183 research outputs found
Extracting the Redox Orbitals in Li Battery Materials with High-Resolution X-Ray Compton Scattering Spectroscopy
We present an incisive spectroscopic technique for directly probing redox
orbitals based on bulk electron momentum density measurements via
high-resolution x-ray Compton scattering. Application of our method to spinel
LixMn2O4, a lithium ion battery cathode material, is discussed. The orbital
involved in the lithium insertion and extraction process is shown to mainly be
the oxygen 2p orbital. Moreover, the manganese 3d states are shown to
experience spatial delocalization involving 0.16 electrons per Mn site during
the battery operation. Our analysis provides a clear understanding of the
fundamental redox process involved in the working of a lithium ion battery.Comment: 24 pages, 3 figure
Direct observation of active material concentration gradients and crystallinity breakdown in LiFePO4 electrodes during charge/discharge cycling of lithium batteries
The phase changes that occur during discharge of an electrode comprised of LiFePO4, carbon, and PTFE binder have been studied in lithium half cells by using X-ray diffraction measurements in reflection geometry. Differences in the state of charge between the front and the back of LiFePO4 electrodes have been visualized. By modifying the X-ray incident angle the depth of penetration of the X-ray beam into the electrode was altered, allowing for the examination of any concentration gradients that were present within the electrode. At high rates of discharge the electrode side facing the current collector underwent limited lithium insertion while the electrode as a whole underwent greater than 50% of discharge. This behavior is consistent with depletion at high rate of the lithium content of the electrolyte contained in the electrode pores. Increases in the diffraction peak widths indicated a breakdown of crystallinity within the active material during cycling even during the relatively short duration of these experiments, which can also be linked to cycling at high rate
Egg Formation in Lepidoptera
Reproductive biology in the Twentieth Century produced comprehensive descriptions of the mechanisms of egg formation in most of the major orders of insects. While many general principles of ovarian development and physiology emerged, every order turned out to have a set of its own special motifs. Discovery of the lepidopteran motifs is summarized in this essay. The emphasis is on developmental mechanisms, beginning with the early growth and differentiation of female germ cells and ending, after many turns in morphogenesis, physiology and biosynthesis, with eggs that are filled with yolk and encased in chorions. Examples of uniquely lepidopteran traits include the cellular composition of ovarian follicles, the number of tubular ovarioles in which they mature, the functions of cell-to-cell junctional complexes in their maturation, their use of glycosaminoglycans to maintain intercellular patency during vitellogenesis, the role of proton and calcium pumps in their ion physiology, a separate postvitellogenic period of water and inorganic ion uptake, and the fine structure and protein composition of their chorions. Discovery of this combination of idiosyncracies was based on advances in the general concepts and techniques of cell and molecular biology and on insights borrowed from studies on other insects. The lepidopteran ovary in turn has contributed much to the understanding of egg formation in insects generally
fabH deletion increases DHA productionin Escherichia coli expressing Pfa genes
Background: Some marine bacteria, such as Moritella marina, produce the nutraceutical docosahexaenoic acid (DHA) thanks to a specific enzymatic complex called Pfa synthase. Escherichia coli heterologously expressing the pfa gene cluster from M. marina also produces DHA. The aim of this study was to find genetic or metabolic conditions to increase DHA production in E. coli. Results: First, we analysed the effect of the antibiotic cerulenin, showing that DHA production increased twofold. Then, we tested a series of single gene knockout mutations affecting fatty acid biosynthesis, in order to optimize the synthesis of DHA. The most effective mutant, fabH, showed a threefold increase compared to wild type strain. The combination of cerulenin inhibition and fabH deletion rendered a 6.5-fold improvement compared to control strain. Both strategies seem to have the same mechanism of action, in which fatty acid synthesis via the canonical pathway (fab pathway) is affected in its first catalytic step, which allows the substrates to be used by the heterologous pathway to synthesize DHA. Conclusions: DHA-producing E. coli strain that carries a fabH gene deletion boosts DHA production by tuning down the competing canonical biosynthesis pathway. Our approach can be used for optimization of DHA production in different organisms.Funding: The work in the FdlC and GM laboratories was financed by the Spanish Ministry of Economy, Industry and Competitiveness Grant BFU2014-55534-C2
Widespread Occurrence of Secondary Lipid Biosynthesis Potential in Microbial Lineages
Bacterial production of long-chain omega-3 polyunsaturated fatty acids (PUFAs),
such as eicosapentaenoic acid (EPA, 20:5n-3) and
docosahexaenoic acid (DHA, 22:6n-3), is constrained to a narrow
subset of marine γ-proteobacteria. The genes responsible for de
novo bacterial PUFA biosynthesis, designated
pfaEABCD, encode large, multi-domain protein complexes akin
to type I iterative fatty acid and polyketide synthases, herein referred to as
“Pfa synthases”. In addition to the archetypal Pfa synthase gene
products from marine bacteria, we have identified homologous type I FAS/PKS gene
clusters in diverse microbial lineages spanning 45 genera representing 10 phyla,
presumed to be involved in long-chain fatty acid biosynthesis. In total, 20
distinct types of gene clusters were identified. Collectively, we propose the
designation of “secondary lipids” to describe these
biosynthetic pathways and products, a proposition consistent with the
“secondary metabolite” vernacular. Phylogenomic analysis reveals a
high degree of functional conservation within distinct biosynthetic pathways.
