pH-induced changes in IgE molecules measured by atomic force microscopy.

The environment surrounding proteins is tightly linked to its dynamics, which can significantly influence the conformation of proteins. This study focused on the effect of pH conditions on the ultrastructure of Immunoglobulin E (IgE) molecules. Herein, the morphology, height, and area of IgE molecules incubated at different pH were imaged by atomic force microscopy (AFM), and the law of IgE changes induced by pH value was explored. The experiment results indicated that the morphology, height and area of IgE molecules are pH dependent and highly sensitive. In particular, IgE molecules were more likely to present small-sized ellipsoids under acidic conditions, while IgE molecules tend to aggregate into large-sized flower-like structures under alkaline conditions. In addition, it was found that the height of IgE first decreased and then increased with the increase of pH, while the area of IgE increased with the increase of pH. This work provides valuable information for further study of IgE, and the methodological approach used in this study is expected to developed into AFM to investigate the changes of IgE molecules mediated by other physical and chemical factors. RESEARCH HIGHLIGHTS: The ultrastructure of IgE molecules is pH dependent and highly sensitive. IgE molecules were tend to present small-sized ellipsoids under acidic pH. Alkaline pH drives IgE self-assembly into flower-like aggregates.

Ionized water-soluble organic nanosheets with light/ultrasound dual excitation channels for efficient killing of multidrug-resistant bacteria.

A novel ionized heavy-atom-free two-dimensional organic nanosheet was prepared and exhibited highly selective generation of singlet oxygen under both light and ultrasound excitation. These ionized nanosheets displayed excellent dispersibility in water and enhanced singlet oxygen production efficiency compared to their non-assembled monomers. Antimicrobial experiments have revealed their potent bactericidal effects on drug-resistant E. coli and S. aureus under both visible light and ultrasound irradiation.

CH3NH3PbI3/Au/Mg0.2Zn0.8O Heterojunction Self-Powered Photodetectors with Suppressed Dark Current and Enhanced Detectivity.

Interface engineering of the hole transport layer in CH3NH3PbI3 photodetectors has resulted in significantly increased carrier accumulation and dark current as well as energy band mismatch, thus achieving the goal of high-power conversion efficiency. However, the reported heterojunction perovskite photodetectors exhibit high dark currents and low responsivities. Herein, heterojunction self-powered photodetectors, composed of p-type CH3NH3PbI3 and n-type Mg0.2Zn0.8O, are prepared through the spin coating and magnetron sputtering. The obtained heterojunctions exhibit a high responsivity of 0.58 A/W, and the EQE of the CH3NH3PbI3/Au/Mg0.2Zn0.8O heterojunction self-powered photodetectors is 10.23 times that of the CH3NH3PbI3/Au photodetectors and 84.51 times that of the Mg0.2ZnO0.8/Au photodetectors. The built-in electric field of the p-n heterojunction significantly suppresses the dark current and improves the responsivity. Remarkably, in the self-supply voltage detection mode, the heterojunction achieves a high responsivity of up to 1.1 mA/W. The dark current of the CH3NH3PbI3/Au/Mg0.2Zn0.8O heterojunction self-powered photodetectors is less than 1.4 × 10-1 pA at 0 V, which is more than 10 times lower than that of the CH3NH3PbI3 photodetectors. The best value of the detectivity is as high as 4.7 × 1012 Jones. Furthermore, the heterojunction self-powered photodetectors exhibit a uniform photodetection response over a wide spectral range from 200 to 850 nm. This work provides guidance for achieving a low dark current and high detectivity for perovskite photodetectors.

Broadband Organic Ternary Bulk Heterojunctions Photodetector Based on Non-Fullerene Acceptor with Enhanced Flat-Spectrum Response Range from 200 to 1100 nm.

