Structure and functional properties of the cold-adapted catalase from Acinetobacter sp. Ver3 native to the Atacama plateau in northern Argentina

2021 ◽  
Vol 77 (3) ◽  
pp. 369-379
Author(s):  
Mariana G. Sartorio ◽  
Néstor Cortez ◽  
Javier M. González
Keyword(s):  
Oxidative Damage ◽  
Specific Activity ◽  
Three Dimensional ◽  
Alkaline Media ◽  
Large Temperature ◽  
Crystallographic Structure ◽  
Methionine Residue ◽  
Structural Differences ◽  
Extreme Uv ◽  
Ph Range

Heme catalases remove hydrogen peroxide by catalyzing its dismutation into water and molecular oxygen, thereby protecting the cell from oxidative damage. The Atacama plateau in northern Argentina, located 4000 m above sea level, is a desert area characterized by extreme UV radiation, high salinity and a large temperature variation between day and night. Here, the heme catalase KatE1 from an Atacama Acinetobacter sp. isolate was cloned, expressed and purified, with the aim of investigating its extremophilic properties. Kinetic and stability assays indicate that KatE1 is maximally active at 50°C in alkaline media, with a nearly unchanged specific activity between 0°C and 40°C in the pH range 5.5–11.0. In addition, its three-dimensional crystallographic structure was solved, revealing minimal structural differences compared with its mesophilic and thermophilic analogues, except for a conserved methionine residue on the distal heme side, which is proposed to comprise a molecular adaptation to oxidative damage.

scholarly journals Fusion of an Oligopeptide to the N Terminus of an Alkaline α-Amylase from Alkalimonas amylolytica Simultaneously Improves the Enzyme's Catalytic Efficiency, Thermal Stability, and Resistance to Oxidation

2013 ◽  
Vol 79 (9) ◽  
pp. 3049-3058 ◽  
Author(s):  
Haiquan Yang ◽  
Xinyao Lu ◽  
Long Liu ◽  
Jianghua Li ◽  
Hyun-dong Shin ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Specific Activity ◽  
Structural Characteristics ◽  
Three Dimensional ◽  
Catalytic Efficiency ◽  
Content Type ◽  
Resistance To Oxidation ◽  
Catalytic Constant ◽  
N Terminus ◽  
Ph Range

ABSTRACTIn this study, we constructed and expressed six fusion proteins composed of oligopeptides attached to the N terminus of the alkaline α-amylase (AmyK) fromAlkalimonas amylolytica. The oligopeptides had various effects on the functional and structural characteristics of AmyK. AmyK-p1, the fusion protein containing peptide 1 (AEAEAKAKAEAEAKAK), exhibited improved specific activity, catalytic efficiency, alkaline stability, thermal stability, and oxidative stability compared with AmyK. Compared with AmyK, the specific activity and catalytic constant (kcat) of AmyK-p1 were increased by 4.1-fold and 3.5-fold, respectively. The following properties were also improved in AmyK-p1 compared with AmyK:kcat/Kmincreased from 1.8 liter/(g·min) to 9.7 liter/(g·min), stable pH range was extended from 7.0 to 11.0 to 7.0 to 12.0, optimal temperature increased from 50°C to 55°C, and the half-life at 60°C increased by ∼2-fold. Moreover, AmyK-p1 showed improved resistance to oxidation and retained 54% of its activity after incubation with H2O2, compared with 20% activity retained by AmyK. Finally, AmyK-p1 was more compatible than AmyK with the commercial solid detergents tested. The mechanisms responsible for these changes were analyzed by comparing the three-dimensional (3-D) structural models of AmyK and AmyK-p1. The significantly enhanced catalytic efficiency and stability of AmyK-p1 suggests its potential as a detergent ingredient. In addition, the oligopeptide fusion strategy described here may be useful for improving the catalytic efficiency and stability of other industrial enzymes.

scholarly journals Self-ordered nanospike porous alumina fabricated under a new regime by an anodizing process in alkaline media

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mana Iwai ◽  
Tatsuya Kikuchi ◽  
Ryosuke O. Suzuki
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Porous Alumina ◽  
Three Dimensional ◽  
Alkaline Media ◽  
Alkaline Electrolyte ◽  
Subsequent Formation ◽  
Interpore Distance ◽  
Wide Range ◽  
Ordered Porous

AbstractHigh-aspect ratio ordered nanomaterial arrays exhibit several unique physicochemical and optical properties. Porous anodic aluminum oxide (AAO) is one of the most typical ordered porous structures and can be easily fabricated by applying an electrochemical anodizing process to Al. However, the dimensional and structural controllability of conventional porous AAOs is limited to a narrow range because there are only a few electrolytes that work in this process. Here, we provide a novel anodizing method using an alkaline electrolyte, sodium tetraborate (Na2B4O7), for the fabrication of a high-aspect ratio, self-ordered nanospike porous AAO structure. This self-ordered porous AAO structure possesses a wide range of the interpore distance under a new anodizing regime, and highly ordered porous AAO structures can be fabricated using pre-nanotexturing of Al. The vertical pore walls of porous AAOs have unique nanospikes measuring several tens of nanometers in periodicity, and we demonstrate that AAO can be used as a template for the fabrication of nanomaterials with a large surface area. We also reveal that stable anodizing without the occurrence of oxide burning and the subsequent formation of uniform self-ordered AAO structures can be achieved on complicated three-dimensional substrates.

