Presence Of Mn Research Articles

Odd-Numbered Agaro-Oligosaccharides Produced by α-Neoagaro-Oligosaccharide Hydrolase Exert Antioxidant Activity in Human Dermal Fibroblasts

Agarases produce agar oligosaccharides with various structures exhibiting diverse physiological activities. α-Neoagaro-oligosaccharide hydrolase (α-NAOSH) specifically cleaves even-numbered neoagaro-oligosaccharides, producing 3,6-anhydro-l-galactose (l-AHG) and odd-numbered agaro-oligosaccharides (OAOSs). In this study, α-NAOSH from the agar-degrading marine bacterium Gilvimarinus agarilyticus JEA5 (Gaa117) was purified and characterized using an E. coli expression system to produce OAOSs and determine their bioactivity. Recombinant Gaa117 (rGaa117) showed maximum activity at pH 6.0 and 35 °C. rGaa117 retained >80% of its initial activity after 120 min at 30 °C. The activity was enhanced in the presence of Mn2+. Km, Vmax, and Kcat/Km values of the enzyme were 22.64 mM, 246.3 U/mg, and 15 s−1/mM, respectively. rGaa117 hydrolyzed neoagarobiose, neoagarotetraose, and neoagarohexaose, producing OAOSs that commonly contained l-AHG. Neoagarobiose and neoagarotetraose mixtures, designated NAO24, and mixtures of l-AHG and agarotriose, designated AO13, were obtained using recombinant rGaa16B (β-agarase) and rGaa117, respectively, and their antioxidant activities were compared. AO13 showed higher hydrogen peroxide-scavenging activity than NAO24 in human dermal fibroblasts in vitro because of structural differences: AOSs have d-galactose at the non-reducing end, whereas NAOSs have l-AHG. In conclusion, OAOSs exhibited high ROS-scavenging activity in H2O2-induced human dermal fibroblasts. They may be applicable in cosmetics and pharmaceuticals for prevention of skin aging.

Molecular insights and functional analysis of isocitrate dehydrogenase in two gram-negative pathogenic bacteria.

Klebsiella pneumoniae and Legionella pneumophila are common Gram-negative bacteria that can cause lung infections. The multidrug resistance of K. pneumoniae presents a significant challenge for treatment. This study focuses on isocitrate dehydrogenase (IDH), a key enzyme in the oxidative metabolic pathway of these two bacteria. KpIDH and LpIDH were successfully overexpressed and purified, and their biochemical characteristics were thoroughly investigated. The study revealed that KpIDH and LpIDH are homodimeric enzymes with molecular weights of approximately 70kDa. They are completely dependent on the coenzyme NADP+ and are inactive towards NAD+. KpIDH exhibits the highest catalytic activity at pH 8.0 in the presence of Mn2+ and at pH 7.8 in the presence of Mg2+. Its optimal catalytic performance is achieved with both ions at 55°C. LpIDH exhibited its highest activity at pH 7.8 in the presence of Mn2+ and Mg2+, respectively, and exhibits optimal catalytic performance at 45°C. Heat inactivation studies showed that KpIDH and LpIDH retained over 80% of their activity after being exposed to 45°C for 20min. Furthermore, we successfully altered the coenzyme specificity of KpIDH and LpIDH from NADP+ to NAD+ by replacing four key amino acid residues. This study provides a comprehensive biochemical characterization of two multidrug-resistant bacterial IDHs commonly found in hospital environments. It enhances our understanding of the characteristics of pathogenic bacteria and serves as a reference for developing new therapeutic strategies.

