Additional Activation Step Research Articles

Controlled preparation of cellulose acetate by deep eutectic solvent homogeneous catalysis

This work proposed a homogeneous preparation strategy of cellulose acetate by using a deep eutectic solvent consisting of zinc chloride/phosphoric acid/water (ZnCl2/PA/H2O). The results showed that the DES (the molar ratio of ZnCl2: PA: H2O = 1:1:3) had good solubility for bamboo pulp with high degree of polymerization. The dynamic dissolution behavior of cellulose in DES was also studied. Cellulose was first moistened and swollen and then dissolved. The crystalline state of cellulose changed from type I to type II after regeneration. Under the synergistic effect of acetic anhydride (Ac2O), the dissolved cellulose in DES could be uniformly acetylated. The effects of temperature, reaction time and molar ratio of Ac2O/anhydrous glucose on degree of substitution (DS) were investigated in their respective ranges (30–50 °C, 2–10 h and 4–24). Cellulose acetate with DS of 0.42–1.81 was successfully prepared. The substituent distribution of the sample was analyzed as C-6 > C-2 > C-3. Moreover, the entire process required no additional catalysts or activation steps, reducing the difficulty of solvent recovery. The insight from this study provides a new idea for the development of greener methods for the homogeneous preparation of cellulose acetate.

Divide and Conquer: Design of Gallium‐Based Liquid Metal Particles for Soft and Stretchable Electronics

AbstractGallium‐based liquid metal (LM) has attracted considerable attention as a promising material for stretchable conductors due to its remarkable combination of deformability and metallic conductivity. However, LM inherently faces challenges such as high surface tension, resistance increase, electrical failure due to leakage, and limited mechanical stability. Recently, researchers have explored the concept of “dividing” bulk LM into microparticles (LMP) as a means of addressing these limitations. Nonetheless, the fabrication of LMP results in inherent electrical insulation, requiring additional activation steps to enable their use as stretchable conductors. In this review, the potential of LMP is discussed as an alternative to bulk LM and explore various methods to generate stable LMP‐based conductors and electrically activate LMP for their implementation in soft and stretchable electronics.

Modification of micro/mesoporous carbon synthesis method from well decomposed peat using ZnCl2 additional activation step

ZnCl2 activation method was used to synthesize micro- and mesoporous carbon material from Estonian well decomposed peat. The synthesized material with the ZnCl2 activation step has an SBET value of 1270 m2 g─1, compared to the SBET value of 270 m2 g─1 without the activation step. The material was tested as an electrode material in a supercapacitor cell with ionic liquid as an electrolyte. The cyclic voltammetry, impedance spectroscopy and constant current charge/discharge cycles data show that the material is useable for stationary electricity storage in local small-scale wind farms and local PV electricity generating fields. The constant power test data show that very high energy densities E = 50 Wh kg─1 at moderate power densities P = 10 kW kg─1 can be achieved.

Sustainable supercapacitor electrodes based on preagglomerated carbon onions and a green binder

Supercapacitors play a major role in the field of energy storage. However, the production of highly efficient and durable supercapacitors using sustainable materials remains a challenge. Herein, we report on a green approach for the production of thin film binder electrodes for electric double layer capacitors (EDLCs) based on onion-like carbon. The active material obtained by high temperature treated detonation nanodiamond offers a specific surface area of 527 m2 g−1 after an additional activation step. The key to facilitate the electrode manufacturing for this active material was the introduction of an agglomeration step of the carbon nano-onions which qualified them for the usage of plant-based carboxymethyl cellulose (CMC) as binder. The new types of electrodes were successfully tested in a supercapacitor full cell setup and benchmarked against electrodes relying on conventional fluorinated polymer (PVDF) as binder. The green electrodes provide about 22% higher specific capacitance of 56 F g−1 at a similar durability over more than 5000 cycles, combining sustainable production with excellent performance.

A new approach for activation of the kiwifruit cysteine protease for usage in in-vitro testing.

