The mitochondrial fusion protein OPA1 is dispensable in the liver and its absence induces mitohormesis to protect liver from drug-induced injury.

Mitochondria are critical for metabolic homeostasis of the liver, and their dysfunction is a major cause of liver diseases. Optic atrophy 1 (OPA1) is a mitochondrial fusion protein with a role in cristae shaping. Disruption of OPA1 causes mitochondrial dysfunction. However, the role of OPA1 in liver function is poorly understood. In this study, we delete OPA1 in the fully developed liver of male mice. Unexpectedly, OPA1 liver knockout (LKO) mice are healthy with unaffected mitochondrial respiration, despite disrupted cristae morphology. OPA1 LKO induces a stress response that establishes a new homeostatic state for sustained liver function. Our data show that OPA1 is required for proper complex V assembly and that OPA1 LKO protects the liver from drug toxicity. Mechanistically, OPA1 LKO decreases toxic drug metabolism and confers resistance to the mitochondrial permeability transition. This study demonstrates that OPA1 is dispensable in the liver, and that the mitohormesis induced by OPA1 LKO prevents liver injury and contributes to liver resiliency.

Ultra-Wideband Electromagnetic Composite Absorber Based on Pixelated Metasurface with Optimization Algorithm.

An ultra-wideband electromagnetic (EM) absorber is proposed. The proposed absorber consists of two thin metasurfaces, four dielectric layers, a glass fiber reinforced polymer (GFRP), and a carbon fiber reinforced polymer (CFRP) which works as a conductive reflector. The thin metasurfaces are accomplished with 1-bit pixelated patterns and optimized by a genetic algorithm. Composite materials of GFRP and CFRP are incorporated to improve the durability of the proposed absorber. From the full-wave simulation, more than 90% absorption rate bandwidth is computed from 2.2 to 18 GHz such that the fractional bandwidth is about 156% for the incidence angles from 0° to 30°. Absorptivity is measured using the Naval Research Laboratory (NRL) arch method in an EM anechoic environment. It was shown that the measured results correlated with the simulated results. In addition, the proposed absorber underwent high temperature and humidity tests under military environment test conditions in order to investigate its durability.

Full-color micro-LED display with photo-patternable and highly ambient-stable perovskite quantum dot/siloxane composite as color conversion layers.

In this paper, we successfully fabricated color conversion layers (CCLs) for full-color-mico-LED display using a perovskite quantum dot (PQD)/siloxane composite by ligand exchanged PQD with silane composite followed by surface activation by an addition of halide-anion containing salt. Due to this surface activation, it was possible to construct the PQD surface with a silane ligand using a non-polar organic solvent that does not damage the PQD. As a result, the ligand-exchanged PQD with a silane compound exhibited high dispersibility in the siloxane matrix and excellent atmospheric stability due to sol-gel condensation. Based on highly ambient stable PQD/siloxane composite based CCLs, full-color micro-LED display has a 1 mm pixel pitch, about 25.4 pixels per inch (PPI) resolution was achieved. In addition, due to the thin thickness of the black matrix to prevent blue light interference, the possibility of a flexible display that can be operated without damage even with a bending radius of 5 mm was demonstrated.

Non-conventional mitochondrial permeability transition: Its regulation by mitochondrial dynamics.

Mitochondrial permeability transition (MPT) is a phenomenon that the inner mitochondrial membrane (IMM) loses its selective permeability, leading to mitochondrial dysfunction and cell injury. Electrophysiological evidence indicates the presence of a mega-channel commonly called permeability transition pore (PTP) whose opening is responsible for MPT. However, the molecular identity of the PTP is still under intensive investigations and debates, although cyclophilin D that is inhibited by cyclosporine A (CsA) is the established regulatory component of the PTP. PTP can also open transiently and functions as a rapid mitochondrial Ca2+ releasing mechanism. Mitochondrial fission and fusion, the main components of mitochondrial dynamics, control the number and size of mitochondria, and have been shown to play a role in regulating MPT directly or indirectly. Studies by us and others have indicated the potential existence of a form of transient MPT that is insensitive to CsA. This "non-conventional" MPT is regulated by mitochondrial dynamics and may serve a protective role possibly by decreasing the susceptibility for a frequent or sustained PTP opening; hence, it may have a therapeutic value in many disease conditions involving MPT.

