Degradation state of organic matter in surface sediments from the Southern Beaufort Sea: a lipid approach

For the next decades significant climatic changes should occur in the Arctic zone. The expected destabilisation of permafrost and its consequences for hydrology and plant cover should increase the input of terrigenous carbon to coastal seas. Consequently, the relative importance of the fluxes of terrestrial and marine organic carbon to the seafloor will likely change, strongly impacting the preservation of organic carbon in Arctic marine sediments. Here, we investigated the lipid content of surface sediments collected on the Mackenzie basin in the Beaufort Sea. Particular attention was given to biotic and abiotic degradation products of sterols and monounsaturated fatty acids. By using sitosterol and campesterol degradation products as tracers of the degradation of terrestrial higher plant inputs and brassicasterol degradation products as tracers of degradation of phytoplanktonic organisms, it could be observed that autoxidation, photooxidation and biodegradation processes act much more intensively on higher plant debris than on phytoplanktonic organisms. Examination of oxidation products of monounsaturated fatty acids showed that photo- and autoxidation processes act more intensively on bacteria than on phytodetritus. Enhanced damages induced by singlet oxygen (transferred from senescent phytoplanktonic cells) in bacteria were attributed to the lack of an adapted antioxidant system in these microorganisms. The strong oxidative stress observed in the sampled sediments resulted in the production of significant amounts of epoxy acids and unusually high proportions of monounsaturated fatty acids with a <i>trans</i> double bond. The formation of epoxy acids was attributed to peroxygenases (enzymes playing a protective role against the deleterious effects of fatty acid hydroperoxides in vivo), while <i>cis/trans</i> isomerisation was probably induced by thiyl radicals produced during the reaction of thiols with hydroperoxides. Our results confirm the important role played by abiotic oxidative processes in the degradation of marine bacteria and do not support the generally expected refractory character of terrigenous material deposited in deltaic systems

Seasonal survey of the composition and degradation state of particulate organic matter in the Rhône River using lipid tracers

International audienceLipid tracers including fatty acids, hydroxyacids, n-alkanols, sterols and triterpenoids were used to determine the origin and fate of suspended particulate organic matter (POM) collected in the Rhône River (France). This seasonal survey (April 2011 to May 2013) revealed a year-round strong terrestrial higher-plant contribution to the particulate organic matter (POM), with significant algal inputs observed in March and attributed to phytoplanktonic blooms likely dominated by diatoms. Major terrigenous contributors to our samples are gymnosperms, and more precisely their roots and stems, as evidenced by the presence of high proportions of ω-hydroxydocosanoic acid (a suberin biomarker). The high amounts of coprostanol detected clearly show that the Rhône River is significantly affected by sewage waters. Specific sterol degradation products were quantified and used to assess the part of biotic and abiotic degradation of POM within the river. Higher-plant-derived organic matter appears to be mainly affected by photo-oxidation and au-toxidation (free radical oxidation), while organic matter of mammal or human origin, evidenced by the presence of co-prostanol, is clearly more prone to bacterial degradation. Despite the involvement of an intense autoxidation-inducing ho-molytic cleavage of peroxy bonds, a significant proportion of hydroperoxides is still intact in higher plant debris. These compounds could affect the degradation of terrestrial material by inducing an intense autoxidation upon its arrival at sea

Monitoring abiotic degradation in sinking versus suspended Arctic sea ice algae during a spring ice melt using specific lipid oxidation tracers

publisher: Elsevier articletitle: Monitoring abiotic degradation in sinking versus suspended Arctic sea ice algae during a spring ice melt using specific lipid oxidation tracers journaltitle: Organic Geochemistry articlelink: http://dx.doi.org/10.1016/j.orggeochem.2016.05.016 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved

Monitoring photo-oxidative and salinity-induced bacterial stress in the Canadian Arctic using specific lipid tracers

Publisher policy: author can archive post-print on open access repository after an embargo period of 18 months.Publisher's version/PDF cannot be used. Must link to publisher version with DOI. Author's post-print must be released with a Creative Commons Attribution Non-Commercial No Derivatives License

