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Dynamin-related protein 1 (Drp1) is a mitochondrial fission protein and a viable target for cardioprotection against myocardial ischaemia-reperfusion injury. Here, we reported a novel Drp1 inhibitor (DRP1i1), delivered using a cardiac-targeted nanoparticle drug delivery system, as a more effective approach for achieving acute cardioprotection. DRP1i1 was encapsulated in cubosome nanoparticles with conjugated cardiac-homing peptides (NanoDRP1i1) and the encapsulation efficiency was 99.3 ± 0.1 %. In vivo, following acute myocardial ischaemia-reperfusion injury in mice, NanoDRP1i1 significantly reduced infarct size and serine-616 phosphorylation of Drp1, and restored cardiomyocyte mitochondrial size to that of sham group. Imaging by mass spectrometry revealed higher accumulation of DRP1i1 in the heart tissue when delivered as NanoDRP1i1. In human cardiac organoids subjected to simulated ischaemia-reperfusion injury, treatment with NanoDRP1i1 at reperfusion significantly reduced cardiac cell death, contractile dysfunction, and mitochondrial superoxide levels. Following NanoDRP1i1 treatment, cardiac organoid proteomics further confirmed reprogramming of contractile dysfunction markers and enrichment of the mitochondrial protein network, cytoskeletal and metabolic regulation networks when compared to the simulated injury group. These proteins included known cardioprotective regulators identified in human organoids and in vivo murine studies following ischaemia-reperfusion injury. DRP1i1 is a promising tool compound to study Drp1-mediated mitochondrial fission and exhibits promising therapeutic potential for acute cardioprotection, especially when delivered using the cardiac-targeted cubosome nanoparticles.

Summary: Polymyxins are often the only effective antibiotics against the “Critical” pathogen Acinetobacter baumannii. Worryingly, highly polymyxin-resistant A. baumannii displaying dependence on polymyxins has emerged in the clinic, leading to diagnosis and treatment failures. Here, we report that arginine metabolism is essential for polymyxin-dependent A. baumannii. Specifically, the arginine degradation pathway was significantly altered in polymyxin-dependent strains compared to wild-type strains, with critical metabolites (e.g., L-arginine and L-glutamate) severely depleted and expression of the astABCDE operon significantly increased. Supplementation of arginine increased bacterial metabolic activity and suppressed polymyxin dependence. Deletion of astA, the first gene in the arginine degradation pathway, decreased phosphatidylglycerol and increased phosphatidylethanolamine levels in the outer membrane, thereby reducing the interaction with polymyxins. This study elucidates the molecular mechanism by which arginine metabolism impacts polymyxin dependence in A. baumannii, underscoring its critical role in improving diagnosis and treatment of life-threatening infections caused by “undetectable” polymyxin-dependent A. baumannii.

Renal fibrosis is a pathological feature of chronic kidney disease and its progression correlates with kidney function impairment. Since there are currently no specific therapies for renal fibrosis, we explored whether inducing local production of the anti-fibrotic molecule relaxin-2 in kidney cells has potential as a strategy for suppressing the development of renal fibrosis. Our study examined whether delivery of relaxin-2 mRNA to kidney cells in vitro and in vivo could inhibit mechanisms leading to renal fibrosis. Transfecting relaxin-2 mRNA into cultured kidney cells inhibited fibrotic responses to TGF-β1 in an autocrine or paracrine manner by reducing fibrotic gene expression in kidney tubules, and reducing proliferation in kidney fibroblasts and mesangial cells. Similarly, cubosomes assisted delivery of relaxin-2 mRNA to mouse kidneys alleviated the fibrosis and inflammation associated with renal injury following unilateral ureter obstruction (UUO). Therefore, relaxin-2 mRNA exhibits potential as a novel therapy for inhibiting fibrosis and inflammation in chronic kidney disease.

