29 research outputs found
Reversible Activation of pH-Responsive Cell-Penetrating Peptides in Model Cell Membrane Relies on the Nature of Lipid
The pH response of
pH-responsive cell-penetrating peptides in cell
membrane is directly associated with many potential applications and
cell activities such as drug delivery, membrane fusion, and protein
folding, but it is still poorly understood. In this study, we used
GALA as a model and applied sum frequency generation vibrational spectroscopy
to systematically investigate the pH response of GALA in lipid bilayers
with different hydrophobic length and lipid head groups. We determined
the GALA structures in lipid bilayers by combining second-ordered
amide I and amide III spectral signals, which can accurately differentiate
the loop and α-helical structures at the interface. It is found
that GALA can insert into fluid-phase lipid bilayers even at neutral
pH, while lies down on the gel-phase lipid bilayer surface. Under
acidic conditions, GALA inserts into both fluid-phase and gel-phase
lipid bilayers. GALA adopts a mixed loop and α-helical structures
in lipid bilayers. Besides, the reversible activation of GALA in lipid
bilayers depends on the nature of lipid. After membrane insertion,
GALA exits from the negative phosphoglycerol and positive ethylphosphocholine
lipid bilayers at neutral pH, while it does not move out from the
zwitterionic phosphocholine lipid bilayers. These findings will help
us to understand how to enhance the efficacy of drug/gene delivery
in cell membrane
Visible-Light-Mediated Anti-Markovnikov Hydration of Olefins
Considering that
stoichiometric borane and oxidant are required
in the classical alkene anti-Markovnikov hydration process, it remains
appealing to achieve the transformation in a catalytic protocol. Herein,
a visible-light-mediated anti-Markovnikov addition of water to alkenes
by using an organic photoredox catalyst in conjunction with a redox-active
hydrogen atom donor was developed, which avoided the need for a transition-metal
catalyst, stoichiometric borane, as well as oxidant. Both terminal
and internal olefins are readily accommodated in this transformation
to obtain corresponding primary and secondary alcohols in good yields
with single regioselectivity. This procedure can be scaled up to gram
scale with a 230 turnover number based on photocatalyst
Transport and Organization of Cholesterol in a Planar Solid-Supported Lipid Bilayer Depend on the Phospholipid Flip-Flop Rate
Understanding
the transport behavior of the cholesterol molecules
within a cell membrane is a key challenge in cell biology at present.
Here, we have applied sum frequency generation vibrational spectroscopy
to characterize the transport and organization of cholesterol in different
kinds of planar solid-supported lipid bilayers by combining achiral-
and chiral-sensitive polarization measurements. This method allows
us to distinguish the organization of cholesterol in tail-to-tail,
head-to-tail, head-to-head, and side-by-side manners. It is found
that the movement of cholesterol in the lipid bilayer largely depends
on the flip-flop rate of the phospholipid. The flip-flop dynamics
of the phospholipid and cholesterol are synchronous. In the solid-supported
zwitterionic phosphocholine lipid bilayer, the cholesterol molecules
flip quickly from the distal leaflet to the neutral proximal leaflet
of the bilayer and form tail-to-tail organization on both leaflets.
The phosphocholine lipid and cholesterol show the same flip-flop rate.
