Hydroxylation Activity Research Articles

Visual and rapid fluorescence sensing for hexavalent chromium by hydroxypropyl chitosan passivated bismuth-based perovskite quantum dots.

Hydroxypropyl chitosan-Cs3Bi2Cl9 perovskite quantum dots (HPCS-PQDs) weresynthesized by a simple ligand-assisted reprecipitation method via green hydroxypropyl chitosan as the ligand and used as the specific signal of a fluorescence probe to achieve the highly sensitive detection of hexavalent chromium(Cr(VI)) and compared with chitosan-Cs3Bi2Cl9 QDs (CS-PQDs). HPCS-PQDs with multiple active hydroxyl passivations were found to enhance the photoluminescence quantum yield (PLQY) by 90%. After being placed in aqueous solution and irradiated with ultraviolet light for 96h the fluorescence intensity of HPCS-PQDs remained above 60%. The blue emission ofHPCS-PQDs hasa good selectivity and short response time (30s) for Cr(VI). Agood linear relationship is established between the fluorescence quenching rate of the HPCS-PQDs and concentration of Cr(VI) from 0.8 to 400µM, with a limit of detection (LOD) of 0.27µM. Thefluorescence quenching mechanism is the static quenching and internal filtration effect caused by HPCS-PQDs forming a non-fluorescent ground-state complex with Cr(VI). Thesensor cannot only be used to detectCr(VI) in water samples with high accuracy but canalso be prepared as a test paper for the detection for Cr(VI).

Screening and performance optimization of fungi for heavy metal adsorption in electrolytes.

The resource recovery and reuse of precious metal-laden wastewater is widely recognized as crucial for sustainable development. Superalloy electrolytes, produced through the electrolysis of superalloy scrap, contain significant quantities of precious metal ions, thereby possessing substantial potential for recovery value. This study first explores the feasibility of utilizing fungi to treat Superalloy electrolytes. Five fungi resistant to high concentrations of heavy metals in electrolytes (mainly containing Co, Cr, Mo, Re, and Ni) were screened from the soil of a mining area to evaluate their adsorption characteristics. All five fungi were identified by ITS sequencing, and among them, Paecilomyces lilacinus showed the best adsorption performance for the five heavy metals; therefore, we conducted further research on its adsorption characteristics. The best adsorption effect of Co, Cr, Mo, Re, and Ni was 37.09, 64.41, 47.87, 41.59, and 25.38%, respectively, under the conditions of pH 5, time 1 h, dosage 26.67 g/L, temperature 25-30°C, and an initial metal concentration that was diluted fivefold in the electrolyte. The biosorption of Co, Mo, Re, and Ni was better matched by the Langmuir model than by the Freundlich model, while Cr displayed the opposite pattern, showing that the adsorption process of P. lilacinus for the five heavy metals is not a single adsorption mechanism, but may involve a multi-step adsorption process. The kinetics study showed that the quasi-second-order model fitted better than the quasi-first-order model, indicating that chemical adsorption was the main adsorption process of the five heavy metals in P. lilacinus. Fourier transform infrared spectroscopy revealed that the relevant active groups, i.e., hydroxyl (-OH), amino (-NH2), amide (- CONH2), carbonyl (-C = O), carboxyl (-COOH), and phosphate (PO43-), participated in the adsorption process. This study emphasized the potential application of P. lilacinus in the treatment of industrial wastewater with extremely complex background values.

Insight into the synergistic effect on thermal behavior in co-pyrolysis of coal slime and sewage sludge: Kinetics, thermodynamics, dendrite neural network modelling, and evolved char structure

