High-Valence W6+ Ions Boost Cr2+ Activity in CrWO4 for Ideal Water Oxidation.

Electrocatalytic activity of multi-valence metal oxides for oxygen evolution reaction (OER) arises from various interactions among the constituent metal elements. Although the high-valence metal ions attract recent attentions due to the interactions with their neighboring 3d transition metal catalytic center, atomic-scale explanations for the catalytic efficiencies are still lacking. Here, by employing density functional theory predictions and experimental verifications, unprecedented electronic isolation of the catalytic 3d center (M2+) induced by the surrounding high-valence ions such as W6+ is discovered in multivalent oxides MWO4 (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn). Due to W6+'s extremely high oxidation state with the minimum electron occupations (d0), the surrounding W6+ blocks electron transfer toward the catalytic M2+ ions and completely isolates the ions electronically. Now, the isolated M2+ ions solely perform OER without any assistant electron flow from the adjacent metal ions, and thus the original strong binding energies of Cr with OER intermediates are effectively moderated. Through exploiting "electron isolators" such as W6+ surrounding the catalytic ion, exploring can be done beyond the conventional materials such as Ni- or Co-oxides into new candidate groups such as Cr and Mn on the left side of the periodic table for ideal OER.

Zwitterionic Conjugated Surfactant Functionalization of Graphene with pH-Independent Dispersibility: An Efficient Electron Mediator for the Oxygen Evolution Reaction in Acidic Media.

The functionalization of graphene has been extensively used as an effective route for modulating the surface property of graphene, and enhancing the dispersion stability of graphene in aqueous solutions via functionalization has been widely investigated to expand its use for various applications across a range of fields. Herein, an effective approach is described for enhancing the dispersibility of graphene in aqueous solutions at different pH levels via non-covalent zwitterion functionalization. The results show that a surfactant with electron-deficient carbon atoms in its backbone structure and large π-π interactive area enables strong interactions with graphene, and the zwitterionic side terminal groups of the molecule support the dispersibility of graphene in various pH conditions. Experimental and computational studies confirm that perylene diimide amino N-oxide (PDI-NO) allows efficient functionalization and pH-independent dispersion of graphene enabled by hydration repulsion effects induced by PDI-NO. The PDI-NO functionalized graphene is successfully used in the oxygen evolution reaction as an electron mediator for boosting the electrocatalytic activity of a Ru-based polyoxometalate catalyst in an acidic medium. The proposed strategy is expected to bring significant advances in producing highly dispersible graphene in aqueous medium with pH-independent stability, thus broadening the application range of graphene.

Nucleation promoted synthesis of large-area ReS2 film for high-speed photodetectors.

Rhenium disulfide (ReS2) is a transition metal dichalcogenide with a layer-independent direct bandgap. Notably, the weak interlayer coupling owing to its T-phase structure enables multi-layer ReS2 to behave similarly to decoupled monolayers. This inherent characteristic makes continuous multilayer ReS2 film a unique platform for large-area electronic applications. To date, the bulk of work on ReS2 has been conducted using mechanically exfoliated samples or small size flakes (<1 mm2) with no potential for large-scale electronics. A chemical vapor deposition (CVD) synthesis of a large area, continuous ReS2 film directly on a SiO2 substrate is also known to be more challenging compared with that of other 2D materials, such as MoS2 and WS2. This is partly due to its tendency to grow into discrete dendritic structures. In this study, a large-area (>1 cm2), continuous multilayer ReS2 film is directly synthesized on a SiO2 substrate without any transfer process. The polycrystalline ReS2 film synthesized by this method exhibits one of the fastest photoresponse speeds (0.03 s rise time and 0.025 s decay time) among the reported CVD films. The photoresponsivity R λ was also the highest among large-area CVD films. The synthesis method for a continuous multilayer ReS2 film is amenable to large-scale integration and will pave the way for practical optoelectronic applications based on 2D layered materials.

Target Proteins of Phloretin for Its Anti-Inflammatory and Antibacterial Activities Against Propionibacterium acnes-Induced Skin Infection.

