Computational Insights into SARS-CoV-2 Main Protease Mutations and Nirmatrelvir Efficacy: The Effects of P132H and P132H-A173V.

Nirmatrelvir, a pivotal component of the oral antiviral Paxlovid for COVID-19, targets the SARS-CoV-2 main protease (Mpro) as a covalent inhibitor. Here, we employed combined computational methods to explore how the prevalent Omicron variant mutation P132H, alone and in combination with A173V (P132H-A173V), affects nirmatrelvir's efficacy. Our findings suggest that P132H enhances the noncovalent binding affinity of Mpro for nirmatrelvir, whereas P132H-A173V diminishes it. Although both mutants catalyze the rate-limiting step more efficiently than the wild-type (WT) Mpro, P132H slows the overall rate of covalent bond formation, whereas P132H-A173V accelerates it. Comprehensive analysis of noncovalent and covalent contributions to the overall binding free energy of the covalent complex suggests that P132H likely enhances Mpro sensitivity to nirmatrelvir, while P132H-A173V may confer resistance. Per-residue decompositions of the binding and activation free energies pinpoint key residues that significantly affect the binding affinity and reaction rates, revealing how the mutations modulate these effects. The mutation-induced conformational perturbations alter drug-protein local contact intensities and the electrostatic preorganization of the protein, affecting noncovalent binding affinity and the stability of key reaction states, respectively. Our findings inform the mechanisms of nirmatrelvir resistance and sensitivity, facilitating improved drug design and the detection of resistant strains.

Struvite and ethylenediaminedisuccinic acid (EDDS) enhance electrokinetic-biological permeable reactive barrier removal of copper and lead from contaminated loess.

Removal of heavy metals using the electrokinetic (EK) remediation technology is restricted by soils containing a fraction of clay particles above 12%. Furthermore, it is also affected by hydroxide precipitation (focusing phenomenon) close to the cathode. A modified EK reactor containing a permeable reactive barrier (PRB) was proposed herein where the enzyme-induced carbonate precipitation (EICP) treatment was incorporated into the PRB. Despite that, NH4+-N pollution induced by the urea hydrolysis resulting from the EICP treatment causes serious threats to surrounding environments and human health. There were four types of tests applied to the present work, including CP, TS1, TS2, and TS3 tests. CP test neglected the bio-PRB, while TS1 test considered the bio-PRB. TS2 test based on TS1 test tackled NH4+-N pollution using the struvite precipitation technology. TS3 test based on TS2 test applied EDDS to enhance the removal of Cu and Pb. In CP test, the removal efficiency applied to Cu and Pb removals was as low as approximately 10%, presumably due to the focusing phenomenon. The removal efficiency was elevated to approximately 24% when the bio-PRB and the electrolyte reservoir were involved in TS1 test. TS2 test indicated that the rate of struvite precipitation was 40 times faster than the ureolysis rate, meaning that the struvite precipitate had sequestered NH4+ before it started threatening surrounding environments. The chelation between Cu2+ and EDDS took place when EDDS played a part in TS3 test. It made Cu2+ negatively surface charged by transforming Cu2+ into EDDSCu2-. The chelation caused those left in S4 and S4 to migrate toward the bio-PRB, whereas it also caused those left in S1 and S2 to migrate toward the anode. Due to this reason, the fraction of Cu2+ removed by the bio-PRB and the electrolyte reservoir is raised to 32% and 26% respectively, and the fraction of remaining Cu was reduced to 41%. Also, the removal efficiency applied to Pb removal was raised to 50%. Results demonstrate the potential of struvite and EDDS-assisted EK-PRB technology as a cleanup method for Cu- and Pb-contaminated loess.

Starch Sodium Octenylsuccinate as a New Type of Stabilizer in the Synthesis of Catalytically Active Gold Nanostructures.

Here, starch derivatives, i.e., sodium starch octenylsuccinate (OSA starch, hereinafter referred to as OSA), were employed as both reducing and stabilizing agents for the unique, inexpensive, and simple synthesis of gold nanoparticles (OSA-AuNPs) in an aqueous solution with gold salt. The obtained OSA-AuNPs were characterized by UV-vis spectrophotometry, transmission electron microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The catalytic activity of the obtained gold colloids was studied in the reduction of organic dyes, including methylene blue (C.I. Basic Blue 9) and rhodamine B (C.I. Basic Violet 10), and food coloring, including tartrazine (E102) and azorubine (E122), by sodium borohydride. Moreover, OSA-AuNPs were utilized as signal amplifiers in surface-enhanced Raman spectroscopy. The obtained results confirmed that gold nanoparticles can be used as effective catalysts in reduction reactions of selected organic dyes, as well as signal enhancers in the SERS technique.

