Ubiquitin and its polymeric forms are conjugated to intracellular proteins to regulate diverse intracellular processes. Intriguingly, polyubiquitin has also been identified as a component of pathological protein aggregates associated with Alzheimer's disease and other neurodegenerative disorders. We recently found that polyubiquitin can form amyloid-like fibrils, and that these fibrillar aggregates can be degraded by macroautophagy. Although the structural properties appear to function in recognition of the fibrils, no structural information on polyubiquitin fibrils has been reported so far. Here, we identify the core of M1-linked diubiquitin fibrils from hydrogen-deuterium exchange experiments using solution nuclear magnetic resonance (NMR) spectroscopy. Intriguingly, intrinsically flexible regions became highly solvent-protected in the fibril structure. These results indicate that polyubiquitin fibrils are formed by inter-molecular interactions between relatively flexible structural components, including the loops and edges of secondary structure elements.

As the depletion of traditional fossil fuels and environmental pollution become serious problems for human society, researchers are actively looking for renewable energy sources. Since hydrogen energy is considered a clean, efficient, and renewable alternative energy source, it is regarded as the most promising option. In this context, how to store hydrogen safely and efficiently has become the major challenge that hinders the actual application. To fill this gap, this paper proposes to utilize surfactant-modified graphene for hydrogen storage. Through a modified Hummers' method and ultrasonic stripping, this study proposes to prepare graphene from graphite oxide with NaBH₄. The surfactant sodium dodecyl benzene sulfonate (SDBS) was used as a dispersant during the reduction process to produce dispersion-stabilized graphene suspensions. Then, to investigate the characteristics of the graphene suspensions, X-ray diffraction (XRD), SEM, TEM, Fourier transform infrared (FT-IR), Raman, XPS, TG, and N₂ adsorption⁻desorption tests were conducted. Finally, analytical models for hydrogen adsorption were investigated with Langmuir and Freundlich fittings. The results show that the application of SDBS can effectively reduce the agglomeration among graphene monolayers and increase the specific surface area of graphene, and that the adsorption behavior is consistent with the Freundlich adsorption model, and is a physical process.

Coffee waste is an abundant biomass that can be converted into high value chemical products, and is used in various renewable biological processes. In this study, oil was extracted from spent coffee grounds (SCGs) and used for polyhydroxyalkanoate (PHA) production through Pseudomonas resinovorans. The oil-extracted SCGs (OESCGs) were hydrolyzed and used for biohydrogen production through Clostridium butyricum DSM10702. The oil extraction yield through n-hexane was 14.4%, which accounted for 97% of the oil present in the SCGs. OESCG hydrolysate (OESCGH) had a sugar concentration of 32.26 g/L, which was 15.4% higher than that of the SCG hydrolysate (SCGH) (27.96 g/L). Hydrogen production using these substrates was 181.19 mL and 136.58 mL in OESCGH and SCGH media, respectively. The consumed sugar concentration was 6.77 g/L in OESCGH and 5.09 g/L in SCGH media. VFA production with OESCGH (3.58 g/L) increased by 40.9% compared with SCGH (2.54 g/L). In addition, in a fed-batch culture using the extracted oil, cell dry weight was 5.4 g/L, PHA was 1.6 g/L, and PHA contents were 29.5% at 24 h.