Phloretin is a natural chalcone with antibacterial and anti-inflammatory effects. This study investigated the anti-acne activity of phloretin against Propionibacterium acnes-induced skin infection and the potential target proteins of its anti-inflammatory and antibacterial effects. Phloretin potently inhibited the growth of P. acnes and P. acnes-induced Toll-like receptor (TLR) 2-mediated inflammatory signaling in human keratinocytes. Secreted embryonic alkaline phosphatase assay confirmed that the anti-inflammatory activity of phloretin is associated with the P. acnes-stimulated TLR2-mediated NF-κB signaling pathway. Phloretin significantly decreased the level of phosphorylated c-Jun N-terminal kinase (JNK), showing a binding affinity of 1.184 × 10-5 M-1. We also found that phloretin binds with micromolar affinity to P. acnes ß-ketoacyl acyl carrier protein (ACP) synthase III (KAS III), an enzyme involved in fatty acid synthesis. Conformation-sensitive native polyacrylamide gel electrophoresis showed that phloretin reduced KAS III-mediated 3-ketoacyl ACP production by over 66%. A docking study revealed that phloretin interacts with the active sites of JNK1 and KAS III, suggesting their involvement in P. acnes-induced inflammation and their potential as targets for the antibacterial activity of phloretin. These results demonstrate that phloretin may be useful in the prevention or treatment of P. acnes infection.

Structure-activity relationship-based screening of antibiotics against Gram-negative Acinetobacter baumannii.

To discover potent antibiotics against the Gram-negative bacteria, we performed a structure-activity relationship (SAR) study of YKsa-6, which was the most potent inhibitor of Staphylococcus aureus ß-ketoacyl acyl carrier protein III in our previous study. We identified and selected 11 candidates, and finally screened two active compounds, YKab-4 (4-[(3-chloro-4-methylphenyl)aminoiminomethyl]benzene-1,3-diol) and YKab-6 (4-[[3-(trifluoromethyl)phenyl]aminoiminomethyl]phenol) as inhibitors of Acinetobacter baumannii KAS III (abKAS III). They showed potent antimicrobial activities at 2 or 8 µg/mL, specifically against Acinetobacter baumannii and a strong binding affinity for abKAS III. From the homology modeling, we defined the three-dimensional (3D) structure of abKAS III for the first time and found that it had an extra loop region compared with common Gram-negative bacteria derived KAS IIIs. The docking study revealed that the hydroxyl groups of inhibitors formed extensive hydrogen bonds and the complicated hydrophobic and cation-stacking interactions are important to binding with abKAS III. We confirmed that the hydrophobicity of these compounds might be the essential factor for their antimicrobial activities against Gram-negative bacteria as well as their structural rigidity, a cooperative feature for retaining the hydrophobic interactions between abKAS III and its inhibitors. This study may provide an insight developing strategies for potent antibiotics against A. baumannii.

Phloretin Exerts Anti-Tuberculosis Activity and Suppresses Lung Inflammation.

An increase in the prevalence of the drug-resistant Mycobacteria tuberculosis necessitates developing new types of anti-tuberculosis drugs. Here, we found that phloretin, a naturally-occurring flavonoid, has anti-mycobacterial effects on H37Rv, multi-drug-, and extensively drug-resistant clinical isolates, with minimum inhibitory concentrations of 182 and 364 µM, respectively. Since Mycobacteria cause lung inflammation that contributes to tuberculosis pathogenesis, anti-inflammatory effects of phloretin in interferon-γ-stimulated MRC-5 human lung fibroblasts and lipopolysaccharide (LPS)-stimulated dendritic cells were investigated. The release of interleukin (IL)-1ß, IL-12, and tumor necrosis factor (TNF)-α was inhibited by phloretin. The mRNA levels of IL-1ß, IL-6, IL-12, TNF-α, and matrix metalloproteinase-1, as well as p38 mitogen-activated protein kinase and extracellular signal-regulated kinase phosphorylation, were suppressed. A mouse in vivo study of LPS-stimulated lung inflammation showed that phloretin effectively suppressed the levels of TNF-α, IL-1ß, and IL-6 in lung tissue with low cytotoxicity. Phloretin was found to bind M. tuberculosis ß-ketoacyl acyl carrier protein synthase III (mtKASIII) with high affinity (7.221 × 107 M-1); a binding model showed hydrogen bonding of A-ring 2'-hydroxy and B-ring 4-hydroxy groups of phloretin with Asn261 and Cys122 of mtKASIII, implying that mtKASIII can be a potential target protein. Therefore, phloretin can be a useful dietary natural product with anti-tuberculosis benefits.