Synthesis and characterization of pH-sensitive nanocarrier based chitosan-g-poly(itaconic acid) for ciprofloxacin delivery for anti-bacterial application.

This study aims to develop pH-sensitive and controlled release of ciprofloxacin from ciprofloxacin-loaded grafted chitosan-coated zinc oxide nanoparticles (Cip@Gchit/Zn-NPs) for the treatment of bacterial infections in the human colon. For this aim, first, the chitosan-g-poly(itaconic acid) [Chit-g-poly (Itac)] was synthesized via grafting of itaconic acid onto chitosan in the presence of cerium ammonium nitrate (CAN) under an inert atmosphere using conventional methods, while zinc oxide nanoparticles (Zn-NPs) were prepared via sol-gel technique. Characterization of the synthesized Cip@Gchit/Zn-NPs was analyzed using XRD, FT-IR, SEM, TGA, and zeta potential analysis. The antibacterial efficacy of Cip@Gchit/Zn-NPs against three pathogenic bacteria, namely Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, was superior to that of tetracycline reference drugs, as evidenced by larger inhibition zones. Cytotoxicity assessment of Cip@Gchit/Zn-NPs on the human chondrocyte cell line C28/I2 via MTT assay revealed 100 % cell viability at a concentration of 500 µg/mL. The loading efficiency of ciprofloxacin into Gchit/Zn-NPs was evaluated at various ratios, demonstrating lower loading efficiency; however, sustained release of ciprofloxacin from Cip@Gchit/Zn-NPs was excellent, with 98.13 % release observed at pH 7.2 over 10 h. Kinetic analysis of ciprofloxacin release followed the first-order kinetic models.

High performance poly(L-lactic acid)-based film by one-step synthesis of poly (L-lactic acid-co-butylene itaconate-co-glycolic acid) for efficient preservation of yogurt storage.

Biodegradable poly(L-lactic acid) (PLLA) has seldom used for dairy packaging due to medium permeability and brittleness. Novel PLLA copolymers, poly (L-lactic acid-co-butylene itaconate-co-glycolic acid) (PLBIGA), were developed by integrating glycolic acid (GA) and poly(butylene itaconate) (PBI) into PLLA's structure using low molecular weight PLLA as a key initiator. Then, packaging materials with better barrier and mechanical properties were obtained by blended PLBIGA with PLLA. Both PLLA/PLBIGA films and polyethylene nylon composite film (PE/NY) were used for stirred yogurt packaging and storage at 4 °C for 25 days. Results revealed that yogurt packed by PLLA/PLBIGA films maintained stabler water-holding capacity, color, and viscosity over the storage period. Moreover, the integrity of the gel structure and the total viable count of lactic acid bacteria in yogurt packaged in PLLA/40-PLBIGA8 were also found to be superior to those in PE/NY packages, highlighting its eco-friendly advantages in dairy packaging.

Structural and functional characterization of itaconyl-CoA hydratase and citramalyl-CoA lyase involved in itaconate metabolism of Pseudomonas aeruginosa.

Itaconate is a key anti-inflammatory/antibacterial metabolite in pathogen-macrophage interactions that induces adaptive changes in Pseudomonas aeruginosa-exposed airways. However, the impact and mechanisms underlying itaconate metabolism remain unclear. Our study reveals that itaconate significantly upregulates the expression of pyoverdine in P. aeruginosa and enhances its tolerance to tobramycin. Notably, the enzymes responsible for efficient itaconate metabolism, PaIch and PaCcl, play crucial roles in both utilizing itaconate and clearing its toxic metabolic intermediates. By using protein crystallography and molecular dynamics simulations analyses, we have elucidated the unique catalytic center and substrate-binding pocket of PaIch, which contribute to its highly efficient catalysis. Meanwhile, analysis of PaCcl has revealed how interactions between domains regulate the conformational changes of the active sites and binding pockets, influencing the catalytic process. Overall, our research uncovers the significance and mechanisms of PaIch and PaCcl in the efficient metabolism of itaconate by P. aeruginosa.