Actinidin (Act d 1), a highly abundant cysteine protease from kiwifruit, is one of the major contributors to the development of kiwifruit allergy. Many studies have focused on the optimization of Act d 1 purification and its role in the development of food allergies. Testing on cell culture monolayers is a common step in the elucidation of food allergen sensitization. In the case of cysteine proteases, an additional activation step with L-cysteine is required before the testing. Hence, we aimed to evaluate whether L-cysteine already present in commonly used cell culture media would suffice for Act d 1 activation. Successfully activated Act d 1 (98.1% of proteolytic activity, as compared to L-cysteine activated Act d 1) was further tested in two commonly used 2D model systems (Caco-2 and HEK293 cells) to evaluate its role on the mRNA expression of cytokines involved in the innate immunity (IL-1β, IL-6, TNFα, TSLP). Furthermore, the contribution of Act d 1 in the promotion of inflammation through regulation of inducible nitric oxide synthase (iNOS) mRNA expression was also examined. These results demonstrate that activation of cysteine proteases can be achieved without previous enzyme incubation in L-cysteine -containing solution. Act d 1 incubated in cell culture medium was able to modulate gene expression of pro-inflammatory cytokines when tested on two model systems of the epithelial barrier.

Ionic Liquid Aggregation Mechanism for Nanoparticle Synthesis.

Nanoparticle synthesis with silylamine reversible ionic liquids (RevILs) has been previously demonstrated to offer unique alternatives to traditional nanoparticle syntheses, allowing for size control and facile deposition onto support surfaces via the switchable nature of the IL. However, the mechanism of nanoparticle synthesis remains uncharacterized. The use of RevILs facilitates the synthesis of size-controlled nanoparticles without the use of additional stabilizing agents (i.e., surfactants, ligands, and polymers) that passivate the nanoparticle surface, which are traditionally required to control the nanoparticle size. Traditional techniques often require harsh activation steps that ultimately impact nanoparticle size and morphology. While RevIL syntheses offer an excellent alternative, as they do not require additional activation steps, the mechanism through which nanoparticles are synthesized in these systems has not been studied previously. Preceding work hypothesized nanoparticles prepared with RevILs are formed via a reverse micelle mechanism, in which nanoparticles are stabilized and templated within the aqueous core of the organized micelle structures. In this work, DOSY-NMR is used to demonstrate that nanoparticles synthesized with 3-aminopropyltriethylsilane RevIL are not formed through a reverse micelle mechanism but rather a switchable aggregation mechanism that affords control over the nanoparticle size via manipulation of the RevIL structure and concentration. Furthermore, it is shown that the addition of water to RevIL systems has detrimental effects on the aggregation behavior of the ionic liquid molecules in solution, causing disassembly of the ion pairs. However, because nanoparticle reduction likely occurs faster than the disassembly of the ion pairs, nanoparticle size is unaffected by the addition of water during nanoparticle reduction.

Effect of Adjusted Gas Nitriding Parameters on Microstructure and Wear Resistance of HVOF-Sprayed AISI 316L Coatings

Gas nitriding is known as a convenient process to improve the wear resistance of steel components. A precipitation-free hardening by low-temperature processes is established to retain the good corrosion resistance of stainless steel. In cases of thermal spray coatings, the interstitial solvation is achieved without an additional surface activation step. The open porosity permits the penetration of the donator media and leads to a structural diffusion. An inhomogeneous diffusion enrichment occurs at the single spray particle edges within the coating’s microstructure. A decreasing diffusion depth is found with increasing surface distance. The present study investigates an adjusted process management for low-temperature gas nitriding of high velocity oxy-fuel-sprayed AISI 316L coatings. To maintain a homogeneous diffusion depth within the coating, a pressure modulation during the process is studied. Additionally, the use of cracked gas as donator is examined. The process management is designed without an additional surface activation step. Regardless of surface distance, microstructural investigations reveal a homogeneous diffusion depth by a reduced processing time. The constant hardening depth allows a reliable prediction of the coatings’ properties. An enhanced hardness and improved wear resistance is found in comparison with the as-sprayed coating condition.

