization of a structural closo↑nido tautomerism, which involves hapticity changes in the ligation of the {SB9H9-(NC5H5)} moiety to the {Rh(dppe)} fragment, with the proton moving between the Rh(1)–B(3) and the B(9)–B(10) edges of the closo- and nido-isomers, respectively. The proton enhances the stereochemical non-rigidity and Lewis acidity of 3versus the neutral 2. This modification of the chemical and structural basis permits the efficient heterolytic splitting of the H–H bond, leading to the formation of new hydridorhodathiaborane isomers [8,8,8-(H)(η2-dppe)-μ-8,9-(H)-9-(NC5H5)-nido-8,7-RhSB9H10]+ (4) that are in equilibrium with the reactants, H2 and 3. [ABSTRACT FROM AUTHOR]

The reaction of the 11-vertex rhodathiaborane, [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1), with NH3 affords inmediately the adduct, [8,8,8-(NH3)(PPh3)2-nido-8,7-RhSB9H10] (4). The NH3-Rh interaction induces the labilization of the PPh3 ligands leading to the dissociation product, [8,8-(NH3)(PPh3)-nido-8,7-RhSB9H10] (5), which can then react with another molecule of NH3 to give [8,8,8-(NH3)2(PPh3)-nido-8,7-RhSB9H10] (6). These clusters have been characterized in situ by multielement NMR spectroscopy at different temeperatures. The variable temperature behavior of the system demonstrates that the intermediates 4-6 are in equilibrium, involving ligand exchange processes. On the basis of low intensity signals present in the 1H NMR spectra of the reaction mixture, some species are tentatively proposed to be the bis- and tris-NH3 ligated clusters, [8,8-(NH3)2-nido-8,7-RhSB9H10] (7) and [8,8,8-(NH3)3-nido-8,7-RhSB9H10] (8). After evaporation of the solvent and the excess of NH3, the system containing species 4-8 regenerates the starting reactant, 1, thus closing a stoichiometric cycle of ammonia addition and loss. After 40 h at room temperature, the reaction of 1 with NH3 gives the hydridorhodathiaborane, [8,8,8-(H)(PPh3)2-nido-8,7-RhSB9H9] (2), as a single product. The reported rhodathiaboranes show reversible H3N-promoted ligand lability, which implies weak Rh-N interactions, leading to a rare case of metal complexes that circumvent "classical" Werner chemistry. [ABSTRACT FROM AUTHOR]

Thereaction between pyridine and [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1) has given the opportunity to synthesize a new family of11-vertex hydridorhodathiaboranes that feature boron-bound N-heterocyclicligands. To explore the scope of this reaction, 1hasbeen treated with the methylpyridine isomers (picolines) 2-Me-NC5H4, 3-Me-NC5H4, and 4-Me-NC5H4, affording the picoline ligated clusters [8,8,8-(H)(PPh3)2-9-(L)-nido-8,7-RhSB9H9], where L = 2-Me-NC5H4(3), 3-Me-NC5H4(4), 4-Me-NC5H4(5). Thermal treatment of these nidoclusters leads to dehydrogenation and the formationof isonido/closo-[1,1-(PPh3)2-3-(L)-1,2-RhSB9H8] (9–11). Compounds 3–5react with ethylene to form [1,1-(η2-C2H4)(PPh3)-3-(L)-1,2-RhSB9H8] (13–15). Similarly, treatmentof 3–5with carbon monoxide produces[1,1-(CO)(PPh3)-3-(L)-1,2-RhSB9H8] (17–19). These series of η2-C2H4and CO ligated 11-vertex isonido/closo-rhodathiaboranes result fromthe substitution of one PPh3ligand by ethylene or CO togetherwith H2loss and a concomitant nidoto closo/isonidocluster structural transformation.The reactivity of 3–5with propene,1-hexene, and cyclohexene under a hydrogen atmosphere is also reportedand compared with the reactivity of the pyridine ligated analogue[8,8,8-(H)(PPh3)2-9-(NC5H5)-nido-8,7-RhSB9H9] (2). Low-temperature NMR studies have allowed the characterizationof intermediates which undergo inter- and intramolecular exchangeprocesses, depending on the nature of the N-heterocyclic ligand. TheCO ligand enhances the nonrigidity of the cluster, opening mechanismsof H2loss. [ABSTRACT FROM AUTHOR]

The copper/Rev-JosiPhos-catalysed asymmetric conjugate addition of Grignard reagents to 2-methylcyclopentenone ( 1) provides 2,3-disubstituted cyclopentanones in high yields and enantioselectivities, and good diastereoselectivities. Reaction of the in situ formed enolate with various alkylating reagents in the presence of 1,3-dimethyltetrahydropyrimidine-2(1 H)-one (DMPU) affords the corresponding products in a one-pot reaction. This procedure creates two vicinal stereocentres, one of them quaternary. [ABSTRACT FROM AUTHOR]

S-Nitrosoglutathione (GSNO) is a nitric oxide-derived molecule that can regulate protein function by a post-translational modification designated S-nitrosylation. GSNO has also been detected in different plant organs under physiological and stress conditions, and it can also modulate gene expression. Thirty-day-old Arabidopsis plants were grown under hydroponic conditions, and exogenous 1 mM GSNO was applied to the root systems for 3 h. Differential gene expression analyses were carried out both in roots and in leaves by RNA sequencing (RNA-seq). A total of 3,263 genes were identified as being modulated by GSNO. Most of the genes identified were associated with the mechanism of protection against stress situations, many of these having previously been identified as target genes of GSNO by array-based methods. However, new genes were identified, such as that for methionine sulfoxide reductase (MSR) in leaves or different miscellaneous RNA (miscRNA) genes in Arabidopsis roots. As a result, 1,945 GSNO-responsive genes expressed differently in leaves and roots were identified, and 114 of these corresponded exclusively to one of these organs. In summary, it is demonstrated that RNA-seq extends our knowledge of GSNO as a signaling molecule which differentially modulates gene expression in roots and leaves under non-stress conditions. [ABSTRACT FROM PUBLISHER]