Functionalized Polyisobutylene and Polyisobutylene‐Based Block Copolymers by Mechanistic Transformation from Cationic to Radical Process

AbstractThe strategy for the preparation of polyisobutylene‐based block copolymers via mechanistic transformation from cationic to radical polymerization is reported. This strategy involves the synthesis of 2‐bromo‐2‐methylpropanoyl‐terminated difunctional polyisobutylene macroinitiator (BiBB‐PIB‐BiBB) via consecutive cationic polymerization, in situ preparation of hydroxyl‐terminated polyisobutylene and its acylation by 2‐bromo‐2‐methylpropanoyl bromide. The Mn2(CO)10−triggered photo‐induced radical polymerization of styrene in bulk using this macroinitiator leads to the formation of multiblock copolymer, while predominantly triblock copolymer is generated during the polymerization of methyl methacrylate. The possibility to functionalize the polyisobutylene by pyrene via photo‐induced radical addition of 1‐bromomethyl pyrene in the presence of Mn2(CO)10 is also demonstrated in this work.

Enhanced saccharification levels of corn starch using as a strategy a novel amylolytic complex (AmyHb) from the thermophilic fungus Humicola brevis var. thermoidea in association with commercial enzyme.

Amylases represent a versatile group of catalysts that are used for the saccharification of starch because they can hydrolyze the glycosidic bonds of starch molecules to release glucose, maltose, and short-chain oligosaccharides. The amylolytic complex of the thermophilic filamentous fungus Humicola brevis var. thermoidea (AmyHb) was produced, biochemically characterized, and compared with the commercial amylase Termamyl. In addition, the biotechnological application of AmyHb in starch saccharification was investigated. The highest production was achieved using a wheat bran medium at 50°C for 5-6days in solid-state fermentation (849.6 ± 18.2U·g-1) without the addition of inducers. Optimum amylolytic activity occurred at pH 5.0 at 60°C, and stability was maintained between pH 5.0 and 6.0, with thermal stability at 50-60°C, especially in the presence of Ca2+. These results were superior to those found with Termamyl. Both enzymes were strongly inhibited by Hg2+, Cu2+, and Ag+; however, AmyHb displayed increased activity in the presence of Mn2+ and Na+. In addition, AmyHb showed greater tolerance to a wide range of ethanol concentrations. AmyHb appears to be a complex consisting of glucoamylase and α-amylase, based on its substrate specificity and TLC. The hydrolysis tests on cornstarch flour showed that the cocktail of AmyHb50% + Termamyl50% significantly increased the release of glucose and total reducing sugars (36.6%) when compared to the enzymes alone. AmyHb exhibited promising physicochemical properties and good performance with commercial amylase; therefore, this complex is a biotechnological alternative candidate for the bioprocessing of starch sources.

Investigation into the impact of Mn2+ and its interaction with calcite in the flotation of rhodochrosite

The unavoidable Mn2+ ions in pulp were considered in the flotation of rhodochrosite, and its effect and relative interaction mechanism on the floatability of calcite served as a typical gangue mineral were investigated through microflotation tests, zeta potential measurements, SEM-EDS detection, solution chemistry calculation, adsorption experiments, FTIR and XPS analyses. There exhibited a good separation performance of rhodochrosite against calcite with OHA collector, but in the presence of Mn2+ ions, the floatability of calcite was closed to rhodochrosite within a pH of 8.0–10.0, which resulted in the separation difficulty between them. As evidenced, the surface of calcite could be modified by Mn2+ ions, its isoelectric point shifted positively from 8.91 to 10.06, and Mn2+ species detected on calcite surfaces were in close proximity to rhodochrosite. It indicated that MnCO3 precipitates were generated on the surface of calcite. After modified by Mn2+, the calcite surface became more active and obviously increased the adsorption amount of OHA. It was verified from zeta potential and XPS analyses that Mn species on the surface of calcite were active sites for OHA adsorption, likely the hydroxamate group of OHA collector chelated with Mn species to form hydrophobic compounds. As a result, Mn2+ ions in pulp would reduce the flotation selectivity of rhodochrosite from calcite, thus it is necessary to eliminate the disadvantage of Mn2+ for strengthening flotation.