We investigated the self-assembled structures and photoresponsive and crystallization behaviors of supramolecules composed of 4-methoxy-4'-hydroxyazobenzene (Azo) molecules and polyethylene glycol (PEG) that were formed through hydrogen-bonding interactions. The Azo/PEG complexes exhibited the characteristics of photoresponse and crystallization, which originated from Azo and PEG, respectively. When Azo/PEG complexes were dissolved in solvents, hydrogen-bonding interaction hindered the rotation and inversion of mesogens, causing a reduction in the photoisomerization rate compared with the photoisomerization rate of the neat Azo. The confinement of Azo/PEG complexes in thin films further resulted in a substantial decrease in the photoisomerization rate but an increase in the amounts of H-aggregated and J-aggregated mesogens. Regarding PEG crystallization, ultraviolet irradiation of Azo/PEG complexes increased the quantity of high-polarity cis isomers, which improved the compatibility between mesogens and PEG, subsequently increasing the crystallization temperature of PEG. Moreover, the complexation of Azo and PEG induced microphase separation, forming a lamellar morphology. Within the Azo-rich microphases, mesogens aggregated to form tilted monosmectic layers. By contrast, PEG crystallization within the PEG-rich microphases was hard confined, indicating that the domain size of the lamellar morphology was unchanged during PEG crystallization.

Within the era of battery technology, the urgent demand for improved and safer electrolytes is immanent. In this work, novel electrolytes, based on pyrrolidinium-bistrifluoromethanesulfonyl-imide polymeric ionic liquids (POILs), equipped with quadrupolar hydrogen-bonding moieties of ureido-pyrimidinone (UPy) to mediate self-healing properties were synthesized. Reversible addition-fragmentation chain-transfer (RAFT) polymerization was employed using S,S-dibenzyl trithiocarbonate as the chain transfer agent to produce precise POILs with a defined amount of UPy and POIL-moieties. Kinetic studies revealed an excellent control over molecular weight and polydispersity in all polymerizations, with a preferable incorporation of UPy monomers in the copolymerizations together with the ionic monomers. Thermogravimetric analysis proved an excellent thermal stability of the polymeric ionic liquids up to 360 °C. By combining the results from differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS), and rheology, a decoupled conductivity of the POILs from glass transition was revealed. While the molecular weight was found to exert the main influence on ionic conductivity, the ultimate strength and the self-healing efficiency (of up to 88%) were also affected, as quantified by tensile tests for both pristine and self-healed samples, evidencing a rational design of self-healing electrolytes bearing both hydrogen bonding moieties and low-molecular-weight polymeric ionic liquids.

To investigate changes in the physical and chemical properties of high-density polyethylene (HDPE) upon the rapid release of hydrogen gas at a pressure of 90 MPa, several characterization techniques have been employed, including optical microscopy, scanning electron microscopy, X-ray diffraction, differential scanning thermal analysis, and attenuated total reflectance Fourier-transform infrared spectroscopy. The results showed that both physical and chemical changes occurred in HDPE upon a rapid release of hydrogen gas. Physically, a partial hexagonal phase was formed within the amorphous region, and the overall crystallinity of HDPE decreased. Chemically, hydrogenation occurred, leading to the addition of hydrogen atoms to the polymer chains. Oxidation also occurred, for example, the formation of ester -C=O groups. Crosslinking and an increase in -CH3 end termination were also observed. These changes suggest that structural transformation and chemical modification of HDPE occurred upon the rapid release of hydrogen gas.

In our previous research, we investigated the anti-inflammatory activity of the agaro-oligosaccharides prepared from the agar of Gracilaria lemaneiformis (AO). In the present study, in order to further explore the bioactivities of AO, the antioxidant activity of AO was investigated in vitro in Vero cells and in vivo in zebrafish. AO scavenged alkyl, 1,1-diphenyl-2-picrylhydrazyl, and hydroxyl radicals at the IC50 value of 4.86 ± 0.13, 3.02 ± 0.44, and 1.33 ± 0.05 mg/mL, respectively. AO significantly suppressed hydrogen peroxide (H2O2)-stimulated oxidative damage by improving cell viability. This happened via suppressing apoptosis by scavenging intracellular reactive oxygen species (ROS). Furthermore, the in vivo results displayed that AO protected zebrafish against H2O2-stimulated oxidative damage by reducing the levels of intracellular ROS, cell death, and lipid peroxidation in a dose-dependent manner. These results indicate that AO effectively alleviated in vitro and in vivo oxidative damage stimulated by H2O2, and suggest the potential of AO in the cosmetic and functional food industries.