The treatment of the hydridorhodathiaboranes, [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSB9H9], where PR3 = PPh3 (2), PMePh2 (3), PPh3 and PMe2Ph (4), or PR3 and PPh3 (5), and [8,8,8-(H)(PMePh2)2-9-(PMePh2)- nido-8,7-RhSB9H9] (6), with TfOH affords [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSB9H10]+ cations, where PR3 = PPh3 (12), PMePh3 (13), PPh3 and PMe2Ph (14), or PR3 and PPh3 (15), and [8,8,8-(H)(PMePh2)2-9- (PMePh2)-nido-8,7-RhSB9H10]+ (16). Compounds 13 and 14 lose H2 to give [1,3-μ-(H)-1,1-(PR3)2-3-(Py)- isonido-1,2-RhSB9H8]+, where PR3 = PMe2Ph (18), PPh3 and PMe2Ph (21), or PMePh2 (22). Similarly, the 11-vertex rhodathiaboranes, [1,1-(PR3)2-3-(Py)-1,2-RhSB9H8], where PR3 = PPh3 (7), PMe2Ph (8), PMe3 (9), or PPh3 and PMe3 (10), react with TfOH to give the corresponding cations, [1,3-μ-(H)-1,1-(PR3)2-3-(Py)- isonido-1,2-RhSB9H8]+, where PR3 = PPh3 (17), PMe2Ph (18), PMe3 (19), or PPh3 and PMe3 (20). Four conformers of 20 are studied by X-ray diffraction methods and DFT-calculations, identifying packing motifs that stabilize different metal-thiaborane linkages, and energy variations that are involved in these conformational changes. It is demonstrated that the proton induces nonrigidity on these clusters as well as an enhancement of their Lewis acidity. [ABSTRACT FROM AUTHOR]

Post-translational modifications (PTMs) mediated by nitric oxide (NO)-derived molecules have become a new area of research, as they can modulate the function of target proteins. Proteomic data have shown that ascorbate peroxidase (APX) is one of the potential targets of PTMs mediated by NO-derived molecules. Using recombinant pea cytosolic APX, the impact of peroxynitrite (ONOO–) and S-nitrosoglutathione (GSNO), which are known to mediate protein nitration and S-nitrosylation processes, respectively, was analysed. While peroxynitrite inhibits APX activity, GSNO enhances its enzymatic activity. Mass spectrometric analysis of the nitrated APX enabled the determination that Tyr5 and Tyr235 were exclusively nitrated to 3-nitrotyrosine by peroxynitrite. Residue Cys32 was identified by the biotin switch method as S-nitrosylated. The location of these residues on the structure of pea APX reveals that Tyr235 is found at the bottom of the pocket where the haem group is enclosed, whereas Cys32 is at the ascorbate binding site. Pea plants grown under saline (150mM NaCl) stress showed an enhancement of both APX activity and S-nitrosylated APX, as well as an increase of H2O2, NO, and S-nitrosothiol (SNO) content that can justify the induction of the APX activity. The results provide new insight into the molecular mechanism of the regulation of APX which can be both inactivated by irreversible nitration and activated by reversible S-nitrosylation. [ABSTRACT FROM PUBLISHER]

The treatment of [1,1-(PR3)2-3-(Py)- closo-1,2-RhSB9H8] (PR3=PMe3 ( 2) or PPh3 and PMe3 ( 3); Py=pyridine) with triflic acid (TfOH) affords [1,3-μ-(H)-1,1-(PR3)2-3-(Py)-1,2-RhSB9H8]+ (PR3=PMe3 ( 4) or PMe3 and PPh3 ( 5)). These products result from the protonation of the 11-vertex closo-cages along the Rh(1)B(3) edge. These unusual cationic rhodathiaboranes are stable in solution and in the solid state and they have been fully characterized by multinuclear NMR spectroscopy. In addition, compound 5 was characterized by single-crystal X-ray diffraction. One remarkable feature in these structures is the presence of three {Rh(PPh3)(PMe3)}-to-{η n-SB9H8(Py)} ( n=4 or 5) conformers in the unit cell, thus giving an uncommon case of conformational isomerism. [1,1-(PPh3)2-3-(Py)- closo-1,2-RhSB9H8] ( 1), that is, the bis-PPh3-ligated analogue of compounds 2 and 3, is also protonated by TfOH, but, in marked contrast, the resulting cation, [1,3-μ-(H)-1,1-(PPh3)2-3-(Py)-1,2-RhSB9H8]+ ( 6), is attacked by a triflate anion with the release of a PPh3 ligand and the formation of [8,8-(OTf)(PPh3)-9-(Py)- nido-8,7-RhSB9H9] ( 9). The result is an equilibrium that involves cationic species 6, neutral OTf-ligated compound 9, and [HPPh3]+, which is formed upon protonation of the released PPh3 ligand. The resulting ionic system reacts readily with H2 to give cationic species [8,8,8-(H)(PPh3)2-9-(Py)- nido-8,7-RhSB9H9]+ ( 7). This reactivity is markedly higher than that previously found for compound 1 and it introduces a new example of proton-assisted H2 activation that occurs on a polyhedral boron-containing compound. [ABSTRACT FROM AUTHOR]

