An NADPH-Oxidase/Polyamine Oxidase Feedback Loop Controls Oxidative Burst Under Salinity

Gé,mes, Katalin,Kim, Yu Jung,Park, Ky Young,Moschou, Panagiotis N.,Andronis, Efthimios,Valassaki, Chryssanthi,Roussis, Andreas,Roubelakis-Angelakis, Kalliopi A. American Society of Plant Biologists 2016 Plant Physiology Vol.172 No.3

<P>The apoplastic polyamine oxidase (PAO) catalyzes the oxidation of the higher polyamines spermidine and spermine, contributing to hydrogen peroxide (H2O2) accumulation. However, it is yet unclear whether apoplastic PAO is part of a network that coordinates the accumulation of reactive oxygen species (ROS) under salinity or if it acts independently. Here, we unravel that NADPH oxidase and apoplastic PAO cooperate to control the accumulation of H2O2 and superoxides (O-2(center dot-)) in tobacco (Nicotiana tabacum). To examine to what extent apoplastic PAO constitutes part of a ROS-generating network, we examined ROS accumulation in guard cells of plants overexpressing or down-regulating apoplastic PAO (lines S2.2 and A2, respectively) or down-regulating NADPH oxidase (line AS-NtRbohD/F). The H2O2-specific probe benzene sulfonyl-H2O2 showed that, under salinity, H2O2 increased in S2.2 and decreased in A2 compared with the wild type. Surprisingly, the O-2(center dot-)-specific probe benzene sulfonyl-So showed that O-2(center dot-) levels correlated positively with that of apoplastic PAO (i.e. showed high and low levels in S2.2 and A2, respectively). By using AS-NtRbohD/F lines and a pharmacological approach, we could show that H2O2 and O-2(center dot-) accumulation at the onset of salinity stress was dependent on NADPH oxidase, indicating that NADPH oxidase is upstream of apoplastic PAO. Our results suggest that NADPH oxidase and the apoplastic PAO form a feed-forward ROS amplification loop, which impinges on oxidative state and culminates in the execution of programmed cell death. We propose that the PAO/NADPH oxidase loop is a central hub in the plethora of responses controlling salt stress tolerance, with potential functions extending beyond stress tolerance.</P>

Local Control of the <i>Cis</i>–<i>Trans</i> Isomerization and Backbone Dihedral Angles in Peptides Using Trifluoromethylated Pseudoprolines

Feytens, Debby,Chaume, Gre&#x301,gory,Chassaing, Gé,rard,Lavielle, Solange,Brigaud, Thierry,Byun, Byung Jin,Kang, Young Kee,Miclet, Emeric American Chemical Society 2012 The Journal of physical chemistry B Vol.116 No.13

<P>NMR studies and theoretical calculations have been performed on model peptides Ac-Ser(ΨPro)-NHMe, (<I>S</I>,<I>S</I>)Ac-Ser(Ψ<SUP>H,CF3</SUP>Pro)-NHMe, and (<I>R,S</I>)Ac-Ser(Ψ<SUP>CF3,H</SUP>Pro)-NHMe. Their thermodynamic and kinetic features have been analyzed in chloroform, DMSO, and water, allowing a precise description of their conformational properties. We found that trifluoromethyl C<SUP>δ</SUP>-substitutions of oxazolidine-based pseudoprolines can strongly influence the <I>cis</I>–<I>trans</I> rotational barriers with only moderate effects on the <I>cis</I>/<I>trans</I> population ratio. In CHCl<SUB>3</SUB>, the configuration of the CF<SUB>3</SUB>–C<SUP>δ</SUP> entirely controls the ψ-dihedral angle, allowing the stabilization of γ-turn-like or PPI/PPII-like backbone conformations. Moreover, in water and DMSO, this C<SUP>δ</SUP>-configuration can be used to efficiently constrain the ring puckering without affecting the <I>cis</I>/<I>trans</I> population ratio. Theoretical calculations have ascertained the electronic and geometric properties induced by the trifluoromethyl substituent and provided a rational understanding of the NMR observations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2012/jpcbfk.2012.116.issue-13/jp300284u/production/images/medium/jp-2012-00284u_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp300284u'>ACS Electronic Supporting Info</A></P>

Extraction of Gold(III) from Acidic Chloride Media Using Phosphonium-based Ionic Liquid as an Anion Exchanger

Nguyen, Viet Tu,Lee, Jae-chun,Jeong, Jinki,Kim, Byung-Su,Cote, Gé,rard,Chagnes, Alexandre American Chemical Society 2015 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.54 No.4

<P>The present work addresses Au(III) extraction from chloride media using phosphonium-based ionic liquid (Cyphos IL 109) as a novel anion exchanger diluted in xylene. Gold(III) is extracted into the organic phase as [P-66614(+)][AuCl4- ] and can easily be stripped by reduction to Au(I) with CS(NH2)(2)/HCl or Na2S2O3. A series of extraction-stripping cycles show a possible recirculation of used solvent without loss of performance, as far as the extraction of gold(III) from HCl/Cl- media is concerned. Au(III) was quantitatively (99.4%) extracted from 0.1 mol L-1 HCl initially containing 100 mg L-1 Au(III) with 0.8 g L-1 Cyphos IL 109 with two counter-current stages at O/A = 1, whereas total stripping as Au(I) with 0.02 mol L-1 CS(NH2)(2) in 5% HCl or 0.02 mol L-1 Na2S2O3 also needed two counter-current stages, at O/A = 3. Simulations of counter-current modes reveal Cyphos IL 109 can be considered a promising new extractant for complete recovery of Au(III) from Cl- media in pilot scale.</P>