Hydrogen-evolution reaction (HER) is a promising technology for renewable energy conversion and storage. Electrochemical HER can provide a cost-effective method for the clean production of hydrogen. In this study, a biomimetic eco-friendly approach to fabricate nitrogen-doped carbon nanosheets, exhibiting a high HER performance, and using a carbonized polydopamine (C-PDA), is described. As a biopolymer, polydopamine (PDA) exhibits high biocompatibility and can be easily obtained by an environmentally benign green synthesis with dopamine. Inspired by the polymerization of dopamine, we have devised the facile synthesis of nitrogen-doped nanocarbons using a carbonized polydopamine for the HER in acidic media. The N-doped nanocarbons exhibit excellent performance for H2 generation. The required overpotential at 5 mA/cm2 is 130 mV, and the Tafel slope is 45 mV/decade. Experimental characterizations confirm that the excellent performance of the N-doped nanocarbons can be attributed to the multisite nitrogen doping, while theoretical computations indicate the promotion effect of tertiary/aromatic nitrogen doping in enhancing the spin density of the doped samples and consequently in forming highly electroactive sites for HER applications.

Anionic polymerization techniques were employed for the synthesis of linear polystyrene (PS) and block copolymer of PS and polyisoprene (PI) PS-b-PI bearing end hydroxyl groups. Following suitable organic chemistry transformation, the -OH end groups were converted to moieties able to form complementary hydrogen bonds including 2,6-diaminopurine, Dap, thymine, Thy, and the so-called Hamilton receptor, Ham. The formation of hydrogen bonds was examined between the polymers PS-Dap and PS-b-PI-Thy, along with the polymers PS-Ham and PS-b-PI-Thy. The conditions under which supramolecular triblock copolymers are formed and the possibility to form aggregates were examined both in solution and in the solid state using a variety of techniques such as 1H-NMR spectroscopy, size exclusion chromatography (SEC), dilute solution viscometry, dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential thermogravimetry (DTG), and differential scanning calorimetry (DSC).

In this work, we report the preparation of Nafion membranes containing two different nanocomposite MF-4SC membranes, modified with polyaniline (PANI) by the casting method through two different polyaniline infiltration procedures. These membranes were evaluated as a polymer electrolyte membrane for water electrolysis. Operating conditions were optimized in terms of current density, stability, and methanol concentration. A study was made on the effects on the cell performance of various parameters, such as methanol concentration, water, and cell voltage. The energy required for pure water electrolysis was analyzed at different temperatures for the different membranes. Our experiments showed that PEM electrolyzers provide hydrogen production of 30 mL/min, working at 160 mA/cm2. Our composite PANI membranes showed an improved behavior over pristine perfluorinated sulfocationic membranes (around 20% reduction in specific energy). Methanol-water electrolysis required considerably less (around 65%) electrical power than water electrolysis. The results provided the main characteristics of aqueous methanol electrolysis, in which the power consumption is 2.34 kW h/kg of hydrogen at current densities higher than 0.5 A/cm2. This value is ~20-fold times lower than the electrical energy required to produce 1 kg of hydrogen by water electrolysis.

The aim of this work was to synthesize carboxymethyl cellulose (CMC) and produce CMC films from the cellulose of palm bunch and bagasse agricultural waste. The effect of various amounts of H2O2 (0-40% v/v) during delignification on the properties of cellulose, CMC, and CMC films was studied. As the H2O2 content increased, yield and the lignin content of the cellulose from palm bunch and bagasse decreased, whereas lightness (L*) and whiteness index (WI) increased. FTIR confirmed the substitution of a carboxymethyl group on the cellulose structure. A higher degree of substitution of CMC from both sources was found when 20%-30% H2O2 was employed. The trend in the L* and WI values of each CMC and CMC film was related to those values in their respective cellulose. Bleaching each cellulose with 20% H2O2 provided the cellulose with the highest viscosity and the CMC films with the greatest mechanical (higher tensile strength and elongation at break) and soluble attributes, but the lowest water vapor barrier. This evidence indicates that cellulose delignification with H2O2 has a strong effect on the appearance and physical properties of both CMCs.