Abstract: The free radical molecule nitric oxide (NO) is involved in a wide range of plant functions such as growth, senescence, fruit ripening, and responses to adverse environmental conditions. NO and NO-derived molecules peroxynitrite and S-nitrosoglutathione are reactive nitrogen species (RNS) that can directly or indirectly interact with a broad spectrum of biomolecules that affect their biological functions. Plant NO research has focused on post-translational modifications in proteins, mainly S-nitrosylation and nitration. There are other potential target biomolecules in plants that have not been studied, which have been studied in animal systems, such as lipids. Nitro-fatty acids (NO2-FAs) are involved in pleiotropic activities in animal systems, including modulation of macrophage activation, prevention of leukocyte and platelet activation, and promotion of blood vessel relaxation. NO2-FAs are therefore novel mediators in NO signaling pathways and metabolism. This review will focus on these molecules and will highlight their potential in relation to the physiology of higher plants. [Copyright &y& Elsevier]

Reactions of [8,8,8-(H)(PPh3)2-9-(Py)-nido-8,7-RhSB9H9 (1), [1,1-(PPh3)2-3-(Py)-closo-l,2-RhSB9H8] (2), and [ 1,1-(CO)(PPh3)-3-(Py)-closo- l,2-RhSB9H8] (4), where Py = Pyridine, with HCl to give the Cl-ligated clusters, [8,8-(Cl)-(PPh3)-9-(Py)-nido-8,7-RhSB9H9] (3) and [8,8,8-(Cl) (CO) (PPh3)-9-(Py)-nido-8,7-RhSB9H8] (5), have recently demonstrated the remarkable nido-to-closo redox flexibility and Afunctional character of this class of 11-vertex rhodathiaboranes. To get a sense of the scope of this chemistry, we report here the reactions of PR3-ligated analogues, [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSBH9], where PR3 = PMePh2 (6), or PPh3 and PMe3 (7); and [1,1-(PR3)2-3-(Py)-closo-1,2-RhSB9H8], where PR3 = PPh3 and PMe3 (8), PMe3 (9) or PMe2Ph (10), with HCl to give Cl-ligated clusters. The results demonstrate that in contrast to the PPh3-ligated compounds, 1, 2, and 3, the reactions with 6--10 are less selective, giving rise to the formation of mixtures that contain monophosphate species, [8,8-(Cl)(PR3)-9-(Py)-nido>-8,7-RhSB9H9], where PR3 = PMe3 (11), PMe2Ph (12), or PMePh2 (15), and bis-Ugated derivatives, [8,8,8-(cl)(PR3)2-9-(Py)-nido-8,7-RhSB9H9], where PR3 = PMe3 (13) or PMe2Ph (14). The {RhCl(PR3)}-containing compounds, 3, 11, 12, and 15, are formally unsaturated 12 skeletal electron pair (sep) clusters with mdo-structures. Density functional theory (DFT) calculations demonstrate that the nido-structure is more stable than the predicted closo-isomers. In addition, studies have been carried out that involve the reactivity of 3 with Lewis bases. Thus, it is reported that 3 interacts with MeCN in solution, and it reacts with CO and pyridine to give the corresponding Rh-L adducts, [8,8,8-(Cl)(L)(PPh3)-9-(Py)-nibp-8,7-RhSB9H9], where L = CO (5) or Py (20). On the other hand, the treatment of 3 and 5 with Proton Sponge (PS) promotes the abstraction of HCl, as [PSH]Cl, from the nido-clusters, and the regeneration of the parent closo-species, completing two new stoichiometric cycles that are driven by Bronsted acid/base chemistry. [ABSTRACT FROM AUTHOR]

The [8,8,8-(H)(PPh3)2-9-(Py)-nido-8,7-RhSB9H9] (2)/[1,1-(PPh3)2-3-(Py)-closo-1,2-RhSB9H8] (3) pair catalyzes the hydrogenationof olefins through nido-to-closotransformations. Substitution of the phosphine ligands can leadto an improvement of the catalytic activity of this system. Therefore,the substitutional chemistry of 2with PMePh2, PMe2Ph, and PMe3has been studied, leadingto the formation of [8,8,8-(H)(PPh3)(PR3)-9-(Py)-nido-8,7-RhSB9H9], where R3= Me2Ph (5) or Me3(6), and [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSB9H9], where R3= MePh2(4) or Me2Ph (7). Kineticstudies on the reaction of PMe2Ph with 2indicatethat the substitutions follow a dissociative mechanism. The thermaldehydrogenation of 5–7affords thecorresponding closo-derivatives [1,1-(L)(PPh3)-3-(Py)-closo-1,2-RhSB9H8], where L = PMe2Ph (9) or PMe3(10), and [1,1-(L)2-3-(Py)-closo-1,2-RhSB9H8], where L = PMe2Ph(11) or PMe3(12). The substitutionof PPh3by the more basic, less bulky phosphines facilitateshydrogen loss and consequent nido-to-closotransformations. The reaction of 5and 6with C2H4promotes a nido-to-closocluster change and the consequent formationof 10and 11together with small amountsof C2H4-ligated [1,1-(η2-C2H4)(L)-3-(Py)-closo-1,2-RhSB9H8], where L = PPh3(13) or PMe3(15), characterized insituby 1H NMR spectroscopy. In the reactionswith ethylene, ethane is detected in situ, indicatingthat the olefin is hydrogenated. The reactions of 5and 6with CO afford the CO-ligated [1,1-(CO)(L)-3-(Py)-closo-1,2-RhSB9H8], where L = PMe2Ph (16) or PMe3(17).The reactivity of the new PR3-ligated nido-clusters versus H2, C2H4, and COis not improved with the phosphines studied in this work; however,the changes found in the chemical beahavior of this system are dramatic,confirming the tailorability of these 11-vertex rhodathiaboranes andthe potential optimization of their catalytic activity by the judiciouschoice of the exo-polyhedral ligands. [ABSTRACT FROM AUTHOR]

