Tube-like Structures Research Articles

ODF2 Negatively Regulates CP110 Levels at the Centrioles/Basal Bodies to Control the Biogenesis of Primary Cilia.

Primary cilia are essential sensory organelles that develop when an inhibitory cap consisting of CP110 and other proteins is eliminated. The degradation of CP110 by the ubiquitin-dependent proteasome pathway mediated by NEURL4 and HYLS1 removes the inhibitory cap. Here, we investigated the suitability of rapamycin-mediated dimerization for centriolar recruitment and asked whether the induced recruitment of NEURL4 or HYLS1 to the centriole promotes primary cilia development and CP110 degradation. We used rapamycin-mediated dimerization with ODF2 to induce their targeted recruitment to the centriole. We found decreased CP110 levels in the transfected cells, but independent of rapamycin-mediated dimerization. By knocking down ODF2, we showed that ODF2 controls CP110 levels. The overexpression of ODF2 is not sufficient to promote the formation of primary cilia, but the overexpression of NEURL4 or HYLS1 is. The co-expression of ODF2 and HYLS1 resulted in the formation of tube-like structures, indicating an interaction. Thus, ODF2 controls primary cilia formation by negatively regulating the concentration of CP110 levels. Our data suggest that ODF2 most likely acts as a scaffold for the binding of proteins such as NEURL4 or HYLS1 to mediate CP110 degradation.

The role of intrinsic disorder in binding of plant microtubule-associated proteins to the cytoskeleton.

Microtubules (MTs) represent one of the main components of the eukaryotic cytoskeleton and support numerous critical cellular functions. MTs are in principle tube-like structures that can grow and shrink in a highly dynamic manner; a process largely controlled by microtubule-associated proteins (MAPs). Plant MAPs are a phylogenetically diverse group of proteins that nonetheless share many common biophysical characteristics and often contain large stretches of intrinsic protein disorder. These intrinsically disordered regions are determinants of many MAP-MT interactions, in which structural flexibility enables low-affinity protein-protein interactions that enable a fine-tuned regulation of MT cytoskeleton dynamics. Notably, intrinsic disorder is one of the major obstacles in functional and structural studies of MAPs and represents the principal present-day challenge to decipher how MAPs interact with MTs. Here, we review plant MAPs from an intrinsic protein disorder perspective, by providing a complete and up-to-date summary of all currently known members, and address the current and future challenges in functional and structural characterization of MAPs.

Exosomes-loaded electroconductive nerve dressing for nerve regeneration and pain relief against diabetic peripheral nerve injury.

Over the years, electroconductive hydrogels (ECHs) have been extensively applied for stimulating nerve regeneration and restoring locomotor function after peripheral nerve injury (PNI) with diabetes, given their favorable mechanical and electrical properties identical to endogenous nerve tissue. Nevertheless, PNI causes the loss of locomotor function and inflammatory pain, especially in diabetic patients. It has been established that bone marrow stem cells-derived exosomes (BMSCs-Exos) have analgesic, anti-inflammatory and tissue regeneration properties. Herein, we designed an ECH loaded with BMSCs-Exos (ECH-Exos) electroconductive nerve dressing to treat diabetic PNI to achieve functional recovery and pain relief. Given its potent adhesive and self-healing properties, this laminar dressing is convenient for the treatment of damaged nerve fibers by automatically wrapping around them to form a size-matched tube-like structure, avoiding the cumbersome implantation process. Our in vitro studies showed that ECH-Exos could facilitate the attachment and migration of Schwann cells. Meanwhile, Exos in this system could modulate M2 macrophage polarization via the NF-κB pathway, thereby attenuating inflammatory pain in diabetic PNI. Additionally, ECH-Exos enhanced myelinated axonal regeneration via the MEK/ERK pathway in vitro and in vivo, consequently ameliorating muscle denervation atrophy and further promoting functional restoration. Our findings suggest that the ECH-Exos system has huge prospects for nerve regeneration, functional restoration and pain relief in patients with diabetic PNI.