Co-pyrolysis of coal slime (CS) and sewage sludge (SS) is a promising technology to achieve waste reduction and recovery of value-added products. For the first time, pyrolysis behavior, kinetics, thermodynamics, dendrite neural network modelling, and evolved char structure were examined in the co-pyrolysis of CS and SS. The results showed that blending CS and SS at a weight ratio of 6:4 yielded a higher synergy in relation to the obtained kinetic and thermodynamic parameters. At lower temperatures, the active hydroxyl radicals released from SS pyrolyzed volatiles accelerate the dehydrogenation reactions of CS. The interaction between oxygen radicals, such as ether bonds in SS volatiles, and aromatics or hydrocarbon compounds in CS char increases the content of oxygenated compounds in the pyrolytic char by significantly enhancing its reactivity. As the temperature rises, the demethylation reaction of aliphatic hydrocarbons in SS volatiles generates a considerable amount of hydrogen radicals. This intensifies the formation of small-ring aromatic compounds during co-pyrolysis, further facilitating the condensation of small-ring aromatics into larger-ring aromatics at higher temperatures. In addition, a novel dendrite neural network model was successfully applied to predict the co-pyrolysis behavior of CS and SS, whereby the transfer function of interaction was obtained.

Excellent interfacial compatibility of phase change capsules/polyurethane foam with enhanced mechanical and thermal insulation properties for thermal energy storage

The incorporation of phase change microcapsule (microPCMs) substantially augmented the temperature regulation capacity of foams, endowing it with outstanding application potential in numerous industrial domains. However, interfacial compatibility issues between the capsule and the substrate always exist and affect foam performance. In this study, a milli-meter macrocapsule (macroPCMs) containing microPCMs was prepared using calcium alginate gel as the second layer wall to physically improve the interfacial compatibility. And poly (N-hydroxymethyl acrylamide) was in situ polymerized in the gel layer and provided active alcohol hydroxyl groups to form chemical grafting with the polyurethane raw materials, which further chemically improved the interfacial compatibility. These measures created a significantly improved foam microstructure and a greatly increased foaming capacity, which thus endow the composite foam with excellent thermal insulation performance and mechanical strength. Compared with conventional microPCMs-based foam, the foaming capacity of the macroPCMs-based foam increased by 40 folds, the temperature regulation duration increased by 7 folds, and the mechanical performance increased by 3 folds. Moreover, the insulated incubator fabricated with the macroPCMs-based foam exhibited two-fold greater thermal insulation efficiency than conventional models containing internal ice incubator, which validated the potential of employing macroPCMs-based polyurethane foam in cold chain logistics applications.

Metabolism of phenolic compounds catalyzed by Tomato CYP736A61

Cytochrome P450s (CYPs) regulate plant growth and stress responses by producing diverse primary and secondary metabolites. However, the function of many plant CYPs remains unknown because, despite their structural similarity, predicting the enzymatic activity of CYPs is difficult. In this study, one member of the CYP736A subfamily (CYP736A61) from tomatoes was isolated and characterized its enzymatic functions. CYP736A61 was successfully expressed in Escherichia coli through co-expression with molecular chaperones. The purified CYP736A61 showed hydroxylation activity toward 7-ethoxycoumarin, producing 7-hydroxycoumarin or 3-hydroxy 7-ethoxycoumarin. Further substrate screening revealed that dihydrochalcone and stilbene derivates (resveratrol and polydatin) are the substrates of CYP736A61. CYP736A61 also mediated the hydroxylation of resveratrol and polydatin, albeit with low activity. Importantly, CYP736A61 mediated the cleavage of resveratrol and polydatin as well as pinostilbene and pterostilbene. Interestingly, CY736A61 also converted phloretin to naringenin chalcone. These results suggest that CYP736A61 is a novel CYP enzyme with stilbene cleavage activity.

Metal-phenolic nanocatalyst rewires metabolic vulnerability for catalytically amplified ferroptosis

