Probing the Caveolin-1 P132L Mutant: Critical Insights into Its Oligomeric Behavior and Structure

Caveolin-1 is the most important protein found in caveolae, which are cell surface invaginations of the plasma membrane that act as signaling platforms. A single point mutation in the transmembrane domain of caveolin-1 (proline 132 to leucine) has deleterious effects on caveolae formation <i>in vivo</i> and has been implicated in various disease states, particularly aggressive breast cancers. Using a combination of gel filtration chromatography and analytical ultracentrifugation, we found that a fully functional construct of caveolin-1 (Cav1_62–178) was a monomer in dodecylphosphocholine micelles. In contrast, the P132L mutant of Cav1_62–178 was dimeric. To explore the dimerization of the P132L mutant further, various truncated constructs (Cav1_82–178, Cav1_96–178, Cav1_62–136, Cav1_82–136, Cav1_96–136) were prepared which revealed that oligomerization occurs in the transmembrane domain (residues 96–136) of caveolin-1. To characterize the mutant structurally, solution-state NMR experiments in <i>lyso</i>-myristoylphosphatidylglycerol were undertaken of the Cav1_96–136 P132L mutant. Chemical shift analysis revealed that, compared to the wild-type, helix 2 in the transmembrane domain was lengthened by four residues (wild-type, residues 111–129; mutant, residues 111–133), which corresponds to an extra turn in helix 2 of the mutant. Lastly, point mutations at position 132 of Cav1_62–178 (P132A, P132I, P132V, P132G, P132W, P132F) revealed that no other hydrophobic amino acid can preserve the monomeric state of Cav1_62–178, which indicates that proline 132 is critical in supporting proper caveolin-1 behavior

A Salt Bridge and Disulfide Bond within the Lassa Virus Fusion Domain Are Required for the Initiation of Membrane Fusion

Infection with Lassa virus (LASV), an Old-World arenavirus that is endemic to West Africa, causes Lassa fever, a lethal hemorrhagic fever. Delivery of LASV’s genetic material into the host cell is an integral component of its lifecycle. This is accomplished via membrane fusion, a process initiated by a hydrophobic sequence known as the fusion domain (FD). The LASV FD (G260–N295) consists of two structurally distinct regions: an N-terminal fusion peptide (FP: G260–T274) and an internal fusion loop (FL: C279–N295) that is connected by a short linker region (P275–Y278). However, the molecular mechanisms behind how the LASV FD initiates fusion remain unclear. Here, we demonstrate that the LASV FD adopts a fusogenic, helical conformation at a pH akin to that of the lysosomal compartment. Additionally, we identified a conserved disulfide bond (C279 and C292) and salt bridge (R282 and E289) within the FL that are pertinent to fusion. We found that the disulfide bond must be present so that the FD can bind to the lipid bilayer and subsequently initiate fusion. Moreover, the salt bridge is essential for the secondary structure of the FD such that it can associate with the lipid bilayer in the proper orientation for full functionality. In conclusion, our findings indicate that the LASV FD preferentially initiates fusion at a pH akin to that of the lysosome through a mechanism that requires a conserved salt bridge and, to a lesser extent, an intact disulfide bond within the internal FL

Enhancing Stability of Perovskite Solar Cells to Moisture by the Facile Hydrophobic Passivation

In this study, a novel and facile passivation process for a perovskite solar cell is reported. Poor stability in ambient atmosphere, which is the most critical demerit of a perovskite solar cell, is overcome by a simple passivation process using a hydrophobic polymer layer. Teflon, the hydrophobic polymer, is deposited on the top of a perovskite solar cell by a spin-coating method. With the hydrophobic passivation, the perovskite solar cell shows negligible degradation after a 30 day storage in ambient atmosphere. Suppressed degradation of the perovskite film is proved in various ways: X-ray diffraction, light absorption spectrum, and quartz crystal microbalance. This simple but effective passivation process suggests new kind of approach to enhance stability of perovskite solar cells to moisture

One-Pot Synthesis of Tin-Embedded Carbon/Silica Nanocomposites for Anode Materials in Lithium-Ion Batteries