Structural and functional insights of itaconyl-CoA hydratase from Pseudomonas aeruginosa highlight a novel N-terminal hotdog fold.

Itaconyl-CoA hydratase in Pseudomonas aeruginosa (PaIch) converts itaconyl-CoA to (S)-citramalyl-CoA upon addition of a water molecule, a part of an itaconate catabolic pathway in virulent organisms required for their survival in humans host cells. Crystal structure analysis of PaIch showed that a unique N-terminal hotdog fold containing a 4-residue short helical segment α3-, named as an "eaten sausage", followed by a flexible loop region slipped away from the conserved ß-sheet scaffold, whereas the C-terminal hotdog fold is similar to all MaoC. A conserved hydratase motif with catalytic residues provides mechanistic insights into catalysis, and existence of a longer substrate binding tunnel may suggest the binding of longer CoA derivatives.

Pharmacokinetics and antioxidant activity of dihydrocaffeic acid grafted chitosan nanomicelles loaded with chicoric acid in broilers.

Chicoric acid (CA) is a natural nutrient found in plants, showcasing diverse biological activities, including anti-inflammatory and antioxidant properties. Despite its valuable properties, CA faces limitations in bioavailability and susceptibility to oxidative breakdown during utilization. Previous research introduced synthesized dihydrocaffeic acid grafted chitosan self-assembled nanomicelles (DA-g-CS), demonstrating its potential to enhance CA absorption. This study aims to investigate the pharmacokinetics, tissue distribution, and antioxidant activity of both CA and DA-g-CS loaded CA (DA-g-CS/CA) in broilers. An IPEC-J2 cell model was established and evaluated to delve deeper into the transport mechanism and antioxidant potential. The in vivo pharmacokinetic analysis in broilers highlighted a substantial difference: the maximum plasma concentration (Cmax) of DA-g-CS/CA exceeded CA by 2.6-fold, yielding a notable increased relative bioavailability to 214%. This evidence underscores the significant enhancement in CA's oral absorption, facilitated by DA-g-CS. The collective evaluation outcomes affirm the successful development of the cell model, indicating its suitability for drug transporter experiments. The findings from the intestinal transit analysis revealed that both CA and DA-g-CS/CA underwent passive entry into IPEC-J2 cells. Notably, the cellular uptake rate of DA-g-CS loaded with CA was significantly amplified, reaching 2.1 times higher than that of CA alone. Intracellular transport mechanisms involved microtubules, lysosomes, and the endoplasmic reticulum, with an additional pathway involving the endoplasmic reticulum observed specifically for DA-g-CS/CA, distinguishing it from CA. Moreover, the results from both in vivo and in vitro antioxidant assessments highlight the potent antioxidant activity of DA-g-CS/CA, showcasing its efficacy in preventing and treating cellular damage induced by oxidative stress. In summary, these findings underscore the significant enhancement of CA's efficacy facilitated by DA-g-CS, establishing a robust theoretical foundation for the prospective application of CA within livestock and poultry farming.

Effects of folate-chicory acid liposome on macrophage polarization and TLR4/NF-κB signaling pathway in ulcerative colitis mouse.