Ferroptosis is associated with excessive lipid peroxidation (LPO) accumulation, followed by membrane fragmentation. Although lipid metabolism is essential for regulating ferroptosis execution in tumors, there has been no use of nanomedicine to modulate the effect of metabolic vulnerability on ferroptosis. This study presents a metal-phenolic nanocatalyst (Fe@MT nanocatalyst), self-assembled using ferric ions (Fe3+) and coordinating with mitoxantrone (MT). This nanocatalyst accumulates lipid peroxides to strengthen ferroptotic vulnerability by initiating reactive oxygen species (ROS) storm and remodeling polyunsaturated fatty acids (PUFAs)-containing lipid metabolism. Fe@MT nanocatalyst catalytically converts endogenous hydrogen peroxide into highly active hydroxyl radical and depletes high intracellular levels of glutathione upon its internalization by U87MG cells, resulting in the release of MT, which in return promotes irreversible ferroptosis by elevating the intracellular production of ROS-sensitive PUFAs and inducing lethal LPO. Fe@MT nanocatalyst exhibits near-infrared photothermal property because of Fe3+ and MT self-assembly, causing photothermal-amplified catalytic ferroptosis therapy. This study sheds new light on promoting the sensitivity and execution of ferroptosis by reinforcing lethal lipid metabolism and accumulating excessive LPO and will establish an exploitable interaction between ferroptosis and lipid metabolic vulnerability in cancer.

Influential versatile potential of Entada rheedii and Myristica beddomei – an ethnobotanical approach

Aim of the study is to determine the anti-inflammatory, antidiabetic (α-amylase activity) and radical scavenging potentials of both leaf and stem ethanolic extracts of Entada rheedii and Myristica beddomei. DPPH, ABTS, H2O2, superoxide, hydroxyl and nitric oxide activity relate to inhibition ratio with different concentrations of extracts (μg/mL). Antidiabetic (α-amylase activity) and anti-inflammatory activities were also analyzed which showed high radical scavenging activity in a dose depending manner. Comparatively, leaves and stems of Entada rheedii showed higher radical scavenging activities compared to Myristica beddomei. Furthermore, both leaves and stem of Entada rheedii showed appreciable α-amylase inhibitory effects when compared with acarbose (standard drug) and also possess a strong anti-inflammatory effect (Diclofenac sodium, standard drug), compared to Myristica beddomei extracts. Overall, our results established the key evidence for Entada rheedii and Myristica beddomei extracts to be considered as a natural therapeutic aliment as the substitution for oxidative stress.

Preparation of graphene supported copper composite materials and study on the catalytic activity of phenol hydroxylation

The hydroxylation of phenol to synthesize dihydroxybenzene (DHB) has recently attracted considerable attention due to its inherent advantages, including its simplicity in industrial applications, environmental friendliness, and remarkable selectivity towards DHB. The hydrothermal method was used to prepare graphene supported copper composites (Cu/GNS) with excellent catalytic properties, which were applied in the phenol hydroxylation for DHB preparation. Cu/GNS with controllable copper content were successfully obtained, achieving the homogeneous dispersion of copper ions on the graphene surface while preventing graphene agglomeration. During catalysis, graphene serves as an electron transport conduit, enhancing the exposure of reactive active sites and facilitating the generation of hydroxyl radicals. The π-π interactions between graphene and phenol enhance the propensity for collision between phenol and hydroxyl radicals. The total selectivity of DHB reached 98.4%, and the phenol conversion reached 85.1%. The composites exhibited high stability, with 80.5% phenol conversion and 93.7% DHB total selectivity even after five reuse cycles.

Comparative antioxidant activity and phytochemical content of five extracts of Pleurotus ostreatus (oyster mushroom)

Reactive oxygen species reacts with numerous molecules in the body system causing oxidative damage, which requires antioxidants to ameliorate. Pleurotus ostreatus, a highly nutritious edible mushroom, has been reported to be rich in bioactive compounds. This study evaluated the comparative antioxidant activity and phytochemical contents of five extracts of P. ostreatus: aqueous (AE), chloroform (CE), ethanol (EE), methanol (ME) and n-hexane (HE). The phytochemical composition and antioxidant activity of the extracts were determined using standard in-vitro antioxidant assay methods. Results showed that the extracts contained alkaloids, tannins, saponins, flavonoids, terpenoids, phenolics, cardiac glycosides, carbohydrates, anthrocyanins, and betacyanins in varied amounts. CE had the highest flavonoid content (104.83 ± 29.46 mg/100 g); AE gave the highest phenol content of 24.14 ± 0.02 mg/100 g; tannin was highest in EE (25.12 ± 0.06 mg/100 g); HE had highest amounts of alkaloids (187.60 ± 0.28 mg/100 g) and saponins (0.16 ± 0.00 mg/100 g). Antioxidant analyses revealed that CE had the best hydroxyl radical activity of 250% at 100 µg/ml and ferric cyanide reducing power of 8495 µg/ml; ME gave the maximum DPPH activity (87.67%) and hydrogen peroxide scavenging activity (65.58%) at 500 µg/ml; EE had the highest nitric oxide radical inhibition of 65.81% at 500 µg/ml and ascorbate peroxidase activity of 1.60 (iU/l). AE had the best total antioxidant capacity (5.27 µg/ml GAE at 500 µg/ml) and ferrous iron chelating activity (99.23% at 100 µg/ml) while HE gave the highest guaiacol peroxidase activity of 0.20(iU/l). The comparative phytochemical and antioxidant characteristics (IC50) of the extracts followed the order: CE > AE > EE > ME > HE. Overall, chloroform was the best extraction solvent for P. ostreatus. The high content of phenolic compounds, flavonoids, and alkaloids in P. ostreatus makes it a rich source of antioxidants and potential candidate for the development of new therapies for a variety of oxidative stress-related disorders.