In this study, Pt nanoparticles-loaded nitrogen-doped mesoporous carbon nanotube (Pt/NMCT) was successfully synthesized through a polydopamine-mediated “one-pot” co-deposition strategy. The Pt source was introduced during the co-deposition of polydopamine and silica on the surface of SiO2 nanowire (SiO2 NW), and Pt atoms were fixed in the skeleton by the chelation of polydopamine. Thus, in the subsequent calcination process in nitrogen atmosphere, the growth and agglomeration of Pt nanoparticles were effectively restricted, achieving the in situ loading of uniformly dispersed, ultra-small (~2 nm) Pt nanoparticles. The method is mild, convenient, and does not require additional surfactants, reducing agents, or stabilizers. At the same time, the use of the dual silica templates (SiO2 NW and the co-deposited silica nanoclusters) brought about a hierarchical pore structure with a high specific surface area (620 m2 g−1) and a large pore volume (1.46 cm3 g−1). The loading process of Pt was studied by analyzing the electron microscope and X-ray photoelectron spectroscopy of the intermediate products. The catalytic performance of Pt/NMCT was investigated in the reduction of 4-nitrophenol. The Pt/NMCT with a hierarchical pore structure had an apparent reaction rate constant of 0.184 min−1, significantly higher than that of the sample, without the removal of the silica templates to generate the hierarchical porosity (0.017 min−1). This work provides an outstanding contribution to the design of supported noble metal catalysts and also highlights the importance of the hierarchical pore structure for catalytic activity.

An increasing prevalence of Gram-negative bacteria increases the interest in nanotherapies to treat antibiotic resistance. Here, the authors examine the antimicrobial activity of polymyxin-loaded cubosomes and explore a polytherapy treatment of pathogens with cubosomes in combination with polymyxin.

Supercapacitors are candidates with the greatest potential for use in sustainable energy resources. Extensive research is being carried out to improve the performances of state-of-art supercapacitors to meet our increased energy demands because of huge technological innovations in various fields. The development of high-performing materials for supercapacitor components such as electrodes, electrolytes, current collectors, and separators is inevitable. To boost research in materials design and production toward supercapacitors, the up-to-date collection of recent advancements is necessary for the benefit of active researchers. This review summarizes the most recent developments of water-in-salt (WIS) and deep eutectic solvents (DES), which are considered significant electrolyte systems to advance the energy density of supercapacitors, with a focus on two-dimensional layered nanomaterials. It provides a comprehensive survey of 2D materials (graphene, MXenes, and transition-metal oxides/dichalcogenides/sulfides) employed in supercapacitors using WIS/DES electrolytes. The synthesis and characterization of various 2D materials along with their electrochemical performances in WIS and DES electrolyte systems are described. In addition, the challenges and opportunities for the next-generation supercapacitor devices are summarily discussed.

A new deep eutectic solvent (DES) made from urea, magnesium chloride, lithium perchlorate and water has been developed as the electrolyte for battery-supercapacitor hybrid devices. The physicochemical characteristics of DES electrolytes and potential interactions between electrolyte components are well analyzed through electrochemical and spectroscopic techniques. It has been discovered that the properties of DES electrolytes are highly dependent on the component ratio, which allows us to engineer the electrolyte to meet the requirement of the battery application. Perylene tetracarboxylic di-imide and reduced graphene oxide ha ve been combined to produce a composite (PTCDI/rGO) that has been tested as the anode in DES electrolyte. This composite shows that the capacitive contribution is greater than 90% in a low scan rate, resulting in the high rate capability. The PTCDI/rGO electrode exhibits no sign of capacity degradation and its coulombic efficiency is close to 99% after 200 cycles, which suggests excellent reversibility and stability. On the other hand, the electrochemical performance of lithium manganese oxide as the cathode material is studied in DES electrolyte, which exhibits the maximum capacity of 76.5 mAh/g at 0.03 A/g current density. After being successfully examined in terms of electrode kinetics, capacity performance, and rate capability, the anode and cathode materials are combined to construct a two-electrode system with DES electrolyte. At a current density of 0.03 A/g, this system offers 43.5 mAh/g specific capacity and displays 55.5% retention of the maximum capacity at 1 A/g. Furthermore, an energy density of 53 Wh/kg is delivered at a power density of 35 W/kg.