We report a facile “one-pot” method for the synthesis of Sn-embedded carbon–silica (CS) mesostructured (nanostructured) composites through the selective interaction of resol (carbon precursor), tetraethylorthosilicate (TEOS), and tributylphenyltin (Sn precursor) with an amphiphilic diblock copolymer, poly(ethylene oxide-<i>b</i>-styrene), PEO-<i>b</i>-PS. A unique morphology transition from Sn nanowires to spherical Sn nanoparticles embedded in CS framework has been obtained. Metallic Sn species are homogeneously embedded in a rigid CS framework and are effectively confined within the nanostructures. The resulting composites are used as anode materials for lithium-ion batteries and exhibit high specific capacities (600 mA h g ^–1 at a current density of 45 mA g^–1, and 440 mA h g^–1 at a current density of 300 mA g^–1) and an excellent cyclability of over 100 cycles with high Coulombic efficiency. Most of all, the novel method developed in this work for synthesizing functional hybrid materials can be extended to the preparation of various functional nanocomposites owing to its versatility and facileness

Block Copolymer Directed Ordered Mesostructured TiNb₂O₇ Multimetallic Oxide Constructed of Nanocrystals as High Power Li-Ion Battery Anodes

In order to achieve high-power and -energy anodes operating above 1.0 V (vs Li/Li⁺), titanium-based materials have been investigated for a long time. However, theoretically low lithium charge capacities of titanium-anodes have required new types of high-capacity anode materials. As a candidate, TiNb₂O₇ has attracted much attention due to the high theoretical capacity of 387.6 mA h g^–1. However, the high formation temperature of the TiNb₂O₇ phase resulted in large-sized TiNb₂O₇ crystals, thus resulting in poor rate capability. Herein, ordered mesoporous TiNb₂O₇ (denoted as m-TNO) was synthesized by block copolymer assisted self-assembly, and the resulting binary metal oxide was applied as an anode in a lithium ion battery. The nanocrystals (∼15 nm) developed inside the confined pore walls and large pores (∼40 nm) of m-TNO resulted in a short diffusion length for lithium ions/electrons and fast penetration of electrolyte. As a stable anode, the m-TNO electrode exhibited a high capacity of 289 mA h g^–1 (at 0.1 C) and an excellent rate performance of 162 mA h g^–1 at 20 C and 116 mA h g^–1 at 50 C (= 19.35 A g^–1) within a potential range of 1.0–3.0 V (vs Li/Li⁺), which clearly surpasses other Ti-and Nb-based anode materials (TiO₂, Li₄Ti₅O₁₂, Nb₂O₅, etc.) and previously reported TiNb₂O₇ materials. The m-TNO and carbon coated m-TNO electrodes also demonstrated stable cycle performances of 48 and 81% retention during 2,000 cycles at 10 C rate, respectively

Ordered Mesoporous Titanium Nitride as a Promising Carbon-Free Cathode for Aprotic Lithium-Oxygen Batteries

Despite the extraordinary gravimetric energy densities, lithium-oxygen (Li-O₂) batteries are still facing a technological challenge; limited round trip efficiency leading to insufficient cycle life. Recently, carbonaceous electrode materials were found to be one of the primary origins of the limited cycle life, as they produce irreversible side products during discharge. A few investigations based on noncarbonaceous materials have demonstrated largely suppressed accumulation of irreversible side products, but such studies have focused mainly on the materials themselves rather than delicate morphology control. As such, here, we report the synthesis of mesoporous titanium nitride (m-TiN) with a 2D hexagonal structure and large pores (>30 nm), which was templated by a block copolymer with tunable chain lengths, and introduce it as a stable air-cathode backbone. Due to the well-aligned pore structure and decent electric conductivity of TiN, the battery reaction was quite reversible, resulting in robust cycling performance for over 100 cycles under a potential cutoff condition. Furthermore, by protecting the Li metal with a poreless polyurethane separator and engaging a lithium iodide redox mediator, the original capacity was retained for 280 cycles under a consistent capacity condition (430 mAh g^–1). This study reveals that when the appropriate structure and material choice of the air-cathode are coupled with an advanced separator and an effective solution-phase redox mediator, the cycle lives of Li-O₂ batteries can be enhanced dramatically

Unbiased Sunlight-Driven Artificial Photosynthesis of Carbon Monoxide from CO₂ Using a ZnTe-Based Photocathode and a Perovskite Solar Cell in Tandem