Support‐induced structural changes in CO2 hydrogenation to higher alcohols over metal/oxide catalysts

AbstractCO2 emissions have received a great deal of attention in recent years. The hydrogenation of CO2 to higher alcohols (HA) by heterogeneous catalysis is a promising artificial carbon cycle pathway, which has important significance for mitigating energy and environmental problems. Among the heterogeneous catalysts, supported catalysts exhibit unique catalytic activity due to their abundance of surface‐tunable active sites such as oxygen vacancies, surface acidic/basic sites, and active hydroxyl groups. Given the complexity in the CO2 hydrogenation reaction networks, however, it is very challenging to reveal the nature and role of unique interfaces/sites induced by oxide support. Herein, we review the progress of several common oxide supports in the CO2 hydrogenation to HA over the last decades, and illustrate the regulatory mechanisms of the oxide‐induced synergy on the activation of intermediates and the C−C coupling reactions. Based on this, we also discuss the present challenges associated with the HA synthesis from CO2 hydrogenation, as well as the thinking oriented on oxide support‐induced structure changes to improve the selectivity and productivity of HA.

In Situ Modulation of Oxygen Vacancies on 2D Metal Hydroxide Organic Frameworks for High-Efficiency Oxygen Evolution Reaction.

The discovery of non-precious catalysts for replacing the precious metal of ruthenium in the oxygen evolution reaction (OER) represents a key step in reducing the cost of green hydrogen production. The 2D d-MHOFs, a new 2D materials with controllable oxygen vacancies formed by controlling the degree of coordination bridging between metal hydroxyl oxide and BDC ligands are synthesized at room temperature, exhibit excellent OER properties with low overpotentials of 207 mV at 10mA cm-2. High-resolution transmission electron microscopy images and density functional theory calculations demonstrate that the introduction of oxygen vacancy sites leads to a lattice distortion and charge redistribution in the catalysts, enhancing the OER activity of 2D d-MHOFs comprehensively. Synchrotron radiation and in situ Raman/Fourier transform infrared spectroscopy indicate that part of oxygen defect sites on the surface of 2D d-MHOFs are prone to transition to highly active metal hydroxyl oxides during the OER process. This work provides a mild strategy for scalable preparation of 2D d-MHOFs nanosheets with controllable oxygen defects, reveals the relationship between oxygen vacancies and OER performance, and offers a profound insight into the basic process of structural transformation in the OER process.

Cytochrome P450 Family 4F2 and 4F11 Haplotype Mapping and Association with Hepatic Gene Expression and Vitamin K Hydroxylation Activity.