Both flat-spectrum responsivity and high external quantum efficiency (EQE) of bulk heterojunction organic photodetectors (BHJ OPDs) are greatly in demand and still challenging to realize from the ultraviolet (UV) to near-infrared (NIR) regions. In this article, conjugated polymer donor poly(3-hexylthiophene) (P3HT) and PTB7-Th are blended with a low band gap nonfullerene acceptor (NFA) IEICO-4F to form a ternary BHJ active layer, thereby forming a BHJ OPD with a broadband responsivity spectrum from UV to visible light to NIR region (200-1100 nm). Under 6 V voltage and in the range from 280 to 810 nm, the ternary BHJ OPD shows a relatively flat responsivity spectrum, and the highest responsivity is 1.348 A/W, which is 1.34 times that of the binary BHJ OPD. Specifically, the ternary BHJ OPD achieved the highest EQE at 285 nm and as high as 449.31%. In addition, the ternary OPD detectivity (D*) is 2.65 times that of the binary BHJ OPD. Therefore, ternary BHJ as an active layer provides an effective method to develop BHJ OPDs with an expanded response range, higher responsivity, improved EQE, and broadband spectrum with flat spectral response from the UV to NIR region.

The oldest record of Saurosphargiformes (Diapsida) from South China could fill an ecological gap in the Early Triassic biotic recovery.

Diversification following the end-Permian mass extinction marks the initiation of Mesozoic reptile dominance and of modern marine ecosystems, yet major clades are best known from the Middle Triassic suggesting delayed recovery, while Early Triassic localities produce poorly preserved specimens or have restricted diversity. Here we describe Pomolispondylus biani gen. et sp. nov. from the Early Triassic Nanzhang-Yuan'an Fauna of China assigned to Saurosphargiformes tax. nov., a clade known only from the Middle Triassic or later, which includes Saurosphargidae, and likely is the sister taxon to Sauropterygia. Pomolispondylus biani is allied to Saurosphargidae by the extended transverse processes of dorsal vertebrae and a low, table-like dorsal surface on the neural spine; however, it does not have the typical extensive osteoderms. Rather an unusual tuberous texture on the dorsal neural spine and rudimentary ossifications lateral to the gastralia are observed. Discovery of Pomolispondylus biani extends the known range of Saurosphargiformes and increases the taxic and ecological diversity of the Nanzhang-Yuan'an Fauna. Its small size fills a different ecological niche with respect to previously found species, but the overall food web remains notably different in structure to Middle Triassic and later ecosystems, suggesting this fauna represents a transitional stage during recovery rather than its endpoint.

High-performance, self-powered flexible MoS2 photodetectors with asymmetric van der Waals gaps.

With an urgent demand for low-energy-consumption and wearable devices, it is desirable to find an easy, effective, and low-cost method to fabricate self-powered flexible photodetectors with simple configurations and high-performance. Self-powered photodetectors are normally fabricated based on either two different materials or the same material in contact with two different metal electrodes. Here, a flexible MoS2 photodetector with the same Au electrodes was fabricated on a polyethylene terephthalate (PET) substrate which exhibits self-powered properties. To our knowledge, its configuration is the simplest, and the fabrication process is easy to implement. At a bias of 0 V, the photodetector exhibits a high responsivity of 431 mA W-1, a short response/recovery time of 40 ms/40 ms, and excellent flexibility. Compared with those at a bias of 2 V, a dark current is sufficiently suppressed, and the response/recovery speed is significantly improved. It is found that the driving force of the self-powered photodetector is provided by the asymmetric Schottky barriers originating from the spontaneous generation of two van der Waals gaps with different widths. The asymmetric barriers exist stably at the interfaces between the 2D material and Au electrodes as further observed for ReS2 or GaSe flakes, which show the generality of asymmetric Schottky barriers between the 2D material and Au electrodes. The discovery here thus gives a new way to generate asymmetric Schottky barriers and develop high-performance self-powered photodetectors.

Identification and engineering on the nonconserved residues of metallo-ß-lactamase-type thioesterase to improve the enzymatic activity.