However, when the proximal leaflet is prepared using negative glycerol
phospholipids, cholesterol organizes itself by mainly forming an α–β
structure on the distal leaflet. Because of the strong interaction
between the glycerol phospholipid and the substrate, no or only partial
cholesterol molecules flip from the distal leaflet to the negatively
charged proximal leaflet. However, the cholesterol molecules undergo
flip-flop in the presence of salt solution because the ions weaken
the interaction between the negative phospholipid and the substrate
CO<sub>2</sub> Fixation, Lipid Production, and Power Generation by a Novel Air-Lift-Type Microbial Carbon Capture Cell System
An air-lift-type microbial carbon
capture cell (ALMCC) was constructed
for the first time by using an air-lift-type photobioreactor as the
cathode chamber. The performance of ALMCC in fixing high concentration
of CO<sub>2</sub>, producing energy (power and biodiesel), and removing
COD together with nutrients was investigated and compared with the
traditional microbial carbon capture cell (MCC) and air-lift-type
photobioreactor (ALP). The ALMCC system produced a maximum power density
of 972.5 mW·m<sup>–3</sup> and removed 86.69% of COD,
70.52% of ammonium nitrogen, and 69.24% of phosphorus, which indicate
that ALMCC performed better than MCC in terms of power generation
and wastewater treatment efficiency. Besides, ALMCC demonstrated 9.98-
and 1.88-fold increases over ALP and MCC in the CO<sub>2</sub> fixation
rate, respectively. Similarly, the ALMCC significantly presented a
higher lipid productivity compared to those control reactors. More
importantly, the preliminary analysis of energy balance suggested
that the net energy of the ALMCC system was significantly superior
to other systems and could theoretically produce enough energy to
cover its consumption. In this work, the established ALMCC system
simultaneously achieved the high level of CO<sub>2</sub> fixation,
energy recycle, and municipal wastewater treatment effectively and
efficiently
Sulfur Hexafluoride (SF<sub>6</sub>) Emission Estimates for China: An Inventory for 1990–2010 and a Projection to 2020
Sulfur hexafluoride (SF<sub>6</sub>) is the most potent greenhouse
gas regulated under the Kyoto Protocol, with a high global warming
potential. In this study, SF<sub>6</sub> emissions from China were
inventoried for 1990–2010 and projected to 2020. Results reveal
that the highest SF<sub>6</sub> emission contribution originates from
the electrical equipment sector (about 70%), followed by the magnesium
production sector, the semiconductor manufacture sector and the SF<sub>6</sub> production sector (each about 10%). Both agreements and discrepancies
were found in comparisons of our estimates with previously published
data. An accelerated growth rate was found for Chinese SF<sub>6</sub> emissions during 1990–2010. Because the relative growth rate
of SF<sub>6</sub> emissions is estimated to be much higher than those
of CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub>O, SF<sub>6</sub> will play an increasing role in greenhouse gas emissions in China.
Global contributions from China increased rapidly from 0.9 ±
0.3% in 1990 to 22.8 ± 6.3% in 2008, making China one of the
crucial contributors to the recent growth in global emissions. Under
the examined Business-as-usual (BAU) Scenario, projected emissions
will reach 4270 ± 1020 t in 2020, but a reduction of about 90%
of the projected BAU emissions would be obtained under the Alternative
Scenario
Image1_The branching architecture of artemisia ordosica and its resistance to wind erosion.TIF
Different branching architectures reflect the adaptation strategies of different plants and affect their resistance to wind erosion. This study presents field-based observations that demonstrate the relationship between the branching architecture of Artemisia ordosica and its resistance to wind erosion. This species is the dominant plant species in the semi-fixed and fixed dunes of the Mu Us Sandy land. The overall bifurcation ratio (OBR) of semi-fixed sandy land is higher than the fixed sandy land 0.27; Similarly, the total stepwise bifurcation ratio (SBR) is higher than the fixed sandy land about 0.74; The length of first levels of total branches is also higher than 8.07. The aerodynamic roughness was greater than the A. ordosica community in the fixed and semi-fixed sandy land than in the bare sandy land. The airflow fields in the cross-wind direction were strongly affected by the windward shape of the plants, which became gradually narrower from the base to the top, while in the leeward direction, the wind speed at different heights behind the plant returned to the incoming airflow velocity. The result confirms that the influence of the windward shape of the plant on the surrounding airflow field is much larger than the influence of plant thickness, porosity or other factors.</p
Anti-Markovnikov Oxidation of β‑Alkyl Styrenes with H<sub>2</sub>O as the Terminal Oxidant
Oxygenation
of alkenes is one of the most straightforward routes
for the construction of carbonyl compounds. Wacker oxidation provides
a broadly useful strategy to convert the mineral oil into higher value-added
carbonyl chemicals. However, the conventional Wacker chemistry remains
problematic, such as the poor activity for internal alkenes, the lack
of anti-Markovnikov regioselectivity, and the high cost and chemical
waste resulted from noble metal catalysts and stoichiometric oxidant.
