65 research outputs found
Bacterial Diversity in Linglong Gold Mine, China
<p>Bacteria have been actively regulating cycles of various elements in the environment. To explore the potential bacterial role in gold biogeochemical cycling, this study analyzed the bacterial diversity of mine rock (MR) and surface soil (SS) samples from Linglong gold mine using 16S rRNA gene clone library analysis and cultivation method. From MR, 24 operational taxonomic units (OTUs) were identified from MR, covering 3 phyla and 18 genera. Meanwhile, 24 OTUs were identified from SS, including 4 phyla and 18 genera. Compared with 16S rRNA gene clone library analysis, 28 aerobic and 34 anaerobic isolates were obtained, whereas 26 aerobic and 71 anaerobic strains were isolated from SS. The cultivable bacteria were affiliated with Firmicutes, Proteobacteria and Actinobacteria phyla, and dominated by Firmicutes. These results underscore the high level of bacterial diversity in the gold mine. Our study provides information on the microbial diversity in Linglong gold mine and sheds light on the existence and potential function of bacteria in the gold biogeochemical cycling.</p
Synthesis and Self-Assembly Behavior of Charged Au Nanocrystals in Aqueous Solution
A series
of water-soluble Au nanocrystals with different core sizes
coated by either negatively or positively charged ligands are synthesized.
We find a ligand interexchange process takes place when positively
and negatively charged nanocrystals are mixed together and heated,
resulting in mixed charged zwitterionic nanocrystals. The ligand exchange
process between nanocrystals is studied in detail by electrophoresis.
Self-assembly properties of the monocharged and zwitterionic nanocrystals
are studied subsequently. By using the solvent evaporation process
only the zwitterionic and positively charged nanocrystals can pack
into well-ordered fcc lattice
films. Under the nonsolvent diffusion condition, only the zwitterionic
nanocrystals can aggregate and form shaped supracrystals. Structural
analysis shows that the interparticle distance of the shaped supracrystal
made of zwitterionic nanocrystals is 1 nm larger than that of the
film one. The different interparticle distance is ascribed to the
different fabrication process. We consider that nanocrystals adopt
the closest packing in the film supracrystal due to the destroyed
electrical double layer during the drying process, while the electrostatic
repulsion plays an important role in determining the interparticle
distance in the shaped supracrystal
Antimony Redox Biotransformation in the Subsurface: Effect of Indigenous Sb(V) Respiring Microbiota
Anaerobic
microbiological antimonate [SbÂ(V)] respiration is a newly
discovered process regulating the Sb redox transformation in soils.
However, little is known about the role microbiological SbÂ(V) respiration
plays in the fate of Sb in the subsurface, especially in the presence
of sulfate and electron shuttles. Herein, we successfully enriched
a SbÂ(V) reducing microbiota (SbRM) from the subsurface near an active
Sb mine. SbRM was dominated by genus <i>Alkaliphilus</i> (18–36%), <i>Clostridiaceae</i> (17–18%), <i>Tissierella</i> (24–27%), and <i>Lysinibacillus</i> (16–37%). The incubation results showed that SbRM reduced
88% of dissolved SbÂ(V) to SbÂ(III), but the total Sb mobility remained
the same as in the abiotic control, indicating that SbRM alone did
not increase the total Sb release but regulated the Sb speciation
in the subsurface. Micro X-ray fluorescence (μ-XRF) analysis
suggested the association of Sb and Fe, and electron shuttles such
as anthraquinone-2,6-disulfonic disodium salt (AQDS) markedly enhanced
the Sb release due to its ability to facilitate Fe mineral dissolution.
Sb L-edge and S K-edge X-ray absorption near edge structure (XANES)
results demonstrated that indigenous SbRM immobilized Sb via Sb<sub>2</sub>S<sub>3</sub> formation, especially in a sulfur-rich environment.
The insights gained from this study shed new light on Sb mobilization
and its risk assessment in the subsurface environment
Co<sub>2</sub>Cu<sub>1</sub>Ce<sub><i>y</i></sub>O<sub><i>x</i></sub> Mixed Metal Oxide Nanoparticles with Oxygen Vacancies as Catalysts for Toluene Oxidation
A multimetal MOF (metal–organic framework), CeÂ(III)/Co2Cu1-MOF-74, has here been synthesized in a simple
and convenient manner by using the mechanical ball milling method.
This method is both energy-saving and environmentally friendly. By
using the obtained product compounds as a template, Co2Cu1CeyOx mixed metal oxides were prepared by calcination to serve as
a catalyst for toluene catalytic oxidation. Co2Cu1CeyOx had
the form of nanoparticles with a uniform morphology. As a result of
the experiments, the conversion percentages of the Co2Cu1Ce0.75Ox catalyst in
catalyzing the toluene oxidation reached 50% (T50) and 90% (T90) at the temperatures
of 196 and 210 °C, respectively. The Co2Cu1Ce0.75Ox catalyst exhibited
an abundance of multiphase interfaces and metal doping effects, which
effectively induced an abundance of oxygen vacancies on the catalyst
surface. Furthermore, the Co2Cu1Ce0.75Ox catalyst exhibited excellent durability
within 24 h and demonstrated remarkable regenerative capabilities
after steam-induced reduction by 5%. Thus, the use of MOFs as precursor
compounds, which were mechanically synthesized in a green and rapid
manner, helped to design high-efficiency multimetal mixed oxide nanoparticle
catalysts with abundant multiphase interfaces, which could be used
for toluene catalytic oxidation. This rendered possibilities for large-scale
applications in related areas
Controlled Hydrophobic Biosurface of Bacterial Cellulose Nanofibers through Self-Assembly of Natural Zein Protein
A novel,
highly biocompatible bacterial cellulose (BC)-zein composite
nanofiber with a controlled hydrophobic biosurface was successfully
developed through a simple and green solution impregnation method,
followed by evaporation-induced self-assembly (EISA) of adsorbed zein
protein. The surface hydrophobicity of the zein-modified BC nanofibers
could be controlled by simply changing the zein concentration, which
is able to tune the morphology of self-assembled zein structures after
EISA, thus affecting the surface roughness of composite membranes.