This study evaluated the underlying mechanistic links between genetic variability in vitamin K metabolic pathway genes (CYP4F2 and CYP4F11) and phylloquinone hydroxylation activity using genotype- and haplotype-based approaches. Specifically, we characterized genetic variability in the CYP4F2/CYP4F11 locus and compared common single allele genotypes and common haplotypes as predictors of hepatic gene expression, enzyme abundance, and phylloquinone (VK1) ω-hydroxylation kinetics. We measured CYP4F2 and CYP4F11 mRNA levels, CYP4F2 and CYP4F11 protein abundances, and the VK1 concentration-dependent ω-hydroxylation rate in matched human liver nucleic acid and microsome samples, utilizing a novel in vitro population modeling approach. Results indicate that accounting for the CYP4F2*3 allele alone is sufficient to capture most of the genetic-derived variability in the observed phenotypes. Additionally, our findings highlight the important contribution that CYP4F11 makes toward vitamin K metabolism in the human liver.

Integration of theory prediction and experimental electrooxidation of glycerol on NiCo2O4 nanosheets

Electrocatalytic refinery of low-value biomass-based glycerol into value-added chemicals formic acid (FA) is an attractive alternative to traditional thermochemical refineries. However, constructing non-precious catalysts with abundant active hydroxyl (OH*) is the main obstacle to the electrocatalytic glycerol oxidation reaction (EGOR). Herein, we combine density functional theory (DFT) and experiments to investigate EGOR over the finely constructed NiCo2O4 nanosheets. DFT results firstly indicate that the NiCo2O4 nanosheets exhibit the highly hydroxylated (311)-OH* surface with the lowest Gibbs free energy, which significantly improves the electrochemical reaction kinetics and can achieve desirable FA yield by adjusting the adsorption energy of the adsorption intermediate. Following the theoretical prediction, ultrathin NiCo2O4 nanosheets (~1.70 nm) are fabricated by a facile electrodeposition method with sufficient OH* on the surface. The charge-transfer resistance of NiCo2O4 nanosheets in EGOR is only 0.94 Ω and the anode power consumption can be reduced by up to 320 mV at 10 mA cm−2, keeping the high glycerol conversion (89%) and FA selectivity (70%) during the 120-h stability test. DFT calculations and experimental tools (e.g., multi-potential step experiments, operational electrochemical impedance spectroscopy) confirm that OH* in-situ generated on the thin nanosheets structure is essential in facilitating charge transfer between catalysts and adsorbed molecules to enhance C–C bond cleavage. This work offers a guideline for the rational design of robust catalysts for the selective upgrading of biomass-derived chemicals.

Preparation of reed fibers reinforced graft-modified starch-based adhesives based on quantum mechanical simulation and molecular dynamics simulation

Starch is a biomass polymer material with a high yield and comprehensive source. It is used as a raw material for preparing adhesives because of its highly active hydroxyl group. However, poor adhesion and water resistance hinder the application of starch-based adhesives (SBAs). Based on this, the starch was modified through graft copolymerization with itaconic acid as a cross-linking agent, methyl methacrylate and methyl acrylate as copolymers. Additionally, reed fibers were synergistically modified with polydopamine deposition to prepare an environmentally friendly SBA used in plywood production. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H NMR), X-ray diffraction (XRD), and thermogravimetric analysis (TG) demonstrate that copolymerization of methyl methacrylate and methyl acrylate with starch improves the shear strength, water resistance, and thermal stability of the SBA. Compared to unmodified starch, the modified SBA exhibits a 129 % increase in dry strength and achieves a wet strength of 1.36 MPa. Fukui function, Frontier orbit theory, and molecular dynamics simulation have shown that itaconic acid promotes the copolymerization of starch and acrylate monomers. The modified starch has fewer hydrogen bonds, less order, and a denser macromolecular network structure, which provides a reference for studying the molecular interaction mechanisms of SBAs.

Application of Chitosan-Based Hydrogel in Promoting Wound Healing: A Review.

Chitosan is a linear polyelectrolyte with active hydroxyl and amino groups that can be made into chitosan-based hydrogels by different cross-linking methods. Chitosan-based hydrogels also have a three-dimensional network of hydrogels, which can accommodate a large number of aqueous solvents and biofluids. CS, as an ideal drug-carrying material, can effectively encapsulate and protect drugs and has the advantages of being nontoxic, biocompatible, and biodegradable. These advantages make it an ideal material for the preparation of functional hydrogels that can act as wound dressings for skin injuries. This review reports the role of chitosan-based hydrogels in promoting skin repair in the context of the mechanisms involved in skin injury repair. Chitosan-based hydrogels were found to promote skin repair at different process stages. Various functional chitosan-based hydrogels are also discussed.

