The denaturation and degradation of stable enzymes at high temperatures

Zirconium Metal-Organic Frameworks as Micromotors with Enzyme-like Activity for Glutathione Detection

Herein, we report a novel UiO-67-Co(bpy)0.35 micromotor synthesized by a facile postsynthesis metalation via introducing cobalt salts ligated with 2,2'-bipyridine-5,5'dicarboxylic acid into UiO-67-bpy0.35 framework. The Co2+ active sites can decompose H2O2 to generate bubbles to power UiO-67-Co(bpy)0.35. Meanwhile, the UiO-67-Co(bpy)0.35 micromotor exhibits robust peroxidase-like activity through catalyzing H2O2 to generate •OH under neutral conditions. Based on this, a sensing platform was constructed for the colorimetric detection of GSH. Due to the synergy of self-driven motion and excellent peroxide-like activity, UiO-67-Co(bpy)0.35 micromotor can sensitively detect GSH with a low analytic limitation as 0.13 μM for GSH detection. This study provides a new sight of using the postsynthesis metalation method to prepare Zr(Co)-MOF micromotor for highly selective, sensitive, and facile detection of GSH.

An update on thermostable keratinases for protein engineering against feather pollutants

Every year, the poultry business worldwide produces at least 8.5 billion tonnes of chicken feathers, making it one of the major landfill pollutants in the world. Biodegradation and recycling of native feathers is difficult due to the presence of numerous disulfide linkages in the feather's major constituent, keratin. Denaturation of such recalcitrant protein is thermodynamically favored at high temperatures. Therefore, the lookout for the enzymes that degrade keratin (keratinases) from thermophilic bacteria resulted in the identification of thermostable enzymes favoring feather degradation at high temperatures. This review presents a comprehensive analysis of the biochemical properties and structural attributes of thermostable keratinases, emphasizing their catalytic mechanisms, stability at high temperatures, and substrate specificity. Our exploration of structural features enables us to understand the molecular architecture of these enzymes for protein engineering that might enhance the keratinolytic activity and thermostability further. As the field of protein engineering advances, there exists a pressing requirement for integration of structural data with pragmatic engineering applications. Our review addresses for the first time the detailed structural aspects of thermostable bacterial keratinolytic enzymes that will facilitate the development of modified keratinases through protein engineering for a broad range of industrial applications, such as in the production of biofuels, leather processing, and waste management. KEYPOINTS: • Efficient eco-friendly bioremediation of feather landfill pollutant using thermophilic keratinases. • Detailed structural and biochemical aspects of different thermophilic bacterial keratinases. • Combinations of thermostable keratinases for the enhanced feather degradation process.

Regulatory Guidelines for the Analysis of Therapeutic Peptides and Proteins

Peptides and proteins have become increasingly important in the treatment of various diseases, including infections, metabolic disorders, and cancers. Over the past decades, the number of approved peptide- and protein-based drugs has grown significantly, now accounting for about 25% of the global pharmaceutical market. This increase has been recorded since the introduction of the first therapeutic peptide, insulin, in 1921. Therapeutic peptides and proteins offer several advantages over small molecule drugs, including high specificity, potency, and safety; however, they also face challenges related to instability in liquid formulations. To address this issue, numerous formulation techniques have been developed to enhance their stability. In either state, physical and chemical characterization of the peptide or protein of interest is crucial for ensuring the identity, purity, and activity of these therapeutic agents. Regulatory bodies such as the FDA, ICH, and EMA have established guidelines for the analysis, stability testing, and quality control of peptides and biologics to ensure the safety and effectiveness of these drugs. In the present review, these guidelines and the consequences thereof are summarized and provided to support the notion of developing tailored bioanalytical workflows for each peptide or protein drug.

Study on the development of nanoparticles based on levan for oral insulin delivery

Oral insulin administration has gained attention as a promising alternative to injections. However, its effectiveness is hindered by the major challenge of degradation by gastric acid. Biopolymer-based nanocarriers have been explored as a solution to address this challenge. This study examines levan, a biopolymer derived fromBacillus licheniformisBK1, for its viability as a nanocarrier for insulin. Levan was modified through acetylation, and both levan (I-Lv) and its acetylated (I-ALv) form were utilized as carriers for insulin in a nanoparticles (NPs) delivery system. The resulting NPs were spherical, with diameters ranging from 250 to 500 nm and encapsulation efficiencies of 78.64% and 88.30%, respectively. The insulin release from I-Lv NPs in simulated gastric fluid exhibited a burst release pattern that was more rapid than that of I-ALv. To further evaluate, the conformational stability of insulin in NPs was analyzed by measuring the transition enthalpy of secondary and tertiary structures. The stability of the secondary structure was determined through alpha-helix content using circular dichroism, while the tertiary structure stability was evaluated via the fluorescence intensity of tryptophan residues. The result revealed that insulin in I-ALv NPs exhibited enhanced conformational stability compared to free-state (FS) insulin and I-Lv NP, with transition enthalpies of 0.91 ± 0.62 and 4.42 ± 0.46 kcal mol-1for secondary and tertiary structures, respectively. Moreover, preliminaryin vivostudies revealed that I-ALv had a significant impact compared to FS insulin and I-Lv, demonstrating reduction in blood glucose levels. These findings highlight the potential of I-ALv as a promising candidate for antidiabetic therapy and an efficient oral delivery system.

Long-term warming and acidification interaction drives plastic acclimation in the diatom Pseudo-nitzschia multiseries

Ocean warming (OW) and acidification (OA) are expected to interactively impact key phytoplankton groups such as diatoms, but the underlying mechanisms, particularly under long-term acclimation, remain poorly understood. In this study, we investigated the responses of the toxic diatom Pseudo-nitzschia multiseries to combined changes in temperature (20 °C and 30 °C) and CO2 concentration (pCO2 400 μatm and 1000 μatm) using a multi-omics approach over an acclimation period of at least 251 generations. Physiological data suggest that elevated temperature, either alone or in combination with CO2, reduced the net photosynthesis and nitrate uptake rate, thus inhibiting P. multiseries growth. Conversely, elevated CO2 alone stimulated P. multiseries growth. Comparative genome analysis revealed the phenotypic plasticity in response to temperature and pCO2 variations, even after more than 251 generations acclimation period. Temperature was identified as the dominant environmental factor, showing stronger effects than CO2. Transcriptomic profiles indicated that genes involved in stress- and intracellular homeostasis such as Hsps, ubiquitination process and antioxidant defense were mostly down-regulated under long-term warming acclimation. This study demonstrates that P.multiseries responds similarly to both short-term and long-term experimental selection, suggesting that short-term experiments can be used to predict long-term responses.