Construction of D-A type porphyrin-phthalocyanine-based polymer hollow tubes for efficient photodegradation and photoelectrochemical sensing of bisphenol A

A series of hollow tubes of porphyrin-phthalocyanine-based conjugated microporous polymer (MPorPc-CMP, M = Co, Ni, Cu, Zn, H2) within periodic multi-channel donor–acceptor (D-A) structure were successfully synthesized using phthalocyanine monomer with poor solubility as a self-template. The unique hollow tube-like structures provided sufficiently exposed active sites for the adsorption of analytes. A wide range of spectral characterization and DFT calculation found that M in the MPor unit can efficiently tune band structures and built-in electric field between MPor and Pc of the MPorPc-CMPs. Among them, the best-matching band structures and the strongest built-in electronic field between NiPor and Pc units were obtained in NiPorPc-CMP, which promoted carrier separation/transport and suppressed the exciton annihilation. Thus, the NiPorPc-CMP showed the highest bisphenol A (BPA) degradation efficiency and H2O2 generation rate (273 μmol⋅g-1h−1) under visible light illumination. Moreover, the significantly improved cathodic photocurrent of NiPorPc-CMP enabled ultra-sensitive and selective BPA detection with a LOD of 0.012 nM within the range of 0.05–5000 nM. This study not only provided a new method for the design and synthesis of morphologically controllable D-A type CMPs but also provided new insights to expand the applications of D-A type CMPs.

Anisotropic Polyimide/Cellulose Nanofibril Composite Aerogels for Thermal Insulation and Flame Retardancy

In this study, we report a series of lightweight, anisotropic polyimide/cellulose nanofibril (PI/CNF) composite aerogels with outstanding thermal insulation and flame retardancy via unidirectional drying and freeze drying methods. Along the axial direction, PI/CNF composite aerogels exhibit an arranged tube-like structure in parallel to ice crystal growth, thus providing superior mechanical properties. Conversely, the composite aerogels show a honeycomb-like pore structure along the radial direction, exhibiting excellent elastic properties. More importantly, the addition of CNF endows the composite aerogels with low thermal conductivity along the radial direction. The surface temperature of the composite aerogels with a thickness of 15 mm is 70% lower than that of hot stage annealing at 180 °C for 60 min. Furthermore, the composite aerogels show flame retardant and self-extinguishing performance in the combustion experiment. Therefore, the anisotropic PI/CNF composite aerogels with thermal insulation and flame retardancy are promising for expanding potential applications in aerospace fields.

Fluorescence sensitively sensing on antibiotic and nitrobenzene of two diverse 2D Zn-organic networks

Two 2D luminous zinc(II) coordination polymers have been synthesized hydrothermally with the formulas of [Zn(4-HDBB)(3-bibz)](1) and [Zn2(4-DBB) (OH)(4,4′-bbpy)1.5]·2H2O(2) (4-H3DBB = 4-(3,5-dicarboxylatobenloxy) benzoic acid, 3-bibz = 3-bis(imidazole-l-ylmethyl) benzene and 4,4′-bbpy = 4,4′-bis (imidazolyl) biphenyl), and characterized by single crystal X-ray diffraction, IR, TG and PXRD technologies. Structural analyses exhibit both of them crystallize in P-1 space group of triclinic crystal system with 2D network structures. 1 possesses the interpenetration of 2D (4,4) networks based on the cross of two kinds of 1D chains. The 2D networks of 2 featuring 1D tube-like structure are linked by the six-number-ring H-bonds clusters. Fluorescence sensing properties on antibiotic of two complexes display 1 could detect of chloramphenicol (LOD = 6.64 × 10−7 mol⋅ L-1) and the detection limit of polymer 2 for tetracycline is 1.22 × 10−7 mol⋅ L-1. Solvents detection show that nitrobenzene in water was completely quenched by all of them, and display the highly sensitive sensing for nitrobenzene with the limit of detection of 5.0 × 10−8 mol L-1(1) and 2.14 × 10−7mol·L-1(2), respectively. Through theoretical calculation, it is found that the sensing mechanism of two complexes on nitrobenzene could be mainly attributed to the photo-induced electron transfer effect (PET). The fact shows that the two complexes can be used multi-functional sensors in the future.