Infections caused by multidrug-resistant (MDR) bacteria are becoming a serious threat to public health worldwide. With an ever-reducing pipeline of last-resort drugs further complicating the current dire situation arising due to antibiotic resistance, there has never been a greater urgency to attempt to discover potential new antibiotics. The use of nanotechnology, encompassing a broad range of organic and inorganic nanomaterials, offers promising solutions. Organic nanomaterials, including lipid-, polymer-, and carbon-based nanomaterials, have inherent antibacterial activity or can act as nanocarriers in delivering antibacterial agents. Nanocarriers, owing to the protection and enhanced bioavailability of the encapsulated drugs, have the ability to enable an increased concentration of a drug to be delivered to an infected site and reduce the associated toxicity elsewhere. On the other hand, inorganic metal-based nanomaterials exhibit multivalent antibacterial mechanisms that combat MDR bacteria effectively and reduce the occurrence of bacterial resistance. These nanomaterials have great potential for the prevention and treatment of MDR bacterial infection. Recent advances in the field of nanotechnology are enabling researchers to utilize nanomaterial building blocks in intriguing ways to create multi-functional nanocomposite materials. These nanocomposite materials, formed by lipid-, polymer-, carbon-, and metal-based nanomaterial building blocks, have opened a new avenue for researchers due to the unprecedented physiochemical properties and enhanced antibacterial activities being observed when compared to their mono-constituent parts. This review covers the latest advances of nanotechnologies used in the design and development of nano- and nanocomposite materials to fight MDR bacteria with different purposes. Our aim is to discuss and summarize these recently established nanomaterials and the respective nanocomposites, their current application, and challenges for use in applications treating MDR bacteria. In addition, we discuss the prospects for antimicrobial nanomaterials and look forward to further develop these materials, emphasizing their potential for clinical translation.

Increasing antibiotic resistance has provoked the urgent need to investigate the interactions of antimicrobials with bacterial membranes. The reasons for emerging antibiotic resistance and innovations in novel therapeutic approaches are highly relevant to the mechanistic interactions between antibiotics and membranes. Due to the dynamic nature, complex compositions, and small sizes of native bacterial membranes, bacterial membrane mimetics have been developed to allow for the in vitro examination of structures, properties, dynamics, and interactions. In this review, three types of model membranes are discussed: monolayers, supported lipid bilayers, and supported asymmetric bilayers; this review highlights their advantages and constraints. From monolayers to asymmetric bilayers, biomimetic bacterial membranes replicate various properties of real bacterial membranes. The typical synthetic methods for fabricating each model membrane are introduced. Depending on the properties of lipids and their biological relevance, various lipid compositions have been used to mimic bacterial membranes. For example, mixtures of phosphatidylethanolamines (PE), phosphatidylglycerols (PG), and cardiolipins (CL) at various molar ratios have been used, approaching actual lipid compositions of Gram-positive bacterial membranes and inner membranes of Gram-negative bacteria. Asymmetric lipid bilayers can be fabricated on solid supports to emulate Gram-negative bacterial outer membranes. To probe the properties of the model bacterial membranes and interactions with antimicrobials, three common characterization techniques, including quartz crystal microbalance with dissipation (QCM-D), surface plasmon resonance (SPR), and neutron reflectometry (NR) are detailed in this review article. Finally, we provide examples showing that the combination of bacterial membrane models and characterization techniques is capable of providing crucial information in the design of new antimicrobials that combat bacterial resistance.

Covalent organic frameworks (COF), a class of emerging microporous polymers, have been restrained for drug delivery applications due to their limited controllability over particle sizes and degradability. Herein, a dendritic mesoporous silica nanosphere (DMSN)-mediated growth strategy is proposed to fabricate hierarchical DMSN@COF hybrids through in situ growing of 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthaldehyde connected COF with acid cleavable C=N bonds. After the removal of the DMSN template, COF hierarchical particles (COF HP) with tailored particle sizes and degradability were obtained. Notably, the COF HP could be degraded by 55% after 24 h of incubation at pH 5.5, whereas the counterpart bulk COF only showed 15% of degradation in the same conditions. Due to the improved porosity and surface area, the COF HP can be utilized to load the chemotherapeutic drug, doxorubicin (DOX), with a high loading (46.8 wt%), outperforming the bulk COF (32.1 wt%). Moreover, around 90% of the loaded DOX can be discharged from the COF HP within 8 h of incubation at pH 5.5, whereas, only ~55% of the loaded DOX was released from the bulk COF. Cell experiments demonstrated that the IC50 value of the DOX loaded in COF HP was 2–3 times lower than that of the DOX loaded in the bulk COF and the hybrid DMSN@COF. Attributed to the high loading capacity and more pH-labile particle deconstruction properties, COF HP shows great potential in the application as vehicles for drug delivery.