Hardening of HVOF-Sprayed Austenitic Stainless-Steel Coatings by Gas Nitriding

Austenitic stainless steel exhibits an excellent corrosion behavior. The relatively poor wear resistance can be improved by surface hardening, whereby thermochemical processes offer an economic option. The successful diffusion enrichment of bulk material requires a decomposition of the passive layer. A gas nitriding of high velocity oxygen fuel spraying (HVOF)-sprayed AISI 316L coatings without an additional activation step was studied with a variation of the process temperature depending on the heat-treatment state of the coating. A successful nitrogen enrichment was found in as-sprayed condition, whereas passivation prevents diffusion after solution heat treatment. The phase composition and microstructure formation were examined. The crystal structure and lattice parameters were determined using X-ray diffraction analysis. The identified phases were assigned to the different microstructural elements using the color etchant Beraha II. In as-sprayed condition, the phase formation in the coating is related to the process temperature. The formation of the S-phase with interstitial solvation of nitrogen is achieved by a process temperature of 420 °C. Precipitation occurs during the heat treatment at 520 °C. In both cases, a significant increase in wear resistance was found. The correlation of the thermochemical process parameters and the microstructural properties contributes to a better understanding of the requirements for the process combination of thermal spraying and diffusion.

Plastid terminal oxidase requires translocation to the grana stacks to act as a sink for electron transport

The plastid terminal oxidase (PTOX) has been shown to be an important sink for photosynthetic electron transport in stress-tolerant plants. However, overexpression studies in stress-sensitive species have previously failed to induce significant activity of this protein. Here we show that overexpression of PTOX from the salt-tolerant brassica species Eutrema salsugineum does not, alone, result in activity, but that overexpressing plants show faster induction and a greater final level of PTOX activity once exposed to salt stress. This implies that an additional activation step is required before activity is induced. We show that that activation involves the translocation of the protein from the unstacked stromal lamellae to the thylakoid grana and a protection of the protein from trypsin digestion. This represents an important activation step and opens up possibilities in the search for stress-tolerant crops.

Nanoarchitecture of advanced core-shell zero-valent iron particles with controlled reactivity for contaminant removal

The optimization of nanoscale zero-valent iron (nZVI) for groundwater remediation applications requires consideration of properties that influence its longevity and transport in porous media and reactivity with contaminants. Here, we report on the stabilization of nZVI by controlled growth of oxide shells of varying thickness and characterization of the resulting materials’ structure and reactivity. Using a thermal oxidation method, nZVI was prepared with shell thickness varying between 4 and 10 nm. These nZVI materials, together with pyrophoric nZVI (without a passivating oxide coating) and two commercial nZVI materials (NANOFER STAR and NANOFER 25), were characterized in detail with respect to morphology, shell thickness, structure, magnetism, stability, and reactivity. The results show that increasing oxidation temperature results in thicker oxide coatings on the particles, but these coatings also have more fractures and other defects. The reactivity of these particles, demonstrated on Cr(VI) and Cu(II) removal, increases with increasing shell thickness, probably as a result of higher extent of defects in thicker shell. Therefore the ability to control thickness and character of the shell leads to possibility to controlling reactivity while keeping comparable content of Fe(0) in the material. These nZVI materials with 7 and 10 nm oxide shell prepared via simple solid-gas synthesis can be used as a suitable alternative to common air-stable nZVI without additional activation steps.

Miniaturized Two Axis Acceleration Sensor Using Direct and Anodic Wafer Bonding for an Implantable Sensor Unit

