Quantitative aspects of the interfacial catalytic oxidation of Dithiothreitol by dissolved oxygen in the presence of carbon nanoparticles

The catalytic nature of particulate matter is often advocated to explain its ability to generate reactive oxygen species, but quantitative data are lacking. We have performed molecular characterization of three different carbonaceous nanoparticles (NP) by 1. identifying and quantifying their surface functional groups based on probe gas-particle titration; 2. studying the kinetics of dissolved oxygen consumption in the presence of suspended NP's and dithiothreitol (DTT). We show that these NP's can reversibly change their oxidation state between oxidized and reduced functional groups present on the NP surface. By comparing the amount of O2 consumed and the number of strongly reducing sites on the NP, its average turnover ranged from 35 to 600 depending on the type of NP. The observed quadratic rate law for O2 disappearance points to a Langmuir-Hinshelwood surface-based reaction mechanism possibly involving semiquinone radical. In the proposed model, the strongly reducing surface site is assumed to be a polycyclic aromatic hydroquinone whose oxidation to the corresponding conjugated quinone is rate-limiting in the catalytic chain reaction. The presence and strength of the reducing surface functional groups are important for explaining the catalytic activity of NP in the presence of oxygen and a reducing agent like DTT

Characterization of surface functional groups present on laboratory-generated and ambient aerosol particles by means of heterogeneous titration reactions

A Knudsen flow reactor has been used to quantify surface functional groups on aerosols collected in the field. This technique is based on a heterogeneous titration reaction between a probe gas and a specific functional group on the particle surface. In the first part of this work, the reactivity of different probe gases on laboratory-generated aerosols (limonene SOA, Pb(NO3)2, Cd(NO3)2) and diesel reference soot (SRM 2975) has been studied. Five probe gases have been selected for the quantitative determination of important functional groups: N(CH3)3 (for the titration of acidic sites), NH2OH (for carbonyl functions), CF3COOH and HCl (for basic sites of different strength), and O3 (for oxidizable groups). The second part describes a field campaign that has been undertaken in several bus depots in Switzerland, where ambient fine and ultrafine particles were collected on suitable filters and quantitatively investigated using the Knudsen flow reactor. Results point to important differences in the surface reactivity of ambient particles, depending on the sampling site and season. The particle surface appears to be multi-functional, with the simultaneous presence of antagonistic functional groups which do not undergo internal chemical reactions, such as acid-base neutralization. Results also indicate that the surface of ambient particles was characterized by a high density of carbonyl functions (reactivity towards NH2OH probe in the range 0.26-6 formal molecular monolayers) and a low density of acidic sites (reactivity towards N(CH3)3 probe in the range 0.01-0.20 formal molecular monolayer). Kinetic parameters point to fast redox reactions (uptake coefficient ?0&gt;10-3 for O3 probe) and slow acid-base reactions (?0&lt;10-4 for N(CH3)3 probe) on the particle surface. [Authors]]]> Vehicle Emissions ; Aerosols ; Particulate Matter ; Oxidative Stress ; Reactive Oxygen Species ; Biological Markers ; Surface Properties ; Occupational Exposure eng https://serval.unil.ch/resource/serval:BIB_B477DBDA9F10.P001/REF.pdf http://nbn-resolving.org/urn/resolver.pl?urn=urn:nbn:ch:serval-BIB_B477DBDA9F105 info:eu-repo/semantics/altIdentifier/urn/urn:nbn:ch:serval-BIB_B477DBDA9F105 info:eu-repo/semantics/acceptedVersion info:eu-repo/semantics/openAccess Copying allowed only for non-profit organizations https://serval.unil.ch/disclaimer application/pdf oai:serval.unil.ch:BIB_B478041350E0 2022-05-07T01:25:26Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_B478041350E0 Négocier pour pacifier. Ambassadeurs et médiateurs durant la guerre de Cent Ans Pibiri, Eva info:eu-repo/semantics/conferenceObject inproceedings La paix des Dames, volet 1, Entre politique, diplomatie et cérémoniel Dumont, Jonathan (ed.) Fragnart, Laure (ed.) Girault, Pierre-Gilles (ed.) Le Roux, Nicolas (ed.) fre oai:serval.unil.ch:BIB_B47924D65A2D 2022-05-07T01:25:26Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_B47924D65A2D Cancer du sein et obésité, une liaison dangereuse [Breast cancer and obesity, a dangerous relation]. info:eu-repo/semantics/altIdentifier/pmid/22734178 Zaman, K. Bodmer, A. Pralong, F. Castiglione-Gertsch, M. info:eu-repo/semantics/review article 2012 Revue Médicale Suisse, vol. 8, no. 342, pp. 1101-1104 info:eu-repo/semantics/altIdentifier/pissn/1660-9379 urn:issn:1660-9379 <![CDATA[Obesity is associated with different cancers including breast cancer, whose incidence is increased in postmenopausal women. It has an adverse impact on the prognosis of the patients, regardless of their menopausal status. The fact of receiving a systemic adjuvant therapy does not neutralize the prognostic role of obesity. Moderate weight loss after cancer diagnosis could improve the outcome of the patients, while a weight gain during treatment seems without significant effect. Currently available data are still too incomplete to justify systematic programs to lose weight with an oncologic therapeutic aim. However, it is worth to encourage and support our patients to have an optimal diet, physical activity, and to lose weight as promotion of general health