Reactive Template-Engaged Synthesis of NiSx/MoS2 Nanosheets Decorated on Hollow and Porous Carbon Microtubes with Optimal Electronic Modulation toward High-Performance Enzyme-like Performance

As a promising cost-effective nanozyme, MoS2 nanosheets (NSs) have been considered as a good candidate for the enzyme-like catalysis. However, their catalytic activity is still restricted by the insufficient active sites and poor conductivity, and thus, the comprehensive performances are still unsatisfactory. To address these issues, herein, we design and fabricate an intelligent tubular nanostructure of hierarchical hollow nanotubes, which are assembled by NiSx/MoS2 NSs encapsulated into N-doped carbon microtubes (NiSx/MoS2@NCMTs). The N-doped carbon microtubes (NCMTs) serve as a conductive skeleton, integrating with NiSx/MoS2 NSs and ensuring their well-distribution, thereby maximally exposing more active sites. Additionally, the tube-like structure is favorable for increasing the mass transfusion to ensure their excellent catalytic performance. Profiting from their component and structural advantages, the obtained NiSx/MoS2@NCMTs exhibit a surprisingly enhanced enzyme-like activity. Based on these, a facile colorimetric sensing platform to detect H2O2 and GSH has been developed. This proposed approach can be expected to synthesize a series of tubular heterostructured MoS2-based composites, which will be widely applied in catalysis, energy storage, disease diagnosis, etc.

Tailing copper cobalt sulfide particle-decorated tube-like structure as efficient active material of battery supercapacitor hybrid

Copper cobalt sulfide (CuCo2S4) has received intensive attentions as one of effective battery-type materials of battery supercapacitor hybrids (BSH), because of numerous redox states and large conductivity. Morphology has been widely reported to play important roles on energy storage ability. Tube-like structure is beneficial for providing large surface area at inner/outer surface, and efficient charge transfer paths in one-dimensional directions. In this study, the CuCo2S4 particle-decorated tube-like structure is firstly designed on nickel foam via the hydrothermal process at different temperatures. The effects on morphology, composition and electrochemical performance are examined. The CuCo2S4 synthesized at 160 °C shows the most uniform rod size and regularly distributed particles on surface. The highest specific capacitance (CF) of 831.7 F/g corresponding to the capacity of 115.6 mAh/g is achieved for the optimal CuCo2S4 electrode, due to the largest electrochemical surface area with multiple active sites. A BSH is fabricated by using the CuCo2S4 positive electrode and the activated carbon negative electrode. A wide potential window of 1.5 V and the maximum energy density of 32.1 Wh/kg at power density of 1.1 kW/kg are achieved. The CF retention of 78.8% and Coulombic efficiency of 95.5% are also attained after 10,000 charge/discharge cycles for the BSH.

HCMV Infection Reduces Nidogen-1 Expression, Contributing to Impaired Neural Rosette Development in Brain Organoids.

Human cytomegalovirus (HCMV) is a leading cause of birth defects in humans. These birth defects include microcephaly, sensorineural hearing loss, vision loss, and cognitive impairment. The process by which the developing fetus incurs these neurological defects is poorly understood. To elucidate some of these mechanisms, we have utilized HCMV-infected induced pluripotent stem cells (iPSCs) to generate in vitro brain organoids, modeling the first trimester of fetal brain development. Early during culturing, brain organoids generate neural rosettes. These structures are believed to model neural tube formation. Rosette formation was analyzed in HCMV-infected and mock-infected brain organoids at 17, 24, and 31 days postinfection. Histological analysis revealed fewer neural rosettes in HCMV-infected compared to mock-infected organoids. HCMV-infected organoid rosettes incurred multiple structural deficits, including increased lumen area, decreased ventricular zone depth, and decreased cell count. Immunofluorescent (IF) analysis found that nidogen-1 (NID1) protein expression in the basement membrane surrounding neural rosettes was greatly reduced by virus infection. IF analysis also identified a similar downregulation of laminin in basement membranes of HCMV-infected organoid rosettes. Knockdown of NID1 alone in brain organoids impaired their development, leading to the production of rosettes with increased lumen area, decreased structural integrity, and reduced laminin localization in the basement membrane, paralleling observations in HCMV-infected organoids. Our data strongly suggest that HCMV-induced downregulation of NID1 impairs neural rosette formation and integrity, likely contributing to many of HCMV's most severe birth defects. IMPORTANCE HCMV infection in pregnant women continues to be the leading cause of virus-induced neurologic birth defects. The mechanism through which congenital HCMV (cCMV) infection induces pathological changes to the developing fetal central nervous system (CNS) remains unclear. Our lab previously reproduced identified clinical defects in HCMV-infected infants using a three dimensional (3D) brain organoid model. In this new study, we have striven to discover very early HCMV-induced changes in developing brain organoids. We investigated the development of neural tube-like structures, neural rosettes. HCMV-infected rosettes displayed multiple structural abnormalities and cell loss. HCMV-infected rosettes displayed reduced expression of the key basement membrane protein, NID1. We previously found NID1 to be specifically targeted in HCMV-infected fibroblasts and endothelial cells. Brain organoids generated from NID1 knockdown iPSCs recapitulated the structural defects observed in HCMV-infected rosettes. Findings in this study revealed HCMV infection induced early and dramatic structural changes in 3D brain organoids. We believe our results suggest a major role for infection-induced NID1 downregulation in HCMV-induced CNS birth defects.

