259 research outputs found
Cis-regulatory control of the SM50 gene, an early marker of skeletogenic lineage specification in the sea urchin embryo
The SM50 gene encodes a minor matrix protein of the sea urchin embryo spicule. We carried out a detailed functional analysis of a cis-regulatory region of this gene, extending 440 bp upstream and 120 bp downstream of the transcription start site, that had been shown earlier to confer accurate skeletogenic expression of an injected expression vector. The distal portion of this fragment contains elements controlling amplitude of expression, while the region from ā200 to +105 contains spatial control elements that position expression accurately in the skeletogenic lineages of the embryo. A systematic mutagenesis analysis of this region revealed four adjacent regulatory elements, viz two copies of a positively acting sequence (element D) that are positioned just upstream of the transcription start site; an indispensable spatial control element (element C) that is positioned downstream of the start site; and further downstream, a second positively acting sequence (element A). We then constructed a series of synthetic expression constructs. These contained oligonucleotides representing normal and mutated versions of elements D, C, and A, in various combinations. We also changed the promoter of the SM50 gene from a TATA-less to a canonical TATA box form, without any effect on function. Perfect spatial regulation was also produced by a final series of constructs that consisted entirely of heterologous enhancers from the CyIIIa gene, the SV40 early promoter, and synthetic D, C, and A elements. We demonstrate that element C exercises the primary spatial control function of the region we analyzed. We term this a ālocatorā element. This differs from conventional ātissue-specific enhancersā in that while it is essential for expression, it has no transcriptional activity on its own, and it requires other, separable, positive regulatory elements for activity. In the normal configuration these ancillary positive functions are mediated by elements A and D. Only positively acting control elements were observed in the SM50 regulatory domain throughout this analysis
Synthesis, determination of the absolute configuration of tonkinelin, and inhibitory action with bovine heart mitochondrial complex I
ArticleBIOORGANIC & MEDICINAL CHEMISTRY. 15(8): 3026-3031 (2007)journal articl
Magnetoresistance characteristics of Fe3Si/CaF2/Fe3Si heterostructures grown on Si(111) by molecular beam epitaxy
AbstractFe3Si/CaF2/Fe3Si magnetic tunnel junctions (MTJs) have been investigated to demonstrate the tunnel magnetoresistance effects. We fabricated Fe3Si(20 nm)/CaF2(2 nm)/Fe3Si(15 nm) heterostructures epitaxially on a Si(111) substrate by molecular beam epitaxy. The current-voltage characteristics for the MTJs measured at room temperature (RT) were well fitted to Simmonsā equation. The fitting yields the barrier height Ļ=2.5Ā eV and the barrier thickness d=1.26Ā nm. The magnetoresistance ratio for the MTJs were approximately 0.28% under a bias voltage of 20Ā mV at RT
Anti-inflammatory sesquiterpenes from Curcuma zedoaria
This is a preprint of an article whose final and definitive form has been published in the NATURAL PRODUCT RESEARCH Ā© 2006 copyright Taylor & Francis; NATURAL PRODUCT RESEARCH is available online at: http://www.informaworld.com/openurl?genre=article&issn=1478-6419&volume=20&issue=7&spage=680ArticleNATURAL PRODUCT RESEARCH. 20(7): 680-685 (2006)journal articl
Seasonal changes in nauplii and adults of Calanus hyperboreus (Copepoda) captured in sediment traps, Amundsen Gulf, Canadian Arctic
AbstractArctic copepods were collected using time-series sediment traps in the Amundsen Gulf, Canadian Arctic, as part of the CASES (Canadian Arctic Shelf Exchange Study) program. Four sediment traps were deployed at three stations (200m depth for CA15, 200 and 400m depths for CA18, and 200m depth for CA20) from October 2003 to July 2004. We collected many copepod nauplii ranging in body length from 155 to 811Ī¼m, among which nauplii (mostly N1ā2) of Calanus with a size of ā¼190Ī¼m apparently increased in abundance from February to mid-March. Mature-stage adult females (AF) of Calanus hyperboreus were collected in the traps from February to March, and adult males of C. hyperboreus appeared from November to December at all stations. The likely spawning period of these AF coincided with the occurrence period of ā¼190Ī¼m-sized nauplii. This finding suggests that these nauplii were derived from C. hyperboreus and that their breeding began at the beginning of November or December at the latest, continuing through April in the Amundsen Gulf
An efficient synthesis of procyanidins. Rare earth metal Lewis acid catalyzed equimolar condensation of catechin and epicatechin
ArticleTETRAHEDRON LETTERS. 48(33): 5891-5894 (2007)journal articl
A Monte Carlo simulation of ion transport at finite temperatures
We have developed a Monte Carlo simulation for ion transport in hot
background gases, which is an alternative way of solving the corresponding
Boltzmann equation that determines the distribution function of ions. We
consider the limit of low ion densities when the distribution function of the
background gas remains unchanged due to collision with ions. A special
attention has been paid to properly treat the thermal motion of the host gas
particles and their influence on ions, which is very important at low electric
fields, when the mean ion energy is comparable to the thermal energy of the
host gas. We found the conditional probability distribution of gas velocities
that correspond to an ion of specific velocity which collides with a gas
particle. Also, we have derived exact analytical formulas for piecewise
calculation of the collision frequency integrals. We address the cases when the
background gas is monocomponent and when it is a mixture of different gases.