Recreating Silk's Fibrillar Nanostructure by Spinning Solubilized, Undegummed Silk

The remarkable toughness (>70 MJ m-3) of silkworm silk is largely attributed to its hierarchically arranged nanofibrillar nanostructure. Recreating such tough fibers through artificial spinning is often challenging, in part because degummed, dissolved silk is drastically different to the unspun native feedstock found in the spinning gland. The present work demonstrates a method to dissolve silk without degumming to produce a solution containing undegraded fibroin and sericin. This solution exhibits liquid-liquid phase separation above 10% (wt/wt), a behavior observed in the silk gland but not in degummed silk solutions to date. This partitioning enhances the stability of the undegummed solution, delaying gelation two-fold compared with degummed silk at the same concentration. When spun under identical conditions, undegummed solutions produces fibers 8× stronger and 218× tougher than degummed silk feedstocks. Through ultrasonication, undegummed wet spun fibers are seen to possess hierarchical structure of densely packed ≈20 nm nanofibrils, similar to native silks, although completely absent from fibers wet-spun from degummed silk solutions. This work demonstrates that the preservation of molecular weight, presence of sericin and stimulation of liquid-liquid phase separation underpin a new pathway to recreate a hierarchical fiber with structures akin to native silk.

Surface exposed and charged residues drive thermostability in fungi

Fungi, though mesophilic, include thermophilic and thermostable species, as well. The thermostability of proteins observed in these fungi is most likely to be attributed to several molecular factors, such as the presence of salt bridges and hydrogen bond interactions between side chains. These factors cannot be generalized for all fungi. Factors impacting thermostability can guide how fungal thermophilic proteins gain thermostability. We curated a dataset of proteins for 14 thermophilic fungi and their evolutionarily closer mesophiles. Additionally, the proteome of Chaetomium thermophilum and its evolutionarily related mesophile Chaetomium globosum was analyzed. Using eggNOG, we categorized the proteomes into clusters of orthologous groups (COGs). While the individual count of proteins is over-represented in mesophiles (for COGs S, G, L, and Q), there are certain features that are significantly enriched in thermophiles (such as charged residues, exposed residues, polar residues, etc.). Since fungi are known to be cellulolytic and chitinolytic by nature, we selected 37 existing carbohydrate-active enzymes (CAZyme) families in Eurotiales, Mucorales, and Sordariales. We looked at closely similar sequences and their modeled structures for further comparison. Comparing solvent accessibilities of thermophilic and mesophilic proteins, exposed and intermediate residues are observed higher in thermophiles whereas buried residues are observed higher in mesophiles. For specific five CAZYme families (GH7, GH11, GH18, GH45, and CBM1) we looked at position-specific substitutions between thermophiles and mesophiles. We also found that there are relatively more intramolecular interactions in thermophiles compared to mesophiles. Thus, we found factors such as surface exposed residues and charged residues that are highly likely to impart thermostability in fungi, and this study sets the stage for further studies in the area of fungal thermostability.

Homeostasis: understanding the effects of impaired mechanisms

This article focuses on homeostasis and offers a pathophysiological perspective. The dynamic mechanisms responsible for maintaining internal balance and disruptive processes will be analysed through the lens of key systems including the nervous, endocrine and renal systems. The environmental factors and their potential impact on homeostasis have been considered. A clinical case study will contextualise homeostasis in clinical practice.

Expression, characterization and cytotoxicity of recombinant l-asparaginase II from Salmonella paratyphi cloned in Escherichia coli

L-asparaginase is a remarkable antineoplastic enzyme used in medicine for the treatment of acute lymphoblastic leukemia (ALL) as well as in food industries. In this work, the L-asparaginase-II gene from Salmonella paratyphi was codon-optimized, cloned, and expressed in E. coli as a His-tag fusion protein. Then, using a two-step chromatographic procedure it was purified to homogeneity as confirmed by SDS-PAGE, which also showed its monomeric molecular weight to be 37 kDa. This recombinant L-asparaginase II from Salmonella paratyphi (recSalA) was optimally active at pH 7.0 and 40 °C temperature. It was highly specific for L-asparagine as a substrate, while its glutaminase activity was low. The specific activity was found to be 197 U/mg and the kinetics elements Km, Vmax, and kcat were determined to be 21 mM, 28 μM/min, and 39.6 S-1, respectively. Thermal stability was assessed using a spectrofluorometer and showed Tm value of 45 °C. The in-vitro effects of recombinant asparaginase on three different human cancerous cell lines (MCF7, A549 and Hep-2) by MTT assay showed remarkable anti-proliferative activity. Moreover, recSalA exhibited significant morphological changes in cancer cells and IC50 values ranged from 28 to 45.5 μg/ml for tested cell lines. To investigate the binding mechanism of SalA, both substrates L-asparagine and l-glutamine were docked with the protein and the binding energy was calculated to be -4.2 kcal mol-1 and - 4.4 kcal mol-1, respectively. In summary, recSalA has significant efficacy as an anticancer agent with potential implications in oncology while its in-vivo validation needs further investigation.

Mass Spectrometry Analysis on the Breakage of Allergens in High-Molecular-Mass Polymer of Roasted Peanuts

Peanut allergy is a prevalent and concerning food allergy. Roasting can introduce structural changes to peanut allergens, affecting their allergenicity, but the structure on the primary structure is unclear. Here, the breakage sites were identified by mass spectrometry and software tools, and structural changes were simulated by molecular dynamics and displayed by PyMOL software. Results revealed that the appearance frequencies of L, Q, F, and E were high at the N-terminal of the breakage site, while S and E were dominant at the C-terminal. In the conformational structure, breakage sites were found close to disulfide bonds and the Cupin domains of Ara h 1 and Ara h 3. The breakage of allergens destroyed linear epitopes and might change the conformation of epitopes, which could influence peanuts' potential allergenicity.

Identification and Validation of Magnolol Biosynthesis Genes in Magnolia officinalis

Bacterial infections pose a significant risk to human health. Magnolol, derived from Magnolia officinalis, exhibits potent antibacterial properties. Synthetic biology offers a promising approach to manufacture such natural compounds. However, the plant-based biosynthesis of magnolol remains obscure, and the lack of identification of critical genes hampers its synthetic production. In this study, we have proposed a one-step conversion of magnolol from chavicol using laccase. After leveraging 20 transcriptomes from diverse parts of M. officinalis, transcripts were assembled, enriching genome annotation. Upon integrating this dataset with current genomic information, we could identify 30 laccase enzymes. From two potential gene clusters associated with magnolol production, highly expressed genes were subjected to functional analysis. In vitro experiments confirmed MoLAC14 as a pivotal enzyme in magnolol synthesis. Improvements in the thermal stability of MoLAC14 were achieved through selective mutations, where E345P, G377P, H347F, E346C, and E346F notably enhanced stability. By conducting alanine scanning, the essential residues in MoLAC14 were identified, and the L532A mutation further boosted magnolol production to an unprecedented level of 148.83 mg/L. Our findings not only elucidated the key enzymes for chavicol to magnolol conversion, but also laid the groundwork for synthetic biology-driven magnolol production, thereby providing valuable insights into M. officinalis biology and comparative plant science.

