An important clue to the mechanism for O(2) tolerance of certain [NiFe]-hydrogenases is the conserved presence of a modified environment around the iron-sulfur cluster that is proximal to the active site. The O(2)-tolerant enzymes contain two cysteines, located at opposite ends of this cluster, which are glycines in their O(2)-sensitive counterparts. The strong correlation highlights special importance for electron-transfer activity in the protection mechanism used to combat O(2). Site-directed mutagenesis has been carried out on Escherichia coli hydrogenase-1 to substitute these cysteines (C19 and C120) individually and collectively for glycines, and the effects of each replacement have been determined using protein film electrochemistry and electron paramagnetic resonance (EPR) spectroscopy. The "split" iron-sulfur cluster EPR signal thus far observed when oxygen-tolerant [NiFe]-hydrogenases are subjected to oxidizing potentials is found not to provide any simple, reliable correlation with oxygen tolerance. Oxygen tolerance is largely conferred by a single cysteine (C19), replacement of which by glycine removes the ability to function even in 1% O(2).

The unusual [4Fe-3S] cluster proximal to the active site plays a crucial role in allowing a class of [NiFe]-hydrogenases to function in the presence of O(2) through its unique ability to undergo two rapid, consecutive one-electron transfers. This property helps to neutralize reactive oxygen species. Mechanistic details and the role of the medial and distal clusters remain unresolved. To probe the Fe-S relay, continuous wave and pulse electron paramagnetic resonance (EPR) studies were conducted on the O(2)-tolerant hydrogenase from Escherichia coli (Hyd-1) and three variants with point mutations at the proximal and/or medial clusters. Reduction potentials of the proximal ([4Fe-3S](5+/4+/3+)) and medial ([3Fe-4S](+/0)) clusters were determined by potentiometry. The medial [3Fe-4S](+/0) reduction potential is exceptionally high, implicating a mechanistic role in O(2)-tolerance. Numerous experiments establish that the distal cluster has a ground state S > 1/2 in all three variants and indicate that this is also the case for native Hyd-1. Concurrent with the Hyd-1 crystal structure, EPR data for the 'superoxidized' P242C variant, in which the medial cluster is 'magnetically silenced', reveal two conformations of the proximal [4Fe-3S](5+) cluster, and X-band HYSCORE spectroscopy shows two (14)N hyperfine couplings attributed to one conformer. The largest, A((14)N) = [11.5,11.5,16.0] ± 1.5 MHz, characterizes the unusual bond between one Fe (Fe(4)) and the backbone amide-N of cysteine-20. The second, A((14)N) = [2.8,4.6,3.5] ± 0.3 MHz, is assigned to N(C19). The (14)N hyperfine couplings are conclusive evidence that Fe(4) is a valence-localized Fe(3+) in the superoxidized state, whose formation permits an additional electron to be transferred rapidly back to the active site during O(2) attack.

Salmonella enterica serovar Typhimurium is a Gram negative bacterial pathogen and a common cause of food‐borne illness. Molecular hydrogen has been shown to be a key respiratory electron donor during infection and H2 oxidation can be catalysed by three genetically‐distinct [NiFe] hydrogenases. Of these, hydrogenases‐1 (Hyd‐1) and Hyd‐2 have well‐characterised homologues in Escherichia coli. The third, designated Hyd‐5 here, is peculiar to Salmonella and is expressed under aerobic conditions. In this work, Salmonella was genetically modified to enable the isolation and characterisation of Hyd‐5. Electrochemical analysis established that Hyd‐5 is a H2‐oxidising enzyme that functions in very low levels of H2 and sustains this activity in high levels of O2. In addition, electron paramagnetic resonance spectroscopy of the Hyd‐5 isoenzyme reveals a complex paramagnetic FeS signal at high potentials which is comparable to that observed for other O2‐tolerant respiratory [NiFe] hydrogenases. Taken altogether, Hyd‐5 can be classified as an O2‐tolerant hydrogenase that confers upon Salmonella the ability to use H2 as an electron donor in aerobic respiration.

Non-stoichiometry and bulk cation transport have been identified as key factors in the release and uptake of hydrogen in the Li-N-H system. Amide halide phases have been synthesized that have ionic conductivities several orders of magnitude greater than lithium amide, a faster rate of hydrogen release and elimination of the by-product, ammonia. Here we report the effect of both anion-and cation-doping on the hydrogen desorption properties of lithium amide, focusing in particular on how the presence of chloride anions and magnesium cations affects and controls the structure of the amide and imide compounds at the sub-nanometre level. Reducing the chloride content resulted in new low-chloride rhombohedral phases that contain around half of the chloride present in earlier amide chlorides, but maintained the enhancements seen in hydrogen desorption properties when compared to the halide-free system. These materials may also have potential in a range of other energy applications such as all solid state lithium ion batteries, supercapacitors, and CO 2 capture and storage membranes.