Reversible H2cleavage promoted by closo to nido transformations of [1,1-(PPh3)2-3-(NC5H5)-closo-1,2-RhSB9H8] (2)/[8,8,8-(PPh3)2(H)-9-(NC5H5)-nido-8,7-RhSB9H9] (1) is a cooperative action with application in catalysis; the treatment of 2and [1,1-(PPh3)(CO)-3-(NC5H5)-closo-RhSB9H8] (3) with either HCl or HOTf in CH2Cl2affords the 11-vertex nido-rhodathiaboranes [8,8-(PPh3)(Cl)-9-(NC5H5)-nido-8,7-RhSB9H9] (4) and [8,8,8-(PPh3)(CO)(Cl)-9-(NC5H5)-nido-8,7-RhSB9H9] (5), respectively. In contrast, the reaction of 1with triflic acid yields the salt [8,8-(PPh3)2(H)-9-(NC5H5)-nido-RhSB9H10][OTf] (6). These results illustrate the bifunctional nature of the clusters and their nido to closo redox flexibility, which open new routes for the tuning of the reactivity of these polyhedral compounds and widen their potential applications. [ABSTRACT FROM AUTHOR]

The reaction of [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1) with PR3in a 1 : 2 ratio affords mixtures that contain the mono-substituted bis-PR3-ligated rhodathiaboranes [8,8-(PPh3)(L)-nido-8,7-RhSB9H10] [L = PMe2Ph (5), PMe3(6)] and the corresponding tris-PR3-ligated compounds [8,8,8-(L)3-nido-8,7-RhSB9H10] [L = PMe2Ph (7), PMe3(8)]. These latter species are more conveniently prepared from the reaction of 1with three equivalents of the monodentate phosphines, PMe2Ph and PMe3. Reaction between 1and PMePh2in a 1 : 2 ratio yields the disubstituted rhodathiaborane [8,8-(PMePh2)2-nido-8,7-RhSB9H10] (4), whereas the use of three equivalents of phosphine leads to the formation of B-ligated eleven-vertex [8,8,8-(PMePh2)2(H)-nido-8,7-RhSB9H9-9-(PMePh2)] (9). Compounds 4–9have been characterized by NMR spectroscopy, and the structures of 8and 9confirmed by X-ray diffraction analyses. The characterization of the cluster compounds has been aided by the use of DFT calculations on some of the species. Variable-temperature NMR studies have demonstrated a lability of the PMePh2ligands in compounds 4and 9, providing mechanistic insights about the ligand substitutional chemistry in these eleven-vertex rhodathiaboranes. [ABSTRACT FROM AUTHOR]

Metalation of 2,4,6-tri(methyl)phenol (MeArOH) and 2,6-di(tert-butyl)-4-methylphenol (BuArOH) with NaN(SiMe3)2 in toluene and in the presence of stoichiometric amounts of the polydentate amines N,N,N′,N′-tetramethylethylenediamine (TMEDA) and N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) affords three new sodium aryloxide complexes [Na(μ-OArBu)(TMEDA)]2 (3), [Na(μ-OArMe)(PMDETA)]2 (4), and [Na(OArBu)(PMDETA)] (5). Complexes 3 to 5 have been isolated as crystalline materials in reasonable yields and characterized in the solid state by X-ray crystallography and in solution by NMR spectroscopy. Complexes 3 to 5 and the related [tris(2-dimethylaminoethyl)amine] (Me6TREN) derivatives [Na(OArMe)(HOArMe)(Me6TREN)] (1) and [Na(OArBu)(Me6TREN)] (2), recently prepared in our group, are shown to be active as initiators for the ring-opening polymerization (ROP) of rac-lactide with benzyl alcohol as a co-initiator. However, during the course of the polymerization reactions intrachain and stereorandom transesterification side-reactions were observed under some of the experimental conditions tested. [ABSTRACT FROM AUTHOR]

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive liver fat deposition in the absence of significant alcohol intake. Since extra virgin olive oil (EVOO) reduces fat accumulation, we analyzed the involvement of nitro-fatty acids (NO2-FA) on the beneficial effects of EVOO consumption on NAFLD. Nitro-fatty acids formation was observed during digestion in mice supplemented with EVOO and nitrite. Mice fed with a high-fat diet (HF) presented lower plasma NO2-FA levels than normal chow, and circulating concentrations recovered when the HF diet was supplemented with 10% EVOO plus nitrite. Under NO2-FA formation conditions, liver hemoxygenase-1 expression significantly increased while decreased body weight and fat liver accumulation. Mitochondrial dysfunction plays a central role in the pathogenesis of NAFLD while NO2-FA has been shown to protect from mitochondrial oxidative damage. Accordingly, an improvement of respiratory indexes was observed when mice were supplemented with both EVOO plus nitrite. Liver mitochondrial complexes II and V activities were greater in mice with EVOO supplementation and further improved in the presence of nitrite. Overall, our results strongly suggest a positive correlation between NO2-OA formation from EVOO and the observed improvement of mitochondrial function in NAFLD. The formation of NO2-FA can account for the health benefits associated with EVOO consumption. [ABSTRACT FROM AUTHOR]

A new mechanism of H2 activation is reported to occur on a carbene-ligated rhodathiaborane that features metal–thiaborane bifunctional synergistic effects. The key is the creation of vacant coordination sites by an isonido-nido structural transformation leading to the heterolytic H–H bond splitting. [ABSTRACT FROM AUTHOR]