Numerical Simulation Of A Microchannel For Microelectronic Cooling

2012 ◽  
Author(s):  
Wai Hing Wong ◽  
Normah Mohd. Ghazali
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Large Temperature ◽  
Rectangular Microchannel ◽  
Numerical Work ◽  
Solid Region ◽  
Wall Interaction

Kertas kerja ini membincangkan simulasi berangka ke atas sinki haba saluran mikro dalam penyejukan alatan mikroelektronik. Model Dinamik Bendalir Berkomputer (CFD) tiga dimensi dibina menggunakan pakej komersil, FLUENT, untuk mengkaji fenomenon aliran bendalir dan pemindahan haba konjugat di dalam suatu sinki haba segi empat yang diperbuat daripada silikon. Model ditentusahkan dengan keputusan daripada uji kaji dan pengkajian berangka yang lepas untuk lingkungan nombor Reynolds kurang daripada 400 berdasarkan diameter hidraulik 86 mm. Kajian ini mengambil kira kesan kelikatan bendalir yang bersandaran dengan suhu dan keadaan aliran pra–membangun dari segi hidrodinamik dan haba. Model memberi maklumat tentang taburan suhu dan fluks haba yang terperinci di dalam sinki haba saluran mikro. Kecerunan suhu yang tinggi dicatat pada kawasan pepejal berdekatan dengan sumber. Fluks haba paling tinggi didapati pada dinding tepi saluran mikro diikuti oleh dinding atas dan bawah. Purata pekali pemindahan haba yang lebih tinggi bagi silikon menjadikan ia bahan binaan sinki haba saluran mikro yang lebih baik berbanding dengan kuprum dan aluminium. Peningkatan nisbah aspek saluran mikro yang bersegi empat memberi kecekapan penyejukan yang lebih tinggi kerana kelebaran saluran yang berkurangan memberi kecerunan halaju yang lebih tinggi dalam saluran. Nisbah aspek yang optimum yang diperoleh adalah dalam lingkungan 3.7 – 4.1. Kata kunci: Saluran mikro, CFD, FLUENT, simulasi berangka, penyejukan mikroelektron The paper discusses the numerical simulation of a micro–channel heat sink in microelectronics cooling. A three–dimensional Computational Fluid Dynamics (CFD) model was built using the commercial package, FLUENT, to investigate the conjugate fluid flow and heat transfer phenomena in a silicon–based rectangular microchannel heatsink. The model was validated with past experimental and numerical work for Reynolds numbers less than 400 based on a hydraulic diameter of 86 mm. The investigation was conducted with consideration of temperaturedependent viscosity and developing flow, both hydrodynamically and thermally. The model provided detailed temperature and heat flux distributions in the microchannel heatsink. The results indicate a large temperature gradient in the solid region near the heat source. The highest heat flux is found at the side walls of the microchannel, followed by top wall and bottom wall due to the wall interaction effects. Silicon is proven to be a better microchannel heatsink material compared to copper and aluminum, indicated by a higher average heat transfer. A higher aspect ratio in a rectangular microchannel gives higher cooling capability due to high velocity gradient around the channel when channel width decreases. Optimum aspect ratio obtained is in the range of 3.7 – 4.1. Key words: Microchannel, CFD, FLUENT, numerical simulation, microeletronics cooling

Performance of Core Exit Thermocouple for PWR Accident Management Action in Vessel Top Break LOCA Simulation Experiment at OECD/NEA ROSA Project

2008 ◽  
Author(s):  
Mitsuhiro Suzuki ◽  
Takeshi Takeda ◽  
Hideo Nakamura
Keyword(s):  
Time Delay ◽  
Large Scale ◽  
Simulation Experiment ◽  
Three Dimensional ◽  
Test Facility ◽  
Large Temperature ◽  
Energy Agency ◽  
Pressurized Water ◽  
The Core ◽  
Accident Management