Neonatal and adult cardiac fibroblasts exhibit inherent differences in cardiac regenerative capacity

Directly reprogramming fibroblasts into cardiomyocytes improves cardiac function in the infarcted heart. However, the low efficacy of this approach hinders clinical applications. Unlike the adult mammalian heart, the neonatal heart has an intrinsic regenerative capacity. Consequently, we hypothesized that birth imposes fundamental changes in cardiac fibroblasts which limit their regenerative capabilities. In support, we found that reprogramming efficacy invitro was markedly lower with fibroblasts derived from adult mice versus those derived from neonatal mice. Notably, fibroblasts derived from adult mice expressed significantly higher levels of pro-angiogenic genes. Moreover, under conditions that promote angiogenesis, only fibroblasts derived from adult mice differentiated into tube-like structures. Targeted knockdown screening studies suggested a possible role for the transcription factor Epas1. Epas1 expression was higher in fibroblasts derived from adult mice, and Epas1 knockdown improved reprogramming efficacy in cultured adult cardiac fibroblasts. Promoter activity assays indicated that Epas1 functions as both a transcription repressor and an activator, inhibiting cardiomyocyte genes while activating angiogenic genes. Finally, the addition of an Epas1 targeting siRNA to the reprogramming cocktail markedly improved reprogramming efficacy invivo with both the number of reprogramming events and cardiac function being markedly improved. Collectively, our results highlight differences between neonatal and adult cardiac fibroblasts and the dual transcriptional activities of Epas1 related to reprogramming efficacy.

Remediation of Methylene Blue Dye from Wastewater by Using Zinc Oxide Nanoparticles Loaded on Nanoclay

Dyes are one of the major environmental pollutants throughout the world, leading to pollution and numerous diseases. Though several techniques have been applied for the remediation of dyes, most of them are ineffective. The authors developed a halloysite clay/zinc oxide nanocomposite (HC/ZnONC) via a chemical route in the present study. The nanocomposite and its constituents, i.e., raw halloysite clay (HC) and zinc oxide nanoparticles (ZnONPs) (synthesized using the same chemical method) were analyzed for their detailed properties by sophisticated instruments. The field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) analysis showed spherical-shaped ZnONPs with an average size of 54.9 nm and tube-like shapes of HC with a diameter ranging from 40–200 nm and a length at the micron scale, while the nanocomposite had incorporated ZnONPs in their tube-like structures. Ultraviolet-Diffuse Reflectance Spectroscopic (UV-DRS) study revealed the photocatalytic ability of the nanocomposite with a band of 3.08 eV. A high surface area of 60.25 m2/g and the microporous and mesoporous nature of the nanocomposite were confirmed by the Brunauer–Emmet–Teller (BET) surface area analyzer. Finally, the developed nanocomposite was used for the remediation of methylene blue from the aqueous solutions, and the efficiency of removal varied from 90 to 97%.