Surface Properties of CVD-Grown Graphene Transferred by Wet and Dry Transfer Processes.

Graphene, an atomically thin material, has unique electrical, mechanical, and optical properties that can enhance the performance of thin film-based flexible and transparent devices, including gas sensors. Graphene synthesized on a metallic catalyst must first be transferred onto a target substrate using wet or dry transfer processes; however, the graphene surface is susceptible to chemical modification and mechanical damage during the transfer. Defects on the graphene surface deteriorate its excellent intrinsic properties, thus reducing device performance. In this study, the surface properties of transferred graphene were investigated according to the transfer method (wet vs. dry) and characterized using atomic force microscopy, Raman spectroscopy, and contact angle measurements. After the wet transfer process, the surface properties of graphene exhibited tendencies similar to the poly(methyl methacrylate) residue remaining after solvent etching. The dry-transferred graphene revealed a surface closer to that of pristine graphene, regardless of substrates. These results provide insight into the utilization of wet and dry transfer processes for various graphene applications.

Bottom-Up Evolution of Diamond-Graphite Hybrid Two-Dimensional Nanostructure: Underlying Picture and Electrochemical Activity.

The diamond-graphite hybrid thin film with low-dimensional nanostructure (e.g., nitrogen-included ultrananocrystalline diamond (N-UNCD) or the alike), has been employed in many impactful breakthrough applications. However, the detailed picture behind the bottom-up evolution of such intriguing carbon nanostructure is far from clarified yet. Here, the authors clarify it, through the concerted efforts of microscopic, physical, and electrochemical analyses for a series of samples synthesized by hot-filament chemical vapor deposition using methane-hydrogen precursor gas, based on the hydrogen-dependent surface reconstruction of nanodiamond and on the substrate-temperature-dependent variation of the growth species (atomic hydrogen and methyl radical) concentration near substrate. The clarified picture provides insights for a drastic enhancement in the electrochemical activities of the hybrid thin film, concerning the detection of important biomolecule, that is, ascorbic acid, uric acid, and dopamine: their limits of detections are 490, 35, and 25 nm, respectively, which are among the best of the all-carbon thin film electrodes in the literature. This work also enables a simple and effective way of strongly enhancing AA detection.

Ultrawideband electromagnetic metamaterial absorber utilizing coherent absorptions and surface plasmon polaritons based on double layer carbon metapatterns.

An ultrawideband electromagnetic metamaterial absorber is proposed that consists of double-layer metapatterns optimally designed by the genetic algorithm and printed using carbon paste. By setting the sheet resistance of the intermediate carbon metapattern to a half of that of the top one, it is possible to find an optimal intermediate metapattern that reflects and absorbs the EM wave simultaneously. By adding an absorption resonance via a constructive interference at the top metapattern induced by the reflection from the intermediate one, an ultrawideband absorption can be achieved without increasing the number of layers. Moreover, it is found that the metapatterns support the surface plasmon polaritons which can supply an additional absorption resonance as well as boost the absorption in a broad bandwidth. Based on the simulation, the [Formula: see text] absorption bandwidth is confirmed from 6.3 to 30.1 GHz of which the fractional bandwidth is 130.77[Formula: see text] for the normal incidence. The accuracy is verified via measurements well matched with the simulations. The proposed metamaterial absorber could not only break though the conventional concept that the number of layers should be increased to extend the bandwidth but also provide a powerful solution to realize a low-profile, lightweight, and low cost electromagnetic absorber.