The impacts of hydrogen bonding on polymerization behavior has been of interest for a long time; however, universality and in-depth understanding are still lacking. For the first time, the effect of hydrogen bonding on the classical alternating-type copolymerization of styrene and maleimide was explored. N-phenylmaleimide (N-PMI)/styrene was chosen as a model monomer pair in the presence of hydrogen bonding donor solvent 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), which interacted with N-PMI via hydrogen bonding. Reversible addition-fragmentation chain transfer polymerization (RAFT) technique was used to guarantee the "living" polymerization and thus the homogeneity of chain compositions. In comparison with the polymerization in nonhydrogen bonding donor solvent (toluene), the copolymerization in HFIP exhibited a high rate and a slight deviation from alternating copolymerization tendency. The reactivity ratios of N-PMI and St were revealed to be 0.078 and 0.068, respectively, while the reactivity ratios in toluene were 0.026 and 0.050. These interesting results were reasonably explained by using computer simulations, wherein the steric repulsion and electron induction by the hydrogen bonding between HFIP and NPMI were revealed. This work first elucidated the hydrogen bonding interaction in the classical alternating-type copolymerization, which will enrich the research on hydrogen bonding-induced polymerizations.

Two coordination polymers (CPs) with chemical formulas, [Ho2(C4O4)2(C2O4)(H2O)8]·4H2O (1) and [Ho(C4O4)1.5(H2O)3] (2), (C4O42- = dianion of squaric acid, C2O42- = oxalate), have been synthesized and their structures were determined by single-crystal X-ray diffractometer (XRD). In compound 1, the coordination environment of Ho(III) ion is eight-coordinate bonded to eight oxygen atoms from two squarate, one oxalate ligands and four water molecules. The squarates and oxalates both act as bridging ligands with 1,2-bis-monodentate and bis-chelating coordination modes, respectively, connecting the Ho(III) ions to form a one-dimensional (1D) ladder-like framework. Adjacent ladders are interlinked via O-HO hydrogen bonding interaction to form a hydrogen-bonded two-dimensional (2D) layered framework and then arranged orderly in an AAA manner to construct its three-dimensional (3D) supramolecular architecture. In compound 2, the coordination geometry of Ho(III) is square-antiprismatic eight coordinate bonded to eight oxygen atoms from five squarate ligands and three water molecules. The squarates act as bridging ligands with two coordination modes, 1,2,3-trismonodentate and 1,2-bis-monodentate, connecting the Ho(III) ions to form a 2D bi-layered framework. Adjacent 2D frameworks are then parallel stacked in an AAA manner to construct its 3D supramolecular architecture. Hydrogen bonding interactions between the squarate ligands and coordinated water molecules in 1 and 2 both play important roles on the construction of their 3D supramolecular assembly. Compounds 1 and 2 both show remarkable ligand-enhanced photo-induced color-changing behavior, with their pink crystals immediately turning to yellow crystals under UV light illumination.

Animal food source production is increasing due to the growing world population. Many sources (e.g., hay) are prone to mold development, resulting in food degradation. This study proposes an environmentally friendly anti-mold fungicide comprising hydrogen peroxide (HP) and thymol entrapped in a polyvinyl alcohol/pyrrolidone (PVA/PVP) hydrogel (PVA is biodegradable and PVP is water soluble and non-toxic) coated on a polyethylene (PE) films for preservative hay packaging. The hydrogels improved the thermal stability of the entrapped HP and thymol, resulting in a prolonged release into the hay and thereby increasing anti-mold activity. The hydrogel composition and morphology, thymol and HP thermal stability, and release rates through indirect (gas phase) contact were investigated. Fungicidal capabilities were tested, indicating wide-range efficiency against mold growth on hay with a clear advantage for the thymol-loaded hydrogels. No visual side effects were observed on hay exposed to the released fumes of HP and/or thymol. These results demonstrate the potential of thymol-loaded hydrogels as effective and safe post-harvest preservatives.