Role of Non-covalent Interaction toward Conductivity in a One-Dimensional Tube-like Silver-Thiolate Structure

We report a new one-dimensional tube-like atomically precise silver-thiolate polymer–chain. The structure consists of Ag14(SR)18 as the building units. Silver atoms are linked with the thiol ligand to form the one-dimensional structure. The non-covalent interactions like argentophilic and C–H···H–C interactions appear as crucial for the long-range structural arrangement. Electronic structure calculations show its semiconductor-type band structure with a band gap of about 2 eV. Conductivity measurements on the single crystal implies its facile charge transfer pathway along the one-dimensional chain. The variation of conductivity between the single crystal and the drop-cast film implies the role of argentophilic and C–H···H–C interactions in the preferred charge transfer pathway.

Membrane remodelling triggers maturation of excitation–contraction coupling in 3D-shaped human-induced pluripotent stem cell-derived cardiomyocytes

The prospective use of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) for cardiac regenerative medicine strongly depends on the electro-mechanical properties of these cells, especially regarding the Ca2+-dependent excitation–contraction (EC) coupling mechanism. Currently, the immature structural and functional features of hiPSC-CM limit the progression towards clinical applications. Here, we show that a specific microarchitecture is essential for functional maturation of hiPSC-CM. Structural remodelling towards a cuboid cell shape and induction of BIN1, a facilitator of membrane invaginations, lead to transverse (t)-tubule-like structures. This transformation brings two Ca2+ channels critical for EC coupling in close proximity, the L-type Ca2+ channel at the sarcolemma and the ryanodine receptor at the sarcoplasmic reticulum. Consequently, the Ca2+-dependent functional interaction of these channels becomes more efficient, leading to improved spatio-temporal synchronisation of Ca2+ transients and higher EC coupling gain. Thus, functional maturation of hiPSC-cardiomyocytes by optimised cell microarchitecture needs to be considered for future cardiac regenerative approaches.

Structure, stability, and properties of cyclo[18]carbon-Zinc super sandwich complexes (C18-Zn-C18)

The unparalleled geometric and electronic structures along with the fascinating properties of cyclo[18]carbon, a new member in the carbon allotrope family, is found to be a riveting molecule. Density functional theory (DFT) calculations were accomplished to probe the structure, stability and properties of sandwich structures of 3d-transition series metal atoms with C18 rings. Results reveal that among all the 3d-transition metal atoms only the Zn atom forms a stable super sandwich-like structure with C18 (i.e., C18-Zn-C18). Ab initio molecular dynamic simulation was carried out to attain the comprehensive understanding of the stability of the C18-Zn-C18 complex. Result indicates that the non-covalent interaction plays a vital role in stabilizing the C18-Zn-C18 super sandwich complex which is further supported by atoms in molecules and extended transition state-natural orbital for chemical valence analysis. The Kohn–Sham band structure and density of state calculations were performed to investigate the periodic tube-like structures obtained using C18 and Zn. The calculated band gap using HSE06 in conjunction with TZP of Zn@C18 is found to be 0.49 eV.

Flow-dependent shear stress affects the biological properties of pericyte-like cells isolated from human dental pulp

BackgroundHuman dental pulp stem cells represent a mesenchymal stem cell niche localized in the perivascular area of dental pulp and are characterized by low immunogenicity and immunomodulatory/anti-inflammatory properties. Pericytes, mural cells surrounding the endothelium of small vessels, regulate numerous functions including vessel growth, stabilization and permeability. It is well established that pericytes have a tight cross talk with endothelial cells in neoangiogenesis and vessel stabilization, which are regulated by different factors, i.e., microenvironment and flow-dependent shear stress. The aim of this study was to evaluate the effects of a pulsatile unidirectional flow in the presence or not of an inflammatory microenvironment on the biological properties of pericyte-like cells isolated from human dental pulp (hDPSCs).MethodsHuman DPSCs were cultured under both static and dynamic conditions with or without pre-activated peripheral blood mononuclear cells (PBMCs). Pulsatile unidirectional flow shear stress was generated by using a specific peristaltic pump. The angiogenic potential and inflammatory properties of hDPSCs were evaluated through reverse phase protein microarrays (RPPA), confocal immunofluorescence and western blot analyses.ResultsOur data showed that hDPSCs expressed the typical endothelial markers, which were up-regulated after endothelial induction, and were able to form tube-like structures. RPPA analyses revealed that these properties were modulated when a pulsatile unidirectional flow shear stress was applied to hDPSCs. Stem cells also revealed a downregulation of the immune-modulatory molecule PD-L1, in parallel with an up-regulation of the pro-inflammatory molecule NF-kB. Immune-modulatory properties of hDPSCs were also reduced after culture under flow-dependent shear stress and exposure to an inflammatory microenvironment. This evidence was strengthened by the detection of up-regulated levels of expression of pro-inflammatory cytokines in PBMCs.ConclusionsIn conclusion, the application of a pulsatile unidirectional flow shear stress induced a modulation of immunomodulatory/inflammatory properties of dental pulp pericyte-like cells.