Single-layer metamaterial bolometer for sensitive detection of low-power terahertz waves at room temperature.

This study demonstrates a metamaterial bolometer that can detect terahertz (THz) waves by measuring variations in electrical resistance. A metamaterial pattern for enhanced THz waves absorption and a composite material with a high temperature coefficient of resistance (TCR) are incorporated into a single layer of the bolometer chip to realize a compact and highly sensitive device. To detect the temperature change caused by the absorption of the THz waves, a polydimethylsiloxane mixed with carbon black microparticles is used. The thermosensitive composite has TCR ranging from 1.88%/K to 3.11%/K at room temperature (22.2-23.8°C). In addition, a microscale metamaterial without a backside reflector is designed to enable the measurement of the resistance and to enhance the sensitivity of the bolometer. The proposed configuration effectively improves thermal response of the chip as well as the absorption of the THz waves. It was confirmed that the irradiated THz waves can be detected via the increment in the electrical resistance. The resistance change caused by the absorption of the THz waves is detectable in spite of the changes in resistance originating from the background thermal noise. The proposed metamaterial bolometer could be applied to detect chemical or biological molecules that have fingerprints in the THz band by measuring the variation of the resistance without using the complex and bulky THz time-domain spectroscopy system.

The short variant of optic atrophy 1 (OPA1) improves cell survival under oxidative stress.

Optic atrophy 1 (OPA1) is a dynamin protein that mediates mitochondrial fusion at the inner membrane. OPA1 is also necessary for maintaining the cristae and thus essential for supporting cellular energetics. OPA1 exists as membrane-anchored long form (L-OPA1) and short form (S-OPA1) that lacks the transmembrane region and is generated by cleavage of L-OPA1. Mitochondrial dysfunction and cellular stresses activate the inner membrane-associated zinc metallopeptidase OMA1 that cleaves L-OPA1, causing S-OPA1 accumulation. The prevailing notion has been that L-OPA1 is the functional form, whereas S-OPA1 is an inactive cleavage product in mammals, and that stress-induced OPA1 cleavage causes mitochondrial fragmentation and sensitizes cells to death. However, S-OPA1 contains all functional domains of dynamin proteins, suggesting that it has a physiological role. Indeed, we recently demonstrated that S-OPA1 can maintain cristae and energetics through its GTPase activity, despite lacking fusion activity. Here, applying oxidant insult that induces OPA1 cleavage, we show that cells unable to generate S-OPA1 are more sensitive to this stress under obligatory respiratory conditions, leading to necrotic death. These findings indicate that L-OPA1 and S-OPA1 differ in maintaining mitochondrial function. Mechanistically, we found that cells that exclusively express L-OPA1 generate more superoxide and are more sensitive to Ca2+-induced mitochondrial permeability transition, suggesting that S-OPA1, and not L-OPA1, protects against cellular stress. Importantly, silencing of OMA1 expression increased oxidant-induced cell death, indicating that stress-induced OPA1 cleavage supports cell survival. Our findings suggest that S-OPA1 generation by OPA1 cleavage is a survival mechanism in stressed cells.

Berardinelli-Seip congenital lipodystrophy 2/SEIPIN determines brown adipose tissue maintenance and thermogenic programing.