The study of the capillary-like network formation of human umbilical vein endothelial cells (HUVECs) in vitro is important for understanding the factors that promote or inhibit angiogenesis. Here, we report the behavior of HUVECs on the composite hydrogels containing hyaluronic acid (HA) and gelatin with different degrees of degradation, inducing the different physicochemical properties of the hydrogels. The hydrogels were obtained through horseradish peroxidase (HRP)-catalyzed hydrogelation consuming hydrogen peroxide (H2O2, 16 ppm) supplied from the air, and the degradation degree was tuned by altering the exposure time to the air. The HUVECs on the composite hydrogel with intermediate stiffness (1.2 kPa) obtained through 120 min of the exposure were more elongated than those on the soft (0.4 kPa) and the stiff (2.4 kPa) composite hydrogels obtained through 15 min and 60 min of the exposure, respectively. In addition, HUVECs formed a capillary-like network only on the stiff composite hydrogel although those on the hydrogels with comparable stiffness but containing gelatin alone or alginate instead of HA did not form the network. These results show that the HA/gelatin composite hydrogels obtained through the H2O2-mediated crosslinking and degradation could be a tool for studies using HUVECs to understand the promotion and inhibition of angiogenesis.

The intermittent and volatile nature of renewable energy sources threatens the stable operation of power grids, necessitating dynamically operated energy storage. Power-to-gas technology is a promising method for managing electricity variations on a large gigawatt (GW) scale. The electrolyzer is a key component that can convert excess electricity into hydrogen with high flexibility. Recently, organic/inorganic composite separators have been widely used as diaphragm membranes; however, they are prone to increase ohmic resistance and gas crossover, which inhibit electrolyzer efficiency. Here, we show that the ceria nanoparticle and polysulfone composite separator exhibits a low area resistance of 0.16 Ω cm2 and a hydrogen permeability of 1.2 × 10-12 mol cm-1 s-1 bar-1 in 30 wt% potassium hydroxide (KOH) electrolyte, which outperformed the commercial separator, the Zirfon PERL separator. The cell using a 100 nm ceria nanoparticle/polysulfone separator and advanced catalysts has a remarkable capability of 1.84 V at 800 mA cm-2 at 30 wt% and 80 °C. The decrease in the average pore size of 77 nm and high wettability (contact angle 75°) contributed to the reduced ohmic resistance and low gas crossover. These results demonstrate that the use of ceria nanoparticle-based separators can achieve high performance compared to commercial zirconia-based separators.

A series of novel blended anion exchange membranes (AEMs) were prepared with hyperbranched brominated poly(arylene ether sulfone) (Br-HB-PAES) and linear chloromethylated poly(phenylene oxide) (CM-PPO). The as-prepared blended membranes were fabricated with different weight ratios of Br-HB-PAES to CM-PPO, and the quaternization reaction for introducing the ionic functional group was performed by triethylamine. The Q-PAES/PPO-XY (quaternized-PAES/PPO-XY) blended membranes promoted the ion channel formation as the strong hydrogen bonds interconnecting the two polymers were maintained, and showed an improved hydroxide conductivity with excellent thermal behavior. In particular, the Q-PAES/PPO-55 membrane showed a very high hydroxide ion conductivity (90.9 mS cm-1) compared to the pristine Q-HB-PAES membrane (32.8 mS cm-1), a result supported by the morphology of the membrane as determined by the AFM analysis. In addition, the rigid hyperbranched structure showed a suppressed swelling ratio of 17.9-24.9% despite an excessive water uptake of 33.2-50.3% at 90 °C, and demonstrated a remarkable alkaline stability under 2.0 M KOH conditions over 1000 h.