Surficial engineering of active hydroxyls for ambient formaldehyde oxidation via enhanced Lewis acidity over Zr-doped cryptomelane materials

Lewis acids of solid catalysts have been featured for a pivotal role in promoting various reactions. Regarding the oxidation protocol to remove formaldehyde, the inherent drawback of the best-studied MnO2 materials in acidic sites has eventually caused deficiency of active hydroxyls to sustain low-temperature activity. Herein, the cryptomelane-type MnO2 was targeted and it was tuned via incorporation of Zr metal, exhibiting great advances in not only the complete HCHO-to-CO2 degradation but also cycling performance. Zr species were existent in doping state in the MnO2 lattice, rendering lower crystallinity and breaking the regular growth of MnO2 crystallites, which thereby tripled surface area and created larger volume of smaller mesopores. Meantime, the local electronic properties of Mn atoms were also changed by Zr doping, i.e., more low-valence Mn species were formed due to the electron transfer from Zr to Mn. The results of infrared studies demonstrate the higher possession of Lewis acid sites on ZrMn, and this high degree of electrophilic agents favored the production of hydroxyl species. Furthermore, the reactivity of surface hydroxyls, as investigated by CO temperature programmed reduction and temperature programmed desorption of adsorbed O2, was obviously improved as well after Zr modification. It is speculated jointly with the characterizations of the post-reaction catalysts that the accelerated production of active hydroxyls helped rapidly convert formaldehyde into key intermediate—formate, which was then degraded into CO2, avoiding the side reaction path with undesired intermediate—hydrocarbonate—over the pristine MnO2, where active sites were blocked and formaldehyde oxidation was inhibited. Additionally, Zr decoration could stabilize Lewis acidity to be more resistant to heat degeneration, and this merit brought about advantageous thermal recyclability for cycled application.

Chicken CYP1A5 is able to hydroxylate aflatoxin B1 to aflatoxin M1

Aflatoxin B1 (AFB1), a naturally-occurring mycotoxin, can cause severe toxicological and carcinogenic effects in livestock and humans. Given that the chicken is one of the most important food-producing animals, knowledge regarding AFB1 metabolism and enzymes responsible for AFB1 transformation in the chicken has important implications for chicken production and food safety. Previously, we have successfully expressed chicken CYP1A5 and CYP3A37 monooxygenases in E. coli, and reconstituted them into a functional CYP system consisting of CYP1A5 or CYP3A37, CPR and cytochrome b5. In this study, we aimed to investigate the roles of CYP1A5 and CYP3A37 in the bioconversion of AFB1 to AFM1. Our results showed that chicken CYP1A5 was able to hydroxylate AFB1 to AFM1. The formation of AFM1 followed the typical Michaelis–Menten kinetics. The kinetics parameters of Vmax and Km were determined as 0.83 ± 0.039 nmol/min/nmol P450 and 26.9 ± 4.52 μM respectively. Docking simulations further revealed that AFB1 adopts a “side-on” conformation in chicken CYP1A5, facilitating the hydroxylation of the C9a atom and the production of AFM1. On the other hand, AFB1 assumes a “face-on” conformation in chicken CYP3A37, leading to the displacement of the C9a atom from the heme iron and explaining the lack of AFM1 hydroxylation activity. The results demonstrate that chicken CYP1A5 possesses efficient hydroxylase activity towards AFB1 to form AFM1.

Self-Cascade Nanozyme Reactor as a Cuproptosis Inducer Synergistic Inhibition of Cellular Respiration Boosting Radioimmunotherapy.