Extra Virgin Olive oil (EVOO) consumption exerts beneficial health effects. Nitro-fatty acids (NO 2 -FA) are endogenously formed in EVOO as well as in gastric conditions, exhibiting pleiotropic anti-inflammatory responses. In this review, we analyzed the conditions that favor the formation of EVOO-derived NO 2 -FA. Firstly, will discuss the formation of NO 2 -FA in contrasting varieties of EVOO and the relationship between the formation of NO 2 -FA and the type of cultivar. Also, the variation of NO 2 -FA levels with the stage of maturation will be discussed. It should be considered that EVOO has other key bioactive components such as polyphenols. We will discuss how polyphenols play a role in modulating NO 2 -FA formation and how all these components would be acting synergistically to exert antioxidant/anti-inflammatory protection. Finally, will discuss how EVOO supplementation is capable of improving cellular respiration in mitochondria from liver disease, mainly due to the presence of NO 2 -FA. Updated data collection strongly supports the proposal of NO 2 -FA as novel EVOO quality markers. The information reviewed here can be useful to make recommendations about which cultivars to use and at what stages of maturation the oil should be extracted to maximize the concentration of these compounds that are so beneficial to human health after consumption. • Endogenous presence of nitro-fatty acids in virgin olive oil and olives. • Gastric conditions reveals additional production of nitro-fatty acids in olive oil. • The presence of polyphenols promotes olive oil fatty acid nitration. • Nitro-fatty acids account for health benefits associated with olive oil consumption. [ABSTRACT FROM AUTHOR]

The influence on the stability of Lactobacillus plantarum CECT 220 (25 °C/60% relative humidity) of microencapsulation by simple coacervation followed by spray-drying using different Ca2+-to-soybean protein isolate ratios was evaluated. After optimisation, the selected soybean protein concentrate (SPC) microparticles were used to evaluate the tolerance of L. plantarum under acidic conditions (lactic acid, pH = 4; and HCl, pH = 3) and heat stress (80 °C for 1 min) in contrast to free cells. Moreover, after the heat treatment, the influence of the simulated gastric fluid was evaluated. Additionally, different foods were formulated using either microencapsulated or freeze-dried L. plantarum, and the stability of cells during the shelf-life of the formulated foods was studied. Results show that encapsulation with SPC enhanced significantly the stability of the Lactic Acid Bacteria all along the probiotic food value chain, from production to the end of the food shelf-life. [ABSTRACT FROM AUTHOR]

Nitro-fatty acids (NO 2 -FAs) are formed from the reaction between nitrogen dioxide ( NO 2 ) and mono and polyunsaturated fatty acids. Knowledge concerning NO 2 -FAs has significantly increased within a few years ago and the beneficial actions of these species uncovered in animal systems have led to consider them as molecules with therapeutic potential. Based on their nature and structure, NO 2 -FAs have the ability to release nitric oxide ( NO) in aqueous environments and the capacity to mediate post-translational modifications (PTM) by nitroalkylation. Recently, based on the potential of these NO-derived molecules in the animal field, the endogenous occurrence of nitrated-derivatives of linolenic acid (NO 2 -Ln) was assessed in plant species. Moreover and through RNA-seq technology, it was shown that NO 2 -Ln can induce a large set of heat-shock proteins (HSPs) and different antioxidant systems suggesting this molecule may launch antioxidant and defence responses in plants. Furthermore, the capacity of this nitro-fatty acid to release NO has also been demonstrated. In view of this background, here we offer an overview on the biological properties described for NO 2 -FAs in plants and the potential of these molecules to be considered new key intermediaries of NO metabolism in the plant field. [ABSTRACT FROM AUTHOR]

The article presents chemical equations related to the article "Copper-Catalyzed Conjugate Addition of Grignard Reagents to 2-Methylcyclopentenone and Sequential Enolate Alkylation" by B.C. Calvo and others, published in the periodical "Advanced Synthesis and Catalysis" in 2014.

Mainly with the purpose of recreation and sharing an identity, the number of teenagers who use social networks has increased substantially in recent years. In this context however, teenagers represent a vulnerable group because of their limited ability of self-regulation and their high susceptibility to peer pressure. Objective. The aim of the present paper was to review the scientific literature on the analysis of negative influences of the use of social networks by both teenagers and young adults on their health-related lifestyles. To this end, a bibliographic tracking and analysis in several databases was conducted. These sources included: PubMed / Medline, ScienceDirect, SciELO, Cuiden, Psicodoc, Dialnet, and Cochrane Library data. After refining search procedures, a final total of 44 studies were selected for analysis, including eight additional articles from the published articles references. Results revealed negative consequences that affect sleep patterns, eating habits, socialization, and even addiction to social networks, and a propensity to facilitate contact with illegal drugs. The authors conclude that is necessary for health professionals to design and implement strategies aimed at preventing misuse of social networks so as to promote health in the context of families and education. The promotion of alternative activities and other hobbies, as well as stimulating face to face communications, and better uses of social networks is strongly suggested. [ABSTRACT FROM AUTHOR]

We aimed to assess the feasibility of TESTA'T COVID strategy among healthcare and education professionals.in Spain during the peak of the 6th wave caused by Omicron variant. Kits were ordered online and sent by mail, participants answered an online acceptability/usability survey and uploaded the picture of results. 492 participants ordered a test, 304 uploaded the picture (61.8%). Eighteen positive cases were detected (5.9%). 92.2% were satisfied/very satisfied with the intervention; and 92.5% found performing the test easy/very easy. We demonstrated that implementing online COVID-19 self-testing in schools and healthcare settings in Spain is feasible. [ABSTRACT FROM AUTHOR]

