Activation of C1 compounds by iron and mackinawite under prebiotic conditions

The role of iron sulfide minerals for the terrestrial origin of life has been discussed over several decades, but until now not fully resolved. Here, mackinawite (FeSm) was found to be selectively formed from the reaction of a wettened mixture of iron and sulfur powders. The structure and composition of the FeSm was analyzed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM) and Mössbauer spectroscopy. When the FeSm from the elements was let in contact with different C1 substrates (CO2, CO, KCN, KSCN, KOCN, CS2, CH3SH, [Fe(CN)6]3-/4- and [Fe(CN)5(NO)]2-) a range of reaction products (CS2, COS, C1 to C5 hydrocarbons, C1 to C4 thiols and oxygenated species) were formed at 25 ° and 80 °C in the presence of various acids (HCl, H2SO4 and H3PO4). Based on the product array, a novel reduction mechanism could be formulated where the sulfide end-groups of the FeSm particles interact with the C atom of the different substrates. To support this assumption, the reduction of KCN was investigated by DFT calculations on an all ferrous Fe4S44 cluster. The nucleophilic attack of a deprotonated end-group towards the C atom was thereby found to be exothermic by – 75.5 kcal mol-1. The subsequent reduction of the C residue into CH4 and CH3SH proceeds in an overall exothermic manner if electrons and protons are available. The selective reaction between iron and sulfur has the potential to change our current view on prebiotic processes as the established chemistry of iron sulfides can now additionally be discussed for environments, other than undersea hydrothermal systems. The transfer of the FeSm chemistry towards on-land scenarios enables reactions that would not be possible in the omnipresence of H2O. Furthermore, substances like CH3CHO and the cyclic organosulfur compounds are interesting precursors for biologically relevant molecules like DNA, RNA, or organometallic complexes like [FeFe]-hydrogenases

Facile Synthesis and Characterization of Pure Tochilinite‐like Materials from Nanoparticulate FeS

Abstract In this work, three different tochilinite‐like materials have been obtained by sophisticated synthetic methods that allow to control the distribution of iron ions. The purity of the samples was confirmed by powder X‐ray diffraction. From elemental analysis and Mössbauer spectroscopy data, detailed compositions could be determined: T1) Fe 0.76 S*0.86 [Fe 2+ 0.01 Fe 3+ 0.56 Mg 2+ 0.43 (OH) 2.01 ]; T2) Fe 0.89 S*0.85 [Fe 2+ 0.55 Fe 3+ 0.11 Al 3+ 0.33 (OH) 1.84 (O) 0.16 ]; T3) Fe 0.71 S*0.79 [Fe 2+ 0.25 Fe 3+ 0.73 Mg 2+ 0.01 Al 3+ 0.01 (OH) 1.98 (O) 0.02 ]. These compositions fit to typical compositions of tochilinite in regard of the amount of iron vacancies and the volume ratio of the hydroxide layers to the sulfide layers. Besides hydroxide ions, oxide ions are also present in the hydroxide layers as a result of surface oxidation after the synthesis due to the high reactivity of the particles. TEM and SEM investigations show that the obtained powders consist mainly of thin sheets accompanied by nanotubes with BET surface areas ranging between 20 m 2 /g and 40 m 2 /g. The thermal stability was investigated by TGA and DSC analysis and it depends significantly on the composition.imag

Insufficient antiretroviral therapy in pregnancy: missed opportunities for prevention of mother-to-child transmission of HIV in Europe

Background: Although mother-to-child transmission (MTCT) rates are at an all-time low in Western Europe, potentially preventable transmissions continue to occur. Duration of antenatal combination antiretroviral therapy (ART) is strongly associated with MTCT risk.Methods: Data on pregnant HIV-infected women enrolled in the Western and Central European sites of the European Collaborative Study between January 2000 and July 2009 were analysed. The proportion of women receiving no antenatal ART or 1-13 days of treatment was investigated, and associated factors explored using logistic regression models.Results: Of 2,148 women, 142 (7%) received no antenatal ART, decreasing from 8% in 2000-2003 to 5% in 2004-2009 (chi(2)=8.73; P= 14 days antenatal ART and 7.4% (10/136) among those with insufficient ART.Conclusions: Over the last 10 years, around one in 11 women in this study received insufficient antenatal ART, accounting for 40% of MTCTs. One-half of these women were diagnosed before conception, suggesting disengagement from care

Enzymatic Fischer-Tropsch-Type Reactions.

The Fischer-Tropsch (FT) process converts a mixture of CO and H2 into liquid hydrocarbons as a major component of the gas-to-liquid technology for the production of synthetic fuels. Contrary to the energy-demanding chemical FT process, the enzymatic FT-type reactions catalyzed by nitrogenase enzymes, their metalloclusters, and synthetic mimics utilize H+ and e- as the reducing equivalents to reduce CO, CO2, and CN- into hydrocarbons under ambient conditions. The C1 chemistry exemplified by these FT-type reactions is underscored by the structural and electronic properties of the nitrogenase-associated metallocenters, and recent studies have pointed to the potential relevance of this reactivity to nitrogenase mechanism, prebiotic chemistry, and biotechnological applications. This review will provide an overview of the features of nitrogenase enzymes and associated metalloclusters, followed by a detailed discussion of the activities of various nitrogenase-derived FT systems and plausible mechanisms of the enzymatic FT reactions, highlighting the versatility of this unique reactivity while providing perspectives onto its mechanistic, evolutionary, and biotechnological implications

KPC-50 confers resistance to ceftazidime-avibactam associated with reduced carbapenemase activity