Antituberculosis Activity of a Naturally Occurring Flavonoid, Isorhamnetin.

Isorhamnetin (1) is a naturally occurring flavonoid having anticancer and anti-inflammatory properties. The present study demonstrated that 1 had antimycobacterial effects on Mycobacterium tuberculosis H37Rv, multi-drug- and extensively drug-resistant clinical isolates with minimum inhibitory concentrations of 158 and 316 µM, respectively. Mycobacteria mainly affect the lungs, causing an intense local inflammatory response that is critical to the pathogenesis of tuberculosis. We investigated the effects of 1 on interferon (IFN)-γ-stimulated human lung fibroblast MRC-5 cells. Isorhamnetin suppressed the release of tumor necrosis factor (TNF)-α and interleukin (IL)-12. A nontoxic dose of 1 reduced mRNA expression of TNF-α, IL-1ß, IL-6, IL-12, and matrix metalloproteinase-1 in IFN-γ-stimulated cells. Isorhamnetin inhibited IFN-γ-mediated stimulation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase and showed high-affinity binding to these kinases (binding constants: 4.46 × 10(6) M(-1) and 7.6 × 10(6) M(-1), respectively). The 4'-hydroxy group and the 3'-methoxy group of the B-ring and the 5-hydroxy group of the A-ring of 1 play key roles in these binding interactions. A mouse in vivo study of lipopolysaccharide-induced lung inflammation revealed that a nontoxic dose of 1 reduced the levels of IL-1ß, IL-6, IL-12, and INF-γ in lung tissue. These data provide the first evidence that 1 could be developed as a potent antituberculosis drug.

Peptoid-Substituted Hybrid Antimicrobial Peptide Derived from Papiliocin and Magainin 2 with Enhanced Bacterial Selectivity and Anti-inflammatory Activity.

Antimicrobial peptides (AMPs) are important components of the host innate immune system. Papiliocin is a 37-residue AMP purified from larvae of the swallowtail butterfly Papilio xuthus. Magainin 2 is a 23-residue AMP purified from the skin of the African clawed frog Xenopus laevis. We designed an 18-residue hybrid peptide (PapMA) incorporating N-terminal residues 1-8 of papiliocin and N-terminal residues 4-12 of magainin 2, joined by a proline (Pro) hinge. PapMA showed high antimicrobial activity but was cytotoxic to mammalian cells. To decrease PapMA cytotoxicity, we designed a lysine (Lys) peptoid analogue, PapMA-k, which retained high antimicrobial activity but displayed cytotoxicity lower than that of PapMA. Fluorescent dye leakage experiments and confocal microscopy showed that PapMA targeted bacterial cell membranes whereas PapMA-k penetrated bacterial cell membranes. Nuclear magnetic resonance experiments revealed that PapMA contained an N-terminal α-helix from Lys(3) to Lys(7) and a C-terminal α-helix from Lys(10) to Lys(17), with a Pro(9) hinge between them. PapMA-k also had two α-helical structures in the same region connected with a flexible hinge residue at Nlys(9), which existed in a dynamic equilibrium of cis and trans conformers. Using lipopolysaccharide-stimulated RAW264.7 macrophages, the anti-inflammatory activity of PapMA and PapMA-k was confirmed by inhibition of nitric oxide and inflammatory cytokine production. In addition, treatment with PapMA and PapMA-k decreased the level of ultraviolet irradiation-induced expression of genes encoding matrix metalloproteinase-1 (MMP-1), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in human keratinocyte HaCaT cells. Thus, PapMA and PapMA-k are potent peptide antibiotics with antimicrobial and anti-inflammatory activity, with PapMA-k displaying enhanced bacterial selectivity.

Electrochemical Evolution of Ru-Based Polyoxometalates into Si,W-Codoped RuOx for Acidic Overall Water Splitting.