The developed techniques described here are required for Monte Carlo
simulations of ion transport and for hybrid models of non-equilibrium plasmas.
The range of energies where it is necessary to apply the technique has been
defined. The results we obtained are in excellent agreement with the existing
ones obtained by complementary methods. Having verified our algorithm, we were
able to produce calculations for Ar ions in Ar and propose them as a new
benchmark for thermal effects. The developed method is widely applicable for
solving the Boltzmann equation that appears in many different contexts in
physics.Comment: 14 page
Hadal water biogeochemistry over the IzuāOgasawara Trench observed with a full-depth CTD-CMS
Full-depth profiles of hydrographic and geochemical
properties at the IzuāOgasawara Trench were observed for the first time
using a CTD-CMS (conductivityātemperatureādepth profiler with
carouselĀ multiple sampling) system. Additionally, comparative samplings were
done at the northern Mariana Trench using the same methods. A well-mixed
hydrographic structure below 7000āÆm was observed within the IzuāOgasawara
Trench. Seawater samples collected from this well-mixed hadal layer
exhibited constant concentrations of nitrate, phosphate, silicate, and
nitrous oxide as well as constant nitrogen and oxygen isotopic compositions
of nitrate and nitrous oxide. These results agree well with previous
observations of the IzuāOgasawara hadal waters and deep-sea
water surrounding the IzuāOgasawara Trench. In turn, methane concentrations and
isotopic compositions indicated spatial heterogeneity within the well-mixed
hadal water mass, strongly suggesting a local methane source within the
trench, in addition to the background methane originating from the general
deep-sea bottom water. Sedimentary compound releases, associated with
sediment re-suspensions, are considered to be the most likely mechanism for
generating this significant CH4 anomaly.</p
Efficient recycling of nutrients in modern and past hypersaline environments
The biogeochemistry of hypersaline environments is strongly influenced by changes in biological
processes and physicochemical parameters. Although massive evaporation events have occurred
repeatedly throughout Earth history, their biogeochemical cycles and global impact remain poorly
understood. Here, we provide the first nitrogen isotopic data for nutrients and chloropigments from
modern shallow hypersaline environments (solar salterns, Trapani, Italy) and apply the obtained
insights to Ī“15N signatures of the Messinian salinity crisis (MSC) in the late Miocene. Concentrations
and Ī“15N of chlorophyll a, bacteriochlorophyll a, nitrate, and ammonium in benthic microbial mats
indicate that inhibition of nitrification suppresses denitrification and anammox, resulting in efficient
ammonium recycling within the mats and high primary productivity. We also suggest that the release
of 15N-depleted NH3(gas) with increasing salinity enriches ammonium 15N in surface brine (ā34.0ā°).
Such elevated Ī“15N is also recorded in geoporphyrins isolated from sediments of the MSC peak (ā20ā°),
reflecting ammonium supply sufficient for sustaining phototrophic primary production. We propose
that efficient nutrient supply combined with frequent bottom-water anoxia and capping of organic-rich
sediments by evaporites of the Mediterranean MSC could have contributed to atmospheric CO2
reduction during the late Miocene.This study was partly supported by a Japan Society for the Promotion of
Science (JSPS) Research Fellowship (16J07844) to YI, Grants-in-Aid (16H02236) and the JAMSTEC President
Fund to NO
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