137 research outputs found
Physiologically Based Pharmacokinetic Model for Inorganic and Methylmercury in a Marine Fish
A physiologically based pharmacokinetic
(PBPK) model was developed
to simulate the uptake, distribution, and elimination of inorganic
mercury [HgĀ(II)] and methylmercury (MeHg) in a marine fish, <i>Terapon jarbua</i>. In this model, fish were schematized as
a six-compartment model by assuming that blood was the medium linking
the exchange between the different compartments. The transfer rates
between blood and other compartments were determined during a period
of 10-day dietary HgĀ(II) or MeHg exposure, followed by a 30-day depuration.
For both Hg species, the exchange rates between liver and blood were
high, indicating that liver served as a ātransferring stationā
in the distribution. Their accumulation in the kidney was relatively
constant and low. The carcass (mainly muscle) represented a large
sink for both HgĀ(II) and MeHg with the highest input rate constants
and relatively lower output rate constants. Significant differences
were observed in the rate constants between the two Hg species, suggesting
great variations in their exchange and transportation routes. Modeling
simulation for the first time demonstrated that the gill was the most
important route in HgĀ(II) elimination in marine fish, with a rate
constant of 0.90 d<sup>ā1</sup>. A long time frame is needed
to study the exact rate of MeHg elimination in marine fish. This study
showed that the PBPK modeling provided critical information for the
uptake, distribution and elimination of HgĀ(II) and MeHg in the fish
body, especially in elucidating the role of each compartment
In Vivo Mercury Demethylation in a Marine Fish (<i>Acanthopagrus schlegeli</i>)
Mercury (Hg) in fish
has attracted public attention for decades,
and methylmercury (MeHg) is the predominant form in fish. However,
the in vivo MeHg demethylation and its influence on Hg level in fish
have not been well-addressed. The present study investigated the in
vivo demethylation process in a marine fish (black seabream, <i>Acanthopagrus schlegeli</i>) under dietary MeHg exposure and
depuration and quantified the biotransformation and interorgan transportation
of MeHg by developing a physiologically based pharmacokinetic (PBPK)
model. After exposure, we observed a 2-fold increase of the whole-body
inorganic Hg (IHg), indicating the existence of an in vivo demethylation
process. The results strongly suggested that the intestine played
a predominant role in MeHg demethylation with a significant rate (6.6
Ā± 1.7 day<sup>ā1</sup>) during exposure, whereas the hepatic
demethylation appeared to be an extremely slow (0.011 Ā± 0.001
day<sup>ā1</sup>) process and could hardly affect the whole-fish
Hg level. Moreover, demethylation in the intestine served as an important
pathway for MeHg detoxification. Our study also pointed out that in
vivo MeHg demethylation could influence Hg level and speciation in
fish although food is the major pathway for Hg accumulation. Enhancing
in vivo MeHg biotransformation (especially in the intestine) could
be a potential key solution in minimizing Hg contamination in fish.
The related factors involved in intestinal demethylation deserve more
attention in the future
Inorganic Nanostructures with Sizes down to 1 nm: A Macromolecule Analogue
Ultrathin nanostructures
exhibit many interesting properties which
are absent or less-pronounced in traditional nanomaterials of larger
sizes. In this work, we report the synthesis of ultrathin nanowires
and nanoribbons of rare earth hydroxides and demonstrate some new
phenomena caused by their atomic-level lateral size (1 nm), including
ligand-induced gelation, self-assembly framework, and conformational
diversity. These features are typically, although not exclusively,
found in polymer solutions. The properties of the inorganic backbone
and the emerging polymeric characteristics combined prove to be very
promising in the design of new hybrid materials
Self-Adjustable Crystalline Inorganic Nanocoils
Biomacromolecules such as proteins,
although extremely complex
in microstructure, can crystallize into macro-sized crystals after
self-adjusting their shapes, based on which the structure of biology
is built. Inorganic nanowires/nanoribbons with a similar one-dimensional
topology but much simpler structures can hardly be as flexible as
macromolecules when constructing superlattice structures because of
their inherent rigidity. Here we report the synthesis of crystalline
indium sulfide nanoribbon-based nanocoils that are formed by spontaneous
self-coiling of ultrathin nanoribbons. The nanostructures are flexible
and appear as relatively random coils because of their ultrathin ribbon
structures (ā¼0.9 nm in thickness) with high aspect ratios.