Quantum Interference Channeling at Graphene Edges

Yang, Heejun,Mayne, Andrew J.,Boucherit, Mohamed,Comtet, Genevie&#x300,ve,Dujardin, Gé,rald,Kuk, Young American Chemical Society 2010 NANO LETTERS Vol.10 No.3

<P>Electron scattering at graphene edges is expected to make a crucial contribution to the electron transport in graphene nanodevices by producing quantum interferences. Atomic-scale scanning tunneling microscopy (STM) topographies of different edge structures of monolayer graphene show that the localization of the electronic density of states along the C−C bonds, a property unique to monolayer graphene, results in quantum interference patterns along the graphene carbon bond network, whose shapes depend only on the edge structure and not on the electron energy.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-3/nl9038778/production/images/medium/nl-2009-038778_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9038778'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9038778'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9038778'>ACS Electronic Supporting Info</A></P>

Effect of Intertube Junctions on the Thermoelectric Power of Monodispersed Single Walled Carbon Nanotube Networks

Piao, Mingxing,Joo, Min-Kyu,Na, Junhong,Kim, Yun-Jeong,Mouis, Mireille,Ghibaudo, Gé,rard,Roth, Siegmar,Kim, Wung-Yeon,Jang, Ho-Kyun,Kennedy, Gary P.,Dettlaff-Weglikowska, Urszula,Kim, Gyu-Tae American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.46

<P>The thermoelectric power (TEP) of single walled carbon nanotube (SWCNT) thin films in pure metallic SWCNT (m-SWCNT) and pure semiconducting SWCNT (s-SWCNT) networks as well as in m- and s-SWCNT mixtures is investigated. The TEP measured on the pure s-SWCNT film (≈88 μV/K) was found to be almost 7 times higher than that of the m-SWCNTs (≈13 μV/K). Moreover, a quasilinear increase of TEP of the mixed SWCNT networks was observed as the fraction of s-SWCNTs is increased. The experimentally determined relationship between TEP and the fraction of s-SWCNTs in the mixture allows fast and simple quantitative analysis of the s:m ratio in any as-prepared heterogeneous SWCNT network. Furthermore, a semiempirical model analyzing the effect of the intertube junctions is proposed and applied to describe the thermoelectric behavior of the prepared SWCNT networks. The results of calculations match well with the experimental data and clearly demonstrate that the measured TEP of thin SWCNT films is principally controlled by the intertube junctions. The fundamental role of junctions in generating thermoelectric power is not limited to only SWCNT networks as discovered here, but also could be applied to systems where nanoparticles/nanotube form percolating paths in thin films and composite materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-46/jp505682f/production/images/medium/jp-2014-05682f_0010.gif'></P>

Oxidation of Cymantrene Analogues of Ferrocifen: Electrochemical, Spectroscopic, and Computational Studies of the Parent Complex 1,1′-Diphenyl-2-cymantrenylbutene

Wu, Kan,Park, Ji Young,Al-Saadon, Rachael,Nam, Hyerim,Lee, Yujin,Top, Siden,Jaouen, Gé,rard,Baik, Mu-Hyun,Geiger, William E. American Chemical Society 2018 Organometallics Vol.37 No.12

<P>The oxidative electrochemical behavior of 1,1′-diphenyl-2-cymantrenylbutene (<B>1</B>), a cymantrene analogue of the breast cancer drug ferrocifen, was shown to involve the sequential electron-transfer series <B>1</B>/<B>1</B><SUP>+</SUP>/<B>1</B><SUP>2+</SUP> in dichloromethane/0.05 M [NBu<SUB>4</SUB>][B(C<SUB>6</SUB>F<SUB>5</SUB>)<SUB>4</SUB>] (<I>E</I><SUB>1/2</SUB> values 0.78 and 1.18 V vs ferrocene). By a combination of spectroscopic and computational techniques, it was shown that the cymantrene functionality plays an important role in dissipating the positive charges in the oxidized compounds and is therefore an active participant in the redox events. The redox-active orbital goes from roughly equal degrees of organometallic and π-organic (diphenylolefin) makeup in <B>1</B> to increasingly organic based fractions in <B>1</B><SUP>+</SUP> and <B>1</B><SUP>2+</SUP>. Structural changes mimicking those of oxidized tetrakis(aryl)ethylenes accompany the one-electron oxidations. There is sufficient unpaired electron density on the manganese center in <B>1</B><SUP>+</SUP> to allow for oxidatively induced ligand exchange of one or more of the carbonyl ligands with donor ligands, including phosphites and pyridine. The complex Mn(CO)<SUB>2</SUB>P(OPh)<SUB>3</SUB>(η<SUP>5</SUP>-C<SUB>5</SUB>H<SUB>4</SUB>(Et)C═C(C<SUB>6</SUB>H<SUB>5</SUB>)<SUB>2</SUB>) was prepared by the “electrochemical switch” method, wherein [Mn(CO)<SUB>2</SUB>P(OPh)<SUB>3</SUB>(η<SUP>5</SUP>-C<SUB>5</SUB>H<SUB>4</SUB>(Et)C═C(C<SUB>6</SUB>H<SUB>5</SUB>)<SUB>2</SUB>)]<SUP>+</SUP>, produced by the oxidation of <B>1</B> in the presence of P(OPh)<SUB>3</SUB>, was reduced back to the neutral CO-substituted complex.</P> [FIG OMISSION]</BR>