Despite intensive studies over decades, the development of electrocatalysts for acidic water splitting still relies on platinum group metals, especially Pt and Ir, which are scarce, expensive, and poorly sustainable. Because such problems can be alleviated, Ru-based bifunctional catalysts such as rutile RuO2 have recently emerged. However, RuO2 has a relatively low activity for hydrogen evolution reactions (HER) and low stability for oxygen evolution reactions (OER) under acidic conditions. In this study, the synthesis of a RuOx -based bifunctional catalyst (RuSiW) for acidic water splitting via the electrochemical evolution from Ru-based polyoxometalates at cathodic potentials is reported. RuSiW consists of the nanocrystalline RuO2 core and Si,W-codoped RuOx shell. RuSiW exhibits outstanding HER and OER activity comparable to Pt/C and RuO2 , respectively, with high stability. Computational analysis suggests that the codoping of RuOx with W and Si synergistically improves the HER activity of otherwise poor RuO2 by shifting the d-band center and optimizing atomic configurations beneficial for proper hydrogen adsorption. This study provides insights into the design and synthesis of unprecedented bifunctional electrocatalysts using catalytically inactive and less explored elements, such as Si and W.

Quantum dot-integrated GaN light-emitting diodes with resolution beyond the retinal limit.

Near-eye display technology is a rapidly growing field owing to the recent emergence of augmented and mixed reality. Ultrafast response time, high resolution, high luminance, and a dynamic range for outdoor use are all important for non-pixelated, pupil-forming optics. The current mainstream technologies using liquid crystals and organic materials cannot satisfy all these conditions. Thus, finely patterned light-emissive solid-state devices with integrated circuits are often proposed to meet these requirements. In this study, we integrated several advanced technologies to design a prototype microscale light-emitting diode (LED) arrays using quantum dot (QD)-based color conversion. Wafer-scale epilayer transfer and the bond-before-pattern technique were used to directly integrate 5-µm-scale GaN LED arrays on a foreign silicon substrate. Notably, the lithography-level alignment with the bottom wafer opens up the possibility for ultrafast operation with circuit integration. Spectrally pure color conversion and solvent-free QD patterning were also achieved using an elastomeric topographical mask. Self-assembled monolayers were applied to selectively alter the surface wettability for a completely dry process. The final emissive-type LED array integrating QD, GaN, and silicon technology resulted in a 1270 PPI resolution that is far beyond the retinal limit.

Contact Engineering of Vertically Grown ReS2 with Schottky Barrier Modulation.

Forming metal contact with low contact resistance is essential for the development of electronics based on layered van der Waals materials. ReS2 is a semiconducting transition metal dichalcogenide (TMD) with an MX2 structure similar to that of MoS2. While most TMDs grow parallel to the substrate when synthesized using chemical vapor deposition (CVD), ReS2 tends to orient itself vertically during growth. Such a feature drastically increases the surface area and exposes chemically active edges, making ReS2 an attractive layered material for energy and sensor applications. However, the contact resistances of vertically grown materials are known to be relatively high, compared to those of common 2H-phase TMDs, such as MoS2. Most reported methods for lowering the contact resistance have been focused on exfoliated 2H-phase materials with only a few devices tested, and few works on distorted T-phase materials exist. Moreover, nearly all reported studies have been conducted on only a few devices with mechanically exfoliated fl Most reported methods for lowering the contact resistance have been 2 contacts was modulated by conformally coating a thin tunneling interlayer between the metal and the dendritic ReS2 film. Over a hundred devices were tested, and contact resistances were extracted for large-scale statistical analysis. Importantly, we compared various known materials and techniques for lowering contact resistance and found an optimized method. Finally, the reductions in barrier height were directly correlated with exponential reductions in contact resistance and increases in drive-current by almost 2 orders of magnitude.

Superaerophobic hydrogels for enhanced electrochemical and photoelectrochemical hydrogen production.

