scholarly journals Quinones and hydroxyquinones as generators and quenchers of singlet molecular oxygen

1997 ◽  
Vol 75 (4) ◽  
pp. 423-428 ◽  
Author(s):  
Isela Gutiérrez ◽  
Sonia G. Bertolotti ◽  
M.A. Biasutti ◽  
Arnaldo T. Soltermann ◽  
Norman A. García
Keyword(s):  
Oxygen Species ◽  
Type Ii ◽  
Carbonyl Groups ◽  
Quenching Mechanism ◽  
Singlet Molecular Oxygen ◽  
Dye Sensitized ◽  
Quenching Process ◽  
First Time ◽  
Excited Oxygen

The role of quinones and hydroxyquinones as sensitizers and as quenchers in Type II photooxygenations has been examined. The second aspect is discussed here, through a systematic study, for the first time in the open literature. Quinonic compounds are excellent generators of O2(1Δg) in aprotic solvents (excluding those quinones possessing substituents in positions adjacent to the carbonyl groups, in the case of anthraquinone derivatives). Benzoquinones, anthraquinones, and hydroxy derivatives are good O2(1Δg) quenchers upon dye-sensitized photoirradiation. The excited oxygen species is deactivated with rate constants in the range 106–107 M−1 s−1 depending on the solvent employed. The quenching process deactivates O2(1Δg) without further destruction of the quinone. The main interaction with O2(1Δg) is driven by the quinone moiety, in spite of the presence of potentially active nuclear substituents. The quenching mechanism could involve a reversible charge transfer intermediate, with the quinonic compound acting as an electron donor. Keywords: photooxidation, quenching, quinones, rose bengal, singlet oxygen.

scholarly journals Type II Secretion-Dependent Aminopeptidase LapA and Acyltransferase PlaC Are Redundant for Nutrient Acquisition duringLegionella pneumophilaIntracellular Infection of Amoebas

mBio ◽  
2018 ◽  
Vol 9 (2) ◽  
pp. e00528-18 ◽  
Author(s):  
Richard C. White ◽  
Felizza F. Gunderson ◽  
Jessica Y. Tyson ◽  
Katherine H. Richardson ◽  
Theo J. Portlock ◽  
...  
Keyword(s):  
Amino Acids ◽  
Substrate Specificity ◽  
Transcriptional Analysis ◽  
Type Ii Secretion ◽  
Major Advance ◽  
Type Ii ◽  
Content Type ◽  
Broad Substrate Specificity ◽  
First Time

ABSTRACTLegionella pneumophilagenes encoding LapA, LapB, and PlaC were identified as the most highly upregulated type II secretion (T2S) genes during infection ofAcanthamoeba castellanii, although these genes had been considered dispensable on the basis of the behavior of mutants lacking eitherlapAandlapBorplaC. AplaCmutant showed even higher levels oflapAandlapBtranscripts, and alapA lapBmutant showed heightening ofplaCmRNA levels, suggesting that the role of the LapA/B aminopeptidase is compensatory with respect to that of the PlaC acyltransferase. Hence, we made double mutants and found thatlapA plaCmutants have an ~50-fold defect during infection ofA. castellanii. These data revealed, for the first time, the importance of LapA in any sort of infection; thus, we purified LapA and defined its crystal structure, activation by another T2S-dependent protease (ProA), and broad substrate specificity. When the amoebal infection medium was supplemented with amino acids, the defect of thelapA plaCmutant was reversed, implying that LapA generates amino acids for nutrition. Since the LapA and PlaC data did not fully explain the role of T2S in infection, we identified, via proteomic analysis, a novel secreted protein (NttD) that promotes infection ofA. castellanii. AlapA plaC nttDmutant displayed an even greater (100-fold) defect, demonstrating that the LapA, PlaC, and NttD data explain, to a significant degree, the importance of T2S. LapA-, PlaC-, and NttD-like proteins had distinct distribution patterns within and outside theLegionellagenus. LapA was notable for having as its closest homologue anA. castellaniiprotein.IMPORTANCETransmission ofL. pneumophilato humans is facilitated by its ability to grow inAcanthamoebaspecies. We previously documented that type II secretion (T2S) promotesL. pneumophilainfection ofA. castellanii. Utilizing transcriptional analysis and proteomics, double and triple mutants, and crystal structures, we defined three secreted substrates/effectors that largely clarify the role of T2S during infection ofA. castellanii. Particularly interesting are the unique functional overlap between an acyltransferase (PlaC) and aminopeptidase (LapA), the broad substrate specificity and eukaryotic-protein-like character of LapA, and the novelty of NttD. Linking LapA to amino acid acquisition, we defined, for the first time, the importance of secreted aminopeptidases in intracellular infection. Bioinformatic investigation, not previously applied to T2S, revealed that effectors originate from diverse sources and distribute within theLegionellagenus in unique ways. The results of this study represent a major advance in understandingLegionellaecology and pathogenesis, bacterial secretion, and the evolution of intracellular parasitism.