Moreover, the nanocoils can self-adjust their shapes and assemble
into two-dimensional superlattices and three-dimensional supercrystals
in solution. The ultrathin nanocoils are expected to bring new insights
into the use of flexible nanocrystals as building blocks for constructing
superstructures
Anion-Exchange-Driven Disassembly of a SiO<sub>2</sub>/CTAB Composite Mesophase: the Formation of Hollow Mesoporous Silica Spheres
Silica-based surfactant/inorganic composite mesophases
have been
extremely studied. In this work, we developed a mild method to realize
the room-temperature disassembly of a SiO<sub>2</sub>/cetyltrimethylammonium
bromide (CTAB) mesophase in a neutral medium. Using KMnO<sub>4</sub> as a typical etching agent, SiO<sub>2</sub>/CTAB mesophase spheres
were partially disassembled into normal or rattle-type hollow structures.
The disassembly of the SiO<sub>2</sub>/CTAB spheres was supposed to
be driven by anion exchange between permanganate and silicate ions.
This unique method makes possible the selective etching of a SiO<sub>2</sub>/CTAB mesophase over a SiO<sub>2</sub> phase
Versatile Inorganic Subnanometer Nanowire Adhesive
Adhesives are applied extensively in daily life and industries,
and people have developed numerous commercial polymeric adhesives.
However, in most cases, these adhesives work on dry surfaces in air
and form permanent bonds with the substrates, limiting the applications
of adhesives. Inspired by the innate adhesive functions of some animals,
such as geckos, spiders, mussels, and clingfish, scientists have developed
various adhesive compositions and structures to meet various conditions.
Here, we show a versatile subnanometer nanowire (SNW) adhesive with
high strength and great reversibility, which could be prepared at
a large scale through a facile room-temperature reaction. The SNW
adhesive contacts the substrates at multiple sites due to the ultrahigh
flexibility, and meanwhile, the multilevel interactions among the
SNWs endow them with strong cohesion, so they exhibit good adhesive
performance. This adhesive is applicable to various substrates, such
as metals, polymers, and glass, and not only possesses good stability
at room temperature in air but also is suitable for underwater environments
and ultralow temperatures. Moreover, this adhesive could be easily
recycled and removed from the substrates without any residue and damage.
The SNW adhesive not only inspires the design of hierarchical adhesive
structures with new contact modes but also has potential for practical
applications
Versatile Inorganic Subnanometer Nanowire Adhesive
Adhesives are applied extensively in daily life and industries,
and people have developed numerous commercial polymeric adhesives.
However, in most cases, these adhesives work on dry surfaces in air
and form permanent bonds with the substrates, limiting the applications
of adhesives. Inspired by the innate adhesive functions of some animals,
such as geckos, spiders, mussels, and clingfish, scientists have developed
various adhesive compositions and structures to meet various conditions.
Here, we show a versatile subnanometer nanowire (SNW) adhesive with
high strength and great reversibility, which could be prepared at
a large scale through a facile room-temperature reaction. The SNW
adhesive contacts the substrates at multiple sites due to the ultrahigh
flexibility, and meanwhile, the multilevel interactions among the
SNWs endow them with strong cohesion, so they exhibit good adhesive
performance. This adhesive is applicable to various substrates, such
as metals, polymers, and glass, and not only possesses good stability
at room temperature in air but also is suitable for underwater environments
and ultralow temperatures. Moreover, this adhesive could be easily
recycled and removed from the substrates without any residue and damage.
The SNW adhesive not only inspires the design of hierarchical adhesive
structures with new contact modes but also has potential for practical
applications
Surface Confinement Etching and Polarization Matter: A New Approach To Prepare Ultrathin PtAgCo Nanosheets for Hydrogen-Evolution Reactions
One of the important
objectives in fuel-cell technology is to improve
the activity and reduce the loading of Pt for hydrogen-evolution electrocatalysis.
Here, an oxidative etching strategy of stacking faults is developed
to prepare PtĀAgCo nanosheets by element-specific anisotropic
growth. Sophisticated use of defects in crystal growth allows tailoring
the morphology and interfacial polarization to improve catalytic performance
of nanosheets for the hydrogen-evolution reaction. Systematic studies
reveal that the presence of the stacking faults may be the knob for
the formation of nanosheets. In particular, the chemical composition
of nanosheets is potentially the key for altering the hydrogen-evolution
reaction. As a result, the PtĀAgCo-II ultrathin nanosheets possess
useful HER properties, achieving a current density up to 705 mA cm<sup>ā2</sup> at a potential of ā400 mV
MOESM1 of Efficient expression of sortase A from Staphylococcus aureus in Escherichia coli and its enzymatic characterizations
Additional file 1. Additional tables
The starting page of the simulation software.
<p>The starting page of the simulation software.</p
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