Incongruence between secondary lipid synthase functional clades and taxonomic
group membership combined with the lack of orthologous gene clusters in closely
related strains suggests horizontal gene transfer has contributed to the
dissemination of specialized lipid biosynthetic activities across disparate
microbial lineages
AVPV neurons containing estrogen receptor-beta in adult male rats are influenced by soy isoflavones
BACKGROUND: Isoflavones, the most abundant phytoestrogens in soy foods, are structurally similar to 17beta-estradiol. It is known that 17beta-estradiol induces apoptosis in anteroventral periventricular nucleus (AVPV) in rat brain. Also, there is evidence that consumption of soy isoflavones reduces the volume of AVPV in male rats. Therefore, in this study, we examined the influence of dietary soy isoflavones on apoptosis in AVPV of 150 day-old male rats fed either a soy isoflavone-free diet (Phyto-free) or a soy isoflavone-rich diet (Phyto-600). RESULTS: The occurrence of apoptosis in AVPV was examined by TUNEL staining. The incidence of apoptosis was about 10 times higher in the Phyto-600 group (33.1 ± 1.7%) than in the Phyto-free group (3.6 ± 1.0%). Furthermore, these apoptotic cells were identified as neurons by dual immunofluorescent staining of GFAP and NeuN as markers of astrocytes and neurons, respectively. Then the dopaminergic neurons in AVPV were detected by immunohistochemistry staining of tyrosine hydroxylase (TH). No significant difference in the number of TH neurons was observed between the diet treatment groups. When estrogen receptor (ER) alpha and beta were examined by immunohistochemistry, we observed a 22% reduction of ERbeta-positive cell numbers in AVPV with consumption of soy isoflavones, whereas no significant change in ERalpha-positive cell numbers was detected. Furthermore, almost all the apoptotic cells were ERbeta-immunoreactive (ir), but not ERalpha-ir. Last, subcutaneous injections of equol (a major isoflavone metabolite) that accounts for approximately 70–90% of the total circulating plasma isoflavone levels did not alter the volume of AVPV in adult male rats. CONCLUSION: In summary, these findings provide direct evidence that consumption of soy isoflavones, but not the exposure to equol, influences the loss of ERbeta-containing neurons in male AVPV
Molecular genetic analysis of podocyte genes in focal segmental glomerulosclerosis—a review
This review deals with podocyte proteins that play a significant role in the structure and function of the glomerular filter. Genetic linkage studies has identified several genes involved in the development of nephrotic syndrome and contributed to the understanding of the pathophysiology of glomerular proteinuria and/or focal segmental glomerulosclerosis. Here, we describe already well-characterized genetic diseases due to mutations in nephrin, podocin, CD2AP, alpha-actinin-4, WT1, and laminin β2 chain, as well as more recently identified genetic abnormalities in TRPC6, phospholipase C epsilon, and the proteins encoded by the mitochondrial genome. In addition, the role of the proteins which have shown to be important for the structure and functions by gene knockout studies in mice, are also discussed. Furthermore, some rare syndromes with glomerular involvement, in which molecular defects have been recently identified, are briefly described. In summary, this review updates the current knowledge of genetic causes of congenital and childhood nephrotic syndrome and provides new insights into mechanisms of glomerular dysfunction
Dorsal penile nerve block for robot-assisted radical prostatectomy catheter related pain: a randomized, double-blind, placebo-controlled trial
Investigation on the Growth and Distribution of Natural Snow Crystals by the Use of Observation Points Distributed Vertically, 3
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