The role of various oxygen species in Mn-based layered double hydroxide catalysts in selective alcohol oxidation

2017 ◽  
Vol 7 (19) ◽  
pp. 4361-4365 ◽  
Author(s):  
Yiyun Du ◽  
Qian Wang ◽  
Xiao Liang ◽  
Pengfei Yang ◽  
Yufei He ◽  
...  
Keyword(s):  
Layered Double Hydroxide ◽  
Alcohol Oxidation ◽  
Oxygen Species ◽  
Precise Identification ◽  
Double Hydroxide ◽  
First Time

Precise identification of oxygen species in LDH-based catalysts was investigated for the first time for alcohol oxidation.

Parvalbumin is overexpressed in the late phase of pharmacological preconditioning in skeletal muscle

2013 ◽  
Vol 91 (11) ◽  
pp. 966-972
Author(s):  
Rosario Solis ◽  
Elba D. Carrillo ◽  
Ascención Hernández ◽  
María C. García ◽  
Jorge A. Sánchez
Keyword(s):  
Skeletal Muscle ◽  
Adult Mouse ◽  
Late Phase ◽  
Oxygen Species ◽  
Partial Protection ◽  
Intracellular Ca ◽  
Ros Scavenger ◽  
First Time ◽  
Pharmacological Preconditioning

Pharmacological preconditioning (PPC) with mitochondrial ATP-sensitive K+ channel openers such as diazoxide, provides protection against ischemia in cardiac muscle, skeletal muscle, and other tissues. Effects on Ca2+ homeostasis during the late phase of PPC have been described in cardiomyocytes, but no information is available regarding intracellular Ca2+ changes in skeletal muscle fibers during late PPC. Intracellular Ca2+ signals were measured in single fibers of adult mouse skeletal muscle, with fluorescent probes, 48 h after the administration of diazoxide. Parvalbumin levels in the myofibers were quantitated by Western blot. Diazoxide induction of late PPC was confirmed by partial protection of muscles from peroxide-induced damage. Late PPC was associated with a significant decrease in the duration of Ca2+ signals during single twitches and tetanus with no changes in peak values. This effect was prevented by the reactive oxygen species (ROS) scavenger tiron. Late PPC was accompanied by a 30% increase in parvalbumin levels, and this effect was also blocked by tiron. Our data show, for the first time, a role of parvalbumin in late PPC in skeletal muscle.

scholarly journals Can aluminum, a non-redox metal, alter the thermodynamics of key biological redox processes? The DPPH-QH 2 radical scavenging reaction as a test case.

2021 ◽  
Author(s):  
Jose Lanuza ◽  
Veronica Postils ◽  
Xabier Lopez
Keyword(s):  
Radical Scavenging ◽  
Test Case ◽  
Redox Processes ◽  
Oxygen Species ◽  
Redox Potentials ◽  
Oxidation Potentials ◽  
Living Organisms ◽  
Experimental Findings ◽  
First Time

The increased bioavailability of aluminum has led to a concern about its toxicity on living systems. Among the most important toxic effects, it has been proven that aluminum increases oxidative stress in biological systems, a controversial fact, however, due to its non-redox nature. In the present work, we characterize in detail how aluminum can alter redox equilibriums by analyzing its effects on the thermodynamics of the redox scavenging reaction between DPPH . , a radical compound often used as a reactive oxygen species model, and hydroquinones, a potent natural antioxidant. For the first time, theoretical and experimental redox potentials within aluminum biochemistry are directly compared. Our results fully agree with experimental reduction and oxidation potentials, unequivocally revealing how aluminum alters the spontaneity of the reaction by stabilizing the reduction of DPPH· to DPPH − and promoting a proton transfer to the diazine moiety, leading to the production of a DPPH-H species. The capability of aluminum to modify redox potentials shown here confirms previous experimental findings on the role of aluminum to interfere with free radical scavenging reactions, affecting the natural redox processes of living organisms.

scholarly journals Trehalose and trehalose-6-phosphate induce stomatal movements and interfere with ABA-induced stomatal closure in grapevine