Mesoporous silica materials have attracted great research interest for various applications ranging from (bio)catalysis and sensing to drug delivery. It remains challenging to prepare hollow mesoporous silica nanoparticles (HMSN) with large center-radial mesopores that could provide a more efficient transport channel through the cell for guest molecules. Here, we propose a novel strategy for the preparation of HMSN with large dendritic mesopores to achieve higher enzyme loading capacity and more efficient bioreactors. The materials were prepared by combining barium sulfate nanoparticles (BaSO4 NP) as a hard template and the in situ-formed 3-aminophenol/formaldehyde resin as a porogen for directing the dendritic mesopores’ formation. HMSNs with different particle sizes, shell thicknesses, and pore structures have been prepared by choosing BaSO4 NP of various sizes and adjusting the amount of tetraethyl orthosilicate added in synthesis. The obtained HMSN-1.1 possesses a high pore volume (1.07 cm3 g−1), a large average pore size (10.9 nm), and dendritic mesopores that penetrated through the shell. The advantages of HMSNs are also demonstrated for enzyme (catalase) immobilization and subsequent use of catalase-loaded HMSNs as bioreactors for catalyzing the H2O2 degradation reaction. The hollow and dendritic mesoporous shell features of HMSNs provide abundant tunnels for molecular transport and more accessible surfaces for molecular adsorption, showing great promise in developing efficient nanoreactors and drug delivery vehicles.

ABSTRACT Polymyxins are a last-line therapy against multidrug-resistant Pseudomonas aeruginosa; however, resistance to polymyxins has been increasingly reported. Therefore, understanding the mechanisms of polymyxin activity and resistance is crucial for preserving their clinical usefulness. This study employed comparative metabolomics and transcriptomics to investigate the responses of polymyxin-susceptible P. aeruginosa PAK (polymyxin B MIC, 1 mg/liter) and its polymyxin-resistant pmrB mutant PAKpmrB6 (MIC, 16 mg/liter) to polymyxin B (4, 8, and 128 mg/liter) at 1, 4, and 24 h, respectively. Our results revealed that polymyxin B at 4 mg/liter induced different metabolic and transcriptomic responses between polymyxin-susceptible and -resistant P. aeruginosa. In strain PAK, polymyxin B significantly activated PmrAB and the mediated arn operon, leading to increased 4-amino-4-deoxy-L-arabinose (L-Ara4N) synthesis and the addition to lipid A. In contrast, polymyxin B did not increase lipid A modification in strain PAKpmrB6. Moreover, the syntheses of lipopolysaccharide and peptidoglycan were significantly decreased in strain PAK but increased in strain PAKpmrB6 due to polymyxin B treatment. In addition, 4 mg/liter polymyxin B significantly perturbed phospholipid and fatty acid levels and induced oxidative stress in strain PAK, but not in PAKpmrB6. Notably, the increased trehalose-6-phosphate levels indicate that polymyxin B potentially caused osmotic imbalance in both strains. Furthermore, 8 and 128 mg/liter polymyxin B significantly elevated lipoamino acid levels and decreased phospholipid levels but without dramatic changes in lipid A modification in wild-type and mutant strains, respectively. Overall, this systems study is the first to elucidate the complex and dynamic interactions of multiple cellular pathways associated with the polymyxin mode of action against P. aeruginosa. IMPORTANCE Pseudomonas aeruginosa has been highlighted by the recent WHO Global Priority Pathogen List due to multidrug resistance. Without new antibiotics, polymyxins remain a last-line therapeutic option for this difficult-to-treat pathogen. The emergence of polymyxin resistance highlights the growing threat to our already very limited antibiotic armamentarium and the urgency to understand the exact mechanisms of polymyxin activity and resistance. Integration of the correlative metabolomics and transcriptomics results in the present study discovered that polymyxin treatment caused significant perturbations in the biosynthesis of lipids, lipopolysaccharide, and peptidoglycan, central carbon metabolism, and oxidative stress. Importantly, lipid A modifications were surprisingly rapid in response to polymyxin treatment at clinically relevant concentrations. This is the first study to reveal the dynamics of polymyxin-induced cellular responses at the systems level, which highlights that combination therapy should be considered to minimize resistance to the last-line polymyxins. The results also provide much-needed mechanistic information which potentially benefits the discovery of new-generation polymyxins.

The function of any given biological membrane is determined largely by the specific set of integral membrane proteins embedded in it, and the peripheral membrane proteins attached to the membrane surface. The activity of these proteins, in turn, can be modulated by the phospholipid composition of the membrane. The reconstitution of membrane proteins into a model membrane allows investigation of individual features and activities of a given cell membrane component. However, the activity of membrane proteins is often difficult to sustain following reconstitution, since the composition of the model phospholipid bilayer differs from that of the native cell membrane. This review will discuss the reconstitution of membrane protein activities in four different types of model membrane — monolayers, supported lipid bilayers, liposomes and nanodiscs, comparing their advantages in membrane protein reconstitution. Variation in the surrounding model environments for these four different types of membrane layer can affect the three-dimensional structure of reconstituted proteins and may possibly lead to loss of the proteins activity. We also discuss examples where the same membrane proteins have been successfully reconstituted into two or more model membrane systems with comparison of the observed activity in each system. Understanding of the behavioral changes for proteins in model membrane systems after membrane reconstitution is often a prerequisite to protein research. It is essential to find better solutions for retaining membrane protein activities for measurement and characterization in vitro.