Here, we describe an unprecedented dehydrogenative oxygenation of
β-alkyl styrenes and their derivatives with water under external-oxidant-free
conditions by utilizing the synergistic effect of photocatalysis and
proton-reduction catalysis that can address these challenges. This
dual catalytic system possesses the single anti-Markovnikov selectivity
due to the property of the visible-light-induced alkene radical cation
intermediate
The integrated genetic map and distribution of QTL affecting grain mineral concentration (GMC) of Fe, Zn, Cd and Pb detected in the two sets of backcross introgression lines (BILs) derived from IR75862, a Zn dense variety as donor parent and two elite <i>indica</i> varieties, Ce258 and Zhongguangxiang1 as recurrent parents.
<p>QTL on the left of the chromosomes show those detected in BILs of Ce258 × IR75862 whereas those on the right of the chromosomes in BILs of Zhongguangxiang1 × IR75862. Digits on the left and inside brackets under QTL bars represent LOD value and additive effect (in 10<sup>3</sup> mg kg<sup>-1</sup>) of QTL. Dotted line box stands for the genetic overlap regions affecting GMC of different mineral elements.</p
Examining Two Sets of Introgression Lines in Rice (<i>Oryza sativa</i> L.) Reveals Favorable Alleles that Improve Grain Zn and Fe Concentrations
<div><p>In the modern world, the grain mineral concentration (GMC) in rice (<i>Oryza sativa</i> L.) not only includes important micronutrient elements such as iron (Fe) and zinc (Zn), but it also includes toxic heavy metal elements, especially cadmium (Cd) and lead (Pb). To date, the genetic mechanisms underlying the regulation of GMC, especially the genetic background and G × E effects of GMC, remain largely unknown. In this study, we adopted two sets of backcross introgression lines (BILs) derived from IR75862 (a Zn-dense rice variety) as the donor parent and two elite <i>indica</i> varieties, Ce258 and Zhongguangxiang1, as recurrent parents to detect QTL affecting GMC traits including Fe, Zn, Cd and Pb concentrations in two environments. We detected a total of 22 loci responsible for GMC traits, which are distributed on all 12 rice chromosomes except 5, 9 and 10. Six genetic overlap (GO) regions affecting multiple elements were found, in which most donor alleles had synergistic effects on GMC. Some toxic heavy metal-independent loci (such as <i>qFe1</i>, <i>qFe2</i> and <i>qZn12</i>) and some regions that have opposite genetic effects on micronutrient (Fe and Zn) and heavy metal element (Pb) concentrations (such as GO-IV) may be useful for marker-assisted biofortification breeding in rice. We discuss three important points affecting biofortification breeding efforts in rice, including correlations between different GMC traits, the genetic background effect and the G × E effect.</p></div
DataSheet1_Quantum chemical calculation study on the thermal decomposition of electrolyte during lithium-ion battery thermal runaway.pdf
Understanding the behavior of lithium-ion battery electrolytes during thermal runaway is essential for designing safer batteries. However, current reports on electrolyte decomposition behaviors often focus on reactions with electrode materials. Herein we use quantum chemical calculations to develop a model for the thermal decomposition mechanism of electrolytes under both electrolyte and ambient atmosphere conditions. The thermal stability is found to be associated with the dielectric constants of electrolyte constituents. Within the electrolyte, the solvation effects between molecules increase electrolyte stability, making thermal decomposition a more difficult process. Furthermore, Li+ is observed to facilitate electrolyte thermal decomposition, as the energy required for the thermal decomposition reactions of molecules decreases when they are bonded with Li+. It is hoped that this study will offer a theoretical basis for understanding the complex reactions occurring during thermal runaway events.</p