Enhancing Robustness of Adhesive Hydrogels through PEG-NHS Incorporation

Tissue wounds are a significant challenge for the healthcare system, affecting millions globally. Current methods like suturing and stapling have limitations as they inadequately cover the wound, fail to prevent fluid leakage, and increase the risk of infection. Effective solutions for diverse wound conditions are still lacking. Adhesive hydrogels, on the other hand, can be a potential alternative for wound care. They offer benefits such as firm sealing without leakage, easy and rapid application, and the provision of mechanical support and flexibility. However, the in vivo durability of hydrogels is often compromised by excessive swelling and unforeseen degradation, which limits their widespread use. In this study, we addressed the durability issues of the adhesive hydrogels by incorporating acrylamide polyethylene glycol N-hydroxysuccinimide (PEG-NHS) moieties (max. 2 wt %) into hydrogels based on hydroxy ethyl acrylamide (HEAam). The results showed that the addition of PEG-NHS significantly enhanced the adhesion performance, achieving up to 2-fold improvement on various soft tissues including skin, trachea, heart, lung, liver, and kidney. We further observed that the addition of PEG-NHS into the adhesive hydrogel network improved their intrinsic mechanical properties. The tensile modulus of these hydrogels increased up to 5-fold, while the swelling ratio decreased up to 2-fold in various media. These hydrogels also exhibited improved durability under the enzymatic and oxidative biodegradation induced conditions without causing any toxicity to the cells. To evaluate its potential for clinical applications, we used PEG-NHS based hydrogels to address tracheomalacia, a condition characterized by inadequate mechanical support of the airway due to weak/malacic cartilage rings. Ex vivo study confirmed that the addition of PEG-NHS to the hydrogel network prevented approximately 90% of airway collapse compared to the case without PEG-NHS. Overall, this study offers a promising approach to enhance the durability of adhesive hydrogels by the addition of PEG-NHS, thereby improving their overall performances for various biomedical applications.

Supercritical CO2/Deep Eutectic Solvent Biphasic System as a New Green and Sustainable Solvent System for Different Applications: Insights from Molecular Dynamics Simulations

Deep eutectic solvents (DESs) are one of the most interesting research subjects in green chemistry nowadays. Due to their low toxicity, simple synthesis, and lower prices, they have gradually taken the place of other green solvents such as ionic liquids (ILs) in sustainable processes. However, problems such as high viscosity and high polarity limit the applications of DESs in areas such as extraction, catalysis, and biocatalysis. In this work, we introduce and evaluate the potential application of scCO2/DES for the first time. Molecular dynamics simulations were used to examine the phase behavior, polarity, molecular mobilities, and microstructure of this system. Results show that CO2 molecules can significantly diffuse to the DES phase, while DES components do not appear in the scCO2 phase. The diffused CO2 molecules significantly enhanced the molecular mobility of the DES components. The presence of CO2 molecules changes the DES polarity so that hexane can be solubilized and dispersed in the DES phase. Radial distribution functions show that the solubilized CO2 molecules have negligible effects on the microstructure of DES. It was shown that chloride and urea are the main interaction sites of CO2 in DES. The results of this study show that scCO2/DES as a new class of green and versatile solvents can open a new promising window for research in sustainable chemistry and engineering.

Formulation of Antioxidant Composites by Controlled Heteroaggregation of Cerium Oxide and Manganese Oxide Nanozymes

Antioxidant composites based on nanozymes [manganese oxide microflakes (MnO2 MFs) and cerium oxide nanoparticles (CeO2 NPs)] were formulated by controlled heteroaggregation. The interparticle attraction via electrostatic forces was systematically tuned with surface functionalization by the poly(diallyldimethyl chloride) (PDADMAC) polyelectrolyte. The PDADMAC-coated MnO2 MFs (PMn) were heteroaggregated with oppositely charged CeO2 NPs to generate the Ce-PMn composite, while the PDADMAC-functionalized CeO2 NPs (PCe) were immobilized onto bare MnO2 MFs, resulting in the Mn-PCe composite. Both the adsorption of PDADMAC and the self-assembly of oppositely charged particles resulted in charge neutralization and charge reversal at appropriately high doses. The interparticle force regimes, the aggregation states, and the physicochemical properties of the relevant dispersions were also highly dependent on the dose of PDADMAC, as well as that of PDADMAC-functionalized metal oxides (PMO) enabling the fine-tuning and control of colloidal stability. The individual enzyme-like activity of either metal oxide was not compromised by PDADMAC adsorption and/or heteroaggregation, leading to the formation of broad-spectrum antioxidant composites exhibiting multiple enzyme-like activities such as superoxide dismutase, oxidase, and peroxidase-type functions. The low cost and ease of preparation, as well as controllable colloidal properties render such composites potential enzyme mimicking agents in various industrial fields, where processable antioxidant systems are needed.

Exploring the Temperature Effect on Enantioselectivity of a Baeyer-Villiger Biooxidation by the 2,5-DKCMO Module: The SLM Approach

Temperature is a crucial parameter for biological and chemical processes. Its effect on enzymatically catalysed reactions has been known for decades, and stereo- and enantiopreference are often temperature-dependent. For the first time, we present the temperature effect on the Baeyer-Villiger oxidation of rac-bicyclo[3.2.0]hept-2-en-6-one by the type II Bayer-Villiger monooxygenase, 2,5-DKCMO. In the absence of a reductase and driven by the hydride-donation of a synthetic nicotinamide analogue, the clear trend for a decreasing enantioselectivity at higher temperatures was observed. "Traditional" approaches such as the determination of the enantiomeric ratio (E) appeared unsuitable due to the complexity of the system. To quantify the trend, we chose to use the 'Shape Language Modelling' (SLM), a tool that allows the reaction to be described at all points in a shape prescriptive manner. Thus, without knowing the equation of the reaction, the substrate ee can be estimated that at any conversion.