The standalone metallo-ß-lactamase-type thioesterase (MßL-TE), belongs to the group V nonreducing polyketide synthase agene cluster, catalyzes the rate-limiting step of product releasing. Our work first investigated on the orthologous MßL-TEs from different origins to determine which nonconserved amino acid residues are important to the hydrolysis efficiency. A series of chimeric MßL-TEs were constructed by fragment swapping and site-directed mutagenesis, in vivo enzymatic assay showed that two nonconserved residues A19 and E75 (numbering in HyTE) were critical to the catalytic performance. Protein structure modeling suggested that these two residues are located in different areas of HyTE. A19 is on the entrance to the active sites, whereas E75 resides in the linker between the two ß strands which hold the metal-binding sites. Combining with computational simulations and comparative enzymatic assay, different screening criteria were set up for selecting the variants on the two noncatalytic and nonconserved key residues to improve the catalytic activity. The rational design on A19 and E75 gave five candidates in total, two (A19F and E75Q) of which were thus found significantly improved the enzymatic performance of HyTE. The double-point mutant was constructed to further improve the activity, which was increased by 28.4-fold on product accumulation comparing to the wild-type HyTE. This study provides a novel approach for engineering on nonconserved residues to optimize enzymatic performance.

Improved responsivity of MgZnO film ultraviolet photodetectors modified with vertical arrays ZnO nanowires by light trapping effect.

The light trapping effect of ZnO nanowires (NWs) is attracting increasing attention as it effectively enhances the photoelectric effect. In this paper, high-density ZnO NWs are grown on a metal-semiconductor-metal structure MgZnO film UV photodetector (PD) as a light trapping unit. The photogenerated carriers diffuse along the longitudinal axis of the ZnO NWs, then diffuse onto the thin film and are collected by an applied bias electrode. When the device is connected to the NWs, the responsivity is about 12 times higher than that of the pure MgZnO film UV PD with a large light-dark current ratio (4.93 × 104). The array structure of the ZnO NWs enhances the number of photogenerated carriers at the top interface and provides a longer optical path length and a larger surface area. The resulting light trapping effect endows the device with excellent photoelectric properties. In this work, the introduction of NWs not only fundamentally improves the performance of the MgZnO thin film UV PD, but the resulting photodetector also demonstrates a sharp contrast between light trapping UV PD and the MgZnO thin film UV PD.

Evidence Supporting Predation of 4-m Marine Reptile by Triassic Megapredator.

Air-breathing marine predators have been essential components of the marine ecosystem since the Triassic. Many of them are considered the apex predators but without direct evidence-dietary inferences are usually based on circumstantial evidence, such as tooth shape. Here we report a fossil that likely represents the oldest evidence for predation on megafauna, i.e., animals equal to or larger than humans, by marine tetrapods-a thalattosaur (∼4 m in total length) in the stomach of a Middle Triassic ichthyosaur (∼5 m). The predator has grasping teeth yet swallowed the body trunk of the prey in one to several pieces. There were many more Mesozoic marine reptiles with similar grasping teeth, so megafaunal predation was likely more widespread than presently conceived. Megafaunal predation probably started nearly simultaneously in multiple lineages of marine reptiles in the Illyrian (about 242-243 million years ago).

Repeated evolution of durophagy during ichthyosaur radiation after mass extinction indicated by hidden dentition.

Marine tetrapods quickly diversified and were established as marine top predators after the end-Permian Mass extinction (EPME). Ichthyosaurs were the forerunner of this rapid radiation but the main drivers of the diversification are poorly understood. Cartorhynchus lenticarpus is a basal ichthyosauriform with the least degree of aquatic adaptation, holding a key to identifying such a driver. The unique specimen appeared edentulous based on what was exposed but a CT scanning revealed that the species indeed had rounded teeth that are nearly perpendicular to the jaw rami, and thus completely concealed in lateral view. There are three dental rows per jaw ramus, and the root lacks infoldings of the dentine typical of ichthyopterygians. The well-developed and worn molariform dentition with three tooth rows supports the previous inference that the specimen is not of a juvenile. The premaxilla and the corresponding part of the dentary are edentulous. Molariform dentition evolved three to five times independently within Ichthyosauriformes in the Early and Middle Triassic. Convergent exploitation of hard-shelled invertebrates by different subclades of ichthyosauriforms likely fueled the rapid taxonomic diversification of the group after EPME.