BACKGROUND: Chichoric acid (CA) is a major active ingredient found in chicory and Echinacea. As a derivative of caffeic acid, it has various pharmacological effects. PURPOSE: Due to the unclear etiology and disease mechanisms, effective treatment methods for ulcerative colitis (UC) are currently lacking. The study investigated the therapeutic effects of the folate-chicory acid liposome on both LPS-induced macrophage inflammation models and dextran sulfate sodium (DSS)-induced mouse UC models. METHODS: Folate-chicory acid liposome was prepared using the double emulsion ultrasonic method with the aim of targeting folate receptors specifically expressed on macrophages. The study investigated the therapeutic effects of the folate-chicory acid liposome on both LPS-induced macrophage inflammation models and DSS -induced mouse UC models. Furthermore, the effects of the liposomes on macrophage polarization and their underlying mechanisms in UC were explored. RESULTS: The average particle size of folate-chicory acid liposome was 120.4 ± 0.46 nm, with an encapsulation efficiency of 77.32 ± 3.19 %. The folate-chicory acid liposome could alleviate macrophage apoptosis induced by LPS, decrease the expression of inflammatory factors in macrophages, enhance the expression of anti-inflammatory factors, inhibit macrophage polarization towards the M1 phenotype, and mitigate cellular inflammation in vetro. In vivo test, folate-chicory acid liposome could attenuate clinical symptoms, increased colon length, reduced DAI scores, CMDI scores, and alleviated the severity of colonic histopathological damage in UC mice. Furthermore, it inhibited the polarization of macrophages towards the M1 phenotype in the colon and downregulated the TLR4/NF-κB signaling pathway, thereby ameliorating UC in mice. CONCLUSION: Folate-chicory acid liposome exhibited a uniform particle size distribution and high encapsulation efficiency. It effectively treated UC mice by inhibiting the polarization of macrophages towards the M1 phenotype in the colon and downregulating the TLR4/NF-κB signaling pathway.

Fabrication of D-α-tocopheryl polyethylene glycol 1000 succinates and human serum albumin conjugated chitosan nanoparticles of bosutinib for colon targeting application; in vitro-in vivo investigation.

For more effective chemotherapy and targeted treatment of colorectal cancer, this study seeks to develop chitosan (CH)-human serum albumin (HAS)-D-α-tocopheryl polyethylene glycol 1000 (TPGS) nanoparticles (BOS-CH-HSA-TPGS-NPs) coated with Bosutinib (BOS). Nuclear magnetic resonance (NMR) indicated that chitosan's structure was modified by carbodiimide coupling with HSA. We used a Box-Behnken design to find the ideal region for particle size, zeta potential, and entrapment efficiency, eventually emerging at a formulation with these values: 187.14 ± 3.2 nm, 76.2 ± 0.96 %, and 21.1 ± 2.3 mV. Differential scanning calorimetry (DSC), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), High-performance liquid chromatography (HPLC) were all used to characterize the sample in detail. At a phosphate buffer pH of 7.4, in vitro drug release tests showed both Higuchi model release (0.954) and Fickian diffusion (n = 0.5). Compared to free BOS, HCT116 cell lines showed considerably higher cytotoxicity in in vitro cytotoxicity assays. In male albino Wistar rats, the BOS-CH-HSA-TPGS-NPs also showed enhanced pharmacokinetics, targeting efficiency, and biocompatibility. When used to the treatment of colorectal cancer, the BOS-CH-HSA-TPGS NPs show promise as a sustained-release therapy with improved therapeutic effects by addressing the challenges of poor solubility, poor permeability, and toxic side effects.

Development of poly(butylene adipate-co-butylene succinate-co-ethylene adipate-co-ethylene succinate) (PBEAS) net twine as biodegradable fishing gear.

Nylon fishing nets have excellent strength and durability, but when lost at sea, their insufficient decomposition destroys habitats and spawning grounds, and pollutes the marine environment. This led to the development of poly(butylene succinate) (PBS) resin for biodegradable fishing gear based on aliphatic fibers. Prompted by the low stiffness and elastic recovery of PBS, we introduced two additional components into the molecular structure of PBS: adipic acid and ethylene glycol. These two new components were combined with succinic acid and 1,4-butanediol, the existing components of PBS, to synthesize poly(butylene adipate-co-butylene succinate-co-ethylene adipate-co-ethylene succinate) (PBEAS) resin via esterification and polycondensation reactions of a quaternary aliphatic copolyester. Although the molecular weight and molecular weight distribution of PBEAS are similar to those of PBS, it has excellent tensile strength, stiffness, elastic recovery, and biodegradability, with a low melting point for good production efficiency. These improvements are expected to allow PBEAS resin to be applied to gill nets for fish that require high stiffness, thereby expanding the use of biodegradable fishing gear.

Discovery of Itaconate-Mediated Lysine Acylation.