Zein self-assembly at low concentrations (5 mg/mL) resulted in the
formation of hierarchical zein structures (spheres and bicontinuous
sponges) on the BC surface, thus increasing the surface roughness
and leading to high hydrophobicity (the water contact angle reached
110.5°). However, at high zein concentrations, these large zein
spheres assembled into a flat zein film, which decreased the surface
roughness and hydrophobicity of membranes. The homogeneous incorporation
of zein structures on the BC surface by hydrogen bonding did not significantly
change the internal structure and mechanical performance of BC nanofibers.
In comparison with pure BC, the BC-zein nanofibers had a better biocompatibility,
showing a significantly increased adhesion and proliferation of fibroblast
cells. This is probably due to the rough surface structure of BC-zein
nanofibers as well as the high biocompatibility of natural zein protein.
The novel BC-zein composite nanofibers with controlled surface roughness
and hydrophobicity could be of particular interest for the design
of BC-based biomaterials and biodevices that require specific surface
properties and adhesion
Mesoporous ZnS-Sb/C Reduced Graphene Oxide Nanostructures as Anode Materials for Sodium-Ion Batteries
Metal-based
sulfides are favored by researchers because
of their
high theoretical capacity, but their inherent volume expansion problems
limit their further applications. To address the above issues, we
prepared ZnS-Sb@C@rGO core–shell nanosphere anode materials
for high-performance sodium-ion batteries (SIBs). The ZnS-Sb heteromeric
core with synergistic effects was designed to facilitate rapid electrolyte
penetration and accelerate Na+ transformation kinetics.
Meanwhile, the double coating of the outer carbon shell and rGO layer
provides rich sodium embedding sites and improves the conductivity
and charge transfer capability of the composite. Its unique layered
heterogeneous structure design provides a lot of buffer space and effectively prevents the shedding of active
substances. The composite has excellent electrochemical properties
in sodium-ion batteries, with a high initial discharge specific capacity
of 1117.1 mAh g–1 at 0.1 A g–1. The battery achieves a long cycle life, and the discharge specific
capacity is 210.3 mAh g–1 after 300 cycles at 1
A g–1. This novel structural design may be one of
the feasible solutions to achieve the excellent properties of SIB
anode materials
Solid-State NMR Shows That Dynamically Different Domains of Membrane Proteins Have Different Hydration Dependence
Hydration has a profound influence
on the structure, dynamics,
and functions of membrane and membrane-embedded proteins. So far the
hydration response of molecular dynamics of membrane proteins in lipid
bilayers is poorly understood. Here, we reveal different hydration
dependence of the dynamics in dynamically different domains of membrane
proteins by multidimensional magic angle spinning (MAS) solid-state
NMR (ssNMR) spectroscopy using 121-residue integral diacylglycerol
kinase (DAGK) in 1,2-dimyristoyl-<i>sn</i>-glycero-3-phosphocholine
(DMPC)/1,2-dimyristoyl-<i>sn</i>-glycero-3-phospho-(1′-<i>rac</i>-glycerol) (DMPG) lipid bilayers as a model system. The
highly mobile and immobile domains of DAGK and their water accessibilities
are identified site-specifically by scalar- and dipolar-coupling based
MAS ssNMR experiments, respectively. Our experiments reveal different
hydration dependence of the dynamics in highly mobile and immobile
domains of membrane proteins. We demonstrate that the fast, large-amplitude
motions in highly mobile domains are not triggered until 20% hydration,
enhanced at 20–50% hydration and unchanged at above 50% hydration.
In contrast, motions on submicrosecond time scale of immobile residues
are observed to be independent of the hydration levels in gel phase
of lipids, and at the temperature near gel–liquid crystalline
phase transition, amplitude of whole-molecule rotations around the
bilayer normal is dominated by the fluidity of lipid bilayers, which
is strongly hydration dependent. The hydration dependence of the dynamics
of DAGK revealed by this study provides new insights into the correlations
of hydration to dynamics and function of membrane proteins in lipid
bilayers
Effects of DFCs on cell sheet formation by HPDLSCs and PPDLSCs in vitro.
<p><b>A:</b> H&E staining of cell sheets. HPDLSCs formed more cell layers and ECM than PPDLSCs. In the co-cultured systems, both HPDLSCs and PPDLSCs formed more cell layers and ECM than in the monocultured systems (hematoxylin-eosin staining, magnification: 400×, scale bar = 50 mm). <b>B:</b> SEM of cell sheets; HPDLSCs secreted richer ECM than PPDLSCs, and co-culture with DFCs enhanced the ECM secretion by both HPDLSCs and PPDLSCs. Notes: DFCs (–), monocultured PDLSCs that were cultured with transwell containing no DFCs; DFCs (+), co-cultured PDLSCs that were cultured with transwells seeded with a specific number of DFCs.</p
Isolation and identification of HPDLSCs, PPDLSCs, and DFCs.
<p><b>A:</b> Morphologies of DFCs, HPDLSCs, and PPDLSCs observed by microscopy. <b>B:</b> Mesenchymal stem cell phenotype examination by flow cytometric analysis.</p
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