Transcriptional responses of winter barley to cold indicate nucleosome remodelling as a specific feature of crown tissues

We report a series of microarray-based comparisons of gene expression in the leaf and crown of the winter barley cultivar Luxor, following the exposure of young plants to various periods of low (above and below zero) temperatures. A transcriptomic analysis identified genes which were either expressed in both the leaf and crown, or specifically in one or the other. Among the former were genes responsible for calcium and abscisic acid signalling, polyamine synthesis, late embryogenesis abundant proteins and dehydrins. In the crown, the key organ for cereal overwintering, cold treatment induced transient changes in the transcription of nucleosome assembly genes, and especially H2A and HTA11, which have been implicated in cold sensing in Arabidopsis thaliana. In the leaf, various heat-shock proteins were induced. Differences in expression pattern between the crown and leaf were frequent for genes involved in certain pathways responsible for osmolyte production (sucrose and starch, raffinose, γ-aminobutyric acid metabolism), sugar signalling (trehalose metabolism) and secondary metabolism (lignin synthesis). The action of proteins with antifreeze activity, which were markedly induced during hardening, was demonstrated by a depression in the ice nucleation temperature

Synthesis of Nitrogenated Heterocycles by Asymmetric Transfer Hydrogenation of N-(tert-Butylsulfinyl)haloimines

Highly optically enriched, protected, nitrogenated heterocycles with different ring sizes have been synthesized by a very efficient methodology consisting of the asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)haloimines followed by treatment with a base to promote an intramolecular nucleophilic substitution process. N-Protected aziridines, pyrrolidines, piperidines, and azepanes bearing aromatic, heteroaromatic, and aliphatic substituents have been obtained in very high yields and diastereomeric ratios up to >99:1. The free heterocycles can be easily obtained by a simple and mild desulfinylation procedure. Both enantiomers of the free heterocycles can be prepared with the same good results by changing the absolute configuration of the sulfur atom of the sulfinyl group.This work was generously supported by the Spanish Ministerio de Ciencia e Innovación (MICINN; grant no. CONSOLIDER INGENIO 2010, CSD2007-00006, CTQ2007-65218 and CTQ2011-24151) and the Generalitat Valenciana (PROMETEO/2009/039 and FEDER). O.P. thanks the Spanish Ministerio de Educación for a predoctoral fellowship (grant no. AP-2008-00989)

Oxidation products of alpha- and beta-amyrins: potential tracers of abiotic degradation of vascular-plant organic matter in aquatic environments

International audienceIn order to fulfil the current need for stable and specific tracers to monitor vascular- plant organic matter degradation in aquatic environments, alpha-amyrin (urs-12-en-3 beta-ol) and beta-amyrin (olean-12-en-3 beta-ol) were oxidised in vitro and their abiotic degradation products quantified in environmental samples from the Rhone River in France. Although they appear inert to photooxidation, they are clearly affected by autoxidation and the tracer potential of the resulting products was confirmed. Autoxidation of alpha- and beta-amyrins produces urs or olean-12-en-3-one, 3 beta-hydroxy-urs or olean-12-en-11- one, urs or olean-12-en-3 beta, 11 alpha-diol and urs or olean-12-en-3,11-dione. 3 beta-Hydroxy-urs-12-en-11-one and 3 beta-hydroxy- olean-12-en-11-one, the main oxidation products detected, were selected as autoxidation tracers. These compounds, specific to autoxidation, were detected in dry leaves of Smilax aspera and in suspended particulate matter samples collected in the Rhone River and evidenced the importance of autoxidation in the degradation of organic matter of terrestrial origin

Task Specific Onium Salts and Ionic liquids as Soluble Supports in Grieco's Multicomponent Synthesis of Tetrahydroquinolines

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Lithium-Mediated Zincation of Pyrazine, Pyridazine, Pyrimidine and Quinoxaline.

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