OBJECTIVE: Understanding the mechanisms that control brown adipose tissue (BAT) mass and functionality is crucial for our understanding of how the disruption of energy homeostasis leads to obesity. Bernerdinali Seip Congenital Lipodystrophy (BSCL) type 2 (BSCL2, a.k.a. SEIPIN), a lipodystrophy-associated protein, has been shown to not be required for brown adipogenesis, but it has been shown to be essential for perinatal BAT development. However, its role in mature BAT maintenance and thermogenic programing remains poorly understood. METHODS: We subjected Bscl2f/f and Bscl2UCP1-BKO (BKO) mice with a brown adipose-specific loss of BSCL2 through UCP1 promoter-driven Cre to environmental, pharmacological and diet interventions to challenge BAT functionality and reprogramming. We carried out physiological, molecular and transcriptomic analyses of BAT. RESULTS: The deletion of BSCL2 in mature brown adipocytes increased sympathetic nervous system-independent cAMP/protein kinase A (PKA) signaling in BAT. Such activation reduced BAT triglyceride content and mass and was sufficient to reduce plasma triglyceride, but not enough to combat thermoneutral and high fat diet-induced obesity. Surprisingly, BKO mice displayed an impaired response to acute and chronic cold challenges despite cAMP/PKA activation. When subjected to chronic cold exposure or the administration of a ß3-adrenergic agonist, CL 316,243, BKO mice failed to induce BAT recruitment and underwent dramatic brown adipocyte loss. Transcriptomic analysis revealed pathological BAT remodeling with inflammation and fibrosis, which was further exacerbated by a chronic thermogenic challenge in BKO mice. Mechanistically, we found abnormal mitochondrial shapes and function in BAT of BKO mice housed at 21 °C; as well as mitochondrial DNA depletion and necroptotic-mediated brown adipocyte death after chronic thermogenic insult. CONCLUSION: BSCL2-mediated lipid catabolism within BAT is crucial for mature brown adipocyte function and survival both during times of activation and quiescence. BSCL2 is an important regulator of mature brown adipocyte mitochondrial metabolism, necroptosis and thus adaptive thermogenesis.

Mitochondrial Membrane Dynamics-Functional Positioning of OPA1.

The maintenance of mitochondrial energetics requires the proper regulation of mitochondrial morphology, and vice versa. Mitochondrial dynamins control mitochondrial morphology by mediating fission and fusion. One of them, optic atrophy 1 (OPA1), is the mitochondrial inner membrane remodeling protein. OPA1 has a dual role in maintaining mitochondrial morphology and energetics through mediating inner membrane fusion and maintaining the cristae structure. OPA1 is expressed in multiple variant forms through alternative splicing and post-translational proteolytic cleavage, but the functional differences between these variants have not been completely understood. Recent studies generated new information regarding the role of OPA1 cleavage. In this review, we will first provide a brief overview of mitochondrial membrane dynamics by describing fission and fusion that are mediated by mitochondrial dynamins. The second part describes OPA1-mediated fusion and energetic maintenance, the role of OPA1 cleavage, and a new development in OPA1 function, in which we will provide new insight for what OPA1 does and what proteolytic cleavage of OPA1 is for.

Graphene-based stretchable and transparent moisture barrier.

We propose an alumina-deposited double-layer graphene (2LG) as a transparent, scalable, and stretchable barrier against moisture; this barrier is indispensable for foldable or stretchable organic displays and electronics. Both the barrier property and stretchability were significantly enhanced through the introduction of 2LG between alumina and a polymeric substrate. 2LG with negligible polymeric residues was coated on the polymeric substrate via a scalable dry transfer method in a roll-to-roll manner; an alumina layer was deposited on the graphene via atomic layer deposition. The effect of the graphene layer on crack generation in the alumina layer was systematically studied under external strain using an in situ micro-tensile tester, and correlations between the deformation-induced defects and water vapor transmission rate were quantitatively analyzed. The enhanced stretchability of alumina-deposited 2LG originated from the interlayer sliding between the graphene layers, which resulted in the crack density of the alumina layer being reduced under external strain.

Asynchronous cracking with dissimilar paths in multilayer graphene.