Solar fuel production, mimicking natural photosynthesis of converting CO₂ into useful fuels and storing solar energy as chemical energy, has received great attention in recent years. Practical large-scale fuel production needs a unique device capable of CO₂ reduction using only solar energy and water as an electron source. Here we report such a system composed of a gold-decorated triple-layered ZnO@ZnTe@CdTe core–shell nanorod array photocathode and a CH₃NH₃PbI₃ perovskite solar cell in tandem. The assembly allows effective light harvesting of higher energy photons (>2.14 eV) from the front-side photocathode and lower energy photons (>1.5 eV) from the back-side-positioned perovskite solar cell in a single-photon excitation. This system represents an example of a photocathode–photovoltaic tandem device operating under sunlight without external bias for selective CO₂ conversion. It exhibited a steady solar-to-CO conversion efficiency over 0.35% and a solar-to-fuel conversion efficiency exceeding 0.43% including H₂ as a minor product

Direct Access to Hierarchically Porous Inorganic Oxide Materials with Three-Dimensionally Interconnected Networks

Hierarchically porous oxide materials have immense potential for applications in catalysis, separation, and energy devices, but the synthesis of these materials is hampered by the need to use multiple templates and the associated complicated steps and uncontrollable mixing behavior. Here we report a simple one-pot strategy for the synthesis of inorganic oxide materials with multiscale porosity. The inorganic precursor and block copolymer are coassembled into an ordered mesostructure (microphase separation), while the in situ-polymerized organic precursor forms organic-rich macrodomains (macrophase separation) around which the mesostructure grows. Calcination generates hierarchical meso/macroporous SiO₂ and TiO₂ with three-dimensionally interconnected pore networks. The continuous 3D macrostructures were clearly visualized by nanoscale X-ray computed tomography. The resulting TiO₂ was used as the anode in a lithium ion battery and showed excellent rate capability compared with mesoporous TiO₂. This work is of particular importance because it (i) expands the base of BCP self-assembly from mesostructures to complex porous structures, (ii) shows that the interplay of micro- and macrophase separation can be fully exploited for the design of hierarchically porous inorganic materials, and therefore (iii) provides strategies for researchers in materials science and polymer science

Sequence alignment of fusion loop sequences of various strains of Ebola virus.

<p>Several conserved hydrophilic residues that might serve as potential pH sensors are highlighted: dark green—histidine, light green—threonine or glutamine, blue—lysine or arginine, red glutamate, orange—aspartates (not highly conserved). The sequence of Zaire EBOV (strain Mayinga-76) was used in this study and its residue numbers and a disulfide link that defines the fusion loop are indicated at the bottom. Basic residues are shown in blue, acidic residues in red, histidines in green, hydrophilic residues in light green, and non-conserved acidic/hydrophilic residues in orange.</p

Soft-Template Simple Synthesis of Ordered Mesoporous Titanium Nitride-Carbon Nanocomposite for High Performance Dye-Sensitized Solar Cell Counter Electrodes

Ordered mesoporous titanium nitride-carbon (denoted as OM TiN-C) nanocomposite with high surface area (389 m² g^–1) and uniform hexagonal mesopores (ca. 5.5 nm) was facilely synthesized via the soft-template method. As a structure-directing agent, Pluronic F127 triblock copolymer formed an ordered structure with inorganic precursors, resol polymer, and prehydrolyzed TiCl₄, followed by a successive heating at 700 °C under nitrogen and ammonia flow. In this study, the amorphous carbon within the parent OM TiO₂-C acted as a rigid support, preventing structural collapse during the conversion process of TiO₂ nanocrystals to TiN nanocrystals. The OM TiN-C was then successfully applied as counter electrode material in dye-sensitized solar cells (DSCs). The organic electrolyte disulfide/thiolate (T₂/T^–) was introduced to study the electrocatalytic property of the OM TiN-C nanocomposite. Because of the existence of TiN nanocrystals and the defect sites of the amorphous carbon, the DSCs using OM TiN-C as a counter electrode showed 6.71% energy conversion efficiency (platinum counter electrode DSCs: 3.32%) in the organic electrolyte system (T₂/T^–). Furthermore, the OM TiN-C counter electrode based DSCs showed an energy conversion efficiency of 8.41%, whereas the DSCs using platinum as a counter electrode showed a conversion efficiency of only 8.0% in an iodide electrolyte system. The superior performance of OM TiN-C counter electrode resulted from the low charge transfer resistance, enhanced electrical conductivity, and abundance of active sites of the OM TiN-C nanocomposite. Moreover, OM TiN-C counter electrode showed better chemical stability in organic electrolyte compared with the platinum counter electrode