Ratiometric fluorescence probe based on carbon dots and p-phenylenediamine-derived nanoparticles for the sensitive detection of manganese ions.

A ratiometric fluorescence probe based on carbon quantum dots with 420nm emission (bCQDs) and a p-phenylenediamine-derived fluorescence probe with 550nm emission (yprobe) is constructed for the detection of Mn2+. The presence of Mn2+ results in the enhanced absorption band at 400nm of yprobe, and the fluorescence of yprobe is significantly enhanced based on the chelation-enhanced fluorescence mechanism. The fluorescence of bCQDs is then quenched based on the inner filtration effect. The ratio (I550/I420) linearly increases with the increase of Mn2+ concentration within 2.00 × 10-7-1.50 × 10-6M, and the limit of detection is 1.76 × 10-9M. Given the fluorescence color changing from blue to yellow, the visual sensing of Mn2+ is feasible based on bCQDs/yprobe coupled with RGB value analysis. The practicability of the proposed method has been verified in tap water, lake water, and sparkling water beverage, indicating that bCQDs/yprobe has promising application in Mn2+ monitoring.

Effect of Mn2+ on RO membrane organic fouling: Insights into the complexation and interfacial interaction

RO process is commonly used to treat and reuse manganese-containing industrial wastewater. Nevertheless, even after undergoing multi-stage treatment, the secondary biochemical effluent still exhibits a high concentration of Mn2+ coupled with organics entering the RO system, leading to membrane fouling. In this work, we systematically analyze the RO membrane organic fouling processes and mechanisms, considering the coexistence of Mn2+ with humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA) and their mixtures (HBS). The impact of Mn2+ on membrane fouling was HBS > SA > HA > BSA, controlling polysaccharide pollutant concentrations should be a priority for mitigating membrane fouling. In the presence of Mn2+ with HA, SA, or HBS, membrane fouling is primarily attributed to the complexation of organics and Mn2+ and the facilitation of interfacial interaction energy. RO membrane BSA fouling was not directly affected by Mn2+, the addition of Mn2+ induced a salting-out effect, leading to the deposition of BSA in a single molecular on the membrane. Simultaneously, adhesion energy hinders the deposition of BSA on the membrane, resulting in milder membrane fouling. This study provided the theoretical basis and suggestions for RO membrane organic fouling control in the presence of Mn2+.

Three-dimensional critical behavior in Mn1.5Cr1.5O4: A material for magnetocaloric energy conversion

The multifunctional and tunable properties of spinel oxides bring their applicability in various sustainable applications. In this line, the current work systematically examines the magnetic and magnetocaloric properties of Mn1.5Cr1.5O4. The presence of Mn2+ ions in the tetragonal site leads to complex magnetic interactions. It undergoes a ferrimagnetic to paramagnetic transition at 58 K. The critical exponents obtained from the modified Arrot plot, β = 0.346 and γ = 1.051, suggests that the system does not fall into any of the universal class. The exchange interaction strength reveals the coexistence of short- and long-range ordering. Mn1.5Cr1.5O4 displays a magnetic entropy change of -4.11 J kg−1K−1 and a relative cooling power of 70.68 J kg−1 at 58 K for a field change of 70 kOe. Thus, the major results of the study recommend the applicability of Mn1.5Cr1.5O4 towards gas (fuel, H2) liquefaction based on solid-state active magnetic refrigeration technology.

