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The cages, dynamics, and structuring of incipient methane clathrate hydrates
Walsh, Matthew R.,Rainey, J. Daniel,Lafond, Patrick G.,Park, Da-Hye,Beckham, Gregg T.,Jones, Michael D.,Lee, Kun-Hong,Koh, Carolyn A.,Sloan, E. Dendy,Wu, David T.,Sum, Amadeu K. Royal Society of Chemistry 2011 Physical chemistry chemical physics Vol.13 No.44
<P>Interest in describing clathrate hydrate formation mechanisms spans multiple fields of science and technical applications. Here, we report findings from multiple molecular dynamics simulations of spontaneous methane clathrate hydrate nucleation and growth from fully demixed and disordered two-phase fluid systems of methane and water. Across a range of thermodynamic conditions and simulation geometries and sizes, a set of seven cage types comprises approximately 95% of all cages formed in the nucleated solids. This set includes the ubiquitous 5<SUP>12</SUP> cage, the 5<SUP>12</SUP>6<SUP><I>n</I></SUP> subset (where <I>n</I> ranges from 2–4), and the 4<SUP>1</SUP>5<SUP>10</SUP>6<SUP><I>n</I></SUP> subset (where <I>n</I> also ranges from 2–4). Transformations among these cages occur <I>via</I> water pair insertions/removals and rotations, and may elucidate the mechanisms of solid–solid structural rearrangements observed experimentally. Some consistency is observed in the relative abundance of cages among all nucleation trajectories. 5<SUP>12</SUP> cages are always among the two most abundant cage types in the nucleated solids and are usually the most abundant cage type. In all simulations, the 5<SUP>12</SUP>6<SUP><I>n</I></SUP> cages outnumber their 4<SUP>1</SUP>5<SUP>10</SUP>6<SUP><I>n</I></SUP> counterparts with the same number of water molecules. Within these consistent features, some stochasticity is observed in certain cage ratios and in the long-range ordering of the nucleated solids. Even when comparing simulations performed at the same conditions, some trajectories yield swaths of multiple adjacent sI unit cells and long-range order over 5 nm, while others yield only isolated sI unit cells and little long-range order. The nucleated solids containing long-range order have higher 5<SUP>12</SUP>6<SUP>2</SUP>/5<SUP>12</SUP> and 5<SUP>12</SUP>6<SUP>3</SUP>/4<SUP>1</SUP>5<SUP>10</SUP>6<SUP>2</SUP> cage ratios when compared to systems that nucleate with little long-range order. The formation of multiple adjacent unit cells of sI hydrate at high driving forces suggests an alternative or addition to the prevailing hydrate nucleation hypotheses which involve formation through amorphous intermediates.</P> <P>Graphic Abstract</P><P>The dominant cages of clathrates are classified and the formation of multiple sI unit cells is reported from large-scale simulations. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cp21899a'> </P>
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Effect of St. John's Wort Standardized Extract and Hypericin on In Vitro Placental Calcium Transport
Aline Oliveira da Conceição,Larissa Takser,Julie Lafond 한국식품영양과학회 2010 Journal of medicinal food Vol.13 No.4
Hypericum perforatum L., known as St. John's wort (SJW), is widely used in human therapeutics for wound healing and to treat depression; however, its recommendation during pregnancy is controversial. Hypericin, a polycyclic quinone isolated from this plant, has been studied and used to standardize the plant extracts. The objective of the present study was to examine the effect of SJW and hypericin on in vitro placental Ca2+ transport. Cell viability, human chorionic gonadotrophin (hCG) production, Ca2+ uptake, and Ca2+ transport proteins expression analysis were conducted using the JEG-3cell line. Toxicity of SJW was seen at high concentrations (≥150μg/mL), but no effect on hCG production was observed using SJW (25μg/mL) or hypericin (7.5 and 75ng/mL). The results showed that cells treated with both SJW and hypericin exhibited increased intracellular Ca2+ concentration after long-term (24-hour) but not short-term (10-minute) period incubation. A significant decrease in translationally controlled tumor protein Ca2+ handling protein was seen only with SJW-treated cells. Hypericin increased the protein expression of the transient receptor potential vanilloid 6 Ca2+ channel and 28-kDa calcium-binding protein and decreased that of plasma membrane Ca2+-ATPase 1/4. In conclusion, SJW and hypericin can increase the trophoblast internal Ca2+ concentration through regulating the protein expression of the Ca2+ transport system, and their intake during pregnancy is still a point of concern.
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Aline Oliveira da Conceição,Maria Helena Rossi,Fernando Faustino de Oliveira,Larissa Takser,Julie Lafond 한국식품영양과학회 2011 Journal of medicinal food Vol.14 No.5
Genipa americana L. (Rubiaceae) is a fruit tree and a traditional medicine used to treat anemia, icterus, asthma, and liver and spleen problems. The aim of the present study was to verify the effect of G. americana fruit ethanolic extract on the mechanism for proliferation and differentiation of trophoblast-like cells. Qualitative analysis of G. americana fruit extract was performed, and BeWo cells, a well-established placental choriocarcinoma cell line that can undergo differentiation, were used to analyze cell viability and proliferation. Methods consisted of cytotoxic and proliferation measurement, detection of release of human chorionic gonadotrophins, cell fusion observation, and evaluation of cell-signaling pathways (production of cyclic adenosine monophosphate and phosphorylation of mitogen-activated protein kinases [MAPKs]). A stock solution of the extract was diluted in Ham's F-12 medium with 10% fetal bovine serum at concentrations ranging from 50 to 1000 μg/mL. Cells treated with dimethylsulfoxide, forskoline, and MAPK inhibitors (PD98059 or SB203580) were used as a control. Forskoline was used to induce the differentiation state in BeWo cells. Phytoanalysis indicated the presence of steroids only. Results showed that the G. americana fruit extract did not cause any cytotoxicity or interference in cell differentiation. However, a significant antiproliferative state related to inhibition and reactivation of ERK1/2 and p38 MAPK in BeWo cells was seen. These results suggest that steroids from G. americana may affect placental cell regulation.
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