The efficient removal of gas bubbles in (photo)electrochemical gas evolution reactions is an important but underexplored issue. Conventionally, researchers have attempted to impart bubble-repellent properties (so-called superaerophobicity) to electrodes by controlling their microstructures. However, conventional approaches have limitations, as they are material specific, difficult to scale up, possibly detrimental to the electrodes' catalytic activity and stability, and incompatible with photoelectrochemical applications. To address these issues, we report a simple strategy for the realization of superaerophobic (photo)electrodes via the deposition of hydrogels on a desired electrode surface. For a proof-of-concept demonstration, we deposited a transparent hydrogel assembled from M13 virus onto (photo)electrodes for a hydrogen evolution reaction. The hydrogel overlayer facilitated the elimination of hydrogen bubbles and substantially improved the (photo)electrodes' performances by maintaining high catalytic activity and minimizing the concentration overpotential. This study can contribute to the practical application of various types of (photo)electrochemical gas evolution reactions.

Tetraruthenium Polyoxometalate as an Atom-Efficient Bifunctional Oxygen Evolution Reaction/Oxygen Reduction Reaction Catalyst and Its Application in Seawater Batteries.

Although development and utilization of efficient catalysts with earth-abundant and cheap elements are desired, precious noble metal-based catalysts are still widely used and studied due to the urgent need to address energy and environmental issues. Polyoxometalates (POMs) can be excellent candidates in this context. In this study, we found that oxo-bridged tetraruthenium polyoxometalate (RuPOM) exhibits excellent electrocatalytic activity for both oxygen evolution and reduction reactions (OER and ORR) with minimal use of noble metal elements and can be used for the development of efficient seawater batteries (SWBs). The deposition of RuPOM on a desired electrode with conducting carbon Ketjen black (KB) by the simple slurry coating method imparted bifunctional OER/ORR activity to the underlying electrode. Although the mass activity was similar, RuPOM/KB mixtures exhibited superior activity even compared to commercially available Pt/C when comparing the activity per noble metal element. Based on these findings, we employed RuPOM to develop efficient SWBs. RuPOM significantly lowered the charging potential and increased the discharging potential of SWBs, which are related to OER and ORR, respectively. This study can provide insights into the development of POM-based electrocatalysts and their application in energy storage and conversion devices.

Caffeoyl-Pro-His amide relieve DNCB-Induced Atopic Dermatitis-Like phenotypes in BALB/c mice.

The main factors involved in the pathogenesis of atopic dermatitis (AD) are skin barrier abnormality, allergy/immunology, and pruritus. Considering how oxidative stress influences these factors, antioxidant agents may be effective candidates in the treatment of AD. To evaluate the effect of Caffeoyl-Pro-His amide (CA-PH), an antioxidant agent, on 2,4-dinitrochlorobenzene (DNCB)-induced AD-like phenotypes in BALB/c mice. Topical sensitization and challenge by DNCB were performed on the dorsal skin of BALB/c mice to induce AD-like cutaneous lesions, phenotypes, and immunologic response. CA-PH was applied topically for 2 weeks to assess its effects on DNCB-induced AD-like phenotypes. As a result, CA-PH relieved DNCB-induced AD-like phenotypes quantified by dermatitis severity score, scratching duration, and trans-epidermal water loss. Histopathological analysis showed that CA-PH decreased epidermal thickening, the number of mast cells, and eosinophil infiltration in dermis. Immunohistochemical staining revealed that CA-PH recovered skin barrier-related proteins: filaggrin, involucrin, and loricrin. As for the immunologic aspects, CA-PH treatment lowered mRNA or protein levels of interleukin (IL)-4, IL-6, IL-17a, IL-1b, IL-31, and IL-33 levels and thymic stromal lymphopoietin (TSLP) levels in cutaneous tissue, reducing the DNCB-induced serum IgE level elevation. In conclusion, topical CA-PH may be a therapeutic option for the treatment of AD.

Catalytic Multilayers for Efficient Solar Water Oxidation through Catalyst Loading and Surface-State Passivation of BiVO4 Photoanodes.