Infrared (IR) spectroscopy has been used to quantify chemical and structural characteristics of a wide range of materials including biological tissues. In this study, we examined spatial changes in the chemical characteristics of rat retina in response to intraocular pressure (IOP) elevation using synchrotron infrared microscopy (SIRM), a non-destructive imaging approach. IOP elevation was induced by placing a suture around the eye of anaesthetised rats. Retinal sections were collected onto transparent CaF2 slides 10 days following IOP elevation. Using combined SIRM spectra and chemical mapping approaches it was possible to quantify IOP induced changes in protein conformation and chemical distribution in various layers of the rat retina. We showed that 10 days following IOP elevation there was an increase in lipid and protein levels in the inner nuclear layer (INL) and ganglion cell layer (GCL). IOP elevation also resulted in an increase in nucleic acids in the INL. Analysis of SIRM spectra revealed a shift in amide peaks to lower vibrational frequencies with a more prominent second shoulder, which is consistent with the presence of cell death in specific layers of the retina. These changes were more substantial in the INL and GCL layers compared with those occurring in the outer nuclear layer. These outcomes demonstrate the utility of SIRM to quantify the effect of IOP elevation on specific layers of the retina. Thus SIRM may be a useful tool for the study of localised tissue changes in glaucoma and other eye diseases.

ABSTRACT The fungal pathogen Candida albicans causes macrophage death and escapes, but the molecular mechanisms remained unknown. Here we used live-cell imaging to monitor the interaction of C. albicans with macrophages and show that C. albicans kills macrophages in two temporally and mechanistically distinct phases. Early upon phagocytosis, C. albicans triggers pyroptosis, a proinflammatory macrophage death. Pyroptosis is controlled by the developmental yeast-to-hypha transition of Candida. When pyroptosis is inactivated, wild-type C. albicans hyphae cause significantly less macrophage killing for up to 8 h postphagocytosis. After the first 8 h, a second macrophage-killing phase is initiated. This second phase depends on robust hyphal formation but is mechanistically distinct from pyroptosis. The transcriptional regulator Mediator is necessary for morphogenesis of C. albicans in macrophages and the establishment of the wild-type surface architecture of hyphae that together mediate activation of macrophage cell death. Our data suggest that the defects of the Mediator mutants in causing macrophage death are caused, at least in part, by reduced activation of pyroptosis. A Mediator mutant that forms hyphae of apparently wild-type morphology but is defective in triggering early macrophage death shows a breakdown of cell surface architecture and reduced exposed 1,3 β-glucan in hyphae. Our report shows how Candida uses host and pathogen pathways for macrophage killing. The current model of mechanical piercing of macrophages by C. albicans hyphae should be revised to include activation of pyroptosis by hyphae as an important mechanism mediating macrophage cell death upon C. albicans infection. IMPORTANCE Upon phagocytosis by macrophages, Candida albicans can transition to the hyphal form, which causes macrophage death and enables fungal escape. The current model is that the highly polarized growth of hyphae results in macrophage piercing. This model is challenged by recent reports of C. albicans mutants that form hyphae of wild-type morphology but are defective in killing macrophages. We show that C. albicans causes macrophage cell death by at least two mechanisms. Phase 1 killing (first 6 to 8 h) depends on the activation of the pyroptotic programmed host cell death by fungal hyphae. Phase 2 (up to 24 h) is rapid and depends on robust hyphal formation but is independent of pyroptosis. Our data provide a new model for how the interplay between fungal morphogenesis and activation of a host cell death pathway mediates macrophage killing by C. albicans hyphae.

