Synthesis and (spectro)electrochemistry of mixedvalent diferrocenyl–dihydrothiopyran derivatives

Three novel diferrocenyl complexes were prepared and characterised. 2,2-Diferrocenyl-4,5-dimethyl- 3,6-dihydro-2H-thiopyran (1, sulphide) was accessible by the hetero-Diels–Alder reaction of diferrocenyl thioketone with 2,3-dimethyl-1,3-butadiene. Stepwise oxidation of 1 gave the respective oxides 2,2- diferrocenyl-4,5-dimethyl-3,6-dihydro-2H-thiopyran-1-oxide (2, sulfoxide) and 2,2-diferrocenyl-4,5- dimethyl-3,6-dihydro-2H-thiopyran-1,1-dioxide (3, sulfone), respectively. The molecular structures of 1 and 3 in the solid state were determined by single crystal X-ray crystallography. The oxidation of sulphide 1 to sulfone 3, plays only a minor role on the overall structure of the two compounds. Electrochemical (cyclic voltammetry (= CV), square wave voltammetry (= SWV)) and spectroelectrochemical (in situ UV-Vis/NIR spectroscopy) studies were carried out. The CV and SWV measurements showed that an increase of the sulphur atom oxidation from −2 in 1 to +2 in 3 causes an anodic shift of the ferrocenylbased oxidation potentials of about 100 mV. The electrochemical oxidation of 1–3 generates mixedvalent cations 1+–3+. These monooxidised species display low-energy electronic absorption bands between 1000 and 3000 nm assigned to IVCT (= Inter-Valence Charge Transfer) electronic transitions. Accordingly, the mixed-valent cations 1+–3+ are classified as weakly coupled class II systems according to Robin and Day.Authors (K. K. and G. M.) thank the National Science Centre (Poland) for financial support (Project Maestro-3; Dec-2012/06/ A/ST5/00219) and R. C. thanks the German Federal Ministry of Education and Research (BMBF) for support. The support from the German Academic Exchange Service (DAAD) in the framework of the exchange program “Ostpartnerschaften” is highly appreciated

Modelling the molecular mechanisms of ageing

This document is the Accepted Manuscript version of a published work that appeared in final form in Bioscience reports. To access the final edited and published work see http://www.bioscirep.org/content/37/1/BSR20160177.The ageing process is driven at the cellular level by random molecular damage which slowly accumulates with age. Although cells possess mechanisms to repair or remove damage, they are not 100% efficient and their efficiency declines with age. There are many molecular mechanisms involved and exogenous factors such as stress also contribute to the ageing process. The complexity of the ageing process has stimulated the use of computational modelling in order to increase our understanding of the system, test hypotheses and make testable predictions. As many different mechanisms are involved, a wide range of models have been developed. This paper gives an overview of the types of models that have been developed, the range of tools used, modelling standards, and discusses many specific examples of models which have been grouped according to the main mechanisms that they address. We conclude by discussing the opportunities and challenges for future modelling in this field

Reduced metabolic rate and oxygen radicals production in stored insect sperm

International audienceAbstractFemales of internally fertilizing species can significantly extend sperm lifespan and functionality during sperm storage. The mechanisms for such delayed cellular senescence remain unknown. Here, we apply current hypotheses of cellular senescence developed for diploid cells to sperm cells, and empirically test opposing predictions on the relationship between sperm metabolic rate and oxygen radical production in an insect model, the cricket Gryllus bimaculatus. Using time-resolved microfluorimetry, we found a negative correlation between metabolic rate (proportion of protein-bound NAD[P]H) and in situ intracellular oxygen radicals production in freshly ejaculated sperm. In contrast, sperm stored by females for periods of 1 h to 26 days showed a positive correlation between metabolic rate and oxygen radicals production. At the same time, stored sperm showed a 37 per cent reduced metabolic rate, and 42 per cent reduced reactive oxygen species (ROS) production, compared with freshly ejaculated sperm. Rank differences between males in ROS production and metabolic rate observed in ejaculated sperm did not predict rank differences in stored sperm. Our method of simultaneously measuring ROS production and metabolic rate of the same sample has the advantage of providing data that are independent of sperm density and any extracellular antioxidants that are proteins. Our method also excludes effects owing to accumulated hydrogen peroxide. Our results unify aspects of competing theories of cellular ageing and suggest that reducing metabolic rate may be an important means of extending stored sperm lifespan and functionality in crickets. Our data also provide a possible explanation for why traits of ejaculates sampled from the male may be rather poor predictors of paternity in sexual selection studies and likelihood of pregnancy in reproductive medicine

Potentialisation de la chimiothérapie en milieu oxygéné (implication des radicaux libres dans l'effet des anthracyclines)