Conformational dynamics control assembly of an extremely long bacteriophage tail tube

Tail tube assembly is an essential step in the lifecycle of long-tailed bacteriophages. Limited structural and biophysical information has impeded an understanding of assembly and stability of their long, flexible tail tubes. The hyperthermophilic phage P74-26 is particularly intriguing as it has the longest tail of any known virus (nearly 1μm) and is the most thermostable known phage. Here, we use structures of the P74-26 tail tube along with an invitro system for studying tube assembly kinetics to propose the first molecular model for the tail tube assembly of long-tailed phages. Our high-resolution cryo-EM structure provides insight into how the P74-26 phage assembles through flexible loops that fit into neighboring rings through tight "ball-and-socket"-like interactions. Guided by this structure, and in combination with mutational, light scattering, and molecular dynamics simulations data, we propose a model for the assembly of conserved tube-like structures across phage and other entities possessing tail tube-like proteins. We propose that formation of a full ring promotes the adoption of a tube elongation-competent conformation among the flexible loops and their corresponding sockets, which is further stabilized by an adjacent ring. Tail assembly is controlled by the cooperative interaction of dynamic intraring and interring contacts. Given the structural conservation among tail tube proteins and tail-like structures, our model can explain the mechanism of high-fidelity assembly of long, stable tubes.

Evolution of the velocity gradient invariants in homogeneous isotropic turbulence with an inverse energy cascade

An investigation of topological features of homogeneous isotropic turbulence with an inverse energy cascade is performed by using a direct numerical simulation. The inverse energy cascade is induced by reversing the velocity field (i.e., under the transformation from ui to −ui) of a freely decaying isotropic turbulence. In the backward energy transfer process, the joint probability density function (PDF) of Q and R exhibits a novel shape, which seems to be symmetric with the well-known teardrop shape about the Q-axis (Q and R are the second and third invariants of the velocity gradients tensor, respectively). The predominance of the top-right (R > 0 and Q > 0) and the bottom-left (R < 0 and Q < 0) quadrants is observed in the backward energy transfer process. This observation is different from that of the forward energy cascade, in which the top-left (R < 0 and Q > 0) and the bottom-right (R > 0 and Q < 0) quadrants are dominant. The unexpected shape of the joint PDF of Q and R indicates that the turbulence with an inverse energy cascade is dominated by vortex compression and tube-like structures. The PDF of the intermediate eigenvalue of the strain-rate tensor in the inverse energy cascade is negatively skewed, which is opposite to the universal feature of the forward energy cascade. Nevertheless, the preferential alignment of vorticity with the intermediate eigenvector is rather robust, no matter whether the direction of the energy transfer is forward or backward. In addition, it is universal that the vorticity is mostly perpendicular to the eigenvector, which corresponds to a strain-rate eigenvalue with the maximum absolute value among the three eigenvalues. Since the velocity gradient invariants are closely related to the local flow topology, the numerical results reported in this work are expected to shed light on the intrinsic dynamics and mechanisms of inverse energy cascade.

Living on hydrazine: Metabolic protein complexes from an anaerobic ammonium oxidizer.