The incorporation of black phosphorus (BP) into methylammonium lead iodide (MAPbI3) perovskites has been investigated and optimized by a high throughput screening method using scanning photoelectrochemical microscopy (SPECM) to determine how the addition of BP affects its photoelectrochemical and photovoltaic properties. An optimum ratio of 2.0 mole% BP/MAPbI3 perovskite composite generates an increased photocurrent response compared to pristine MAPbI3 for 2 mM benzoquinone (BQ) reduction at −0.6 V vs Ag/AgNO3 on a spot array electrode under illumination. Due to the relatively high quantum yield of MAPbI3, time-resolved photoluminescence measurements have been conducted to investigate photophysical behaviors of BP/MAPbI3 composites. The optimal 2.0 mole% BP/MAPbI3 exhibits an increased electron-hole diffusion lifetime compared to the pristine MAPbI3 perovskite. Finally, we demonstrate the enhanced efficiency and stability of 2.0% BP/MAPbI3-based perovskite solar cells arising from impeded Pb0-defect generation and suppressed charge-carrier recombination. [ABSTRACT FROM AUTHOR]

Inflammation is a pathological feature of kidney injury and its progression correlates with the development of kidney fibrosis which can lead to kidney function impairment. This project investigated the regulatory function of WNT1-inducible signaling pathway protein 1 (WISP1) in kidney inflammation. Administration of recombinant WISP1 protein to healthy mice induced kidney inflammation (macrophage accrual and production of tumor necrosis factor α (TNF-α), CCL2 and IL-6), which could be prevented by inhibition of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB). Furthermore, inhibition of WISP1, by gene knockdown or neutralising antibody, could inhibit cultured macrophages producing inflammatory cytokines following stimulation with lipopolysaccharides (LPSs) and kidney fibroblasts proliferating in response to TNFα, which both involved NF-κB signaling. Kidney expression of WISP1 was found to be increased in mouse models of progressive kidney inflammation-unilateral ureter obstruction (UUO) and streptozotocin (STZ)-induced diabetic nephropathy (DN). Treatment of UUO mice with WISP1 antibody reduced the kidney inflammation in these mice. Therefore, pharmacological blockade of WISP1 exhibits potential as a novel therapy for inhibiting inflammation in kidney disease. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is a notorious human bacterial pathogen with considerable capacity to develop antibiotic resistance. We have observed that human infections caused by highly drug-resistant S. aureus are more prolonged, complicated, and difficult to eradicate. Here we describe a metabolic adaptation strategy used by clinical S. aureus strains that leads to resistance to the last-line antibiotic, daptomycin, and simultaneously affects host innate immunity. This response was characterized by a change in anionic membrane phospholipid composition induced by point mutations in the phospholipid biosynthesis gene, cls2, encoding cardiolipin synthase. Single cls2 point mutations were sufficient for daptomycin resistance, antibiotic treatment failure, and persistent infection. These phenotypes were mediated by enhanced cardiolipin biosynthesis, leading to increased bacterial membrane cardiolipin and reduced phosphatidylglycerol. The changes in membrane phospholipid profile led to modifications in membrane structure that impaired daptomycin penetration and membrane disruption. The cls2 point mutations also allowed S. aureus to evade neutrophil chemotaxis, mediated by the reduction in bacterial membrane phosphatidylglycerol, a previously undescribed bacterial-driven chemoattractant. Together, these data illustrate a metabolic strategy used by S. aureus to circumvent antibiotic and immune attack and provide crucial insights into membrane-based therapeutic targeting of this troublesome pathogen. [ABSTRACT FROM AUTHOR]

A fundamental understanding of the effect of amphiphilic protein encapsulation on the nanostructure of the bicontinuous cubic phase is crucial to progressing biomedical and biological applications of these hybrid protein-lipid materials, including as drug delivery vehicles, as biosensors, biofuel cells and for in meso crystallization. The relationship between the lipid nanomaterial and the encapsulated protein, however, remains poorly understood. In this study, we investigated the effect of incorporating the five transmembrane and lipo-proteins which make up the β-barrel assembly machinery from Gram-negative bacteria within a series of bicontinuous cubic phases. The transmembrane β-barrel BamA caused an increase in lattice parameter of the cubic phase upon encapsulation. By contrast, the mainly hydrophilic lipo-proteins BamB-E caused the cubic phase lattice parameters to decrease, despite their large size relative to the diameter of the cubic phase water channels. Analysis of the primary amino acid sequence was used to rationalize this effect, based on specific interactions between aromatic amino acids within the proteins and the polar-apolar interface. Other factors that were found to have an effect were lateral bilayer pressure and rigidity within the lipid bilayer, water channel diameter, and size and structure of the lipo-proteins. The data presented suggest that hydrophilic bioactive molecules can be selectively encapsulated within the cubic phase by using a lipid anchor or aromatic amino acids, for drug delivery or biosensing applications. [ABSTRACT FROM AUTHOR]