We studied the kinetics of photoelectrochemical (PEC) water oxidation using a model photoanode BiVO4 modified with various water oxidation catalysts (WOCs) by electrochemical impedance spectroscopy. In particular, we prepared BiVO4 photoanodes with catalytic multilayers (CMs), where cationic polyelectrolytes and anionic polyoxometalate (POM) WOCs were assembled in a desired amount at a nanoscale precision, and compared their performance with those with well-known WOCs such as cobalt phosphate (CoPi) and NiOOH. Our comparative kinetics analysis suggested that the deposition of the CMs improved the kinetics of both the photogenerated charge carrier separation/transport in bulk BiVO4 due to passivation of surface recombination centers and water oxidation at the electrode/electrolyte interface due to deposition of efficient molecular WOCs. On the contrary, the conventional WOCs were mostly effective in the former and less effective in the latter, which is consistent with previous reports. These findings explain why the CMs exhibit an outstanding performance. We also found that separated charge carriers can be efficiently transported to POM WOCs via a hopping mechanism due to the delicate architecture of the CMs, which is reminiscent of natural photosynthetic systems. We believe that this study can not only broaden our understanding on the underlying mechanism of PEC water oxidation but also provide insights for the design and fabrication of novel electrochemical and PEC devices, including efficient water oxidation photoanodes.

Finite Element Plastic Limit Loads of Complex Cracks in Pipes With Two-Layered Materials.

Based on the detailed three-dimensional (3D) finite element (FE) limit analyses, the present study investigates the plastic limit loads of complex-cracked pipes with two-layered materials for determining maximum load-carrying capacity or critical crack length of pipes with two-layered materials. The complex cracks in pipes with two-layered materials consist of a partial through-wall crack and 360-deg circumferential surface crack in the inner side of pipe in the same plane in pipe, which could be developed in the preemptive weld overlay region on the dissimilar metal weld (DMW) of nuclear pipe. In terms of FE limit analyses for complex-cracked pipes with two-layered materials, total thickness of pipe, depth of 360-deg internal surface crack, length of partial through-wall crack and the effect of strength mismatch between two materials are systematically considered in the present study. As for loading conditions, axial tension, global bending moment, and internal pressure are employed in the present FE analyses, and then, the confidence of the present FE procedure is confirmed by comparing the FE results with the existing solutions for complex cracks in single material. The results of the present FE plastic limit loads are compared with the existing solutions for complex-cracked pipes with two-layered materials. Also, a simple approach using equivalent single material based on the weighted average concept instead of using the properties of two materials is suggested for predicting plastic limit loads of two-layered materials. The present results can be applied to leak-before-break (LBB) analyses of nuclear piping with weld overlay.

Graphene-Edge Electrode on a Cu-Based Chalcogenide Selector for 3D Vertical Memristor Cells.

Resistive memristors are considered to be key components in the hardware implementation of complex neuromorphic networks because of their simplicity, compactness, and manageable power dissipation. However, breakthroughs with respect to both the selector material technology and the bit-cost-effective three-dimensional (3D) device architecture are necessary to provide sufficient device density while maintaining the advantages of a two-terminal device. Despite substantial progress in the scaling of the memristor devices, the scaling potential of the selector materials remains unclear. A majority of the selector materials are unlikely to form conductive filaments, and the effect of the highly concentrated electrical fields on such materials is not well understood. In this study, the atomically thin graphene edge in a 3D vertical memory architecture is utilized to study the effect of highly focused electrical fields on a CuGeS chalcogenide selector layer. We demonstrate that additional interface resistance can improve the nonlinearity and reduce leakage current by almost three orders of magnitude; however, even a relatively low Cu+ ion density can adversely affect leakage because of the highly asymmetric electrode configuration. This study presents a meaningful step toward understanding the characteristics of mobile ions in solid chalcogenide electrolytes and the potential for ultrascaled selector devices.

Antimicrobial and anti-inflammatory activities of chemokine CXCL14-derived antimicrobial peptide and its analogs.