The discovery of anammox bacteria in the 1990s has dramatically changed our understanding of the global nitrogen cycle. Anammox bacteria are now believed to be responsible for up to 30 to 70% of the nitrogen removal from the oceans. These organisms have the unique metabolic ability to combine ammonium and nitrite to form dinitrogen gas, a process that takes place in a special cellular compartment, the anammoxosome. To elucidate how bacteria perform such extraordinary chemistry, we have determined the structures of the key enzymes in this process. Central to harvesting the energy from hydrazine is the hydrazine dehydrogenase (HDH), which converts hydrazine into dinitrogen gas, liberating four extremely low-potential electrons (−750 mV). Our crystal and cryo-EM structures reveal that this 1.7-MDa complex contains an extended system of 192 heme groups spanning the entire complex, which is only accessible via narrow holes in the side of the complex. Moreover, we identified an unexpected assembly factor for this complex. In addition, anammox bacteria obtain additional reducing equivalents through the oxidation of nitrite to nitrate, which is catalyzed by a nitrite oxidoreductase (NXR) related to the NXR from nitrifying bacteria. Despite its importance in the biogeochemical nitrogen cycle, essential issues on NXR functions remain unanswered, particularly due to the lack of structural information. To meet this challenge, we used a multiscale approach combining cryo-electron tomography, crystallography, single-particle cryo-EM together with reconstitution studies and enzyme kinetics to characterize NXR. We show that, in contrast to what was shown for NXR in NOB, NXR of anammox bacteria forms tubule-like structures inside the anammoxosome held together by a novel subunit NXR-T. As with the hydrazine dehydrogenase structure, our multiscale structure of the anammox NXR tubules suggest how electrons are passed on to redox partners.

Effector protein Hcp2a of avian pathogenic Escherichia coli interacts with the endoplasmatic reticulum associated RPL23 protein of chicken DF-1 fibroblasts

The type VI secretion system (T6SS) is a secretion apparatus widely found in pathogenic Gram-negative bacteria and is important for competition among various bacteria and host cell pathogenesis. Hcp is a core component of functional T6SS and transports toxic effectors into target cells by assembling to form tube-like structures. Studies have shown that Hcp simultaneously acts as an effector to influence cellular physiological activities; however, the mechanism of its activity in host cells remains unclear. To investigate the target of effector protein Hcp2a in a chicken fibroblast cell line, we first detected the subcellular localization of Hcp2a in DF-1 cells by indirect immunofluorescence assay. The results showed that Hcp2a protein was localized in the endoplasmic reticulum of DF-1 cells. We also used a streptavidin–biotin affinity pull-down assay combined with LC–MS/MS to screen DF-1 cell lysates for proteins that interact with Hcp2a and analyze the cellular functional pathways affected by them. The results showed that Hcp2a interacted with 52 DF-1 cellular proteins that are involved in multiple intracellular pathways. To further explore the mechanism of Hcp2a protein targeting the endoplasmic reticulum of DF-1 cells, we screened three endoplasmic reticulum-associated proteins (RSL1D1, RPS3A, and RPL23) from 52 prey proteins of Hcp2a for protein–protein molecular docking analysis. The docking analysis showed that the effector protein Hcp2a and the RPL23 protein had good complementarity. Overall, we propose that Hcp2a has strong binding activity to the RPL23 protein in DF-1 cells and this may help Hcp2a anchor to the endoplasmic reticulum in DF-1 cells.

Non-Destructive Study of Egyptian Emeralds Preserved in the Collection of the Museum of the Ecole des Mines

In the present study, rough emerald single crystals and rough emeralds in the host rock from the ruins of Alexandria and from the Mount Zabargad in Egypt, preserved in the collection of the museum of the Ecole des Mines (Mines Paris—PSL) since the late 19th or early 20th century, are investigated. All samples were characterized by non-destructive spectroscopic and chemical methods during a week-long loan to the LFG. Raman, FTIR and UV-Vis-NIR spectroscopy revealed that Egyptian emeralds contain H2O molecules accompanied by relatively high concentrations of alkali ions and are colored by chromium and iron. Additionally, EDXRF showed that the emeralds from Egypt contain up to 84 ppm Rb and low amounts (below 200 ppm) of Cs. Inclusions and parts of the host rock were also observed under optical microscope and analyzed with Raman spectroscopy. Tube-like structures, quartz, calcite, dolomite, albite and phlogopite are associated minerals, and inclusions are identified in these historic emeralds from Egypt. This work will hopefully further contribute to the characterization of emeralds of archaeological significance.