Itaconate is an important antimicrobial and immunoregulatory metabolite involved in host-pathogen interactions. A key mechanistic action of itaconate is through the covalent modification of cysteine residues via Michael addition, resulting in "itaconation". However, it is unclear whether itaconate has other regulatory mechanisms. In this work, we discovered a novel type of post-translational modification by promiscuous antibody enrichment and data analysis with the open-search strategy and further confirmed it as the lysine "itaconylation". We showed that itaconylation and its precursor metabolite itaconyl-CoA undergo significant upregulation upon lipopolysaccharides (LPS) stimulation in RAW264.7 macrophages. Quantitative proteomics identified itaconylation sites in multiple functional proteins, including glycolytic enzymes and histones, some of which were confirmed by synthetic peptide standards. The discovery of lysine itaconylation opens up new areas for studying how itaconate participates in immunoregulation via protein post-translational modification.

Synthesis and Structure-Property Relationships of Novel High Molecular Weight Fully Biobased 2,5-Thiophenedicarboxylic Acid-Based Polyesters.

High molecular weight fully biobased poly(propylene succinate-co-2,5-thiophenedicarboxylate) (PPSTF) random copolyesters based on the emerging biobased aromatic diacid, 2,5-thiophenedicarboxylic acid (TFDCA), in full composition range were synthesized via melt polycondensation. Their crystallization behavior, thermal-mechanical, gas barrier, and biodegradable properties were systematically investigated. A certain level of comonomer cocrystallization was evidenced by XRD, and PTF units had stronger crystallization competitive capability compared to PS units due to the higher stiffness of TFDCA units. These copolyesters exhibited excellent thermal stability, and mechanical properties can be easily controlled by tuning the varied ratio of flexible to rigid segments. Gas barrier properties were studied from both theoretically calculated and experimental perspectives, and the copolyesters even with 50 mol % PS units still showed superior gas permeation resistance. The selected lipase from Aspergillus oryzae can degrade the copolyesters with up to 60 mol % PTF units. The nonbiodegradable-biodegradable transition was found to occur at the number-average sequence length of aromatic PTF units as low as about 3. Interestingly, when compared with their terephthalic acid-based (TA-based) and 2,5-furandicarboxylic acid-based (FDCA-based) analogues with the same content of aromatic units, the apparent degradation rate constant (k) and half period (t1/2) of PPSTF60 were actually between them. These findings offer much promise for the application of polyesters containing odd-carbon diol monomers in green packaging and other fields.

Enhanced Insecticidal Effect and Interface Behavior of Nicotine Hydrochloride Solution by a Vesicle Surfactant.

Nicotine hydrochloride (NCT) has a good control effect on hemiptera pests, but its poor interfacial behavior on the hydrophobic leaf leads to few practical applications. In this study, a vesicle solution by the eco-friendly surfactant, sodium diisooctyl succinate sulfonate (AOT), was prepared as the pesticide carrier for NCT. The physical chemical properties of NCT-loaded AOT vesicles (NCT/AOT) were investigated by techniques such as dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryo-TEM). The results showed that the pesticide loading and encapsulation efficiency of NCT/AOT were 10.6% and 94.8%, respectively. The size of NCT/AOT vesicle was about 177 nm. SAXS and surface tension results indicated that the structure of the NCT/AOT vesicle still existed with low surface tension even after being diluted 200 times. The contact angle of NCT/AOT was always below 30°, which means it could wet the surface of the cabbage leaf well. Consequently, NCT/AOT vesicles could effectively reduce the bounce of pesticide droplets. In vitro release experiments showed that NCT/AOT vesicles had sustained release properties; 60% of NCT in NCT/AOT released after 24 h, and 80% after 48 h. Insecticidal activity assays against aphids revealed that AOT vesicles exhibited insecticidal activity and could have a synergistic insecticidal effect with NCT after the loading of NCT. Thus, the NCT/AOT vesicles significantly improved the insecticidal efficiency of NCT, which has potential application in agricultural production activities.

Biodegradable chelant-metal complexes enhance cadmium phytoextraction efficiency of Solanum americanum.