Structure Prediction and Characterization of Thermostable Aldehyde Dehydrogenase from Newly Isolated Anoxybacillus geothermalis Strain D9

In nature, aldehyde dehydrogenase (ALDH) is widely distributed and mainly involved in the oxidation of aldehydes. Thermostability is one of the key features for industrial enzymes. The ability of enzymes to withstand a high operating temperature offers many advantages, including enhancing productivity in industries. This study was conducted to understand the structural and biochemical features of ALDH from thermophilic bacterium, Anoxybacillus geothermalis strain D9. The 3D structure of A. geothermalis ALDH was predicted by YASARA software and composed of 24.3% β-sheet located at the center core region. The gene, which encodes 504 amino acids with a molecular weight of ~56 kDa, was cloned into pET51b(+) and expressed in E.coli Transetta (DE3). The purified A. geothermalis ALDH showed remarkable thermostability with optimum temperature at 60 °C and stable at 70 °C for 1 h. The melting point of the A. geothermalis ALDH is at 65.9 °C. Metal ions such as Fe3+ ions inhibited the enzyme activity, while Li+ and Mg2+ enhanced by 38.83% and 105.83%, respectively. Additionally, this enzyme showed tolerance to most non-polar organic solvents tested (xylene, n-dedocane, n-tetradecane, n-hexadecane) in a concentration of 25% v/v. These findings have generally improved the understanding of thermostable A. geothermalis ALDH so it can be widely used in the industry.

Nanocomposite of MgFe2O4 and Mn3O4 as Polyphenol Oxidase Mimic for Sensing of Polyphenols

Polyphenol oxidase (PPO) mimics have advantage of detection and remediation of polyphenols. This work demonstrates rapid and sensitive colorimetric detection of phenolic compounds using nanocomposite of magnesium ferrite (MgFe₂O₄) and manganese oxide (Mn₃O₄) nanoparticles as PPO mimic. The catalytic properties of MgFe₂O₄ and Mn₃O₄ displayed synergistic effect in the nanocomposite. The synthesized nanocomposite and nanoparticles were fully characterized using various analytical techniques. The ratio of MgFe₂O₄ and Mn₃O₄ in the nanocomposite was optimized. Catechol and resorcinol were taken as model polyphenols. The best PPO-activity was shown by MgFe₂O₄@Mn₃O₄ nanocomposite with of w/w ratio 1:2. The results correlated with its higher surface area. Reaction parameters viz. pH, temperature, contact time, substrate concentration, and nanoparticles dose were studied. The synthesized MgFe₂O₄@Mn₃O₄ nanocomposite was used for the detection of catechol in the linear range of 0.1–0.8 mM with the detection limit of 0.20 mM, and resorcinol in the range of 0.01–0.08 mM with the detection limit of 0.03 mM. The estimated total phenolic content of green and black tea correlated well with the conventional method. These results authenticate promising future potential of MgFe₂O₄@Mn₃O₄ nanocomposite as PPO-mimic

Simulated Enzyme Activity and Efficient Antibacterial Activity of Copper-Doped Single-Atom Nanozymes

Nanozymes with good biocompatibility are novel antibacterial agents because they mimic the structure and properties of enzymes and destroy bacterial structures by generating reactive oxygen species in large quantities. Herein, we synthesized a Cu single-atom nanozyme (Cu-N-C) with intrinsic peroxidase- and oxidase-like activities. Cu-N-C can generate ·OH and O₂^·- during oxidase-catalyzed reactions, which have good antibacterial effects. Meanwhile, the antimicrobial performance can be further enhanced by light emitting diode light incubation due to photocatalysis. Lethal disruption of the membrane structure was confirmed by biofilm staining and scanning electron microscopy analysis. Notably, the antibacterial effect of Cu-N-C (MIC = 16 μg/mL) was significantly better than that of vancomycin (MIC = 1500 μg/mL), a commonly used drug for methicillin-resistant Staphylococcus aureus, and Cu-N-C outperformed the positive control cephalexin and gentamicin in terms of resistance development (27.3% less production of drug-resistant bacteria). Good biocompatibility was also verified using the MTT method, hemolysis analysis, and routine blood measurements in mice. The results of this work suggest that Cu-N-C has great potential for clinical applications as an efficient metal antimicrobial agent.

Decolorization and detoxification of synthetic dye compounds by laccase immobilized in vault nanoparticles

This study presents an eco-friendly and efficient technology, using immobilized enzymes, vault-encapsulated laccases (vlaccase), for decolorization and detoxification of dyes. Vault encapsulation remarkably improved the performance of laccase at industrially relevant conditions, including neutral to alkaline pH and relatively high temperatures. Two representative anthraquinone and azo dyes, Reactive Blue 19 and Acid Orange 7, respectively, were rapidly decolorized (72% and 80%) by vlaccase treatment while natural laccase (nlaccase) achieved 40% and 32% decolorization. The toxicity of treated and untreated dyes was tested on model bacterial, algal, and insect cells. The inhibitory effects of dyes towards selected bacteria were reduced in vlaccase-treated samples. The chlorophyll synthesis in algae was less inhibited by dyes after vlaccase treatment. Furthermore, the toxicity of dye degradation products to insect cells was significantly mitigated in the vlaccase group. Collectively, these results indicate that vlaccase is a stable and strong enzymatic system for removing dyes from waters.

Molecular photoswitches in aqueous environments

Molecular photoswitches enable dynamic control of processes with high spatiotemporal precision, using light as external stimulus, and hence are ideal tools for different research areas spanning from chemical biology to smart materials. Photoswitches are typically organic molecules that feature extended aromatic systems to make them responsive to (visible) light. However, this renders them inherently lipophilic, while water-solubility is of crucial importance to apply photoswitchable organic molecules in biological systems, like in the rapidly emerging field of photopharmacology. Several strategies for solubilizing organic molecules in water are known, but there are not yet clear rules for applying them to photoswitchable molecules. Importantly, rendering photoswitches water-soluble has a serious impact on both their photophysical and biological properties, which must be taken into consideration when designing new systems. Altogether, these aspects pose considerable challenges for successfully applying molecular photoswitches in aqueous systems, and in particular in biologically relevant media. In this review, we focus on fully water-soluble photoswitches, such as those used in biological environments, in both in vitro and in vivo studies. We discuss the design principles and prospects for water-soluble photoswitches to inspire and enable their future applications.

High surface area nitrogen-functionalized Ni nanozymes for efficient peroxidase-like catalytic activity

Nitrogen-functionalization is an effective means of improving the catalytic performances of nanozymes. In the present work, plasma-assisted nitrogen modification of nanocolumnar Ni GLAD films was performed using an ammonia plasma, resulting in an improvement in the peroxidase-like catalytic performance of the porous, nanostructured Ni films. The plasma-treated nanozymes were characterized by TEM, SEM, XRD, and XPS, revealing a nitrogen-rich surface composition. Increased surface wettability was observed after ammonia plasma treatment, and the resulting nitrogen-functionalized Ni GLAD films presented dramatically enhanced peroxidase-like catalytic activity. The optimal time for plasma treatment was determined to be 120 s; when used to catalyze the oxidation of the colorimetric substrate TMB in the presence of H2O2, Ni films subjected to 120 s of plasma treatment yielded a much higher maximum reaction velocity (3.7⊆10-8 M/s vs. 2.3⊆10-8 M/s) and lower Michaelis-Menten coefficient (0.17 mM vs. 0.23 mM) than pristine Ni films with the same morphology. Additionally, we demonstrate the application of the nanozyme in a gravity-driven, continuous catalytic reaction device. Such a controllable plasma treatment strategy may open a new door toward surface-functionalized nanozymes with improved catalytic performance and potential applications in flow-driven point-of-care devices.