L hypoxie tumorale peut induire une résistance aux traitements par l adriamycine (ADR), et l effet anti-cancéreux de l anthracycline peut augmenter sous oxygénation hyperbare. Cependant, les mécanismes d action impliqués dans ce gain d efficacité thérapeutique restent à élucider.Nous avons évalué l implication de la production d espèces réactives de l oxygène (ROS) dans l amélioration de l effet de l ADR sur des cellules lymphoblastiques humaines CCRF-CEM sous hypoxie (2% O2) et sous normoxie (21% O2). Nous avons utilisé une nouvelle méthode de détection de ROS basée sur la mesure de la durée de vie de fluorescence de l'acide 1-pyrène butyrique. L analyse d images numériques des populations cellulaires après triple-marquage a fourni des informations morphométriques (tailles cellulaire et nucléaire) et fonctionnelles (activité mitochondriale, teneur en ADN) permettant (i) de quantifier l induction de l apoptose, et (ii) d établir la distribution du cycle cellulaire par analyse multiparamétrique des données.Nous avons observé que le blocage du cycle cellulaire par l'ADR ne dépend pas des conditions d'oxygénation, alors que l induction de l apoptose et la production de ROS dues au traitement sont plus importantes sous condition oxygénée (21% O2). Si on admet que la condition normoxique est une hyperoxygénation comparée à l état d hypoxie tumorale in vivo, alors le gain d efficacité thérapeutique de l ADR fournit par une oxygénation hyperbare pourrait résulter d'une plus forte production de ROS par l'anthracycline, qui entraînerait une induction des processus apoptotiques plus importante.Tumour hypoxia is causally related with resistance to adriamycin (ADR) treatment. However, how hyperbaric oxygen therapy leads to therapeutic gain of the drug is unclear.We investigated the relation of reactive oxygen species (ROS) generation with anti-tumoural effect of ADR on human lymphoblastic CCRF-CEM cells under hypoxic (2% O2) and normoxic (21% O2) conditions. A new method was used to measure intracellular ROS variations through the fluorescence lifetime of 1-pyrenebutyric acid. Numerical image analysis of cell populations labelled with different vital stains allowed to collect morphometric (cellular and nuclear sizes) and physiological (mitochondrial activity, DNA content) informations used to (i) quantify apoptosis induction, and (ii) determine the cell cycle distribution through multiparametric analysis of collected data.We observed that oxygen level has no effect on the cell cycle arrest induced by ADR, whereas apoptosis induction and ROS production resulting from treatment are higher under oxygenated conditions (i.e. normoxia). Considering normoxia as a hyperoxygenated condition compared to in vivo hypoxic tumour level, we suggested that improvement of anti-cancerous effect of ADR due to hyperbaric oxygen therapy results from higher intracellular ROS generation by the drug, leading to a greater induction of apoptosis.PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

Functional study of REBELOTE gene of Arabidopsis thaliana

Ponts entre les séquences d'acides nucléiques et les protéines, les ribosomes sont des composants essentiels des cellules vivantes. Composé d'ARN et de protéines ribosomiques, ils sont transportés, durant leurs biogenèses, du nucléole au cytoplasme, où ils traduisent les ARN messagers (ARNm) en protéines. Ces dernières années,  il a été montré que nombre de protéines ribosomiques étaient impliquées dans le développement d'Arabidopsis en intervenant sur la division et l'élongation cellulaire. L'impact d'un défaut de biogenèse des ribosomes sur le développement pourrait être expliqué par un effet dose, par une spécificité des ribosomes pour leur ARNm cibles ou par la multifonctionnalité de protéines ribosomiques. Les résultats obtenus montrent que REBELOTE (RBL), l'un des deux homologues chez Arabidopsis de la protéine NOC2p de levure, intervient probablement durant la biogenèse des ribosomes. Des mutations dans le gène RBL causent une gamme de phénotype de la létalité embryonnaire aux défauts de croissance (réduction de la taille de la plante, altération de la forme des feuilles...). Afin de mieux comprendre les processus contrôlés par RBL, la fonction ribosomique de RBL a été étudiée et ses interacteurs protéiques recherchés. Nous nous sommes ensuite focalisé sur les effets des mutations rbl sur la division et l'élongation cellulaire. Ce travail montre que les défauts observés aux niveaux moléculaire et cellulaire peuvent expliquer les retards de croissance des mutants rbl.Bridges between nucleic acids sequences and proteins, ribosomes are central components and the “auletes” of living cells.  Composed of ribosomal proteins and RNA, they move during their biogenesis from the nucleolus to the cytoplasm, where they translate RNA messengers into proteins. In the past years, some mutants of ribosomal-biogenesis-related proteins have shown the importance of these proteins during cell division and Arabidopsis development. The impact of ribosomal defects on development could be explained by dose effect (which could be important for cell fitness), specificity of ribosomes for some mRNA or multifunctional ribosomal proteins (Mary E. Byrne, 2009). Here I present our work on REBELOTE (RBL), one of the two Arabidopsis homologs of the yeast NOC2 protein, which act during the ribosomal 60S subunit biogenesis. Mutations in REBELOTE gene cause a range of phenotypes, from embryo lethality to growth defects (reduced plant size, altered leaf shape…). To have a better understanding of RBL-controlled processes, we first analyzed the ribosomal function of RBL, and searched for its protein partners. Our results shows that RBL act in two different nucleolar complexes supposed to regulate 60S ribosomal subunit biogenesis. Subsequently, we focused on the effects of rbl mutations on the cell division/elongation processes. Our work shows that defects observed at molecular and cellular levels could explain the slow down of cell divisions and growth delay in rbl mutants

