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

CO₂ 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 CO₂, 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^–3 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 CO₂ 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 CO₂ fixation, energy recycle, and municipal wastewater treatment effectively and efficiently

Sulfur Hexafluoride (SF₆) Emission Estimates for China: An Inventory for 1990–2010 and a Projection to 2020

Sulfur hexafluoride (SF₆) is the most potent greenhouse gas regulated under the Kyoto Protocol, with a high global warming potential. In this study, SF₆ emissions from China were inventoried for 1990–2010 and projected to 2020. Results reveal that the highest SF₆ emission contribution originates from the electrical equipment sector (about 70%), followed by the magnesium production sector, the semiconductor manufacture sector and the SF₆ 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 SF₆ emissions during 1990–2010. Because the relative growth rate of SF₆ emissions is estimated to be much higher than those of CO₂, CH₄, and N₂O, SF₆ 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 H₂O 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 10³ mg kg^-1) 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

Phenotypic values of grain mineral concentrations detected in three parents and two sets of BILs in two environments (mg kg^-1).

<p>¹⁾ NN09: 2009 summer season in Nanning, SY10: 2010 winter season in Sanya</p><p>²⁾ *, ** and *** represent significant differences at the P ≤ 0.05, 0.01 and 0.001 levels, respectively.</p><p>Phenotypic values of grain mineral concentrations detected in three parents and two sets of BILs in two environments (mg kg^-1).</p