KPC-50 is a KPC-3 variant identified from a Klebsiella pneumoniae clinical isolate recovered in Switzerland in 2019. Compared to KPC-3, KPC-50 shows (i) a three- amino-acid insertion (Glu-Ala-Val) between amino acids 276 and 277, (ii) an increased affinity to ceftazidime, (iii) a decreased sensitivity to avibactam, explaining the ceftazidime-avibactam resistance, and (iv) an association with a sharp reduction of its carbapenemase activity

Nitrogenase Fe Protein: A Multi-Tasking Player in Substrate Reduction and Metallocluster Assembly

The Fe protein of nitrogenase plays multiple roles in substrate reduction and metallocluster assembly. Best known for its function to transfer electrons to its catalytic partner during nitrogenase catalysis, the Fe protein is also a key player in the biosynthesis of the complex metalloclusters of nitrogenase. In addition, it can function as a reductase on its own and affect the ambient reduction of CO2 or CO to hydrocarbons. This review will provide an overview of the properties and functions of the Fe protein, highlighting the relevance of this unique FeS enzyme to areas related to the catalysis, biosynthesis, and applications of the fascinating nitrogenase system

Fatty acid composition and volatile compounds of caviar from farmed white sturgeon (Acipenser transmontanus)

The present study was conducted to characterize caviar obtained from farmed white sturgeons (Acipenser transmontanus) subjected to different dietary treatments. Twenty caviar samples from fish fed two experimental diets containing different dietary lipid sources have been analysed for chemical composition, fatty acids and flavour volatile compounds. Fatty acid make up of caviar was only minimally influenced by dietary fatty acid composition. Irrespective of dietary treatments, palmitic acid (16:0) and oleic acid (OA, 18:1 n-9) were the most abundant fatty acid followed by docosahexaenoic acid (DHA, 22:6 n-3) and eicopentaenoic (EPA, 20:5 n-3).Thirty-three volatile compounds were isolated using simultaneous distillation&ndash;extraction (SDE) and identified by GC&ndash;MS. The largest group of volatiles were represented by aldehydes with 20 compounds, representing the 60% of the total volatiles. n-Alkanals, 2-alkenals and 2,4-alkadienals are largely the main responsible for a wide range of flavours in caviar from farmed white surgeon<br /

Pueblos y paisajes antiguos de la selva amazónica

Durante algo más de 50 años antropólogos, arqueólogos, linguistas y geógrafos se han ocupado seriamente del pasado de la Amazonia. Más recientemente otros académicos, entre ellos genetistas y ecólogos, se han fascinado por el mismo. Durante más de 10.000 años los nativos han participado e interpretado esta historia. una historia que unos y otros leen y descifran a partir de diversas claves, como lo pueden ser las formas del paisaje, algunos objetos antiguos y los testimonios y tradiciones orales que tienen a su alcance. Los resultados son múltiples. Estos revelan tanto desacuerdos entre los especialistas como mundos insospechados. Se hacen evidentes caminos que se cruzan y se mezclan; en una dirección convergen y en otra divergen. El lector encontrará en este volumen una fracción de este universo, la misma va acompañada de una invitación a participar en un diálogo amplio que contribuya a enriquecer nuestra visión de un mundo por explorar

Efficacy and safety of tenecteplase in combination with enoxaparin, abciximab, or unfractionated heparin: The ASSENT-3 randomised trial in acute myocardial infarction

Background: Current fibrinolytic therapies fail to achieve optimum reperfusion in many patients. Low-molecular-weight heparins and platelet glycoprotein IIb/IIIa inhibitors have shown the potential to improve pharmacological reperfusion therapy. We did a randomised, open-label trial to compare the efficacy and safety of tenecteplase plus enoxaparin or abciximab, with that of tenecteplase plus weight-adjusted unfractionated heparin in patients with acute myocardial infarction. Methods: 6095 patients with acute myocardial infarction of less than 6 h were randomly assigned one of three regimens: full-dose tenecteplase and enoxaparin for a maximum of 7 days (enoxaparin group; n=2040), half-dose tenecteplase with weight-adjusted low-dose unfractionated heparin and a 12-h infusion of abciximab (abciximab group; n=2017), or full-dose tenecteplase with weight-adjusted unfractionated heparin for 48 h (unfractionated heparin group; n=2038). The primary endpoints were the composites of 30-day mortality, in-hospital reinfarction, or in-hospital refractory ischaemia (efficacy endpoint), and the above endpoint plus in-hospital intracranial haemorrhage or in-hospital major bleeding complications (efficacy plus safety endpoint). Analysis was by intention to treat. Findings: There were significantly fewer efficacy endpoints in the enoxaparin and abciximab groups than in the unfractionated heparin group: 233/2037 (11.4%) versus 315/2038 (15.4%; relative risk 0.74 [95% CI 0.63-0.87], p=0.0002) for enoxaparin, and 223/2017 (11.1%) versus 315/2038 (15.4%; 0.72 [0.61-0.84], p&lt;0.0001) for abciximab. The same was true for the efficacy plus safety endpoint: 280/2037 (13.7%) versus 347/2036 (17.0%; 0.81 [0.70-0.93], p=0.0037) for enoxaparin, and 287/2016 (14.2%) versus 347/2036 (17.0%; 0.84 [0.72-0.96], p=0.01416) for abciximab. Interpretation: The tenecteplase plus enoxaparin or abciximab regimens studied here reduce the frequency of ischaemic complications of an acute myocardial infarction. In light of its ease of administration, tenecteplase plus enoxaparin seems to be an attractive alternative reperfusion regimen that warrants further study