Background: S-nitrosylaton is implicated in the regulation of numerous signaling pathways with a diversity of regulatory roles. The high lability of the S-NO bond makes the study of proteins regulated by S-nitrosylation/ denitrosylation a challenging task and most studies have focused on already S-nitrosylated proteins. We hypothesize that: i) S-nitrosoglutathione (GSNO) transnitrosylation is a feasible mechanism to account for the physiological S-nitrosylation of rather electropositive sulfur atoms from proteins, ii) affinity chromatography is a suitable approach to isolate proteins that are prone to undergo S-transnitrosylation and iii) vinyl sulfone silica is a suitable chromatographic bead. Results: The combination of vinyl sulfone silica with GSNO yielded an affinity resin that withstood high ionic strength without shrinking or deforming and that it was suitable to isolate potential GSNO transnitrosylation target candidates. Fractions eluted at 1500 mM NaCl resulted in a symmetrical peak for both, protein and S-nitrosothiols, supporting the idea of transnitrosylation by GSNO as a selective process that involves strong and specific interactions with the target protein. Proteomic analysis led to the identification of 22 physiological significant enzymes that differ with the tissue analyzed, being regulatory proteins the most abundant group in hypocotyls. The identification of chloroplastidic FBPase, proteasome, GTP-binding protein, heat shock Hsp70, syntaxin, catalase I, thioredoxin peroxidase and cytochrome P450 that have already been reported as S-nitrosylated by other techniques can be considered as internal positive controls that validate our experimental approach. An additional validation was provided by the prediction of the S-nitrosylation sites in 19 of the GSNO transnitrosylation target candidates. Conclusions: Vinyl sulfone silica is an open immobilization support that can be turned ad hoc and in a straightforward manner into an affinity resin. Its potential in omic sciences was successfully put to test in the context of the analysis of post-translational modification by S-nitrosylation with two different tissues: mature pea leaves and embryogenic sunflower hypocotyls. The identified proteins reveal an intriguing overlap among S-nitrosylation and both tyrosine nitration and thioredoxin regulation. Chloroplastidic FBPase is a paradigm of such overlap of post-translational modifications since it is reversible modified by thioredoxin and S-nitrosylation and irreversibly by tyrosine nitration. Our results suggest a complex interrelation among different modulation mechanisms mediated by NO-derived molecules [ABSTRACT FROM AUTHOR]

Protein tyrosine nitration is a post-translational modification mediated by reactive nitrogen species (RNS) that is associated with nitro-oxidative damage. No information about this process is available in relation to higher plants during development and senescence. Using pea plants at different developmental stages (ranging from 8 to 71 days), tyrosine nitration in the main organs (roots, stems, leaves, flowers, and fruits) was analysed using immunological and proteomic approaches. In the roots of 71-day-old senescent plants, nitroproteome analysis enabled the identification a total of 16 nitrotyrosine-immunopositive proteins. Among the proteins identified, NADP-isocitrate dehydrogenase (ICDH), an enzyme involved in the carbon and nitrogen metabolism, redox regulation, and responses to oxidative stress, was selected to evaluate the effect of nitration. NADP-ICDH activity fell by 75% during senescence. Analysis showed that peroxynitrite inhibits recombinant cytosolic NADP-ICDH activity through a process of nitration. Of the 12 tyrosines present in this enzyme, mass spectrometric analysis of nitrated recombinant cytosolic NADP-ICDH enabled this study to identify the Tyr392 as exclusively nitrated by peroxynitrite. The data as a whole reveal that protein tyrosine nitration is a nitric oxide-derived PTM prevalent throughout root development and intensifies during senescence. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) has emerged as an essential biological messenger in plant biology that usually transmits its bioactivity by post-translational modifications such as S-nitrosylation, the reversible addition of an NO group to a protein cysteine residue leading to S-nitrosothiols (SNOs). In recent years, SNOs have risen as key signalling molecules mainly involved in plant response to stress. Chief among SNOs is S-nitrosoglutathione (GSNO), generated by S-nitrosylation of the key antioxidant glutathione (GSH). GSNO is considered the major NO reservoir and a phloem mobile signal that confers to NO the capacity to be a long-distance signalling molecule. GSNO is able to regulate protein function and gene expression, resulting in a key role for GSNO in fundamental processes in plants, such as development and response to a wide range of environmental stresses. In addition, GSNO is also able to regulate the total SNO pool and, consequently, it could be considered the storage of NO in cells that may control NO signalling under basal and stress-related responses. Thus, GSNO function could be crucial during plant response to environmental stresses. Besides the importance of GSNO in plant biology, its mode of action has not been widely discussed in the literature. In this review, we will first discuss the GSNO turnover in cells and secondly the role of GSNO as a mediator of physiological and stress-related processes in plants, highlighting those aspects for which there is still some controversy. [ABSTRACT FROM AUTHOR]

Peroxisomes are subcellular organelles characterized by a simple morphological structure but have a complex biochemical machinery involved in signaling processes through molecules such as hydrogen peroxide (HO) and nitric oxide (NO). Nicotinamide adenine dinucleotide phosphate (NADPH) is an essential component in cell redox homeostasis, and its regeneration is critical for reductive biosynthesis and detoxification pathways. Plants have several NADPH-generating dehydrogenases, with NADP-isocitrate dehydrogenase (NADP-ICDH) being one of these enzymes. Arabidopsis contains three genes that encode for cytosolic, mitochondrial/chloroplastic, and peroxisomal NADP-ICDH isozymes although the specific function of each of these remains largely unknown. Using two T-DNA insertion lines of the peroxisomal NADP-ICDH designated as picdh-1 and picdh-2, the data show that the peroxisomal NADP-ICDH is involved in stomatal movements, suggesting that peroxisomes are a new element in the signaling network of guard cells. [ABSTRACT FROM AUTHOR]

S-Nitrosothiols (SNOs) is a family of nitric oxide (NO)-derived molecules resulting from NO binding to sulphhydryl (-SH) groups present in specific cysteine residues of peptides and proteins. This redox modification is reversible and is regarded as a cellular mechanism to extend the physiological function of NO. SNOs are classified as having either low or high molecular mass, with S-nitrosoglutathione and proteins being the most commonly studied, respectively. This article provides an overview of the importance of SNOs, especially in stress situations where NO content appears to be unaffected or even downregulated, with SNOs being responsible for the generation of nitrooxidative stress under these stress conditions. [ABSTRACT FROM AUTHOR]