Toxic contaminants (metals and metal-containing compounds) are accumulating in the environment at an astonishing rate and jeopardize human health. Remarkable industrial revolution and the spectacular economic growth are the prime causes for the release of such toxic contaminants in the environment. Cadmium (Cd) is ranked the 7th most toxic compound by the Agency for Toxic Substances and Disease Registry (USA), owing to its high carcinogenicity and non-biodegradability even at miniscule concentration. The present study assessed the efficiency of four biodegradable chelants [nitrilotriacetic acid (NTA), ethylenediamine disuccinate (EDDS), ethylene glycol tetraacetic acid (EGTA), and citric acid (CA)] and their dose (5 mM and 10 mM) in enhancing metal accumulation in Solanum americanum Mill. (grown under 24 mg Cd kg-1 soil) through morpho-physiological and metal extraction parameters. Significant variations were observed for most of the studied parameters in response to chelants and their doses. However, ratio of root and shoot length, and plant height stress tolerance index differed non-significantly. The potential of chelants to enhance Cd removal efficiency was in the order - EGTA (7.44%) > EDDS (6.05%) > NTA (4.12%) > CA (2.75%). EGTA and EDDS exhibited dose-dependent behavior for Cd extraction with 10 mM dose being more efficient than 5 mM dose. Structural equation model (SEM) depicted strong positive interaction of metal extraction parameters with chelants (Z-value = 11.61, p = 0.001). This study provides insights into the importance of selecting appropriate dose of biodegradable chelants for Cd extraction, as high chelant concentration might also result in phytotoxicity. In the future, phytoextraction potential of these chelants needs to be examined through field studies under natural environmental conditions.

Preparation and physiochemical properties of enzymatically modified octenyl succinate starch.

The high viscosity and low solubility of octenyl succinate starch (OSAS) in water often lead to low reaction efficiency and uneven distribution of OSA groups, which can be solved by subjecting OSA starch to enzymatic digestion. Waxy corn starch is used to produce OSAS. The molecular weight of enzymolysis modified octenyl succinate starches (E-OSAS) decreased with the addition of enzyme, and the substitution of enzymatically digested OSAS was larger than that of OSAS. As the addition of pullulanase increased, the substitution of E-OSAS tended to increase and the apparent viscosity decreased significantly. The smaller its particle size and polydispersity index (PDI), the larger the absolute value of the zeta potential. E40 -OSAS with the smallest particle size and best homogeneity and stability had the smallest weight average molecular weight (1.38 × 106  g/mol), the smallest number average molecular weight (1.37 × 105  g/mol), and the largest degree of substitution of 0.019. The E-OSAS has not been investigated deeply enough, and the enzymatic treatment by pullulanase is not much studied, so this study is of great importance to provide some basis for the research of new microcapsules. PRACTICAL APPLICATION: This work aims to provide wall materials with lower viscosity and better encapsulation properties for the food industry. Waxy corns starch is used to manufacture OSAS. This wall material is a partly biodegradable material that is hydrophilic on the outside and hydrophobic on the inside, and its preparation process is in line with the concept of green chemistry.

Four-Octyl Itaconate Protects Chondrocytes against H2O2-Induced Oxidative Injury and Attenuates Osteoarthritis Progression by Activating Nrf2 Signaling.

Nrf2 is a critical regulator of the antioxidant defense systems in cellular protection. Emerging evidence has shown that four-octyl itaconate (OI) activates Nrf2 cascade. In this study, the chondroprotective effects of OI on H2O2-stimulated chondrocytes and DMM-induced osteoarthritis (OA) progression were investigated. In primary murine chondrocytes, OI interrupted the binding of Keap1 and Nrf2, leading to accumulation and nuclear translocation of Nrf2 protein, as well as transcription and expression of Nrf2-dependent genes, such as HO-1, NQO1, and GCLC. Furthermore, OI inhibited cell death and apoptosis, as well as H2O2-stimulated ROS generation, lipid peroxidation, superoxide accumulation, and mitochondrial depolarization in chondrocytes, which were abolished by the silence or depletion of Nrf2. In addition, in vivo experiments revealed the therapeutic effects of OI on OA progression in a DMM mouse model. Collectively, these results suggested that OI might serve as a potential treatment for OA progression.

Inactive pseudoenzyme subunits in heterotetrameric BbsCD, a novel short-chain alcohol dehydrogenase involved in anaerobic toluene degradation.

