3D ABX3 organic–inorganic halide perovskite (OIHP) semiconductors like CH3NH3PbI3 have received great attention because of their various properties for wide applications. However, although a number ...of low‐dimensional lead‐based OIHP ferroelectric semiconductors have been documented, obtaining 3D ABX3 OIHP ferroelectric semiconductors is challenging. Herein, an A‐site cation CH3PH3+ (methylphosphonium, MP) is employed to successfully obtain a lead‐free 3D ABX3 OIHP ferroelectric semiconductor MPSnBr3, which shows clear above‐room‐temperature ferroelectricity and a direct bandgap of 2.62 eV. It is emphasized that MPSnBr3 is a multiaxial molecular ferroelectric with the number of ferroelectric polar axes being as many as 12, which is far more than those of the other OIHP ferroelectric semiconductors and even the classical inorganic perovskite ferroelectric semiconductors BiFeO3 (4 polar axes) and BaTiO3 (3 polar axes). MPSnBr3 is the first MP‐based 3D ABX3 OIHP ferroelectric semiconductor. This finding throws light on the exploration of other excellent 3D ABX3 OIHP ferroelectric semiconductors with great application prospects.
MPSnBr3 (MP = methylphosphonium) is the first MP‐based 3D ABX3 hybrid perovskite ferroelectric semiconductor. MPSnBr3 is lead‐free and shows clear ferroelectricity with the number of ferroelectric polar axes up to 12, much more than that of other hybrid perovskite ferroelectric semiconductors. MPSnBr3 also exhibits a direct bandgap of 2.62 eV.
Hybrid perovskite materials are famous for their great application potential in photovoltaics and optoelectronics. Among them, lead‐iodide‐based perovskites receive great attention because of their ...good optical absorption ability and excellent electrical transport properties. Although many believe the ferroelectric photovoltaic effect (FEPV) plays a crucial role for the high conversion efficiency, the ferroelectricity in CH3NH3PbI3 is still under debate, and obtaining ferroelectric lead iodide perovskites is still challenging. In order to avoid the randomness and blindness in the conventional method of searching for perovskite ferroelectrics, a design strategy of fluorine modification is developed. As a demonstration, a nonpolar lead iodide perovskite is modified and a new 2D fluorinated layered hybrid perovskite material of (4,4‐difluorocyclohexylammonium)2PbI4, 1, is obtained, which possesses clear ferroelectricity with controllable spontaneous polarization. The direct bandgap of 2.38 eV with strong photoluminescence also guarantees the direct observation of polarization‐induced FEPV. More importantly, the 2D structure and fluorination are also expected to achieve both good stability and charge transport properties. 1 is not only a 2D fluorinated lead iodide perovskite with confirmed ferroelectricity, but also a great platform for studying the effect of ferroelectricity and FEPV in the context of lead halide perovskite solar cells and other optoelectronic applications.
Through a design strategy of fluorine modification, a nonpolar lead iodide perovskite is modified and a new 2D fluorinated layered hybrid perovskite material of (4,4‐difluorocyclohexylammonium)2PbI4 is obtained, which possesses clear ferroelectricity with controllable spontaneous polarization and ferroelectric photovoltaic effect. The discovery of such a material provides a great platform for the fundamental study of lead halide perovskite solar cells and other optoelectronic applications.
Intrinsic apoptotic stimuli initiate mammalian cells’ apoptotic program by first activating the proteins that have only Bcl-2 homology domain 3 (BH3), such as Bcl-2 interacting mediator of cell death ...(Bim) and truncated BH3 interacting death domain agonist (tBid), which in turn trigger conformational changes in BCL2-associated X (Bax) and BCL2-antagonist/killer (Bak) proteins that enable oligomer formation on the mitochondria, causing cytochrome c and other apoptogenic proteins in the intermembrane space to leak out. Leaked cytochrome c then initiates apoptotic caspase activation through a well-defined biochemical pathway. However, how oligomerized Bax and Bak cause cytochrome c release from mitochondria remains unknown. We report here the establishment of cell lines in which Bim or tBid can be inducibly expressed to initiate apoptosis in a controlled, quantitative manner. We used these cell lines to examine apoptotic events after Bax and Bak oligomerization but before cytochrome c release. The mitochondrial metalloprotease OMA1 was activated in this system in a Bax- and Bak-dependent fashion. Activated OMA1 cleaved the dynamin-like GTPase, optical nerve atrophy 1, an event that is critical for remodeling of mitochondrial cristae. Knockdown or knockout of OMA1 in these cells attenuated cytochrome c release. Thus it is clear that oligomerized Bax and Bak trigger apoptosis by causing both the permeabilization of the mitochondrial outer membrane and activation OMA1.