The packaging of MEMS (Micro-Electro-Mechanical-Systems) such as acceleration, pressure and optical sensors requires a permanent and hermetically sealed bond interface of two or more wafers. In the area of system integration more and more new and heterogeneous materials have to be integrated and bonded at wafer level. In particular, silicon fusion and anodic bonding has a major advantage within the MEMS packaging. Both techniques enables joining without additional intermediate layers and with minimal technological effort. The bond mechanism of the fusion bonding at room temperature (pre-bond) is caused after contacting the two wafers by hydrogen bonds between the water molecules located on the opposite wafer surfaces. After the pre-bond a heat treatment (annealing) takes place, in order to form covalent siloxane bonds. Consequently, the interface water is removed by diffusion, whereby the bond strength is significantly increased. To activate these diffusion processes, surface plasma activation prior to the bonding process is one possibility. The pre-treatment of the substrate surfaces with plasma causes different interface and surface effects, such as the removal of contaminants on the wafer surface, an increase in the amount of silanol groups, an improvement of the diffusivity of water and gas trapped at the interface and an enhancement of viscous flow. Due to these mechanisms, the bonding and annealing process is supported. The anodic bonding process itself is characterized by the bond voltage, temperature and current limitation. This technique uses an electrostatic field (200-1000 V) caused by the atomic contact of two clean and smooth surfaces at temperatures of 400-500°C. By application of heat the alkali ions in the glass become free and moveable. The electrical field cause positive alkali ions to move to the electrode. A space charge region is formed between glass and silicon. The space charge region forces the materials into molecular contact. Oxygen and silicon are then forming a chemical bond between substrates. Within this work, we report the hermetic encapsulation of a two-axis acceleration sensor using fusion and anodic bonding processes. In order to achieve the required miniaturization, the acceleration sensor was developed in a MEMS technology. The MEMS sensor technology is based on previously reported approaches of the so-called BDRIE technology. BDRIE stands for Bonding and Deep Reactive Ion Etching. Both Si-Si-glass as well as Si-Si-Si configurations required six lithography steps with the sensor manufacturing on 6-inch wafer level and pre-etched Si or glass cap wafer. For wet etching of 40 µm deep cavities in the glass cap wafer, a masking layer stack consisting of Cr, Au and photoresist is used. The subsequent wet etch process is carried out in a spin-etch tool. The hermetic encapsulation with a glass cap wafer is accomplished with an anodic bonding process performed at 400°C with a voltage of -250 V in a standard bonding equipment. The pressure in the bond chamber can be adjusted according to the requirements of the application. In order to minimize damping, low vacuum conditions was chosen. For hermetic encapsulation with a pre-etched Si wafer, a fusion bonding process including an additional plasma activation step has been applied. Pre-bonding is done in the standard bonding equipment at a tool pressure of 2 bar. Afterwards, an annealing step at 800°C for 5 h in nitrogen contributes to increase the bond strength. The MEMS core die (sensor area) has a dimension of 1 x 1 mm². The overall die size is 1.2 x 1.5 mm². The maximum height of the sensor chip is 0.65 mm. The Figure shows the miniaturized xy acceleration sensors (Si-Si-glass variant). First characterization tests showed that both the Si-Si-glass and Si-Si-Si system is working and the results are quite promising. The sensitivity of at least 20 measured sensors (Si-Si-glass variant), obtained by 4-wire measurement, is 125±14 fF/g (x-axis) and 88±14 fF/g (y-axis). These values are even slightly higher than the target value (75 fF/g). Further work is focused on the comparison of the sensing properties using glass or silicon cap wafer. The final system is a implantable sensor unit. Besides the acceleration, the implantable sensor module detects pressure, temperature, voltage, and impedance. Except for the MEMS and pressure sensor all other sensor functions are integrated in an ASIC (application-specific integrated circuit). The three individual components (pressure, acceleration, ASIC) are mounted on a ceramic interposer module. Figure 1

Of Thiols and Disulfides: Methods for Chemoselective Formation of Asymmetric Disulfides in Synthetic Peptides and Polymers.

In protein or peptide chemistry, thiols are frequently chosen as a chemical entity for chemoselective modification reactions. Although it is a well-established methodology to address cysteines and homocysteines in aqueous media to form S-C bonds, possibilities for the chemoselective formation of asymmetric disulfides have been less approached. Focusing on bioreversibility in conjugation chemistry, the formation of disulfide bonds is highly desirable for the attachment of thiol-containing bioactive agents to proteins or in cross-linking reactions, because disulfide bonds can combine stability in blood with degradability inside cells. In this Concept article, recent approaches in the field of activating groups for thiol moieties incorporated in peptide and polymer materials are highlighted. Advantageous combinations of stability during synthesis of the material with high reactivity towards thiols are explored focusing on simplification and prevention of side reactions as well as additional deprotection and activation steps prior to disulfide formation. Moreover, applications of this chemistry are highlighted and future perspectives are envisioned.

Kinetic analysis of the isoleucyl-tRNA synthetase mechanism: the next reaction cycle can start before the previous one ends.

