Vulgar Towers

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Non-heme iron hydroperoxo species in superoxide reductase as a catalyst for oxidation reactions

International audienceThe non-hemehigh-spin ferric iron hydroperoxo species formed in superoxide reductase catalyzesoxidative aldehyde deformylation through its nucleophile character.This species also acts as an electrophile to catalyze oxygen atom transfer in sulfoxidation reactions, highlighting the oxidation potential of non-heme iron hydroperoxo species. The mechanisms of oxygen activation and oxidation reactions catalyzed by metalloenzymes have been thoroughly investigated during the last past decades. 1-5 For cytochrome P450 5, 6 and several non-heme iron monooxygenases, 4, 7, 8 it is now well admitted that high-valent iron-oxo species formed at their active site is the effective oxidant for organic substrate oxidation and oxygen transfer. Nevertheless, the fact that alternative species, e.g. ferric iron (hydro)peroxide intermediate, 1 or other metal-oxidant adducts, 9

Control of the Evolution of Iron Peroxide Intermediate in Superoxide Reductase from Desulfoarculus baarsii. Involvement of Lysine 48 in Protonation

International audienceSuperoxide reductase is a nonheme iron metalloenzyme that detoxifies superoxide anion radicals O(2)(•-) in some microorganisms. Its catalytic mechanism was previously proposed to involve a single ferric iron (hydro)peroxo intermediate, which is protonated to form the reaction product H(2)O(2). Here, we show by pulse radiolysis that the mutation of the well-conserved lysine 48 into isoleucine in the SOR from Desulfoarculus baarsii dramatically affects its reaction with O(2)(•-). Although the first reaction intermediate and its decay are not affected by the mutation, H(2)O(2) is no longer the reaction product. In addition, in contrast to the wild-type SOR, the lysine mutant catalyzes a two-electron oxidation of an olefin into epoxide in the presence of H(2)O(2), suggesting the formation of iron-oxo intermediate species in this mutant. In agreement with the recent X-ray structures of the peroxide intermediates trapped in a SOR crystal, these data support the involvement of lysine 48 in the specific protonation of the proximal oxygen of the peroxide intermediate to generate H(2)O(2), thus avoiding formation of iron-oxo species, as is observed in cytochrome P450. In addition, we proposed that the first reaction intermediate observed by pulse radiolysis is a ferrous-iron superoxo species, in agreement with TD-DFT calculations of the absorption spectrum of this intermediate. A new reaction scheme for the catalytical mechanism of SOR with O(2)(•-) is presented in which ferrous iron-superoxo and ferric hydroperoxide species are reaction intermediates, and the lysine 48 plays a key role in the control of the evolution of iron peroxide intermediate to form H(2)O(2)

Midwives' experiences of referring obese women to either a community or home-based antenatal weight management service:Implications for service providers and midwifery practice

Objective a variety of services to support women to undertake weight management behaviours during pregnancy have recently been implemented as a means to reduce the risks to mother and infant. In the UK, midwives lead the care of the majority of pregnant women and are seen as the ideal source of referral into antenatal services. However, midwives have reported concerns regarding raising the topic of weight with obese women and negative referral experiences have been cited as a reason not to engage with a service. This study explored midwives’ experiences of referring women to one of two antenatal weight management services. Design qualitative, cross-sectional interview and focus group study, with data analysed thematically. Setting midwifery teams in the West Midlands, England. Participants midwives responsible for referring to either a home-based, one to one service (N=12), or a community-based, group service (N=11). Findings four themes emerged from the data. Participants generally had a positive View of the service, but their Information needs were not fully met, as they wanted more detail about the service and feedback regarding the women they had referred. Approaches to referral differed, with some participants referring all women who met the eligibility criteria, and some offering women a choice to be referred or not. Occasionally the topic was not raised at all when a negative reception was anticipated. Reasons for poor uptake of the services included pragmatic barriers, and their perception of women's lack of interest in weight management. Key conclusions midwives’ differing views on choice and gaining agreement to refer means referral practices vary, which could increase the risk that obese women have inequitable access to weight management services. However, midwives’ confidence in the services on offer may be increased with more detailed information about the service and feedback on referrals, which would additionally act as prompts to refer. Implications for practice weight management services need to improve communication with their referral agents and try to overcome practical and psychosocial barriers to uptake. It would be beneficial to develop a shared understanding of the concept of ‘informed choice’ specifically regarding referral to health promotion services among midwives. Training which demonstrates effective methods of sensitively introducing a weight management service to obese women may increase midwives’ confidence to consistently include this in their practice. These measures may improve women's engagement with services which have the potential to reduce the risks associated with maternal obesity

Hexa-μ2-benzoato-bis­(2,2′-bipyrid­yl)trimanganese(II) monohydrate

The complex molecule of the title compound, [Mn3(C7H5O2)6(C10H8N2)2]·H2O, contains a linear array of divalent manganese ions. The central MnII atom, which is located on a crystallographic inversion center, is coordinated octa­hedrally by six benzoate O atoms. The two terminal MnII ions are six-coordinated by four benzoate O atoms and two N atoms of 2,2′-bipyridyl. The central MnII atom and the terminal MnII ions are bridged by four benzoate ligands in a bidentate fashion, whereas the other two carboxyl­ate ligands form bridges through one O atom only and chelate the terminal MnII atom. The mol­ecules pack together via van der Waals attractions and C—H⋯O hydrogen bonds

Introduction to the French GEOTRACES North Atlantic Transect (GA01): GEOVIDE cruise

The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this special issue (https://www.biogeosciences.net/special_issue900.html), results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among 18 articles. Here, the scientific context, project objectives, and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue

Artificial Enzymes Crystals: New heterogeneous Catalysts for a sustainable oxidation

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​La perception et le jugement de l’enseignant sur les élèves

Quel peut être l'impact de l'estime de l'enseignant sur l'estime de soi des élèves. Le jugement de l'enseignant peut-il avoir une influence sur leur motivation et leurs résultats scolaires ? Le bien être des élèves est-il lié à leur environnement scolaire ? Quelle influence peut avoir le climat de classe sur la scolarité des élèves

Flori Lugdunensis Opera omnia, t. I, Collectio ex dictis XII Patrum, pars prima

Menage Christian. Flori Lugdunensis Opera omnia, t. I, Collectio ex dictis XII Patrum, pars prima. In: Bibliothèque de l'école des chartes. 2003, tome 161, livraison 2. pp. 731-732

Dissertation sur les sonnets pour la belle matineuse

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