Extra virgin olive oil (EVOO) and olives, key sources of unsaturated fatty acids in the Mediterranean diet, provide health benefits to humans. Nitric oxide (•NO) and nitrite (NO2−)-dependent reactions of unsaturated fatty acids yield electrophilic nitroalkene derivatives (NO2-FA) that manifest salutary pleiotropic cell signaling responses in mammals. Herein, the endogenous presence of NO2-FA in both EVOO and fresh olives was demonstrated by mass spectrometry. The electrophilic nature of these species was affirmed by the detection of significant levels of protein cysteine adducts of nitro-oleic acid (NO2-OA-cysteine) in fresh olives, especially in the peel. Further nitration of EVOO by NO2− under acidic gastric digestive conditions revealed that human consumption of olive lipids will produce additional nitro-conjugated linoleic acid (NO2-cLA) and nitro-oleic acid (NO2-OA). The presence of free and protein-adducted NO2-FA in both mammalian and plant lipids further affirm a role for these species as signaling mediators. Since NO2-FA instigate adaptive anti-inflammatory gene expression and metabolic responses, these redox-derived metabolites may contribute to the cardiovascular benefits associated with the Mediterranean diet. [ABSTRACT FROM AUTHOR]

Abstract: Background: Protein tyrosine nitration is a post-translational modification (PTM) mediated by nitric oxide-derived molecules. Peroxisomes are oxidative organelles in which the presence of nitric oxide (NO) has been reported. Methods: We studied peroxisomal nitroproteome of pea leaves by high-performance liquid chromatography with tandem mass spectrometry (LC–MS/MS) and proteomic approaches. Results: Proteomic analysis of peroxisomes from pea leaves detected a total of four nitro-tyrosine immunopositive proteins by using an antibody against nitrotyrosine. One of these proteins was found to be the NADH-dependent hydroxypyruvate reductase (HPR). The in vitro nitration of peroxisomal samples caused a 65% inhibition of HPR activity. Analysis of recombinant peroxisomal NADH-dependent HPR1 activity from Arabidopsis in the presence of H2O2, NO, GSH and peroxynitrite showed that the ONOO− molecule caused the highest inhibition of activity (51% at 5mM SIN-1), with 5mM H2O2 having no inhibitory effect. Mass spectrometric analysis of the nitrated recombinant HPR1 enabled us to determine that, among the eleven tyrosine present in this enzyme, only Tyr-97, Tyr-108 and Tyr-198 were exclusively nitrated to 3-nitrotyrosine by peroxynitrite. Site-directed mutagenesis confirmed Tyr198 as the primary site of nitration responsible for the inhibition on the enzymatic activity by peroxynitrite. Conclusion: These findings suggest that peroxisomal HPR is a target of peroxynitrite which provokes a loss of function. General significance: This is the first report demonstrating the peroxisomal NADH-dependent HPR activity involved in the photorespiration pathway is regulated by tyrosine nitration, indicating that peroxisomal NO metabolism may contribute to the regulation of physiological processes under no-stress conditions. [Copyright &y& Elsevier]

Abstract: Protein tyrosine nitration is a post-translational modification (PTM) mediated by reactive nitrogen species (RNS) and it is a new area of research in higher plants. Previously, it was demonstrated that the exposition of sunflower (Helianthus annuus L.) seedlings to high temperature (HT) caused both oxidative and nitrosative stress. The nitroproteome analysis under this stress condition showed the induction of 13 tyrosine-nitrated proteins being the carbonic anhydrase (CA) one of these proteins. The analysis of CA activity under high temperature showed that this stress inhibited the CA activity by a 43%. To evaluate the effect of nitration on the CA activity in sunflower it was used 3-morpholinosydnonimine (SIN-1) (peroxynitrite donor) as the nitrating agent. Thus the CA activity was inhibited by 41%. In silico analysis of the pea CA protein sequence suggests that Tyr205 is the most likely potential target for nitration. [Copyright &y& Elsevier]

In this work, a method for the determination of trace nitrotyrosine (NOTyr) and tyrosine (Tyr) in Arabidopsis thaliana cell cultures is proposed. Due to the complexity of the resulting extracts after protein precipitation and enzymatic digestion and the strong electrospray signal suppression displayed in the detection of both Tyr and NOTyr from raw A. thaliana cell culture extracts, a straightforward sample cleanup step was proposed. It was based on the use of mixed-mode solid-phase extraction (SPE) using MCX-type cartridges (Strata™-X-C), prior to identification and quantitation using fast liquid chromatography-electrospray time-of-flight mass spectrometry. Unambiguous confirmation of both amino acids was accomplished with accurate mass measurements (with errors lower than 2 ppm) of each protonated molecule along with a characteristic fragment ion for each species. Recovery studies were accomplished to evaluate the performance of the SPE sample preparation step obtaining average recoveries in the range 92-101 %. Limit of quantitation obtained for NOTyr in A. thaliana extracts was 3 nmol L. Finally, the proposed method was applied to evaluate stress conditions of the plant upon different concentrations of peroxynitrite, a protein-nitrating compound, which induces the nitration of Tyr at the nanomolar range. Detection and confirmation of the compounds demonstrated the usefulness of the proposed approach. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