Lipidic bicontinuous cubic mesophaseswith encapsulated amphiphilicproteins are widely used in a range of biological and biomedical applications,including in meso crystallization, as drug delivery vehicles for therapeuticproteins, and as biosensors and biofuel cells. However, the effectof amphiphilic protein encapsulation on the cubic phase nanostructureis not well-understood. In this study, we illustrate the effect ofincorporating the bacterial amphiphilic membrane protein Ag43, andits individual hydrophobic β43and hydrophilic α43domains, in bicontinuous cubic mesophases. For the monoolein,monoalmitolein, and phytantriol cubic phases with and without 8% w/wcholesterol, the effect of the full length amphiphilic protein Ag43on the cubic phase nanostructure was more significant than the sumof the individual hydrophobic β43and hydrophilicα43domains. Several factors were found to potentiallyinfluence the impact of the hydrophobic β43domainon the cubic phase internal nanostructure. These include the sizeof the hydrophobic β43domain relative to the thicknessof the lipid bilayer, as well as its charge and diameter. The sizeof the hydrophilic α43domain relative to the waterchannel radius of the cubic mesophase was also found to be important.The secondary structure of the Ag43 proteins was affected by the hydrophobicthickness and physicochemical properties of the lipid bilayer andthe water channel diameter of the cubic phase. Such structural changesmay be small but could potentially affect membrane protein function. [ABSTRACT FROM AUTHOR]

In this work, nickel and cobalt binary sulfide nanoparticles are successfully decorated on the surface of multi-walled carbon nanotubes to form a composite (Ni-CoS/MWCNT) via a facile glucose-assisted hydrothermal method. By introducing the conductive MWCNT and tuning the Ni/Co molar ratio for the Ni-CoS/MWCNT composites, the optimized one shows a high capacity up to 153 mAh g-1, superior rate capability and excellent electrochemical stability. On this basis, advanced hybrid supercapacitor (HSC) is assembled by using the Ni-CoS/MWCNT composite as the cathode and reduced graphene oxide as the anode. As-fabricated HCS is able to be operated reversibly in a full voltage region of 0-1.6 V and achieves a high specific capacity of 33 mAh g-1 at 1 A g-1, therefore delivering a maximum energy density of 23 Wh k g-1 at a power density of 684 W k g-1. Furthermore, the HSC still retains 90% of its initial discharge capacity after 2000-cycle consecutive charge/discharge test at 4 A g-1. [ABSTRACT FROM AUTHOR]

The function of any given biological membrane is determined largely by the specific set of integral membrane proteins embedded in it, and the peripheral membrane proteins attached to the membrane surface. The activity of these proteins, in turn, can be modulated by the phospholipid composition of the membrane. The reconstitution of membrane proteins into a model membrane allows investigation of individual features and activities of a given cell membrane component. However, the activity of membrane proteins is often difficult to sustain following reconstitution, since the composition of the model phospholipid bilayer differs from that of the native cell membrane. This review will discuss the reconstitution of membrane protein activities in four different types of model membrane--monolayers, supported lipid bilayers, liposomes and nanodiscs, comparing their advantages in membrane protein reconstitution. Variation in the surrounding model environments for these four different types of membrane layer can affect the three-dimensional structure of reconstituted proteins and may possibly lead to loss of the proteins activity. We also discuss examples where the same membrane proteins have been successfully reconstituted into two or more model membrane systems with comparison of the observed activity in each system. Understanding of the behavioral changes for proteins in model membrane systems after membrane reconstitution is often a prerequisite to protein research. It is essential to find better solutions for retaining membrane protein activities for measurement and characterization in vitro. [ABSTRACT FROM AUTHOR]

The lipopeptide surfactin from Bacillus subtilisstrains exhibits strong surface and biological activity, the latter probably because of its interaction with biological membranes. We have investigated the interaction of aqueous solutions of surfactin with supported bilayers of diphosphatidylcholine (DPPC) on silica using neutron reflectometry. We have also used small-angle neutron scattering (SANS) to study the solubilized aggregates formed as a result of the destruction of the supported membrane by surfactin. Although surfactin on its own does not attach to the silica supporting surface, it is taken up from solution by the membrane, confirming that there is an attractive interaction between DPPC and surfactin. The surfactin concentration in the layer can reach up to about 20 mol % relative to DPPC. The membrane is stable provided that the surfactin concentration is below its critical micelle concentration (cmc, 5 × 10−5M). Above the cmc, however, the membrane is solubilized and removed from the surface, though not always completely, over a period of hours. There are signs that there is an induction period while the surfactin concentration builds up in the membrane. This would be consistent with the need for a threshold concentration of surfactin in the bilayer. The presence of a surfactin correlation peak in the SANS showed that in the bulk solution, at the same concentrations as used for the deposition, surfactin forms aggregates that must be localized in the DPPC multilamellar vesicles at a separation of about 160 Å. The structure could be fitted with an approximate model where the surfactin has an aggregation number of 50 ± 10 with a radius of about 27 Å. Given the very small water thicknesses in the DPPC lamellar aggregates, the surfactin must exist as aggregates in the phospholipid bilayer, and these structures are responsible for solubilizing the DPPC. [ABSTRACT FROM AUTHOR]