Two-dimensional MnC as a potential anode material for Na/K-ion batteries: a theoretical study.

Sodium (Na)-ion batteries (NIBs) and potassium (K)-ion batteries (KIBs) have grabbed great attention because they are cheaper, more abundant in earth, and safer alternatives of lithium-ion batteries. However, the lack of anode materials for NIBs/KIBs with good performance has been the main obstacle. In this paper, we studied monolayer MnC by carrying out calculations on the basis of first principle study to see if it can be a potential anode material for NIBs and KIBs. Calculation results show that monolayer MnC processes good negative adsorption energies of - 2.83 eV for Na and - 2.16 eV for K. Moreover, MnC has comparable theoretical capacities for Na and K of 475 mAh/g and 253 mAh/g, respectively. Our calculation results manifest that the MnC can be a promising anode material for NIBs. MnC monolayer absorbed with two layers of Na atoms.

Enlarged responsivity-ZnO honeycomb nanomaterials UV photodetectors with light trapping effect.

The ability of ZnO photodetectors to absorb UV light plays a key role in enhancing responsivity and performance in electronic, optical, and photonic devices. Herein, the light trapping effect of ZnO is used to design and fabricate a novel honeycomb-like ZnO nanomaterial-based UV photodetector with an excellent photoelectric performance. Compared with the traditional ZnO film UV photodetector, the photoresponsivity of the film with honeycomb nanomaterials can reach up to 4.79 A W-1, which is an improvement of about 300 times. In addition, the honeycomb ZnO nanomaterials UV photodetectors exhibit an improved light absorption, a very photo-to-dark current ratio (2.46 × 103), and an excellent detectivity (4.61 × 1012 Jones). The ZnO honeycomb nanostructure synthesized in this work exhibits a strong trapping effect, providing new insights into the research of nanomaterials used for UV photodetectors.

The new ichthyosauriform Chaohusaurus brevifemoralis (Reptilia, Ichthyosauromorpha) from Majiashan, Chaohu, Anhui Province, China.

A new species of ichthyosauriform is recognized based on 20 specimens, including nearly complete skeletons, and named Chaohusaurus brevifemoralis. A part of the specimens was previously identified as Chaohusaurus chaoxianensis and is herein reassigned to the new species. The new species differs from existing species of Chaohusaurus in a suite of features, such as the bifurcation of the caudal peak neural spine and a short femur relative to trunk length. The specimens include both complete and partially disarticulated skulls, allowing rigorous scrutiny of cranial sutures. For example, the squamosal does not participate in the margin of the upper temporal fenestra despite previous interpretations. Also, the frontal unequivocally forms a part of the anterior margin of the upper temporal fenestra, forming the most medial part of the anterior terrace. The skull of the holotype largely retains three-dimensionality with the scleral rings approximately in situ, revealing that the eyeball was uncovered in two different directions, that is, laterally and slightly dorsally through the main part of the orbit, and dorsally through the medial extension of the orbit into the skull roof. This skull construction is likely a basal feature of Ichthyosauromorpha. Phylogenetic analyses place the new species as a sister taxon of Chaohusaurus chaoxianensis.

Metabolic engineering of Saccharomyces cerevisiae for efficient production of endocrocin and emodin.