Marine Bacillus haynesii chitinase: Purification, characterization and antifungal potential for sustainable chitin bioconversion

The development of chitinase tailored for the bioconversion of chitin to chitin oligosaccharides has attracted significant attention due to its potential to alleviate environmental pollution associated with chemical conversion processes. In this present investigation, we purified extracellular chitinase derived from marine Bacillus haynesii to homogeneity and subsequently characterized it. The molecular weight of BhChi was approximately 35 kDa. BhChi displayed its peak catalytic activity at pH 6.0, with an optimal temperature of 37 °C. It exhibited stability across a pH range of 6.0–9.0. In addition, BhChi showed activation in the presence of Mn2+ with the improved activity of 105 U mL−1. Ca2+ and Fe2+ metal ions did not have any significant impact on enzyme activity. Under the optimized enzymatic conditions, there was a notable enhancement in catalytic activity on colloidal chitin with Km of 0.01 mg mL−1 and Vmax of 5.75 mmol min−1. Kcat and catalytic efficiency were measured at 1.91 s−1 and 191 mL mg−1 s−1, respectively. The product profiling of BhChi using thin layer chromatography and Mass spectrometric techniques hinted an exochitinase mode of action with chitobiose and N-Acetyl glucosamine as the products. This study represents the first report on an exochitinase from Bacillus haynesii. Furthermore, the chitinase showcased promising antifungal properties against key pathogens, Fusarium oxysporum and Penicillium chrysogenum, reinforcing its potential as a potent biocontrol agent.

Characterization of a novel inulosucrase from Lactiplantibacillus plantarum

Fructansucrases produce fructans by polymerizing the fructose moiety released from sucrose. Here, we describe the recombinant expression and characterization of a unique fructansucrase from Lactiplantibacillus plantarum DKL3 that showed low sequence similarity with previously characterized fructansucrases. The optimum pH and temperature of fructansucrase were found to be 4.0 and 35 °C, respectively. Enzyme activity increased in presence of Ca2+ and distinctly in presence of Mn2+. The enzyme was characterized as an inulosucrase (LpInu), based on the production of an inulin-type fructan as assessed byNMR spectroscopy and methylation analysis. In addition to β-2,1-linkages, the inulin contained a few β-2,1,6-linked branchpoints. High-performance size exclusion chromatography with refractive index detection (HPSEC-RI) revealed the production of inulin with a lower molecular weight compared to other characterized bacterial inulin. LpInu and its inulin product represent novel candidates to be explored for possible food and biomedical applications.

Immobilized Dipeptidase in Manganese Ion-Loaded Polyethylenimine-Induced Calcium Phosphate Nanocrystals for Carnosine Synthesis.

Carnosine is a natural bioactive dipeptide with important physiological functions widely used in food and medicine. Dipeptidase (PepD) from Serratia marcescens can catalyze the reverse hydrolytic reaction of β-alanine with l-histidine to synthesize carnosine in the presence of Mn2+. However, it remains challenging to practice carnosine biosynthesis due to the low activity and high cost of the enzyme. Therefore, the development of biocatalysts with high activity and stability is of significance for carnosine synthesis. Here, we proposed to chelate Mn2+ to polyethylenimine (PEI) that induced rapid formation of calcium phosphate nanocrystals (CaP), and Mn-PEI@CaP was used for PepD immobilization via electrostatic interaction. Mn-PEI@CaP as the carrier enhanced the stability of the immobilized enzyme. Moreover, Mn2+ loaded in the carrier acted as an in situ activator of the immobilized PepD for facilitating the biocatalytic process of carnosine synthesis. The as-prepared immobilized enzyme (PepD-Mn-PEI@CaP) kept similar activity with free PepD plus Mn2+ (activity recovery, 102.5%), while exhibiting elevated thermal stability and pH tolerance. Moreover, it exhibited about two times faster carnosine synthesis than the free PepD system. PepD-Mn-PEI@CaP retained 86.8% of the original activity after eight cycles of batch catalysis without the addition of free Mn2+ ions during multiple cycles. This work provides a new strategy for the co-immobilization of PepD and Mn2+, which greatly improves the operability of the biocatalysis and demonstrates the potential of the immobilized PepD system for efficient carnosine synthesis.