OENO One ◽  
2015 ◽  
Vol 49 (3) ◽  
pp. 165 ◽  
Author(s):  
Magdalena Gamm ◽  
Marie-Claire Héloir ◽  
Marielle Adrian
Keyword(s):  
Stomatal Closure ◽  
Guard Cells ◽  
Oxygen Species ◽  
Light Conditions ◽  
Whole Plant ◽  
Low Concentrations ◽  
Stomatal Movements ◽  
Plant Level ◽  
First Time

<p style="text-align: justify;"><strong>Aims</strong>: The effects of trehalose and trehalose-6-phosphate (T6P), among other sugars, were assessed on grapevine stomatal movements.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Epidermal peels were used to assess the effects of sugars. Low concentrations of trehalose and T6P (1 µM) induced an osmotic-independent reduction of the stomatal aperture in light conditions. Furthermore, ABA-induced stomatal closure was reduced by sugar application in association with lower accumulation of reactive oxygen species in guard cells. Similar effects, although weaker, were observed in response to the disaccharides sucrose and maltose, but not in response to the monosaccharides fructose and glucose.</p><p style="text-align: justify;"><strong>Conclusion</strong>: This study clearly highlights the effects of sugars, especially trehalose and T6P, on grapevine stomatal movements.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: This is the first time that such effects are described in grapevine and the results obtained provide new insights about the role of sugars on stomatal regulation at the whole plant level.</p>

scholarly journals Intracellular Redox-Balance Involvement in Temozolomide Resistance-Related Molecular Mechanisms in Glioblastoma

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1315 ◽  
Author(s):  
Alessia Lo Dico ◽  
Daniela Salvatore ◽  
Cristina Martelli ◽  
Dario Ronchi ◽  
Cecilia Diceglie ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Molecular Mechanisms ◽  
Redox Balance ◽  
Oxygen Species ◽  
Cytotoxic Effects ◽  
Mitochondrial Ros ◽  
Resistance Fluctuations ◽  
First Time ◽  
Chaperone Mediated Autophagy

Glioblastoma (GBM) is the most common astrocytic-derived brain tumor in adults, characterized by a poor prognosis mainly due to the resistance to the available therapy. The study of mitochondria-derived oxidative stress, and of the biological events that orbit around it, might help in the comprehension of the molecular mechanisms at the base of GBM responsiveness to Temozolomide (TMZ). Sensitive and resistant GBM cells were used to test the role of mitochondrial ROS release in TMZ-resistance. Chaperone-Mediated Autophagy (CMA) activation in relation to reactive oxygen species (ROS) release has been measured by monitoring the expression of specific genes. Treatments with H2O2 were used to test their potential in reverting resistance. Fluctuations of cytoplasmic ROS levels were accountable for CMA induction and cytotoxic effects observed in TMZ sensitive cells after treatment. On the other hand, in resistant cells, TMZ failed in producing an increase in cytoplasmic ROS levels and CMA activation, preventing GBM cell toxicity. By increasing oxidative stress, CMA activation was recovered, as also cell cytotoxicity, especially in combination with TMZ treatment. Herein, for the first time, it is shown the relation between mitochondrial ROS release, CMA activation and TMZ-responsiveness in GBM.

scholarly journals Oxidative Stress in Cutaneous Lichen Planus—A Narrative Review

2021 ◽  
Vol 10 (12) ◽  
pp. 2692
Author(s):  
Simona Roxana Georgescu ◽  
Cristina Iulia Mitran ◽  
Madalina Irina Mitran ◽  
Ilinca Nicolae ◽  
Clara Matei ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Lichen Planus ◽  
Inflammatory Infiltrate ◽  
Skin Lesions ◽  
Skin Condition ◽  
Oxygen Species ◽  
Immune Mediated ◽  
Induce Cell Apoptosis ◽  
First Time

Lichen planus (LP) is a chronic, immune-mediated inflammatory skin condition that mainly affects the skin (cutaneous LP, CLP) and oral mucosa (oral LP, OLP). However, the mechanisms involved in the pathogenesis of the disease are not fully elucidated. Over time, several theories that could explain the appearance of LP lesions have been postulated. The key players in LP pathogenesis are the inflammatory infiltrate consisting of T cells and the proinflammatory cytokines. The cytokines stimulate the production of reactive oxygen species that induce cell apoptosis, a defining element encountered in LP. The lead inquiry triggered by this revolves around the role of oxidative stress in LP development. There are currently numerous studies showing the involvement of oxidative stress in OLP, but in terms of CLP, data are scarce. In this review, we analyze for the first time the currently existing studies on oxidative stress in CLP and summarize the results in order to assess the role of oxidative stress in skin lesions offering a fresher updated perspective.

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