Multilayer graphene consists of a stack of single-atomic-thick monolayer graphene sheets bound with π-π interactions and is a fascinating model material opening up a new field of fracture mechanics. In this study, fracture behavior of single-crystalline multilayer graphene was investigated using an in situ mode I fracture test under a scanning electron microscope, and abnormal crack propagation in multilayer graphene was identified for the first time. The fracture toughness of graphene was determined from the measured load-displacement curves and the realistic finite element modelling of specimen geometries. Nonlinear fracture behavior of the multilayer graphene is discussed based on nonlinear elastic fracture mechanics. In situ scanning electron microscope images obtained during the fracture test showed asynchronous crack propagation along independent paths, causing interlayer shear stress and slippages. We also found that energy dissipation by interlayer slippages between the graphene layers is the reason for the enhanced fracture toughness of multilayer graphene. The asynchronous cracking with independent paths is a unique cracking and toughening mechanism for single-crystalline multilayer graphene, which is not observed for the monolayer graphene. This could provide a useful insight for the design and development of graphene-based composite materials for structural applications.

Carbon Textile Decorated with Pseudocapacitive VC/Vx Oy for High-Performance Flexible Supercapacitors.

It is demonstrated that, via V2 O5 coating by low temperature atomic layer deposition and subsequent pyrolysis, ubiquitous cotton textile can readily turn into high-surface-area carbon textile fully decorated with pseudocapacitive Vx Oy /VC widely usable as electrodes of high-performance supercapacitor. It is found that carbothermic reduction of V2 O5 (C + V2 O5 → C' + VC + CO/CO2 (g)) leads to chemical/mechanical activation of carbon textile, thereby producing high-surface-area conductive carbon textile. In addition, sequential phase transformation and carbide formation (V2 O5 → Vx Oy → VC) occurred by carbothermic reduction trigger decoration of the carbon textile with redox-active Vx Oy /VC. Thanks to the synergistic effect of electrical double layer and pseudocapacitance, the supercapacitors made of the hybrid carbon textile exhibit far better energy density (over 30-fold increase) with excellent cycling stability than the carbon textile simply undergone pyrolysis. The method can open up a promising and facile way to synthesize hybrid electrode materials for electrochemical energy storages possessing advantages of both electrical double layer and pseudocapacitive material.

The short variant of the mitochondrial dynamin OPA1 maintains mitochondrial energetics and cristae structure.

The protein optic atrophy 1 (OPA1) is a dynamin-related protein associated with the inner mitochondrial membrane and functions in mitochondrial inner membrane fusion and cristae maintenance. Inner membrane-anchored long OPA1 (L-OPA1) undergoes proteolytic cleavage resulting in short OPA1 (S-OPA1). It is often thought that S-OPA1 is a functionally insignificant proteolytic product of L-OPA1 because the accumulation of S-OPA1 due to L-OPA1 cleavage is observed in mitochondrial fragmentation and dysfunction. However, cells contain a mixture of both L- and S-OPA1 in normal conditions, suggesting the functional significance of maintaining both OPA1 forms, but the differential roles of L- and S-OPA1 in mitochondrial fusion and energetics are ill-defined. Here, we examined mitochondrial fusion and energetic activities in cells possessing L-OPA1 alone, S-OPA1 alone, or both L- and S-OPA1. Using a mitochondrial fusion assay, we established that L-OPA1 confers fusion competence, whereas S-OPA1 does not. Remarkably, we found that S-OPA1 alone without L-OPA1 can maintain oxidative phosphorylation function as judged by growth in oxidative phosphorylation-requiring media, respiration measurements, and levels of the respiratory complexes. Most strikingly, S-OPA1 alone maintained normal mitochondrial cristae structure, which has been commonly assumed to be the function of OPA1 oligomers containing both L- and S-OPA1. Furthermore, we found that the GTPase activity of OPA1 is critical for maintaining cristae tightness and thus energetic competency. Our results demonstrate that, contrary to conventional notion, S-OPA1 is fully competent for maintaining mitochondrial energetics and cristae structure.

Ultimate Control of Rate-Dependent Adhesion for Reversible Transfer Process via a Thin Elastomeric Layer.