Production of heat-resistant blastospores by Cordyceps javanica IF-1106 through optimizing metal ions composition

Heat tolerance of fungi is critical for field stability and efficacy of fungal insecticides. Components of the medium, such as carbon source, nitrogen source and metal ions, contribute to the thermotolerance of fungi. In this study, several metal ions were detected to establish their effects on the sporulation and thermotolerance of the blastospores of Cordyceps javanica IF-1106 when cultured in liquid medium. The results showed that metal ions play different roles in sporulation and thermotolerance of the fungi. Mn2+ greatly increased the thermotolerance of the blastospores, and Fe2+ increased the thermotolerance slightly. However, both has no or negative effects on sporulation of the fungi. In the case of Cu2+ and Fe3+, sporulation yield and thermotolerance of the blastospores increased significantly. In addition, intracellular trehalose and mannitol involved in thermotolerance of fungi were extracted and then quantified by ion chromatography. We find that the trehalose and mannitol are higher in the presence of Mn2+, implying that Mn2+ could adjust the intracellular trehalose and mannitol level confers the blastospores with higher tolerance to thermal stress. Further, Response Surface Methodology (RSM) was applied to screen the optimal composition of metal ions. When the formula was MnSO4·H2O 8 mg/L, CuSO4·5H2O 5 mg/L, FeSO4·7H2O 11 mg/L, FeCl3·6H2O 8 mg/L, maximum sporulation yield and GT50 were obtained. Lastly, the virulence of the blastospores to Acyrthosiphon pisum was validated, a higher virulence is achieved with decreased LT50 (2 d) and LC50 (2.37 × 104 blastospores mL−1). In conclusion, thermotolerant blastospores of C. javanica IF-1106 and higher sporulation yield could be achieved by optimizing the metal ions composition, which helps to determine the formula for larger scale fermentation process.

Tumor microenvironment activated mussel-inspired hollow mesoporous nanotheranostic for enhanced synergistic photodynamic/chemodynamic therapy

Anti-tumor therapies reliant on reactive oxygen species (ROS) as primary therapeutic agents face challenges due to a limited oxygen substrate. Photodynamic therapy (PDT) is particularly hindered by inherent hypoxia, while chemodynamic therapy (CDT) encounters obstacles from insufficient endogenous hydrogen peroxide (H2O2) levels. In this study, we engineered biodegradable tumor microenvironment (TME)-activated hollow mesoporous MnO2-based nanotheranostic agents, designated as HAMnO2A. This construct entails loading artemisinin (ART) into the cavity and surface modification with a mussel-inspired polymer ligand, namely hyaluronic acid-linked poly(ethylene glycol)-diethylenetriamine-conjugated (3,4-dihydroxyphenyl) acetic acid, and the photosensitizer Chlorin e6 (mPEG-HA-Dien-(Dhpa/Ce6)), facilitating dual-modal imaging-guided PDT/CDT synergistic therapy. In vitro experimentation revealed that HAMnO2A exhibited ideal physiological stability and enhanced cellular uptake capability via CD44-mediated endocytosis. Additionally, it was demonstrated that accelerated endo-lysosomal escape through the pH-dependent protonation of Dien. Within the acidic and highly glutathione (GSH)-rich TME, the active component of HAMnO2A, MnO2, underwent decomposition, liberating oxygen and releasing both Mn2+ and ART. This process alleviates hypoxia within the tumor region and initiates a Fenton-like reaction through the combination of ART and Mn2+, thereby enhancing the effectiveness of PDT and CDT by generating increased singlet oxygen (1O2) and hydroxyl radicals (•OH). Moreover, the presence of Mn2+ ions enabled the activation of T1-weighted magnetic resonance imaging. In vivo findings further validated that HAMnO2A displayed meaningful tumor-targeting capabilities, prolonged circulation time in the bloodstream, and outstanding efficacy in restraining tumor growth while inducing minimal damage to normal tissues. Hence, this nanoplatform serves as an efficient all-in-one solution by facilitating the integration of multiple functions, ultimately enhancing the effectiveness of tumor theranostics.