Evaluating the Arrhenius equation for developmental processes

The famous Arrhenius equation is well suited to describing the temperature dependence of chemical reactions but has also been used for complicated biological processes. Here, we evaluate how well the simple Arrhenius equation predicts complex multi-step biological processes, using frog and fruit fly embryogenesis as two canonical models. We find that the Arrhenius equation provides a good approximation for the temperature dependence of embryogenesis, even though individual developmental intervals scale differently with temperature. At low and high temperatures, however, we observed significant departures from idealized Arrhenius Law behavior. When we model multi-step reactions of idealized chemical networks, we are unable to generate comparable deviations from linearity. In contrast, we find the two enzymes GAPDH and β-galactosidase show non-linearity in the Arrhenius plot similar to our observations of embryonic development. Thus, we find that complex embryonic development can be well approximated by the simple Arrhenius equation regardless of non-uniform developmental scaling and propose that the observed departure from this law likely results more from non-idealized individual steps rather than from the complexity of the system.

A critical comparison of natural enzymes and nanozymes in biosensing and bioassays

Nanozymes (NZs) are nanomaterials that mimic enzyme-like catalytic activity. They have attracted substantial attention due to their inherent physicochemical properties for use as promising alternatives to natural enzymes (NEs) in a variety of research fields. Particularly, in biosensing and bioassays, NZs have opened a new horizon to eliminate the intrinsic limitations of NEs, including their denaturation at extreme pH values and temperatures, poor reusability and recyclability, and high production costs. Moreover, the catalytic activity of NZs can be modulated in the preparation step by following an appropriate synthesis strategy. This review aims to gain insight into the potential substitution of NEs by NZs in biosensing and bioassays while considering both the pros and cons.

Carbonic Anhydrase Carrying Electrospun Nanofibers for Biocatalysis Applications

BACKGROUND

Enzymes are efficient biocatalysis that catalysis a large number of reactions due to their chemical, regional, or stereo specifities and selectivity. Their usage in bioreactor or biosensor systems has great importance. Carbonic anhydrase enzyme catalyzes the interconversion between carbon dioxide and water and the dissociated ions of carbonic acid. In organisms, the carbonic anhydrase enzyme has crucial roles connected with pH and CO₂ homeostasis, respiration, and transport of CO₂/bicarbonate, etc. So, immobilization of the enzyme is important in stabilizing the catalyst against thermal and chemical denaturation in bioreactor systems when compared to the free enzyme that is unstable at high temperatures and extreme pH values, as well as in the presence of organic solvents or toxic reagents. Nano-scale composite materials have attracted considerable attention in recent years, and electrospinning based all-nanocomposite materials have a wide range of applications. In this study, electrospun nanofibers were fabricated and used for the supporting media for carbonic anhydrase enzyme immobilization to enhance the enzyme storage and usage facilities.

OBJECTIVE

In this article, our motivation is to obtain attractive electrospun support for carbonic anhydrase enzyme immobilization to enhance the enzyme reusability and storage ability in biocatalysis applications.

METHODS

In this article, we propose electrospun nanofibers for carbonic anhydrase carrying support for achieving our aforementioned object. In the first part of the study, agar with polyacrylonitrile (PAN) nanofibers was directly fabricated from an agar-PAN mixture solution using the electrospinning method, and fabricated nanofibers were cross-linked via glutaraldehyde (GA). The morphology, chemical structure, and stability of the electrospun nanofibers were characterized. In the second part of the study, the carbonic anhydrase enzyme was immobilized onto fabricated electrospun nanofibers. Then, enzyme activity, the parameters that affect enzyme immobilization such as pH, enzyme amount, immobilization time, etc. and reusability were investigated.

RESULTS

When the scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analysis results are combined in the characterization process of the synthesized electrospun nanofibers, the optimum cross-linking time is found to be 8 hours using 5% glutaraldehyde cross-linking agent. Then, thermal stability measurements showed that the thermal stability of electrospun nanofibers has an excellent characteristic for biomedical applications. The optimum temperature value was found 37°C, pH 8 was determined as an optimum pH, and 100 ppm carbonic anhydrase enzyme concentration was found to be optimum enzyme concentration for the carbonic anhydrase enzyme immobilization. According to the kinetic data, carbonic anhydrase immobilized electrospun nanofibers acted as a biocatalyst in the conversion of the substrate to the product in 83.98%, and immobilized carbonic anhydrase enzyme is reusable up to 9 cycles in biocatalysis applications.

CONCLUSION

After applying the framework, we get a new biocatalysis application platform for carbonic anhydrase enzyme. Electrospun nanofibers were chosen as the support material for enzyme immobilization. By using this approach, the carbonic anhydrase enzyme could easily be used in the industrial area by cost-effective advantageous aspects.

Effects of mancozeb on heat Shock protein 70 (HSP70) and its relationship with the thermal physiology of Physalaemus henselii (Peters, 1872) tadpoles (Anura: Leptodactylidae)

Negative impacts on amphibians have been reported due to contamination by agrochemicals. However, until now, no study has tested the effect of the fungicide mancozeb (MZ) on thermal tolerance and its relationship with the expression of heat shock proteins (HSPs). MZ is the best-selling broad-spectrum fungicide in the world, which negatively affects non-target organisms. Here, we tested for the first time the effects of MZ on critical thermal maximum (CTmax) and its relationship to the expression of heat shock protein 70 (HSP70) in tadpoles of Physalameus henselii, a colder-adapted species in southernmost of the Neotropical region. A sublethal concentration of 2 mg/L was used. We found that the CTmax of the MZ-treated group was lower than that of the control group. In addition, there was an increase in HSP70 expression in tadpoles exposed to MZ and in tadpoles that underwent heat treatment. However, tadpoles subjected to MZ and heat treatment showed no induced HSP70 protein expression. Our results demonstrated that sublethal doses of the fungicide MZ negatively affected the thermal physiology and heat shock protein expression in tadpoles of P. henselii by inducing an increase in HSP70 concentration and by reducing the critical CTmax supported by tadpoles. It is important to understand the relationship between environmental contamination and physiological thermal limits in our current scenario of high rates of habitat conversion associated with unrestricted use of agrochemicals, as well as the challenging environmental changes induced by global warming.