Adhesion between a stamp with an elastomeric layer and various devices or substrates is crucial to successfully fabricate flexible electronics using a transfer process. Although various transfer processes using stamps with different adhesion strengths have been suggested, the controllable range of adhesion is still limited to a narrow range. To precisely transfer devices onto selected substrates, however, the difference in adhesion between the picking and placing processes should be large enough to achieve a high yield. Herein, we report a simple way to extend the controllable adhesion range of stamps, which can be achieved by adjusting the thickness of the elastomeric layer and the separation velocity. The adhesion strength increased with decreasing layer thickness on the stamp due to a magnification of the confinement and rate-dependent effects on the adhesion. This enabled the controllable range of the adhesion strength for a 15 µm-thick elastomeric layer to be extended up to 12 times that of the bulk under the same separation conditions. The strategy of designing stamps using simple adhesion tests is also introduced, and the reversible transfer of thin Si chips was successfully demonstrated. Tuning and optimizing the adhesion strength of a stamp according to the design process suggested here can be applied to various materials for the selective transfer and replacement of individual devices.

Activated Carbon Textile via Chemistry of Metal Extraction for Supercapacitors.

Carbothermic reduction in the chemistry of metal extraction (MO(s) + C(s) → M(s) + CO(g)) using carbon as a sacrificial agent has been used to smelt metals from diverse oxide ores since ancient times. Here, we paid attention to another aspect of the carbothermic reduction to prepare an activated carbon textile for high-rate-performance supercapacitors. On the basis of thermodynamic reducibility of metal oxides reported by Ellingham, we employed not carbon, but metal oxide as a sacrificial agent in order to prepare an activated carbon textile. We conformally coated ZnO on a bare cotton textile using atomic layer deposition, followed by pyrolysis at high temperature (C(s) + ZnO(s) → C'(s) + Zn(g) + CO(g)). We figured out that it leads to concurrent carbonization and activation in a chemical as well as mechanical way. Particularly, the combined effects of mechanical buckling and fracture that occurred between ZnO and cotton turned out to play an important role in carbonizing and activating the cotton textile, thereby significantly increasing surface area (nearly 10 times) compared with the cotton textile prepared without ZnO. The carbon textiles prepared by carbothermic reduction showed impressive combination properties of high power and energy densities (over 20-fold increase) together with high cyclic stability.

Mitochondrial fission and fusion.

Mitochondrial fission and fusion have been recognized as critical processes in the health of mitochondria and cells. Two decades of studies have generated a great deal of information about mitochondrial fission and fusion; however, still much needs to be understood for the basic molecular mechanisms of these important cellular processes. The core protein factors for mitochondrial fission and fusion are dynamin proteins that possess membrane-remodeling properties. This short review covers a recent development and understanding of the mechanisms by which these mechanochemical enzymes mediate mitochondrial fission and fusion.

A graphene meta-interface for enhancing the stretchability of brittle oxide layers.

Oxide materials have recently attracted much research attention for applications in flexible and stretchable electronics due to their excellent electrical properties and their compatibility with established silicon semiconductor processes. Their widespread uptake has been hindered, however, by the intrinsic brittleness and low stretchability. Here we investigate the use of a graphene meta-interface to enhance the electromechanical stretchability of fragile oxide layers. Electromechanical tensile tests of indium tin oxide (ITO) layers on polymer substrates were carried out with in situ observations using an optical microscope. It was found that the graphene meta-interface reduced the strain transfer between the ITO layer and the substrate, and this behavior was well described using a shear lag model. The graphene meta-interface provides a novel pathway for realizing flexible and stretchable electronic applications based on oxide layers.

A robust and conductive metal-impregnated graphene oxide membrane selectively separating organic vapors.

A small amount of Zn impregnated by ALD triggered enhancement of the mechanical as well as electrical properties of the graphene oxide (GO) membrane. In addition, the Zn-impregnated membranes selectively separated diverse organic vapors while maintaining high water permeability.