The anthraquinones endocrocin and emodin are synthesized by a special class of type I NR-PKSs and a discrete MßL-TE. In this work, we first reconstituted a biosynthetic pathway of endocrocin and emodin in S. cerevisiae by combining enzymes from different sources. We functionally characterized a TE-less NR-PKS (SlACAS) and a MßL-TE (SlTE) from S. lycopersici as well as four orthologous MßL-TEs. SlACAS was coexpressed with different MßL-TEs in S. cerevisiae. SlACAS generated the highest amount of endocrocin when coupled with HyTE, the yield was 115.6% higher than that with the native SlTE. To accumulate more emodin, seven decarboxylases with high homology to HyDC were identified and introduced into the biosynthetic pathway. Among these orthologs, AfDC exhibited the highest catalytic activity and the conversion rate reached 98.6%. A double-point mutant acetyl-CoA carboxylase, ACC1S659A, S1157A, was further introduced to increase the production of malonyl-CoA as a precursor of these anthraquinones. The production of endocrocin (233.6 ±â€¯20.3 mg/L) and emodin (253.2 ±â€¯21.7 mg/L) then dramatically increased. We also optimized the carbon source in the medium and conducted fed-batch fermentation with the engineered strains. The titers of endocrocin and emodin obtained were 661.2 ±â€¯50.5 mg/L and 528.4 ±â€¯62.7 mg/L, respectively, which are higher than previously reported. In this work, by screening a small library of orthologous biosynthetic bricks, an efficient biosynthetic pathway of endocrocin and emodin was first created in S. cerevisiae. This study provides a novel metabolic engineering approach for optimization of the production of desired molecules.

Improved responsivity performance of ZnO film ultraviolet photodetectors by vertical arrays ZnO nanowires with light trapping effect.

The light trapping effect of zinc oxide (ZnO) ultraviolet photodetectors (UV PDs) has been established as a promising way to optimize the performance of optoelectronic devices. In this paper, we report a light trapping fabricated metal-semiconductor-metal structure, consisting of a ZnO nanowire array as a top layer light absorber supported by a ZnO film. The ZnO film is bridged between two interdigitated metal electrodes for collecting photo-generated carriers. In this connection, high-dense ZnO nanowires can be used as a light trapping unit and to transmit the photogenerated carriers towards the ZnO film. The photogenerated carriers diffuse along the longitudinal direction of the ZnO nanowire and then to the ZnO film and are collected by the applied bias electrode. Compared to present ZnO thin film UV PDs, our device has an effective light trapping effect and the enhancement of photo-generated carriers at the top interface by a ZnO nanowire array structure are highly beneficial to UV light detection as they can provide a long optical path and more surface area. In addition, when the device was connected with nanowires, a 10 times augment of responsivity appeared accompanied by a giant photo-to-dark current ratio (1.6 × 103). This novel work not only enhanced fundamental improvement of nanowires to ZnO film UV PDs, but also provided a distinct contrast between light trapping UV PDs and ZnO film UV PDs.

Early Triassic marine reptile representing the oldest record of unusually small eyes in reptiles indicating non-visual prey detection.

The end-Permian mass extinction (EPME) led to reorganization of marine predatory communities, through introduction of air-breathing top predators, such as marine reptiles. We report two new specimens of one such marine reptile, Eretmorhipis carrolldongi, from the Lower Triassic of Hubei, China, revealing superficial convergence with the modern duckbilled platypus (Ornithorhynchus anatinus), a monotreme mammal. Apparent similarities include exceptionally small eyes relative to the body, snout ending with crura with a large internasal space, housing a bone reminiscent of os paradoxum, a mysterious bone of platypus, and external grooves along the crura. The specimens also have a rigid body with triangular bony blades protruding from the back. The small eyes likely played reduced roles during foraging in this animal, as with extant amniotes (group containing mammals and reptiles) with similarly small eyes. Mechanoreceptors on the bill of the animal were probably used for prey detection instead. The specimens represent the oldest record of amniotes with extremely reduced visual capacity, utilizing non-visual cues for prey detection. The discovery reveals that the ecological diversity of marine predators was already high in the late Early Triassic, and challenges the traditional view that the ecological diversification of marine reptiles was delayed following the EPME.

Separating sexual dimorphism from other morphological variation in a specimen complex of fossil marine reptiles (Reptilia, Ichthyosauriformes, Chaohusaurus).