Significance The release of cytochrome c from its normal intermembrane space in mitochondria marks the initiation of apoptosis in mammalian cells. The process is triggered by the aggregation of B-cell leukemia/lymphoma 2 (BCL2)-associated X (Bax) and BCL2-antagonist/killer (Bak) proteins on the surface of mitochondria. We found that a mitochondrial inner membrane protease, OMA1 (overlapping activity with m -AAA protease), is specifically activated and is responsible for cleaving another inner membrane protein, optical nerve atrophy 1 (OPA1), upon Bax/Bak aggregation. The cleavage of OPA1 triggers the remodeling of mitochondrial cristae, allowing the majority of cytochrome c inside the cristae to be released. This finding provided a more comprehensive understanding of this critical molecular event during apoptosis.
AbstractObjectiveTo study the clinical characteristics of patients in Zhejiang province, China, infected with the 2019 severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) responsible for ...coronavirus disease 2019 (covid-2019).DesignRetrospective case series.SettingSeven hospitals in Zhejiang province, China.Participants62 patients admitted to hospital with laboratory confirmed SARS-Cov-2 infection. Data were collected from 10 January 2020 to 26 January 2020.Main outcome measuresClinical data, collected using a standardised case report form, such as temperature, history of exposure, incubation period. If information was not clear, the working group in Hangzhou contacted the doctor responsible for treating the patient for clarification.ResultsOf the 62 patients studied (median age 41 years), only one was admitted to an intensive care unit, and no patients died during the study. According to research, none of the infected patients in Zhejiang province were ever exposed to the Huanan seafood market, the original source of the virus; all studied cases were infected by human to human transmission. The most common symptoms at onset of illness were fever in 48 (77%) patients, cough in 50 (81%), expectoration in 35 (56%), headache in 21 (34%), myalgia or fatigue in 32 (52%), diarrhoea in 3 (8%), and haemoptysis in 2 (3%). Only two patients (3%) developed shortness of breath on admission. The median time from exposure to onset of illness was 4 days (interquartile range 3-5 days), and from onset of symptoms to first hospital admission was 2 (1-4) days.ConclusionAs of early February 2020, compared with patients initially infected with SARS-Cov-2 in Wuhan, the symptoms of patients in Zhejiang province are relatively mild.
Topological defects, such as vortices and skyrmions, provide a wealth of splendid possibilities for new nanoscale devices because of their marvelous electronic, magnetic, and mechanical behaviors. ...Recently, great advances have been made in the study of the ferroelectric vortex in conventional perovskite oxides, such as BaTiO3 and BiFeO3. Despite extensive interest, however, no intriguing ferroelectric vortex structures have yet been found in organic–inorganic hybrid perovskites (OIHPs), which are desirable for their mechanical flexibility, ease of fabrication, and low acoustical impedance. We observed the robust vortex–antivortex topological configurations in a two-dimensional (2D) layered OIHP ferroelectric (4,4-DFPD)2PbI4 (4,4-DFPD is 4,4-difluoropiperidinium). This provides future directions for the study of perovskites and makes it a promising alternative for nanoscale ferroelectric devices in medical, micromechanical, and biomechanical applications.
Phospholipid transfer protein (PLTP) is one of the major modulators of lipoprotein metabolism and atherosclerosis development in humans; however, we still do not quite understand the mechanisms. In ...mouse models, PLTP overexpression induces atherosclerosis, while its deficiency reduces it. Thus, mouse models were used to explore the mechanisms. In this review, I summarize the major progress made in the PLTP research field and emphasize its impact on lipoprotein metabolism and atherosclerosis, as well as its regulation.
Bidirectional signaling by cell adhesion molecules is thought to mediate synapse formation, but the mechanisms involved remain elusive. We found that the adhesion G protein-coupled receptors ...latrophilin-2 and latrophilin-3 selectively direct formation of perforant-path and Schaffer-collateral synapses, respectively, to hippocampal CA1-region neurons. Latrophilin-3 binds to two transcellular ligands: fibronectin leucine-rich repeat transmembrane proteins (FLRTs) and teneurins. In transgenic mice in vivo, both binding activities were required for input-specific synapse formation, which suggests that coincident binding of both ligands is necessary for synapse formation. In cultured neurons in vitro, teneurin or FLRT alone did not induce excitatory synapse formation, whereas together they potently did so. Thus, postsynaptic latrophilins promote excitatory synapse formation by simultaneous binding of two unrelated presynaptic ligands, which is required for formation of synaptic inputs at specific dendritic localizations.