In vanadium redox flow batteries (VRFBs), simultaneously achieving high proton conductivity, low vanadium-ion permeability, and outstanding chemical stability using electrolyte membranes is a significant challenge. In this study, we report the fabrication of a tri-directional poly(2,5-benzimidazole) (T-ABPBI) membrane using a direct casting method. The direct-cast T-ABPBI (D-T-ABPBI) membrane was fabricated by modifying the microstructure of the membrane while retaining the chemical structure of ABPBI, having outstanding chemical stability. The D-T-ABPBI membrane exhibited lower crystallinity and an expanded free volume compared to the general solvent-cast T-ABPBI (S-T-ABPBI) membrane, resulting in enhanced hydrophilic absorption capabilities. Compared to the S-T-ABPBI membrane, the enhanced hydrophilic absorption capability of the D-T-ABPBI membrane resulted in a decrease in the specific resistance (the area-specific resistance of S-T-ABPBI and D-T-ABPBI membrane is 1.75 and 0.98 Ωcm2, respectively). Additionally, the D-T-ABPBI membrane showed lower vanadium permeability (3.40 × 10-7 cm2 min-1) compared to that of Nafion 115 (5.20 × 10-7 cm2 min-1) due to the Donnan exclusion effect. Owing to the synergistic effects of these properties, the VRFB assembled with D-T-ABPBI membrane had higher or equivalent coulomb efficiencies (>97%) and energy efficiencies (70-91%) than Nafion 115 at various current densities (200-40 mA cm-2). Furthermore, the D-T-ABPBI membrane exhibited stable performance for over 300 cycles at 100 mA cm-2, suggesting its outstanding chemical stability against the highly oxidizing VO2+ ions during practical VRFB operation. These results indicate that the newly fabricated D-T-ABPBI membranes are promising candidates for VRFB application.

High performing proton exchange membrane fuel cells (PEMFCs) that can operate at low relative humidity is a continuing technical challenge for PEMFC developers. In this work, micro-patterned membranes are demonstrated at the cathode side by solution casting techniques using stainless steel moulds with laser-imposed periodic surface structures (LIPSS). Three types of patterns, lotus, lines, and sharklet, are investigated for their influence on the PEMFC power performance at varying humidity conditions. The experimental results show that the cathode electrolyte pattern, in all cases, enhances the fuel cell power performance at 100% relative humidity (RH). However, only the sharklet pattern exhibits a significant improvement at 25% RH, where a peak power density of 450 mW cm-2 is recorded compared with 150 mW cm-2 of the conventional flat membrane. The improvements are explored based on high-frequency resistance, electrochemically active surface area (ECSA), and hydrogen crossover by in situ membrane electrode assembly (MEA) testing.

PEMWE is becoming one of the most promising technologies for efficient and green hydrogen production, while the anode OER process is deeply restricted by the now commercially used iridium oxide with sluggish reaction kinetics and super high cost. Deeply exploring the essential relationship between the underlying substrate materials and the performance of PEMWE cells while simultaneously excavating new practical and convenient methods to reduce costs and increase efficiency is full of challenges. Herein, two representative kinds of iridium oxide were studied, and their performance difference in PEMWE was precisely analyzed with electrochemical techniques and physical characterization and further linked to the ionomer/catalyst compound features. A novel anode with a uniform thin ionomer coating was successfully constructed, which simultaneously optimized the ionomer/catalyst aggregates as well as electrical conductivity, resulting in significantly enhanced PEMWE performance. This rigorous qualitative analysis of the structure-performance relationship as well as effective ionomer-affinitive optimization strategies are of great significance to the development of next-generation high-performance PEM water electrolyzers.