Diversité biologique tropicale et innovation thérapeutique : les recherches menées par l'ORSTOM

Les organismes vivants élaborent des molécules dont la complexité dépasse l'imagination des chimistes. Leurs complexités chimiques vont de pair avec leurs remarquables propriétés biologiques. Les forêts tropicales sont avec les récifs coralliens parmi les biomes les plus riches en nombre d'espèces et constituent un gisement encore peu exploré de nouvelles molécules. En Nouvelle-Calédonie, l'ORSTOM dispose de moyens océanographiques indispensables pour l'étude et la récolte des Organismes Marins vivant dans le plus grand lagon du monde. De nombreux organismes marins ont été étudiés dans le cadre du programme SMIB (ORSTOM-CNRS) à Nouméa. Les extraits de ces organismes sont soumis à un large criblage biologique. Certains des composés isolés, comme la girolline, en sont au stade des essais cliniques. Pour ce qui est des espèces végétales, les chances de découverte de principes actifs sont augmentées grâce à l'ethnobotanique qui valorise l'expérience ancestrale des guérisseurs. En Bolivie, une équipe franco-bolivienne étudie l'activité leishmanicide des drogues végétales employées dans la médecine traditionnelle. L'étude des extraits actifs, #in vitro et #in vivo, sur les leishmanies du nouveau monde a été conduite jusqu'à l'isolement et la détermination des composés responsables de l'activité appartenant aux groupes chimiques des alcaloïdes, des quinones et des terpènes. En conclusion, les enjeux scientifiques et géopolitiques de la biodiversité sont rappelés. (Résumé d'auteur

Biological activities of 13, 28-epoxyoleanane triterpene saponins from two peruvian Myrsinaceae

Two known 13,28-epoxy-oleanane triterpene saponins (1) and (2), were isolated from the 95% ethanolic extract of the roots of Myrsine coriaceae and Myrsine andina. Their structures were deduced by combined spectral analysis and chemical evidences based on data reported in the literature. Compounds 1 and 2 were evaluated in vitro against different cellular models such as Mycobacterium tuberculosis, Leishmania amazonensis axenic amastigotes, six human cancer cell lines (Hs683, T98G, U251, HT29, MCF7, SKMEL28) and two murine cell lines (CT26 and B16F10). Compound 1 was found to exhibit antileishmanial activity (IC50 = 16 µg/mL) whereas compound 2 was inactive (IC50 > 50 µg/mL). Furthermore, compound 1 exhibited stronger inhibition activity on human cancer cells (IC50 = 15 µg/mL) and on murine cell lines (IC50 = 10 µg/mL) than compound 2 (IC50 > 82 and 42 µg/mL, respectively). As the only difference between 1 and 2 is due to a substitution of an aldehyde group by a hydroxymethyl moiety, these results showed the crucial role of the aldehyde function at C-30 for the cytotoxicity. In contrast, none of the tested compounds revealed activity against M. tuberculosis

Biomarkers of oxidative stress and its association with the urinary reducing capacity in bus maintenance workers

<p>Abstract</p> <p>Background</p> <p>Exposure to particles (PM) induces adverse health effects (cancer, cardiovascular and pulmonary diseases). A key-role in these adverse effects seems to be played by oxidative stress, which is an excess of reactive oxygen species relative to the amount of reducing species (including antioxidants), the first line of defense against reactive oxygen species. The aim of this study was to document the oxidative stress caused by exposure to respirable particles <it>in vivo</it>, and to test whether exposed workers presented changes in their urinary levels for reducing species.</p> <p>Methods</p> <p>Bus depot workers (n = 32) exposed to particles and pollutants (respirable PM₄, organic and elemental carbon, particulate metal content, polycyclic aromatic hydrocarbons, NO_x, O₃) were surveyed over two consecutive days. We collected urine samples before and after each shift, and quantified an oxidative stress biomarker (8-hydroxy-2'-deoxyguanosine), the reducing capacity and a biomarker of PAH exposure (1-hydroxypyrene). We used a linear mixed model to test for associations between the oxidative stress status of the workers and their particle exposure as well as with their urinary level of reducing species.</p> <p>Results</p> <p>Workers were exposed to low levels of respirable PM₄(range 25-71 μg/m³). However, urinary levels of 8-hydroxy-2'-deoxyguanosine increased significantly within each shift and between both days for non-smokers. The between-day increase was significantly correlated (p < 0.001) with the concentrations of organic carbon, NO_x, and the particulate copper content. The within-shift increase in 8OHdG was highly correlated to an increase of the urinary reducing capacity (Spearman ρ = 0.59, p < 0.0001).</p> <p>Conclusions</p> <p>These findings confirm that exposure to components associated to respirable particulate matter causes a systemic oxidative stress, as measured with the urinary 8OHdG. The strong association observed between urinary 8OHdG with the reducing capacity is suggestive of protective or other mechanisms, including circadian effects. Additional investigations should be performed to understand these observations.</p