Quenching of long lifetime emitting fluorophores with paramagnetic molecules

International audienceIn this work, we have studied quenching of the fluorescence of two well-known oxygen probes, 1-pyrene butyric acid (PBA) and tris(2,2'-bipyridine)ruthenium ([Ru(bpy)(3)](2+)) by reactive oxygen species (superoxide anion, nitric oxide derivative, hydrogen peroxide) and by the O(2) molecule. Both, time-resolved and steady state fluorescence measurements were performed in solution (ethanol, dimethyl sufoxide, water) and in micelles of Sodium Dodecyl Sulfate that serve as a model for membrane-containing biological structures. We have found that only the free radicals and O(2) can actively quench for the two probes, but not the diamagnetic H(2)O(2). Our data correspond to the classical Stern-Volmer equation. H(2)O(2) has an effect only at high molar concentrations (>0.1 M). In contrast, effective concentrations of free radicals and O(2) that lead to quenching are in millimolar range. In conclusion, our methods allows for detecting global ROS that are small free radicals without interference from the reactive hydroxyl radical. Our data suggest that the method can be used for the quantification of ROS in individual living cells based on the measurement of fluorescence lifetime of those probe

A comparative study of Caesalpinia bonduc (L.) Roxb. root extracts on sexual behaviour in male Wistar rats

International audienc

Etude fonctionnelle du gène REBELOTE chez Arabidopsis thaliana

Ponts entre les séquences d'acides nucléiques et les protéines, les ribosomes sont des composants essentiels des cellules vivantes. Composé d'ARN et de protéines ribosomiques, ils sont transportés, durant leurs biogenèses, du nucléole au cytoplasme, où ils traduisent les ARN messagers (ARNm) en protéines. Ces dernières années, il a été montré que nombre de protéines ribosomiques étaient impliquées dans le développement d'Arabidopsis en intervenant sur la division et l'élongation cellulaire. L'impact d'un défaut de biogenèse des ribosomes sur le développement pourrait être expliqué par un effet dose, par une spécificité des ribosomes pour leur ARNm cibles ou par la multifonctionnalité de protéines ribosomiques. Les résultats obtenus montrent que REBELOTE (RBL), l'un des deux homologues chez Arabidopsis de la protéine NOC2p de levure, intervient probablement durant la biogenèse des ribosomes. Des mutations dans le gène RBL causent une gamme de phénotype de la létalité embryonnaire aux défauts de croissance (réduction de la taille de la plante, altération de la forme des feuilles...). Afin de mieux comprendre les processus contrôlés par RBL, la fonction ribosomique de RBL a été étudiée et ses interacteurs protéiques recherchés. Nous nous sommes ensuite focalisé sur les effets des mutations rbl sur la division et l'élongation cellulaire. Ce travail montre que les défauts observés aux niveaux moléculaire et cellulaire peuvent expliquer les retards de croissance des mutants rbl.Bridges between nucleic acids sequences and proteins, ribosomes are central components and the auletes of living cells. Composed of ribosomal proteins and RNA, they move during their biogenesis from the nucleolus to the cytoplasm, where they translate RNA messengers into proteins. In the past years, some mutants of ribosomal-biogenesis-related proteins have shown the importance of these proteins during cell division and Arabidopsis development. The impact of ribosomal defects on development could be explained by dose effect (which could be important for cell fitness), specificity of ribosomes for some mRNA or multifunctional ribosomal proteins (Mary E. Byrne, 2009). Here I present our work on REBELOTE (RBL), one of the two Arabidopsis homologs of the yeast NOC2 protein, which act during the ribosomal 60S subunit biogenesis. Mutations in REBELOTE gene cause a range of phenotypes, from embryo lethality to growth defects (reduced plant size, altered leaf shape ). To have a better understanding of RBL-controlled processes, we first analyzed the ribosomal function of RBL, and searched for its protein partners. Our results shows that RBL act in two different nucleolar complexes supposed to regulate 60S ribosomal subunit biogenesis. Subsequently, we focused on the effects of rbl mutations on the cell division/elongation processes. Our work shows that defects observed at molecular and cellular levels could explain the slow down of cell divisions and growth delay in rbl mutants.LYON-ENS Sciences (693872304) / SudocSudocFranceF