We have investigated the formation of supported surfactin−phospholipid mixed bilayers using neutron reflectometry. Micellar mixtures of phospholipid (diphosphatidyl choline, DPPC), surfactin, and β-d-dodecyl maltoside were used to make the deposition. When the surfactin concentration is at its critical micelle concentration (CMC = 6 × 10−6M) in the bulk solution, there is no adsorption at all on the silica. When the surfactin concentration is lowered below the CMC, a mixed bilayer of surfactin and DPPC is formed. Since surfactin does not adsorb on silica from solutions of surfactin alone, this shows that there is a strong attraction between surfactin and DPPC. The variation of adsorbed amount, composition, and structure of the adsorbed layer are consistent with the attractive interaction between surfactin and DPPC and with their respective negative and positive affinities for the silica surface. Three phospholipid isotopic contrasts were measured and used to define the composition and structure of the surfactin−phospholipid bilayer. The maximum amount of surfactin in the bilayer reaches a mole fraction of about 0.2 and this is located in the outer leaflet of the bilayer within the headgroup and part of the adjacent chain region. [ABSTRACT FROM AUTHOR]

Neutron reflectometry has been used to study the structure of the biosurfactant, surfactin, at the air/water and at the hydrophobic solid/water interfaces. Three different deuterated surfactins were produced from the Bacillus subtilisstrain: one perdeuterated, one with the four leucines perdeuterated, and one with everything except the four leucines perdeuterated. The neutron reflectivity profiles of these three samples in null reflecting water and in D2O with a seventh profile of the protonated surfactin in D2O were measured at pH 7.5. This combination of different isotopic compositions made it possible to deduce the distribution of each type of labeled fragment in the surfactin. Surfactin is found to adopt a ball-like structure with a thickness of 14 ± Å and an area per molecule of 147 ± 5 Å2. This makes it more like a hydrophobic nanoparticle, whose solubility in water is maintained only by its charge, than a conventional surfactant. This is probably what makes it surface-active at such low concentrations and what contributes to its forming very compact surface layers that are more dense than observed for most conventional amphiphiles. The reflectivity data were fitted by a model in which the structure of surfactin was divided into three fragments: the four leucines taken as a group, the hydrocarbon chain, and a hydrophilic group containing the two negative charges. An analysis of the reflectivity gave the following separations between fragments, where zero corresponds to the Gibbs plane for zero water adsorption: chain−water 7 Å, hydrophile−water 1 Å, and leucines−water 6.5 Å, all ±1 Å. The overall structure of the layer appears to be identical at a hydrophobic octadecyltrichlorosilane-coated silicon surface where the thickness of the surfactin layer is 15 ± 1 Å and the area per molecule is 145 ± 5 Å2. Finally, the structure of surfactin micelles has been examined by means of small-angle neutron scattering. The aggregation number was found to be unusually small at 20 ± 5. The structure of the micelle is of the core−shell type with the hydrocarbon chain and the four hydrophobic leucines forming the core of the micelle. [ABSTRACT FROM AUTHOR]

Mitochondria fulfill central functions in cellular energetics,metabolism, and signaling.The outer membrane translocator complex (the TOM complex) imports most mitochondrial proteins, but its architecture is unknown. Using a cross-linking approach, we mapped the active translocator down to single amino acid residues, revealing different transport paths for preproteins through the Tom40 channel. An N-terminal segment of Tom40 passes from the cytosol through the channel to recruit chaperones from the intermembrane space that guide the transfer of hydrophobic preproteins.The translocator contains three Tom40 β-barrel channels sandwiched between a central α-helical Tom22 receptor cluster and external regulatory Tom proteins.The preprotein-translocating trimeric complex exchanges with a dimeric isoform to assemble new TOM complexes. Dynamic coupling of α-helical receptors, β-barrel channels, and chaperones generates a versatile machinery that transports about 1000 different proteins. [ABSTRACT FROM AUTHOR]