Anaerobic toluene degradation proceeds by fumarate addition to produce (R)-benzylsuccinate as first intermediate, which is further degraded via ß-oxidation by five enzymes encoded in the conserved bbs operon. This study characterizes two enzymes of this pathway, (E)-benzylidenesuccinyl-CoA hydratase (BbsH), and (S,R)-2-(α-hydroxybenzyl)succinyl-CoA dehydrogenase (BbsCD) from Thauera aromatica. BbsH, a member of the enoyl-CoA hydratase family, converts (E)-benzylidenesuccinyl-CoA to 2-(α-hydroxybenzyl)succinyl-CoA and was subsequently used in a coupled enzyme assay with BbsCD, which belongs to the short-chain dehydrogenases/reductase (SDR) family. The BbsCD crystal structure shows a C2-symmetric heterotetramer consisting of BbsC2 and BbsD2 dimers. BbsD subunits are catalytically active and capable of binding NAD+ and substrate, whereas BbsC subunits represent built-in pseudoenzyme moieties lacking all motifs of the SDR family required for substrate binding or catalysis. Molecular modeling studies predict that the active site of BbsD is specific for conversion of the (S,R)-diastereomer of 2-(α-hydroxybenzyl)succinyl-CoA to (S)-2-benzoylsuccinyl-CoA by hydride transfer to the re-face of nicotinamide adenine dinucleotide (NAD)+ . Furthermore, BbsC subunits are not engaged in substrate binding and merely serve as scaffold for the BbsD dimer. BbsCD represents a novel clade of related enzymes within the SDR family, which adopt a heterotetrameric architecture and catalyze the ß-oxidation of aromatic succinate adducts.

Ag/LDH-itaconic acid-gellan gam nanocomposites: Facile and green synthesis, characterization, and excellent catalytic reduction of 4-nitrophenol.

The catalytic reduction reaction is one of the most commonly used solutions to convert high-risk contaminants into safe or low-risk materials. Today, with the increasing water pollution, the urgent need for efficient and effective catalysts is felt more than ever. For this purpose, for the first time, a green catalyst composed of silver nanoparticles anchored on itaconic acid-modified Ca-Al layered double hydroxide/gellan gum nanocomposite (Ag/LDH-ITA-GG NC) was prepared from a green approach without the use of any toxic organic solvents. To gain an in-depth insight into the physicochemical properties of the catalyst, different techniques including nitrogen adsorption-desorption isotherms, FESEM/mapping, FTIR, TGA, and XRD were used. The catalytic performance of the Ag/LDH-ITA-GG NC toward 4-nitrophenol reduction by NaBH4 was investigated. The calculated values of the apparent rate constant for this reaction are 0.2142 min-1 (for 1.0 mg of the catalyst), 0.2375 min-1 (for 3.0 mg of the catalyst), and 0.2550 min-1 (for 5.0 mg of the catalyst), indicating that the catalytic conversion of 4-nitrophenol to 4-aminophenol on the Ag/LDH-ITA-GG NC catalyst follows the pseudo-first-order kinetics and is comparable to the previous findings in the literature. The results of this study indicated that Ag/LDH-ITA-GG NC can potentially be utilized as an auspicious high efficient green catalyst for the reduction of pollutants like 4-nitrophenol.

Evaluation of gum ghatti-g-poly(itaconic acid) magnetite nanocomposite as an adsorbent material for water purification.

A porous hydrogel nanocomposite has been made by grafting poly(itaconic acid) on the polysaccharide, gum ghatti and by embedding magnetite nanoparticles in the copolymer gel matrix. This novel functional material Ggh-g-PIA/Fe3O4 was characterized by FTIR, TGA, SEM, EDS, XRD, BET, Zeta potential measurements and VSM techniques. The nanocomposite possesses mesoporous structure with high surface area and exhibits super-paramagnetic behavior due to the presence of magnetite nanoparticles. The hydrogel nanocomposite was evaluated as an adsorbent material for removal of dyes and divalent metal ions. Significant adsorption capacities of 410.2, 387.6, 416.5 and 401.4 mg g-1 towards methylene blue, rhodamine 6G, Cu (II) and Hg (II) ions respectively were observed. The adsorption isotherms were well described by the Freundlich isotherm model and kinetic studies demonstrated the adsorption to be a pseudo second order kinetic process. Intraparticle diffusion model suggested adsorption to occur by a multi-step diffusion process. Thermodynamic studies indicated a spontaneous and endothermic adsorption. Further, the desorption study indicated the possibility of successful regeneration of the adsorbent. A high removal efficiency, recyclability, convenient recovery after use due to the magnetic nature makes this polysaccharide based nanocomposite an environment friendly adsorbent material for water purification.