MIPs for commercial application in low-cost sensors and assays - An overview of the current status quo

Molecularly imprinted polymers (MIPs) have emerged over the past few decades as interesting synthetic alternatives due to their long-term chemical and physical stability and low-cost synthesis procedure. They have been integrated into many sensing platforms and assay formats for the detection of various targets, ranging from small molecules to macromolecular entities such as pathogens and whole cells. Despite the advantages MIPs have over natural receptors in terms of commercialization, the striking success stories of biosensor applications such as the glucose meter or the self-test for pregnancy have not been matched by MIP-based sensor or detection kits yet. In this review, we zoom in on the commercial potential of MIP technology and aim to summarize the latest developments in their commercialization and integration into sensors and assays with high commercial potential. We will also analyze which bottlenecks are inflicting with commercialization and how recent advances in commercial MIP synthesis could overcome these obstacles in order for MIPs to truly achieve their commercial potential in the near future.

Nucleophilic Transformations of Lewis Acid-Activated Disubstituted Epoxides with Catalyst-Controlled Regioselectivity

Due to their inherent ring strain and electrophilicity, epoxides are highly attractive building blocks for fundamental organic reactions. However, controlling the regioselectivity of disubstituted epoxide transformations is often particularly challenging. Most Lewis acid-mediated processes take advantage of intrinsic steric or electronic substrate bias to influence the site of nucleophilic attack. Therefore, the scope of many of these systems is frequently quite limited. Recent efforts to generate catalysts that can overcome substrate bias have expanded the synthetic utility of these well-known reactions. In this Perspective, we highlight various regioselective transformations of disubstituted epoxides, emphasizing those that have inspired the production of challenging, catalyst-controlled processes.

Mesophilic Pyrophosphatase Function at High Temperature: A Molecular Dynamics Simulation Study

The mesophilic inorganic pyrophosphatase from Escherichia coli (EcPPase) retains function at 353 K, the physiological temperature of hyperthermophilic Thermococcus thioreducens, whereas the homolog protein (TtPPase) from this hyperthermophilic organism cannot function at room temperature. To explain this asymmetric behavior, we examined structural and dynamical properties of the two proteins using molecular dynamics simulations. The global flexibility of TtPPase is significantly higher than its mesophilic homolog at all tested temperature/pressure conditions. However, at 353 K, EcPPase reduces its solvent-exposed surface area and increases subunit compaction while maintaining flexibility in its catalytic pocket. In contrast, TtPPase lacks this adaptability and has increased rigidity and reduced protein/water interactions in its catalytic pocket at room temperature, providing a plausible explanation for its inactivity near room temperature.

Comparative modelling studies of fruit bromelain using molecular dynamics simulation

Fruit bromelain is a cysteine protease accumulated in pineapple fruits. This proteolytic enzyme has received high demand for industrial and therapeutic applications. In this study, fruit bromelain sequences QIM61759, QIM61760 and QIM61761 were retrieved from the National Center for Biotechnology Information (NCBI) Genbank Database. The tertiary structure of fruit bromelain QIM61759, QIM61760 and QIM61761 was generated by using MODELLER. The result revealed that the local stereochemical quality of the generated models was improved by using multiple templates during modelling process. Moreover, by comparing with the available papain model, structural analysis provides an insight on how pro-peptide functions as a scaffold in fruit bromelain folding and contributing to inactivation of mature protein. The structural analysis also disclosed the similarities and differences between these models. Lastly, thermal stability of fruit bromelain was studied. Molecular dynamics simulation of fruit bromelain structures at several selected temperatures demonstrated how fruit bromelain responds to elevation of temperature.

Protein Assays on Organic Electronics: Rational Device and Material Designs for Organic Transistor-Based Sensors

Artificial receptor-based protein assays have various attractive features such as a long-term stability, a low-cost production process, and the ease of tuning the target specificity. However, such protein sensors are still immature compared with conventional immunoassays. To enhance the application potential of synthetic sensing materials, organic field-effect transistors (OFETs) are some of the suitable platforms for protein assays because of their solution processability, durability, and compact integration. Importantly, OFETs enable the electrical readout of the protein recognition phenomena of artificial receptors on sensing electrodes. Thus, we believe that OFETs functionalized with artificial protein receptors will be a powerful tool for the on-site analyses of target proteins. In this Minireview, we summarize the recent progress of the OFET-based protein assays including the rational design strategies for devices and sensing materials.

Rapid mechanochemical encapsulation of biocatalysts into robust metal-organic frameworks

Metal–organic frameworks (MOFs) have recently garnered consideration as an attractive solid substrate because the highly tunable MOF framework can not only serve as an inert host but also enhance the selectivity, stability, and/or activity of the enzymes. Herein, we demonstrate the advantages of using a mechanochemical strategy to encapsulate enzymes into robust MOFs. A range of enzymes, namely β-glucosidase, invertase, β-galactosidase, and catalase, are encapsulated in ZIF-8, UiO-66-NH₂, or Zn-MOF-74 via a ball milling process. The solid-state mechanochemical strategy is rapid and minimizes the use of organic solvents and strong acids during synthesis, allowing the encapsulation of enzymes into three prototypical robust MOFs while maintaining enzymatic biological activity. The activity of encapsulated enzyme is demonstrated and shows increased resistance to proteases, even under acidic conditions. This work represents a step toward the creation of a suite of biomolecule-in-MOF composites for application in a variety of industrial processes.

Metal–organic frameworks (MOFs) are attractive for encapsulating enzymes for industrial purposes because they can increase selectivity, stability, and/or activity of the enzymes. Here, the authors developed an economical solid-state mechanochemical method to encapsulate enzymes during MOF synthesis.

Chemical Sensing Platforms Based on Organic Thin-Film Transistors Functionalized with Artificial Receptors

Organic thin-film transistors (OTFTs) have attracted intense attention as promising electronic devices owing to their various applications such as rollable active-matrix displays, flexible nonvolatile memories, and radiofrequency identification (RFID) tags. To further broaden the scope of the application of OTFTs, we focus on the host-guest chemistry combined with the electronic devices. Extended-gate types of OTFTs functionalized with artificial receptors were fabricated to achieve chemical sensing of targets in complete aqueous media. Organic and inorganic ions (cations and anions), neutral molecules, and proteins, which are regarded as target analytes in the field of host-guest chemistry, were electrically detected by artificial receptors. Molecular recognition phenomena on the extended-gate electrode were evaluated by several analytical methods such as photoemission yield spectroscopy in the air, contact angle goniometry, and X-ray photoelectron spectroscopy. Interestingly, the electrical responses of the OTFTs were highly sensitive to the chemical structures of the guests. Thus, the OTFTs will facilitate the selective sensing of target analytes and the understanding of chemical conversions in biological and environmental systems. Furthermore, such cross-reactive responses observed in our studies will provide some important insights into next-generation sensing systems such as OTFT arrays. We strongly believe that our approach will enable the development of new intriguing sensor platforms in the field of host-guest chemistry, analytical chemistry, and organic electronics.