ABSTRACT High temperature (HT) is considered a major abiotic stress that negatively affects both vegetative and reproductive growth. Whereas the metabolism of reactive oxygen species (ROS) is well established under HT, less is known about the metabolism of reactive nitrogen species (RNS). In sunflower ( Helianthus annuus L.) seedlings exposed to HT, NO content as well as S-nitrosoglutathione reductase (GSNOR) activity and expression were down-regulated with the simultaneous accumulation of total S-nitrosothiols (SNOs) including S-nitrosoglutathione (GSNO). However, the content of tyrosine nitration (NO2-Tyr) studied by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) and by confocal laser scanning microscope was induced. Nitroproteome analysis under HT showed that this stress induced the protein expression of 13 tyrosine-nitrated proteins. Among the induced proteins, ferredoxin-NADP reductase (FNR) was selected to evaluate the effect of nitration on its activity after heat stress and in vitro conditions using 3-morpholinosydnonimine (SIN-1) (peroxynitrite donor) as the nitrating agent, the FNR activity being inhibited. Taken together, these results suggest that HT augments SNOs, which appear to mediate protein tyrosine nitration, inhibiting FNR, which is involved in the photosynthesis process. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) and related molecules such as peroxynitrite, S-nitrosoglutathione (GSNO), and nitrotyrosine, among others, are involved in physiological processes as well in the mechanisms of response to stress conditions. In sunflower seedlings exposed to five different adverse environmental conditions (low temperature, mechanical wounding, high light intensity, continuous light, and continuous darkness), key components of the metabolism of reactive nitrogen species (RNS) and reactive oxygen species (ROS), including the enzyme activities L-arginine-dependent nitric oxide synthase (NOS), S-nitrosogluthathione reductase (GSNOR), nitrate reductase (NR), catalase, and superoxide dismutase, the content of lipid hydroperoxide, hydrogen peroxide, S-nitrosothiols (SNOs), the cellular level of NO, GSNO, and GSNOR, and protein tyrosine nitration [nitrotyrosine (NO2-Tyr)] were analysed. Among the stress conditions studied, mechanical wounding was the only one that caused a down-regulation of NOS and GSNOR activities, which in turn provoked an accumulation of SNOs. The analyses of the cellular content of NO, GSNO, GSNOR, and NO2-Tyr by confocal laser scanning microscopy confirmed these biochemical data. Therefore, it is proposed that mechanical wounding triggers the accumulation of SNOs, specifically GSNO, due to a down-regulation of GSNOR activity, while NO2-Tyr increases. Consequently a process of nitrosative stress is induced in sunflower seedlings and SNOs constitute a new wound signal in plants. [ABSTRACT FROM PUBLISHER]

Background: Freshwater planarians are an attractive model for regeneration and stem cell research and have become a promising tool in the field of regenerative medicine. With the availability of a sequenced planarian genome, the recent application of modern genetic and high-throughput tools has resulted in revitalized interest in these animals, long known for their amazing regenerative capabilities, which enable them to regrow even a new head after decapitation. However, a detailed description of the planarian transcriptome is essential for future investigation into regenerative processes using planarians as a model system. Results: In order to complement and improve existing gene annotations, we used a 454 pyrosequencing approach to analyze the transcriptome of the planarian species Schmidtea mediterranea Altogether, 598,435 454- sequencing reads, with an average length of 327 bp, were assembled together with the ∼10,000 sequences of the S. mediterranea UniGene set using different similarity cutoffs. The assembly was then mapped onto the current genome data. Remarkably, our Smed454 dataset contains more than 3 million novel transcribed nucleotides sequenced for the first time. A descriptive analysis of planarian splice sites was conducted on those Smed454 contigs that mapped univocally to the current genome assembly. Sequence analysis allowed us to identify genes encoding putative proteins with defined structural properties, such as transmembrane domains. Moreover, we annotated the Smed454 dataset using Gene Ontology, and identified putative homologues of several gene families that may play a key role during regeneration, such as neurotransmitter and hormone receptors, homeoboxcontaining genes, and genes related to eye function. Conclusions: We report the first planarian transcript dataset, Smed454, as an open resource tool that can be accessed via a web interface. Smed454 contains significant novel sequence information about most expressed genes of S. mediterranea. Analysis of the annotated data promises to contribute to identification of gene families poorly characterized at a functional level. The Smed454 transcriptome data will assist in the molecular characterization of S. mediterranea as a model organism, which will be useful to a broad scientific community. [ABSTRACT FROM AUTHOR]

Tyrosine nitration is recognized as an important post-translational protein modification in animal cells that can be used as an indicator of a nitrosative process. However, in plant systems, there is scant information on proteins that undergo this process. In sunflower hypocotyls, the content of tyrosine nitration (NO2-Tyr) and the identification of nitrated proteins were studied by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) and proteomic approaches, respectively. In addition, the cell localization of nitrotyrosine proteins and peroxynitrite were analysed by confocal laser-scanning microscopy (CLSM) using antibodies against 3-nitrotyrosine and 3′-(p-aminophenyl) fluorescein (APF) as the fluorescent probe, in that order. The concentration of Tyr and NO2-Tyr in hypocotyls was 0.56 μmol mg−1 protein and 0.19 pmol mg−1 protein, respectively. By proteomic analysis, a total of 21 nitrotyrosine-immunopositive proteins were identified. These targets include proteins involved in photosynthesis, and in antioxidant, ATP, carbohydrate, and nitrogen metabolism. Among the proteins identified, S-adenosyl homocysteine hydrolase (SAHH) was selected as a model to evaluate the effect of nitration on SAHH activity using SIN-1 (a peroxynitrite donor) as the nitrating agent. When the hypocotyl extracts were exposed to 0.5 mM, 1 mM, and 5 mM SIN-1, the SAHH activity was inhibited by some 49%, 89%, and 94%, respectively. In silico analysis of the barley SAHH sequence, characterized Tyr448 as the most likely potential target for nitration. In summary, the present data are the first in plants concerning the content of nitrotyrosine and the identification of candidates of protein nitration. Taken together, the results suggest that Tyr nitration occurs in plant tissues under physiological conditions that could constitute an important process of protein regulation in such a way that, when it is overproduced in adverse circumstances, it can be used as a marker of nitrosative stress. [ABSTRACT FROM PUBLISHER]