Biochemical Characterization of a Novel Thermostable 1,4-α-Glucoamylase from Aspergillus brasiliensis Strain Isolated in the Brazilian Atlantic Forest.

Glucoamylases are exo-enzymes that cleave the ends of the starch chain, releasing glucose units. In the current work, we described a novel 1,4-α-glucoamylase from an A. brasiliensis strain isolated from an environmental sample. The purified glucoamylase, GlaAb, has a molecular mass of 69kDa and showed a starch binding domain. GlaAb showed a similar sequence to other fungal glucoamylases, and the molecular 3D model analysis of GlaAb suggests an overall structure as described in the literature, except by elongation in the loop connecting the 4th and 5th α-helices. The enzyme showed activity over a wide range of pH and temperature, with maximum activity at pH 4.5 and 60°C. GlaAb was stable at 50°C for 7h, maintaining 67% residual activity, and it was not inhibited by glucose up to 0.1M. The glucoamylase was 65% more active in the presence of Mn2+ and showed a Km of 2.21mgmL-1, Vmax of 155 U mg-1, Kcat 179s-1, and Kcat/Km 81.06mgmL-1s-1 using potato starch as substrate. The results obtained are promising and provide the basis for the development of applications of GlaAb in the industrial process.

Biochemical characterization and mutational analysis of the NurA protein from the hyperthermophilic euryarchaeon Thermococcus barophilus Ch5

Archaeal NurA protein plays a key role in producing 3′-single stranded DNA used for homologous recombination repair, together with HerA, Mre11, and Rad50. Herein, we describe biochemical characteristics and roles of key amino acid residues of the NurA protein from the hyperthermophilic euryarchaeon Thermococcus barophilus Ch5 (Tba-NurA). Tba-NurA possesses 5′–3′ exonuclease activity for degrading DNA, displaying maximum efficiency at 45 °C–65 °C and at pH 8.0 in the presence of Mn2+. The thermostable Tba-NurA also possesses endonuclease activity capable of nicking plasmid DNA and circular ssDNA. Mutational data demonstrate that residue D49 of Tba-NurA is essential for exonuclease activity and is involved in binding ssDNA since the D49A mutant lacked exonuclease activity and reduced ssDNA binding. The R96A and R129A mutants had no detectable dsDNA binding, suggesting that residues R96 and R129 are important for binding dsDNA. The abolished degradation activity and reduced dsDNA binding of the D120A mutant suggest that residue D120 is essential for degradation activity and dsDNA binding. Additionally, residues Y392 and H400 are important for exonuclease activity since these mutations resulted in exonuclease activity loss. To our knowledge, it is the first report on biochemical characterization and mutational analysis of the NurA protein from Thermococcus.

Effects of transition-metal ions on the reduction of N-nitrosodimethylamine in water by zinc

The influencing factors, products and mechanism of N-nitrosodimethylamine (NDMA) reduction by zinc (Zn) in the presence of transition-metal ions (Mn2+, Co2+ and Ni2+), were investigated. The NDMA removal by Zn was significantly improved by them, and the promoting effect of Co2+ and Ni2+ were better than Mn2+. With the decrease of pH values and dissolved oxygen concentrations, the removals of NDMA were enhanced in all reaction systems. NDMA was mainly reduced to unsymmetrical dimethylhydrazine (UDMH) in Zn and Zn/Mn2+ systems. It was mainly reduced to dimethylamine (DMA) and ammonium (NH4+) in Zn/Co2+ and Zn/Ni2+ systems. There were undetected products in all reaction systems. Catalytic hydrogenation was the main mechanism, and active hydrogen atom was the main active species. The presence of Mn2+, Co2+ and Ni2+ promoted the corrosion of Zn and changed the surface morphology of Zn. The formation of type I film on Zn surface was promoted in the presence of Co2+ and Ni2+, which was conducive to the continuous corrosion of Zn and hydrogen generation. While type II film which would inhibit the corrosion of Zn formed on Zn surface in the presence of Mn2+. MnO2, Co3O4 and Ni(OH)2 were formed in Zn/Mn2+, Zn/Co2+ and Zn/Ni2+ systems, respectively. They would facilitate more generation of active hydrogen atoms.