The Effect of Dimethyl Sulfoxide on the Lysozyme Unfolding Kinetics, Thermodynamics, and Mechanism

The thermal stability of proteins in the presence of organic solvents and the search for ways to increase this stability are important topics in industrial biocatalysis and protein engineering. The denaturation of hen egg-white lysozyme in mixtures of water with dimethyl sulfoxide (DMSO) with a broad range of compositions was studied using a combination of differential scanning calorimetry (DSC), circular dichroism (CD), and spectrofluorimetry techniques. In this study, for the first time, the kinetics of unfolding of lysozyme in DMSO–water mixtures was characterized. In the presence of DMSO, a sharp decrease in near-UV CD and an increase in the fluorescence signal were observed at lower temperatures than the DSC denaturation peak. It was found that differences in the temperatures of the CD and DSC signal changes increase as the content of DMSO increases. Changes in CD and fluorescence are triggered by a break of the tertiary contacts, leading to an intermediate state, while the DSC peak corresponds to a subsequent complete loss of the native structure. In this way, the commonly used two-state model was proven to be unsuitable to describe the unfolding of lysozyme in the presence of DMSO. In kinetic studies, it was found that even high concentrations of DMSO do not drastically change the activation energy of the initial stage of unfolding associated with a disruption of the tertiary structure, while the enthalpy of denaturation shows a significant dependence on DMSO content. This observation suggests that the structure of the transition state upon unfolding remains similar to the structure of the native state.

Directed Evolution of Clostridium thermocellum β-Glucosidase A Towards Enhanced Thermostability

β-Glucosidases are key enzymes in the process of cellulose utilization. It is the last enzyme in the cellulose hydrolysis chain, which converts cellobiose to glucose. Since cellobiose is known to have a feedback inhibitory effect on a variety of cellulases, β-glucosidase can prevent this inhibition by hydrolyzing cellobiose to non-inhibitory glucose. While the optimal temperature of the Clostridium thermocellum cellulosome is 70 °C, C. thermocellum β-glucosidase A is almost inactive at such high temperatures. Thus, in the current study, a random mutagenesis directed evolutionary approach was conducted to produce a thermostable mutant with Kcat and Km, similar to those of the wild-type enzyme. The resultant mutant contained two mutations, A17S and K268N, but only the former was found to affect thermostability, whereby the inflection temperature (Ti) was increased by 6.4 °C. A17 is located near the central cavity of the native enzyme. Interestingly, multiple alignments revealed that position 17 is relatively conserved, whereby alanine is replaced only by serine. Upon the addition of the thermostable mutant to the C. thermocellum secretome for subsequent hydrolysis of microcrystalline cellulose at 70 °C, a higher soluble glucose yield (243%) was obtained compared to the activity of the secretome supplemented with the wild-type enzyme.

Improved Thermostability of Maltooligosyltrehalose Synthase from Arthrobacter ramosus by Directed Evolution and Site-Directed Mutagenesis

Maltooligosyltrehalose synthase (MTSase) is a key enzyme in trehalose production. MTSase from Arthrobacter ramosus has poor thermostability, limiting its industrial use. In this study, mutant G415P was obtained by directed evolution and S361R/S444E was subsequently generated based on a structure analysis of the region around G415. The t_1/2 of G415P and S361R/S444E at 60 °C increased by 3.0- and 3.2-fold, respectively, compared with the wild-type enzyme. A triple mutant (G415P/S361R/S444E) was obtained through a combination of the above mutants, and its t_1/2 significantly increased by 19.7-fold. Kinetic and thermodynamic stability results showed that the T₅₀ and T_m values of the triple mutant increased by 7.1 and 7.3 °C, respectively, compared with those of the wild-type enzyme. When the triple mutant was used in trehalose production, the yield reached 71.6%, higher than the 70.3% achieved with the wild-type. Thus, the mutant has a potential application for industrial trehalose production.

Highly stable enzyme-mimicking nanocomposite of antioxidant activity

A highly stable nanocomposite of antioxidant activity was developed by immobilization of a superoxide dismutase-mimicking metal complex on copolymer-functionalized nanoclay. The layered double hydroxide (LDH) nanoclays were synthesized and surface modification was performed by adsorbing poly(vinylpyridine-b-methacrylic acid) (PVPMAA). The effect of the adsorption on the charging and aggregation properties was investigated and the copolymer dose was optimized to obtain stable LDH dispersions. The LDH-PVPMAA hybrid particles showed high resistance against salt-induced destabilization in aqueous dispersions. Copper(II)-histamine (Cu(Hsm)₂) complexes were immobilized via the formation of dative bonds between the metal ions and the nitrogen atoms of the functional groups of the copolymer adsorbed on the particles. Changes in the coordination geometry of the complex upon immobilization led to higher superoxide radical anion scavenging activity than the one determined for the non-immobilized complex. Comparison of superoxide dismutase (SOD)-like activity of the obtained hybrid LDH-PVPMAA-Cu(Hsm)₂ with the nanoclay-immobilized SOD enzyme revealed that the developed composite maintained its activity over several days and was able to function at elevated temperature, while the immobilized native enzyme lost its activity under these experimental conditions. The developed nanocomposite is a promising antioxidant candidate in applications, where high electrolyte concentration and elevated temperature are applied.

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics

Infectious diseases claim millions of lives each year. Robust and accurate diagnostics are essential tools for identifying those who are at risk and in need of treatment in low-resource settings. Inorganic complexes and metal-based nanomaterials continue to drive the development of diagnostic platforms and strategies that enable infectious disease detection in low-resource settings. In this review, we highlight works from the past 20 years in which inorganic chemistry and nanotechnology were implemented in each of the core components that make up a diagnostic test. First, we present how inorganic biomarkers and their properties are leveraged for infectious disease detection. In the following section, we detail metal-based technologies that have been employed for sample preparation and biomarker isolation from sample matrices. We then describe how inorganic- and nanomaterial-based probes have been utilized in point-of-care diagnostics for signal generation. The following section discusses instrumentation for signal readout in resource-limited settings. Next, we highlight the detection of nucleic acids at the point of care as an emerging application of inorganic chemistry. Lastly, we consider the challenges that remain for translation of the aforementioned diagnostic platforms to low-resource settings.