A Molecular Thermochromic Ferroelectric Liu, Jun‐Chao; Liao, Wei‐Qiang; Li, Peng‐Fei ...
Angewandte Chemie International Edition,
February 24, 2020, Volume:
59, Issue:
9
Journal Article
Peer reviewed
Molecular ferroelectrics have attracted considerable interests because of their easy and environmentally friendly processing, low acoustical impedance and mechanical flexibility. Herein, a molecular ...thermochromic ferroelectric, N,N′‐dimethyl‐1,4‐diazoniabicyclo2.2.2octonium tetrachlorocuprate(II) (DMe‐DABCOCuCl4) is reported, which shows both excellent ferroelectricity and intriguing thermochromism. DMe‐DABCOCuCl4 undergoes a ferroelectric phase transition from Pca21 to Pbcm at a significantly high Curie temperature of 413 K, accompanied by a color change from yellow to red that is due to the remarkable deformation of CuCl42− tetrahedron, where the ferroelectric and paraelectric phases correspond to yellow and red, respectively. Combined with multiple bistable physical properties, DMe‐DABCOCuCl4 would be a promising candidate for next‐generation smart devices, and should inspire further exploration of multifunctional molecular ferroelectrics.
Set phases to stun: A molecular thermochromic ferroelectric, N,N′‐dimethyl‐1,4‐diazoniabicyclo2.2.2octonium tetrachlorocuprate(II), undergoes a ferroelectric phase transition from Pca21 to Pbcm at the significantly high Curie temperature (Tc) of 413 K. This is accompanied by a color change from yellow to red that is due to the remarkable deformation of the CuCl42− tetrahedron.
Ferroelectric lithography, which can purposefully control and pattern ferroelectric domains in the micro‐/nanometer scale, has extensive applications in data memories, field‐effect transistors, ...race‐track memory, tunneling barriers, and integrated biochemical sensors. In pursuit of mechanical flexibility and light weight, organic ferroelectric polymers such as poly(vinylidene fluoride) are developed; however, they still suffer from complicated stretching processes of film fabrication and poor degradability. These poor features severely hinder their applications. Here, the ferroelectric lithography on the biocompatible and biodegradable poly(lactic acid) (PLA) thin films at room temperature is demonstrated. The semicrystalline PLA thin film can be easily fabricated through the melt‐casting method, and the desired domain structures can be precisely written according to the predefined patterns. Most importantly, the coercive voltage (Vc) of PLA thin film is relatively low (lower than 30 V) and can be further reduced with the decrease of the film thickness. These intriguing behaviors combined with satisfying biodegradability make PLA thin film a desirable candidate for ferroelectric lithography and enable its future application in the field of bioelectronics and biomedicine. This work sheds light on further exploration of ferroelectric lithography on other polymer ferroelectrics as well as their application as nanostructured devices.
Ferroelectric lithography—a technique that can precisely pattern the ferroelectric domain in the micro‐ and nanometer scale in accordance with the predefined pattern—is observed on the semicrystalline biomaterial poly(lactic acid) thin films fabricated with a simple melt‐casting method, providing new possibility for their applications as high‐precision ferroelectric memory.
As the major component of cell membranes, phosphatidylcholine (PC) is synthesized de novo in the Kennedy pathway and then undergoes extensive deacylation-reacylation remodeling via Lands' cycle. The ...re-acylation is catalyzed by lysophosphatidylcholine acyltransferase (LPCAT) and among the four LPCAT members in human, the LPCAT3 preferentially introduces polyunsaturated acyl onto the sn-2 position of lysophosphatidylcholine, thereby modulating the membrane fluidity and membrane protein functions therein. Combining the x-ray crystallography and the cryo-electron microscopy, we determined the structures of LPCAT3 in apo-, acyl donor-bound, and acyl receptor-bound states. A reaction chamber was revealed in the LPCAT3 structure where the lysophosphatidylcholine and arachidonoyl-CoA were positioned in two tunnels connected near to the catalytic center. A side pocket was found expanding the tunnel for the arachidonoyl CoA and holding the main body of arachidonoyl. The structural and functional analysis provides the basis for the re-acylation of lysophosphatidylcholine and the substrate preference during the reactions.
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