CXCL14 is a CXC chemokine family that exhibits antimicrobial activity and contains an amphipathic cationic α-helical region in the C-terminus, a characteristic structure of antimicrobial peptides (AMPs). In this study, we designed three analogs of CXCL1459-75 (named CXCL14-C17) corresponding to the C-terminal α-helix of CXCL14, which displayed potential antimicrobial activity against a wide variety of gram-negative and gram-positive bacteria with minimum inhibitory concentrations of 4-16 µM without mammalian cell toxicity. Furthermore, two CXCL14-C17 analogs (CXCL14-C17-a1 and CXCL14-C17-a3) with improved cell selectivity were engineered by introducing Lys, Arg, or Trp in CXCL14-C17. Additionally, CXCL14-C17 analogs showed much greater synergistic effect (FICI: 0.3125-0.375) with chloramphenicol and ciprofloxacin against multidrug-resistant Pseudomonas aeruginosa (MDRPA) than LL-37 did (FICI: 0.75-1.125). CXCL14-C17 analogs were more active against antibiotic-resistant bacteria including methicillin-resistant Staphylococcus aureus (MRSA), MDRPA, and vancomycin-resistant Enterococcus faecium (VREF) than LL-37 and melittin. In particular, CXCL14-C17-a2 and CXCL14-C17-a3 completely inhibited the biofilm formation at sub-MIC and all of the peptides were able to eliminate pre-formed biofilm as well. Membrane depolarization, flow cytometry, sytox green uptake, ONPG hydrolysis and confocal microscopy revealed the possible target of the native peptide (CXCL14-C17) to likely be intracellular, and the amphipathic designed analogs targeted the bacterial membrane. CXCL14-C17 also showed DNA binding characteristic activity similar to buforin-2. Interestingly, CXCL14-C17-a2 and CXCL14-C17-a3 effectively inhibited the production and expression of nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and monocyte chemoattractant protein (MCP)-1 from lipopolysaccharide (LPS)-stimulated RAW264.7 cells, suggesting that these peptides could be promising anti-inflammatory and antimicrobial agents.

Interface Engineering of Hematite with Nacre-like Catalytic Multilayers for Solar Water Oxidation.

An efficient water oxidation photoanode based on hematite has been designed and fabricated by tailored assembly of graphene oxide (GO) nanosheets and cobalt polyoxometalate (Co-POM) water oxidation catalysts into a nacre-like multilayer architecture on a hematite photoanode. The deposition of catalytic multilayers provides a high photocatalytic efficiency and photoelectrochemical stability to underlying hematite photoanodes. Compared to the bare counterpart, the catalytic multilayer electrode exhibits a significantly higher photocurrent density and large cathodic shift in onset potential (∼369 mV) even at neutral pH conditions due to the improved charge transport and catalytic efficiency from the rational and precise assembly of GO and Co-POM. Unexpectedly, the polymeric base layer deposited prior to the catalytic multilayers improves the performance even more by facilitating the transfer of photogenerated holes for water oxidation through modification of the flat band potential of the underlying photoelectrode. This approach utilizing polymeric base and catalytic multilayers provides an insight into the design of highly efficient photoelectrodes and devices for artificial photosynthesis.

Biophysical Studies Reveal Key Interactions between Papiliocin-Derived PapN and Lipopolysaccharide in Gram-Negative Bacteria.

Papiliocin, isolated from the swallowtail butterfly (Papilio xuthus), is an antimicrobial peptide with high selectivity against gram-negative bacteria. We previously showed that the N-terminal helix of papiliocin (PapN) plays a key role in the antibacterial and anti-inflammatory activity of papiliocin. In this study, we measured the selectivity of PapN against multidrug-resistant gram-negative bacteria, as well as its anti-inflammatory activity. Interactions between Trp2 of PapN and lipopolysaccharide (LPS), which is a major component of the outer membrane of gram-negative bacteria, were studied using the Trp fluorescence blue shift and quenching in LPS micelles. Furthermore, using circular dichroism, we investigated the interactions between PapN and LPS, showing that LPS plays critical roles in peptide folding. Our results demonstrated that Trp2 in PapN was buried deep in the negatively charged LPS, and Trp2 induced the α-helical structure of PapN. Importantly, docking studies determined that predominant electrostatic interactions of positively charged arginine residues in PapN with phosphate head groups of LPS were key factors for binding. Similarly, hydrophobic interactions by aromatic residues of PapN with fatty acid chains in LPS were also significant for binding. These results may facilitate the development of peptide antibiotics with anti-inflammatory activity.