Aminoacyl‐tRNA synthetases join correct amino acids to their cognate tRNA at the start of the protein synthesis. Through the kinetic analysis, it is possible to estimate how their functional details correspond to the known structural features. Kinetic analysis of the isoleucyl‐tRNA synthetase (IleRS) from Escherichia coli was accomplished. Sixteen different steady‐state two‐ligand experiments were statistically analysed simultaneously so that the same rate equations and same rate and dissociation constants applied to all experiments. The so‐called rapid equilibrium segments procedure was used to derive the rate equations. The final best‐fit mechanism included the normal activation and transfer steps, and reorganization of the steps between them and after the transfer step. In addition, the analysis strongly suggested an additional activation step, formation of a new isoleucyl‐AMP before the isoleucyl‐tRNA was freed from the enzyme. The removal of Ile‐tRNA was possible without the formation of Ile‐AMP if both isoleucine and ATP were bound to the E‐Ile‐tRNA complex, but this route covered only 11% of the total formation of Ile‐tRNA. In addition to the Mg2+ in MgATP or MgPPi, only two tRNA‐bound Mg2+ were required to explain the magnesium dependence in the best‐fit mechanism. The first Mg2+ could be present in all steps before the second activation and was obligatory in the first reorganizing step and transfer step. The second Mg2+ was present only at the transfer step, whereas elsewhere it prevented the reaction, including the activation reactions. Chloride inhibited the IleRS reaction, while 100 mm KCl caused 50% inhibition if the ionic strength was kept constant with K‐acetate. The Kmapp (tRNA) value was increased from 0.057 to 1.37 μm when the KCl concentration was increased from 0 to 200 mm. The total rate equation helps to understand the reaction route and how the simultaneous presence of Ile‐tRNA and Ile‐AMP can cause new possibilities to proofreading mechanisms of this enzyme.EnzymeIsoleucyl‐tRNA synthetase (EC 6.1.1.5)

Superior potassium storage in chitin-derived natural nitrogen-doped carbon nanofibers

Potassium ion batteries (KIBs) are drawing intensive attention as the next-generation energy storage technology, owning to their similar electrochemical properties to lithium system and rich abundance of potassium resources. The carbonaceous materials with low cost, nontoxicity and high safety have been considered as promising candidates for KIBs anodes. However, they still suffer from several problems, such as poor cycling and rate capability, complex activation process steps and multiple procedures to import heteroatoms doping. Herein, the N-doped carbon nanofibers (NCFs) are fabricated by direct pyrolysis of bio-waste chitin, which is the second most abundant biopolymer throughout nature. The as-prepared NCFs used as KIBs anodes, without any additional activation steps, are systematically investigated for the first time. They deliver high capacity, excellent rate capability and long-term cycling stability, which benefit from the multiple synergistic effects of suitable interlayer spacing, heteroatom doping and unique one dimensional mesoporous structure. With the spotlight of environmental friendliness, low cost and high energy density in energy storage field, the chitin-based NCFs demonstrate great potential for future low-cost energy storage applications.

Design of reactive-end DNA oligomers via incorporation of oxanine into oligonucleotides using terminal deoxynucleotidyl transferase

Abstract Oxanine (Oxa, O), a modified nucleobase, has a novel O-acylisourea structure. Oxa-incorporated oligodeoxynucleotides (ODNs) are reactive DNA oligomers that permit conjugation with various nucleophilic molecules in an activation-free manner. In this study, we developed a new procedure for enzymatic preparation of reactive-end DNA oligomers, using terminal deoxynucleotidyl transferase (TdT), in which a reactive Oxa base is incorporated into the 3′-end of ODNs. One limitation of TdT, an enzyme widely used for end labeling of DNA oligomers, is that it is difficult to control the number of incorporated labels, because it shows template-independent extension with random nucleotides. Notably, TdT showed a rate and efficiency of incorporation of the modified nucleobase, Oxa, different from that of natural bases. We investigated the conditions of TdT-mediated DNA incorporation of Oxa and achieved incorporation of Oxa at the 3′-end of ODNs by optimizing reaction parameters such as temperature and enzyme, cofactor, and substrate concentrations. We also confirmed the reactive functionality of Oxa after incorporation into ODNs by amide bonding conjugation with a polyamine (spermine) under physiological conditions, without need for an additional activation step.