Protection effect of polyols on Rhizopus chinensis lipase counteracting the deactivation from high pressure and high temperature treatment

The influence of polyols on Rhizopus chinensis lipase (RCL) was investigated under high pressure. The poor stability of RCL was observed at 500 MPa at 60 °C without polyols which protected RCL against the loss of activity. The lipase is more stable in phosphate buffer than in tris buffer despite the protection of polyols. The activity was maintained 63% by the sorbitol of 2 mol/L in Tris-HCl buffer but 73% in phosphate buffer after the treatment at 500 MPa and 60 °C for 25 min. The same protective effects could be observed at 1 mol/L of sorbitol, erythritol, xylitol, and mannitol. However, further increase of hydroxyl group number could not significantly improve the enzyme stability. The protection of polyols on RCL appears to depend on both of the polyol nature and the hydroxyl group number. Together with fluorescence spectra, circular dichroism spectra indicated that the chaotic conformation of RCL under high pressure became more ordered with 1 mol/L sorbitol. The results showed that sorbitol effectively stabilized the lipase conformation including the hydrophobic core under extreme conditions. It might be attributed to the interaction of polyols with RCL surface to modify intra-/intermolecular hydrogen bonds, maintaining the hydrophobic interactions within RCL.

Molecular dynamics analysis of the effects of GTP, GDP and benzimidazole derivative on structural dynamics of a cell division protein FtsZ from Mycobacterium tuberculosis

The prevailing multi-drug resistance in Mycobacterium tuberculosis continues to remain one of the main challenges to combat tuberculosis. Hence, it becomes imperative to focus on novel drug targets. Filamenting temperature-sensitive mutant Z (FtsZ) is an essential cell division protein, a eukaryotic tubulin homologue and a promising drug target. During cytokinesis, FtsZ polymerises in the presence of GTP to form Z-ring and recruits other proteins at this site that eventually lead to the formation of daughter cells. Benzimidazoles were experimentally shown to inhibit Mtb-FtsZ, with one of the benzimidazole derivatives, M1, being reported to have the minimum inhibitory concentration (MIC) value of 3.13 µg/mL. In the present study, mechanism of destabilisation of FtsZ in the presence of M1 was computationally investigated in the presence of its substrate GTP/GDP employing molecular dynamics (MD) simulation analysis, principal component analysis (PCA), molecular mechanics combined with the generalised Born and surface area continuum salvation (MM-GBSA) and density functional theory (DFT). From the analyses, it is proposed that binding of M1 in the inter-domain cleft induces structural changes in the GTP-binding region that affect GTP binding, thus switching the preference of this protein towards depolymerised state and eventually inhibiting the cell division. Hence, this study provides mechanistic insights into the design of novel benzimidazole inhibitors against Mtb-FtsZ. Communicated by Ramaswamy H. Sarma.

Enzyme-assisted extraction of polyphenols from green yerba mate

Abstract The enzyme-assisted extraction of bioactive compounds from plants has been studied as an alternative green technology and the carbohydrases have been candidates to improve the extraction process of numerous such compounds from plants. Polyphenols are secondary plant metabolites, generally involved in the defense against different types of stress and yerba mate (Ilex paraguariensis A. St.-Hil., Aquifoliaceae) is a natural source of these antioxidant compounds. The aim of this work was to evaluate the enzyme-assisted extraction of polyphenols from green yerba mate employing response surface methodology (RSM), in order to determine the best extraction conditions. The independent variables were temperature (33.2 to 66.8 °C), enzyme concentration (0 to 336 FGBU/100g), reaction time (19 to 221 minutes) and pH (2.82 to 6.18). The use of carbohydrases increased the extraction of polyphenols from about 38.67% to 52.08%. The present results showed that all the independent variables were significant at the linear level and that temperature and pH were not significant at the quadratic level. The interactions of temperature and pH; enzyme and reaction time; and enzyme and pH were significant. The regression model presented a determination coefficient (R2) close to 0.85 and a fitted value close to 0.45. Considering the results of this study and their industrial viability, the best conditions for the extraction of polyphenols from green yerba mate are a temperature of 50.0 °C, enzyme concentration of 168 FGB/100 g, reaction time of 120 minutes and pH value of 4.50. This study was the first RSM-based report of the optimization of the enzyme-assisted extraction of total phenolic compounds from green yerba mate.

Cooperativity of covalent attachment and ion exchange on alcalase immobilization using glutaraldehyde chemistry: Enzyme stabilization and improved proteolytic activity

Alcalase was scarcely immobilized on monoaminoethyl-N-aminoethyl (MANAE)-agarose beads at different pH values (<20% at pH 7). The enzyme did not immobilize on MANAE-agarose activated with glutaraldehyde at high ionic strength, suggesting a low reactivity of the enzyme with the support functionalized in this manner. However, the immobilization is relatively rapid when using low ionic strength and glutaraldehyde activated support. Using these conditions, the enzyme was immobilized at pH 5, 7, and 9, and in all cases, the activity vs. Boc-Ala-ONp decreased to around 50%. However, the activity vs. casein greatly depends on the immobilization pH, while at pH 5 it is also 50%, at pH 7 it is around 200%, and at pH 9 it is around 140%. All immobilized enzymes were significantly stabilized compared to the free enzyme when inactivated at pH 5, 7, or 9. The highest stability was always observed when the enzyme was immobilized at pH 9, and the worst stability occurred when the enzyme was immobilized at pH 5, in agreement with the reactivity of the amino groups of the enzyme. Stabilization was lower for the three preparations when the inactivation was performed at pH 5. Thus, this is a practical example on how the cooperative effect of ion exchange and covalent immobilization may be used to immobilize an enzyme when only one independent cause of immobilization is unable to immobilize the enzyme, while adjusting the immobilization pH leads to very different properties of the final immobilized enzyme preparation. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2768, 2019.

Ion-Induced Localized Nanoscale Polymer Reflow for Three-Dimensional Self-Assembly

Thermal reflow of polymers is a well-established phenomenon that has been used in various microfabrication processes. However, present techniques have critical limitations in controlling the various attributes of polymer reflow, such as the position and extent of reflow, especially at the nanoscale. These challenges primarily result from the reflow heat source supplying heat energy to the entire substrate rather than a specific area. In this work, a focused ion beam (FIB) microscope is used to achieve controllable localized heat generation, leading to precise control over the nanoscale polymer reflow. Through the use of the patterning capability of FIB microscopy, dramatically different reflow performances within nanoscale distances of each other are demonstrated in both discrete periodic and continuous polymer structures. Further, we utilize a self-assembly process induced by nanoscale polymer reflow to realize 3D optical devices, specifically, vertically aligned nanoresonators and graphene-based nanocubes. HFSS and Comsol simulations have been carried out to analyze the advantages of the polymer-based 3D metamaterials as opposed to those fabricated with a metallic hinge. The simulation results clearly demonstrate that the polymer hinges have a dual advantage; first, the removal of any interference from the transmission spectrum leading to strong and distinct resonance peaks and, second, the elimination of parasitic leeching of the enhanced field by the metallic hinge resulting in stronger volumetric enhancement. Thus, the 2-fold advantages existing in 3D polymer-hinge optical metamaterials can open pathways for applications in 3D optoelectronic devices and sensors, vibrational molecular spectroscopy, and other nanoscale 3D plasmonic devices.