Lithium MagnesiumAmide chlorides Powder X-ray diffraction a b s t r a c t Two new amide chloride phases, with approximate stoichiometries Li 7 (NH 2 ) 6 Cl and Li 6 Mg 0.5 (NH 2 ) 6 Cl, have been identified by powder X-ray diffraction, and their hydrogen storage properties studied. Both phases released hydrogen on reaction with LiH at a lower temperature than observed for lithium amide, and ammonia release was suppressed. The chloride ions were maintained within the structure after hydrogen desorption and rehydrogenation, raising the possibility that the materials might be cycled. The desorption properties of Li 7 (NH 2 ) 6 Cl were found to be similar to the previously reported amide chloride Li 4 (NH 2 ) 3 Cl but with a much reduced gravimetric penalty owing to chloride incorporation.Rehydrogenation of the imide products of reaction of both Li 7 (NH 2 ) 6 Cl and Li 6 Mg 0.5 (NH 2 ) 6 Cl with LiH occurred more readily at 90 bar and 300 C than that of Li 4 (NH 2 ) 3 Cl.

a b s t r a c tAn investigation has been carried out into the lower limits of halide incorporation in lithium amide (LiNH 2 ). It was found that the lithium amide iodide Li 3 (NH 2 ) 2 I was unable to accommodate any variation in stoichiometry. In contrast, some variation in stoichiometry was accommodated in Li 7 (NH 2 ) 6 Br, as shown by a decrease in unit cell volume when the bromide content was reduced. The amide chloride Li 4 (NH 2 ) 3 Cl was found to adopt either a rhombohedral or a cubic structure depending on the reaction conditions. Reduction in chloride content generally resulted in a mixture of phases, but a new rhombohedral phase with the stoichiometry Li 7 (NH 2 ) 6 Cl was observed. In comparison to LiNH 2 , this new lowchloride phase exhibited similar improved hydrogen desorption properties as Li 4 (NH 2 ) 3 Cl but with a much reduced weight penalty through addition of chloride. Attempts to dope lithium amide with fluoride ions have so far proved unsuccessful.Ó 2015 Published by Elsevier B.V.

Improving nutritional status during pregnancy is a global interest. Frequently, women either fail to meet or exceed nutrient recommendations. Current strategies to improve maternal nutrition focuses on a “one-size-fits-all” approach and fail to consider individual factors that affect the mother's overall nutritional status. The objectives of this review were to determine the importance of key nutrients for optimal maternal and fetal health, to explore to what extent current recommendations consider individual factors, and to explore novel strategies to close the gap between current guidelines and real-world challenges through more personalized approaches. This review intercalated different nutritional guidelines and recent scientific publications and research initiatives related to maternal nutrition. Based on that, an overview of current recommendations, challenges related to present approaches, and perspectives for future directions are described. Current guidelines are not optimally supporting adequate nutrient intake and health of expectant mothers and their offspring. Existing recommendations are not consistent and do not sufficiently take into account how interindividual variation leads to differences in nutrient status. Personalized nutrition offers women the opportunity to improve their health by using strategies that are tailored to their unique nutritional needs. Such strategies can include personalized supplementation, holistic lifestyle interventions, digital and application-based technologies, and dietary assessment through blood biomarker and genetic analysis. However, these approaches warrant further investigation and optimization. More personalized approaches have the potential to optimize mothers’ and their offspring's health outcomes more appropriate to their nutritional needs before, during, and after pregnancy. Moving away from a generalized “one-size-fits-all” approach can be achieved through a variety of means. Future aims should be to provide supporting evidence to create customized subpopulation-based or individualized recommendations, improve nutrition education, and develop novel approaches to improve adherence to dietary and lifestyle interventions.

Scope: Milk fat globule membrane (MFGM) is an essential component of milk. Bovine MFGM (bMFGM) has been shown to support cognitive development and increase relative concentrations of serum phospholipids. This study investigates bioavailability of bMFGM components after oral administration in two preclinical models to explore whether dietary bMFGM induces parallel changes to plasma and brain lipidomes. Methods and results: Transgenic APOE*3.Leiden mice (n = 18 per group) and Sprague-Dawley rats (n = 12 per group) are fed bMFGM-enriched (MFGM+) or Control diet, followed by phospholipid profile-determination in plasma, hippocampus, and prefrontal cortex tissue by targeted mass spectrometry. Multivariate analysis of lipidomic profiles demonstrates a separation between MFGM+ and Control plasma across rodents. In plasma, sphingomyelins contributed the most to the separation of lipid patterns among both models, where three sphingomyelins (d18:1/14:0, d18:1/23:0, d18:1/23:1[9Z]) are consistently higher in the circulation of MFGM+ groups. A similar trend is observed in rat prefrontal cortex, although no significant separation of the brain lipidome is demonstrated. Conclusion: bMFGM-enriched diet alters plasma phospholipid composition in rodents, predominantly increasing sphingomyelin levels in the systemic circulation with similar, but non-significant, trends in central brain regions. These changes may contribute to the beneficial effects of bMFGM on neurodevelopment during early life.