Porous nitrogen-doped carbon monoliths derived from biopolymer-structured liquid precursors

Nitrogen-doped carbon monoliths can be prepared from liquid, deep eutectic mixtures of urea and hexaketocyclohexane octahydrate, which are structured by chitosan as a natural in-situ scaffold and support. The as-formed polymer monolith can then be transformed into the respective nitrogen-doped carbon monolith with a high surface area, high mesoporosity and high nitrogen-content. The surface functionality as well as the access to the internal pore structure were demonstrated by carbon dioxide and dye sorption experiments. The applied synthetic procedure is simple, does not require additional activation steps and uses cheap and naturally abundant compounds avoiding typical and hazardous formaldehyde resins. Eventually, this offers a safe and sustainable alternative to current carbon monolith synthesis.

The Prodomain-bound Form of Bone Morphogenetic Protein 10 Is Biologically Active on Endothelial Cells

BMP10 is highly expressed in the developing heart and plays essential roles in cardiogenesis. BMP10 deletion in mice results in embryonic lethality because of impaired cardiac development. In adults, BMP10 expression is restricted to the right atrium, though ventricular hypertrophy is accompanied by increased BMP10 expression in a rat hypertension model. However, reports of BMP10 activity in the circulation are inconclusive. In particular, it is not known whether in vivo secreted BMP10 is active or whether additional factors are required to achieve its bioactivity. It has been shown that high-affinity binding of the BMP10 prodomain to the mature ligand inhibits BMP10 signaling activity in C2C12 cells, and it was proposed that prodomain-bound BMP10 (pBMP10) complex is latent. In this study, we demonstrated that the BMP10 prodomain did not inhibit BMP10 signaling activity in multiple endothelial cells, and that recombinant human pBMP10 complex, expressed in mammalian cells and purified under native conditions, was fully active. In addition, both BMP10 in human plasma and BMP10 secreted from the mouse right atrium were fully active. Finally, we confirmed that active BMP10 secreted from mouse right atrium was in the prodomain-bound form. Our data suggest that circulating BMP10 in adults is fully active and that the reported vascular quiescence function of BMP10 in vivo is due to the direct activity of pBMP10 and does not require an additional activation step. Moreover, being an active ligand, recombinant pBMP10 may have therapeutic potential as an endothelial-selective BMP ligand, in conditions characterized by loss of BMP9/10 signaling.

Andexanet alfa for reversal of factor Xa inhibitors induced-anticoagulation in nonclinical and clinical studies

Andexanet alfa for reversal of factor Xa inhibitors induced-anticoagulation in nonclinical and clinical studies

Insulation lifetime improvement of polyimide thin film neural implants

Objective. This work deals with studying and improving the insulation lifetime of polyimide-insulated thin film neural implants, or related polyimide-based medical implants. Approach. The evolution of the leak impedance of insulated conductors was investigated in saline water at 40 °C. The fabrication process as commonly found in literature for polyimide/platinum/polyimide microelectrode arrays was compared with three possible improvements: one based on lowering the curing temperature of the lower layer, one based on chemical activation and one based on an additional plasma activation step. Main results. The lower curing temperature process was found to yield a 7.5-fold improved lifetime compared with the state of the art process. Also, the leak impedances found after soak testing are an order of magnitude higher compared to the standard process. Significance. By improving the lifetime and insulation impedance of polyimide insulation with one order of magnitude, this work increases the applicability of polyimide in chronic thin film neural implants considerably.

Guanidination of lysine residue improves the sensitivity and facilitates the interpretation of free radical initiated peptide sequencing (FRIPS) mass spectrometry results

Lysine-containing peptides, which are often found in tryptic peptide mixtures, frequently undergo double conjugations with o-TEMPO-Bz-C(O)- groups in TEMPO-assisted free radical-initiated peptide sequencing (FRIPS) mass spectrometry applications because of the facile conjugation reaction at the ɛ-primary amino group of the lysine side chain. Doubly conjugated peptides required an additional collisional activation step because they include two free radical initiators, which is not favorable for the applications of the FRIPS approach in practical peptide MS analysis. To avoid this issue, this study introduces a new strategy of guanidinating lysine-containing peptides prior to the o-TEMPO-Bz-C(O)- conjugation. The guanidination step was found to be readily incorporated into our TEMPO-assisted FRIPS procedure with high yield. More importantly, the guanidinated peptides were demonstrated to undergo radical-driven peptide backbone fragmentations, similar to peptides that lack a lysine residue. In summary, combined with the guanidination step, the TEMPO-assisted FRIPS MS offers another practical tool that can be used to analyze and characterize peptides.