Intrinsic or acquired radioresistance remained an important challenge in the successful management of cancer. Herein, a novel "smart" multifunctional copper-based nanocomposite (RCL@Pd@CuZ) to improve radiotherapy (RT) sensitivity is designed and developed. In this nanoplatform, DSPE-PEG-RGD modified on the liposome surface enhanced tumor targeting and permeability; capsaicin inserted into the phospholipid bilayer improved the hypoxic conditions in the tumor microenvironment (TME) by inhibiting mitochondrial respiration; a Cu MOF porous cube encapsulated in liposome generated highly active hydroxyl radicals (OH·), consumed GSH and promoted cuproptosis by releasing Cu2+; the ultrasmall palladium (Pd) nanozyme within the cubes exhibited peroxidase activity, catalyzing toxic OH· generation and releasing oxygen from hydrogen peroxide; and lastly, Pd, as an element with a relatively high atomic number (Z) enhanced the photoelectric and Compton effects of X-rays. Therefore, RCL@Pd@CuZ enhance RT sensitivity by ameliorating hypoxia, promoting cuproptosis, depleting GSH, amplifying oxidative stress, and enhancing X-ray absorption , consequently potently magnifying immunogenic cell death (ICD). In a mouse model , RCL@Pd@CuZ combined with RT yielded >90% inhibition compared with that obtained by RT alone in addition to a greater quantity of DC maturation and CD8+ T cell infiltration. This nanoplatform offered a promising remedial modality to facilitate cuproptosis-related cancer radioimmunotherapy.

Inorganic-Organic Antioxidant Gel for Preventing the Spread of Forest Fires

ABSTRACT It is easier and cheaper to prevent forest fires than to extinguish them, therefore, the development of long-lasting and environmentally friendly fire-retarding materials is highly desirable to prevent the spread of forest fires. In this study, soluble carboxymethyl starch replaced insoluble carboxymethyl cellulose to improve the compressive strength of inorganic gel and overcome the weakness of fragility. When the concentration of polymer carboxymethyl starch and crosslinking agent aluminum citrate were 0.5% and 0.3%, respectively, the inorganic/organic composite gel showed the best comprehensive performance (including gelation time, water retention, seepage velocity and strength). Additionally, the antioxidant tannin was introduced into the inorganic/organic gel, which effectively inhibited the oxidation of wood flour, making its inhibition rate reached 23.1%, about twice that of pure inorganic gel. This is mainly attributed to the ability of tannin to inhibit the oxidation process of active groups, including carbon-oxygen, hydroxyl, and methyl of the wood powder, thereby enhancing the flame resistance of the composite gel. Probable mechanism of forest fire suppression by the antioxidant composite gel is proposed, which involves oxygen isolation, evaporative cooling, and chain reaction inhibition.

Biosynthesis of eriodictyol in citrus waster by endowing P450BM3 activity of naringenin hydroxylation.

The flavonoid naringenin is abundantly present in pomelo peels, and the unprocessed naringenin in wastes is not friendly for the environment once discarded directly. Fortunately, the hydroxylated product of eriodictyol from naringenin exhibits remarkable antioxidant and anticancer properties. The P450s was suggested promising for the bioconversion of the flavonoids, but less naturally existed P450s show hydroxylation activity to C3' of the naringenin. By well analyzing the catalytic mechanism and the conformations of the naringenin in P450, we proposed that the intermediate Cmpd I ((porphyrin)Fe = O) is more reasonable as key conformation for the hydrolyzation, and the distance between C3'/C5' of naringenin to the O atom of CmpdI determines the hydroxylating activity for the naringenin. Thus, the "flying kite model" that gradually drags the C-H bond of the substrate to the O atom of CmpdI was put forward for rational design. With ab initio design, we successfully endowed the self-sufficient P450-BM3 hydroxylic activity to naringenin and obtained mutant M5-5, with kcat, Km, and kcat/Km values of 230.45min-1, 310.48µM, and 0.742min-1µM-1, respectively. Furthermore, the mutant M4186 was screened with kcat/Km of 4.28-fold highly improved than the reported M13. The M4186 also exhibited 62.57% yield of eriodictyol, more suitable for the industrial application. This study provided a theoretical guide for the rational design of P450s to the nonnative compounds. KEY POINTS: •The compound I is proposed as the starting point for the rational design of the P450BM3 •"Flying kite model" is proposed based on the distance between O of Cmpd I and C3'/C5' of naringenin •Mutant M15-5 with 1.6-fold of activity than M13 was obtained by ab initio modification.