The Early Triassic Chaohu Fauna from Anhui Province, China, contains the oldest record of Mesozoic marine reptiles, such as Cartorhynchus and Sclerocormus. Most specimens from the fauna belong to the ichthyosauriform Chaohusaurus, more specifically resembling C. chaoxianensis. However, a wide range of morphological variation exists within about 40 skeletons that have been prepared, likely reflecting mixed signals from both sexual and taxonomic differences. We test whether the sexual and taxonomic signals are separable based on quantification, aided by the knowledge of sexual dimorphism in extant marine tetrapods. There are two different suites of dimorphism that divide the specimens differently from each other yet consistently within each suite, resulting in four morphotypes in combination, likely representing two sexes of two taxa. Presumed males have larger 'organ of prehension' sensu Darwin, specifically limbs in the present case, for a given body length. This sexing criterion is supported by the only specimen of a gravid female, which belongs to the morphotype with short limbs. Males also have larger skulls for the trunk length compared to females. This study demonstrates that sexual and taxonomic signals are separable in fossil reptiles, with a sufficient sample size and careful analyses.

Significant Enhancement of MgZnO Metal-Semiconductor-Metal Photodetectors via Coupling with Pt Nanoparticle Surface Plasmons.

We proposed and demonstrated MgZnO metal-semiconductor-metal (MSM) ultraviolet photodetectors (UV) assisted with surface plasmons (SPs) prepared by the radio frequency magnetron sputtering deposition method. After the decoration of their surface with Pt nanoparticles (NPs), the responsivity of all the electrode spacing (3, 5, and 8 µm) photodetectors were enhanced dramatically; to our surprise, comparing with them the responsivity of larger spacing sample, more SPs were gathered which are smaller than others in turn. A physical mechanism focused on SPs and depletion width is given to explain the above results.

Pre- versus post-mass extinction divergence of Mesozoic marine reptiles dictated by time-scale dependence of evolutionary rates.

The fossil record of a major clade often starts after a mass extinction even though evolutionary rates, molecular or morphological, suggest its pre-extinction emergence (e.g. squamates, placentals and teleosts). The discrepancy is larger for older clades, and the presence of a time-scale-dependent methodological bias has been suggested, yet it has been difficult to avoid the bias using Bayesian phylogenetic methods. This paradox raises the question of whether ecological vacancies, such as those after mass extinctions, prompt the radiations. We addressed this problem by using a unique temporal characteristic of the morphological data and a high-resolution stratigraphic record, for the oldest clade of Mesozoic marine reptiles, Ichthyosauromorpha. The evolutionary rate was fastest during the first few million years of ichthyosauromorph evolution and became progressively slower over time, eventually becoming six times slower. Using the later slower rates, estimates of divergence time become excessively older. The fast, initial rate suggests the emergence of ichthyosauromorphs after the end-Permian mass extinction, matching an independent result from high-resolution stratigraphic confidence intervals. These reptiles probably invaded the sea as a new ecosystem was formed after the end-Permian mass extinction. Lack of information on early evolution biased Bayesian clock rates.

Eccentricity and obliquity paced carbon cycling in the Early Triassic and implications for post-extinction ecosystem recovery.

The timing of marine ecosystem recovery following the End Permian Mass Extinction (EPME) remains poorly constrained given the lack of radiometric ages. Here we develop a high-resolution carbonate carbon isotope (δ(13)Ccarb) record for 3.20 million years of the Olenekian in South China that defines the astronomical time-scale for the critical interval of major evolutionary and oceanic events in the Spathian. δ(13)Ccarb documents eccentricity modulation of carbon cycling through the period and a strong obliquity signal. A shift in phasing between short and long eccentricity modulation, and amplification of obliquity, is nearly coincident with a 2% decrease in seawater δ(13)CDIC, the last of a longer-term stepped decrease through the Spathian. The mid-Spathian shift in seawater δ(13)CDIC to typical thermocline values is interpreted to record a major oceanic reorganization with global climate amelioration. Coincidence of the phasing shift with the first occurrence of marine reptiles (248.81 Ma), suggests that their invasion into the sea and the onset of a complex ecosystem were facilitated by restoration of deep ocean ventilation linked mechanistically to a change in the response of the oceanic carbon reservoir to astronomical forcing. Together these records place the first constraints on the duration of the post-extinction recovery to 3.35 myr.