Reductive sequestration of Cr (VI) by phosphorylated nanoscale zerovalent iron

The cracked phosphorylated nanoscale zerovalent iron (p-nZVI) has a strong electron selectivity towards the reductive removal of many heavy metal ions in waters. However, the unintended environmental risk after interactions with impurities or wastewater are not involved. Therefore, in this study, the phosphate group was successfully adsorbed into p-nZVI, and the cracked p-nZVI was successfully prepared with an optimal P/Fe ratio of 0.5%. The dosages of p-nZVI and temperatures were positively correlated with the removal rates. The removal process of Cr(VI) was more suitable by the Langmuir isothermal model（R2 > 0.99). The process of Cr (VI) (10, 20 and 40 mg/L) removal more fitted the pseudo first-order reaction model, while the process of Cr (VI) (60, 80 mg/L) removal more fitted the pseudo second-order reaction model. The Cr (VI) removal rates gradually decreased when the pH was increased. Dissolved oxygen slowed nanoiron reaction rates. The order of inhibition on the reactivity towards Cr(VI) was SiO32− > SO42− > PO43− > NO3− > HCO3−.The facilitation followed the order of Cd2+>Cu2+>Mg2+>Mn2+>Ca2+. Ca2+ showed an inhibitory effect, but all other cations showed different degrees of facilitation. The promotion effect is relatively similar in presence of Mn2+ or Mg2+. HA had a significant inhibitory effect. Environmental friendly p-nZVI had a good effect in simulated groundwater, seawater, river water and secondary effluent of the urban sewage treatment plant. The main pathway to remove Cr (VI) was in situ reduction by p-nZVI. The improved adsorption and reduction effect of p-nZVI on heavy metal ions in water was due to the structural change and the phosphate group.

Mn2+-induced structural flexibility enhances the entire catalytic cycle and the cleavage of mismatches in prokaryotic argonaute proteins.

Prokaryotic Argonaute (pAgo) proteins, a class of DNA/RNA-guided programmable endonucleases, have been extensively utilized in nucleic acid-based biosensors. The specific binding and cleavage of nucleic acids by pAgo proteins, which are crucial processes for their applications, are dependent on the presence of Mn2+ bound in the pockets, as verified through X-ray crystallography. However, a comprehensive understanding of how dissociated Mn2+ in the solvent affects the catalytic cycle, and its underlying regulatory role in this structure-function relationship, remains underdetermined. By combining experimental and computational methods, this study reveals that unbound Mn2+ in solution enhances the flexibility of diverse pAgo proteins. This increase in flexibility through decreasing the number of hydrogen bonds, induced by Mn2+, leads to higher affinity for substrates, thus facilitating cleavage. More importantly, Mn2+-induced structural flexibility increases the mismatch tolerance between guide-target pairs by increasing the conformational states, thereby enhancing the cleavage of mismatches. Further simulations indicate that the enhanced flexibility in linkers triggers conformational changes in the PAZ domain for recognizing various lengths of nucleic acids. Additionally, Mn2+-induced dynamic alterations of the protein cause a conformational shift in the N domain and catalytic sites towards their functional form, resulting in a decreased energy penalty for target release and cleavage. These findings demonstrate that the dynamic conformations of pAgo proteins, resulting from the presence of the unbound Mn2+ in solution, significantly promote the catalytic cycle of endonucleases and the tolerance of cleavage to mismatches. This flexibility enhancement mechanism serves as a general strategy employed by Ago proteins from diverse prokaryotes to accomplish their catalytic functions and provide useful information for Ago-based precise molecular diagnostics.

Production and characterization of an extracellular Mn2+ activated ß-D-fructofuranosidase from Aspergillus labruscus ITAL 28.255 with transfructosylating activity

Fungal ß-D-fructofuranosidases present biotechnological potential for use in food, beverage, and pharmaceutical industries. In light of this, the best culture conditions for the production of ß-D-fructofuranosidase by Aspergillus labruscus ITAL 28.255 were obtained with an M-5 medium maintained at 30°C and 100 rpm for 120 h. The use of a mixture of rye flour and sucrose (1.5:0.5, m/m) and 2% yeast extract as the carbon and nitrogen sources, respectively, proportioned the best production of the enzyme. The extracellular ß-D-fructofuranosidase was purified 17-fold, with 9% recovery, and was characterized as a glycoprotein with 67 kDa (SDS-PAGE) and 40.7% carbohydrate content. The best temperature and pH for enzyme activity were 55°C and 5.5, respectively. The enzyme activity was maintained around 75% at 40 and 50°C for 1 h, with a half-life of 5 min at 70°C. The hydrolytic activity was increased in the presence of Mn2+. The Vmax and KM were 4.74 mM and 140.3 U/mg using sucrose; while, in the presence of Mn2+, the KM was 2.17 mM and the Vmax was 292.9 U/mg. The enzyme performed the transfructosylation reaction, enabling the production of FOS, mainly 1-kestose. This is the first report on the potential of A. labruscus to produce β-fructofuranosidase with transfructosylation activity.

Study of Effect of Calcinations Temperature on Structural and Magnetic Properties of MgMnO2-λ Nanocrystallines

The researchers are interested in studying nanoparticulates as a result of their specific Physical, Chemical and Biological traits. These nanoparticulates are additionally applicable to a wide array of industries, which includes solar cell coatings, transparent sunscreen, self-cleaning windows and scratch-resistant eyewear. Nanoparticulates have significant properties at nano scale because of high surface to volume ratio. The advanced properties of these nanoparticulates increase the interest of today’s researchers and scientist. The metal oxide nanoparticulates of MgO have enhanced properties in the field of industries, defense and medical world. Metal oxide nanoparticulates like MgO and MnO2 are currently the subject of substantial research because of their well-known antibacterial activity against several kinds of bacteria and their advanced uses in the field of storage for hydrogen gas. In the current work, pure MgO and Mn (10%) doped MgO nanoparticulates were prepared via a microwave irradiated chemical co precipitation process . The samples were further calcined at 200o , 400o , 600o and 800o Celsius for two hours constant heating. XRD, FTIR, FESEM, and VSM examinations have been conducted on the calcined materials. The XRD results revels that nanoparticulates were formed with FCC crystal structures and no phase transformation occurred with addition of Mn dopant concentration in MgO. However, the presence of Mn2+ ion in place of Mg2+ ion were recognized via broadening of peak resulted by micro strain lattice. The grain size of nanoparticulates were calculated by use of Debye Scherer estimation and crystalline size 29.47nm, 27.68nm, 36.80nm and 46.14 nm pattern shows that crystallite size increases with increase in calcinations temperature. The IR sharp peaks inspected at 409cm-1 (pure MgO/800OC), 395cm-1 (pure MgO/600oC), 402cm-1 (pure MgO/400oC) and 409cm-1 (pure MgO/200oC) respectively and for Mn doped MgO nanoparticulates sharp peaks inspected at 450 cm-1 (Mn10%/600OC),400cm1 (Mn20%/600oC) respectively and were attributed by O-Mn-O molecule vibration were confirmed the XRD analyses that is Mn2+ ion exist at Mg2+ lattice site. The electron microscopic image of sample shows that cauliflower leaf like structure was seen with size nanometer in scale. The VSM characteristic of sample concluded that saturation magnetization gradually decreases with increase of calcinations temperature and all substances were ferromagnetic in behavior. The materials have recommended property in applications as electromagnet formation.