Presented are experiment results of the Large Scale Test Facility (LSTF) conducted at the Japan Atomic Energy Agency (JAEA) with a focus on core exit thermocouple (CET) performance to detect core overheat during a vessel top break loss-of-coolant accident (LOCA) simulation experiment. The CET temperatures are used to start accident management (AM) action to quickly depressurize steam generator (SG) secondary sides in case of core temperature excursion. Test 6-1 is the first test of the OECD/NEA ROSA Project started in 2005, simulating withdraw of a control rod drive mechanism penetration nozzle at the vessel top head. The break size is equivalent to 1.9% cold leg break. The AM action was initiated when CET temperature rose up to 623K. There was no reflux water fallback onto the CETs during the core heat-up period. The core overheat, however, was detected with a time delay of about 230s. In addition, a large temperature discrepancy was observed between the CETs and the hottest core region. This paper clarifies the reasons of time delay and temperature discrepancy between the CETs and heated core during boil-off including three-dimensional steam flows in the core and core exit. The paper discusses applicability of the LSTF CET performance to pressurized water reactor (PWR) conditions and a possibility of alternative indicators for earlier AM action than in Test 6-1 is studied by using symptom-based plant parameters such as a reactor vessel water level detection.

Studies on growth and symbiotic nitrogen fixation of Rhizobium of Vigna radiata under stress conditions

1984 ◽  
Vol 102 (2) ◽  
pp. 399-404
Author(s):  
R. Rai ◽  
V. Prasad
Keyword(s):  
Nitrogen Fixation ◽  
Yeast Extract ◽  
Vigna Radiata ◽  
Symbiotic Nitrogen Fixation ◽  
Alkaline Media ◽  
Growth Behaviour ◽  
Soil Stress ◽  
Wide Ph Range ◽  
Yeast Extract Mannitol ◽  
Ph Range

SummaryOne fast-growing acid-producing Rhizobium strain 995 of Vigna radiata was screened for growth behaviour in acid, saline and alkaline media. It grew well in yeast-extract mannitol broth of wide pH range as well as varying concentrations of NaCl, Na2SO4 and MnCl2. Variation in nodulation and N2-fixation efficiency occurred on different varieties of green gram, while strain characteristics were not affected by soil stress.

A hydrostable and twofold interpenetrating three-dimensional zinc–organic framework with rob topology based on 4,4′-oxydibenzoate and 3,3′-dimethyl-4,4′-bipyridine ligands

2016 ◽  
Vol 72 (5) ◽  
pp. 373-378 ◽  
Author(s):  
Feng-Lan Liang ◽  
De-Yun Ma ◽  
Liang Qin
Keyword(s):  
Title Compound ◽  
Three Dimensional ◽  
New Class ◽  
Pyramidal Geometry ◽  
Potential Applications ◽  
Metal Organic ◽  
Ph Range ◽  
Square Pyramidal Geometry ◽  
Bright Blue Fluorescence ◽  
Bright Blue

Metal–organic frameworks (MOFs) are a new class of porous materials that have received widespread attention due to their potential applications in gas storage and/or separation, catalysis, luminescence, and so on. The title compound, poly[[(μ2-3,3′-dimethyl-4,4′-bipyridine-κ2N:N′)bis(μ4-4,4′-oxydibenzoato-κ4O:O′:O′′:O′′′)dizinc] tetrahydrate], {[Zn2(C14H8O5)2(C12H12N2)]·4H2O}n, has been prepared by the solvothermal assembly of Zn(NO3)2·6H2O, 4,4′-oxydi(benzoic acid) and 3,3′-dimethyl-4,4′-bipyridine. The two ZnIIatoms adopt the same five-coordinated distorted square-pyramidal geometry (i.e.ZnO4N), bonding to four O atoms from four different 4,4′-oxydibenzoate (oba) ligands and one N atom from a 3,3′-dimethyl-4,4′-bipyridine (dmbpy) ligand. The supramolecular secondary building unit (SBU) is a paddle-wheel [Zn2(COO)4] unit and these units are linked by oba ligands within the layer to form a two-dimensional net parallel to thebaxis, with the dmbpy ligands pointing alternately up and down, which is further extended by dmbpy ligands to form a three-dimensional framework withrobtopology. The single net leaves voids that are filled by mutual interpenetration of an independent equivalent framework in a twofold interpenetrating architecture. The title compound shows thermal stability up to 673 K and is stable in aqueous solutions in the pH range 5–9. Excitation and luminescence data observed at room temperature show that it emits a bright-blue fluorescence.

scholarly journals Introducing a Thermo-Alkali-Stable, Metallic Ion-Tolerant Laccase Purified From White Rot Fungus Trametes hirsuta

2021 ◽  
Vol 12 ◽  
Author(s):  
Jing Si ◽  
Hongfei Ma ◽  
Yongjia Cao ◽  
Baokai Cui ◽  
Yucheng Dai
Keyword(s):  
Specific Activity ◽  
Endocrine Disrupting Chemicals ◽  
Environmental Pollutants ◽  
Fold Increase ◽  
Industrial Applications ◽  
White Rot ◽  
White Rot Fungus ◽  
Metallic Ions ◽  
Trametes Hirsuta ◽  
Ph Range

This study introduces a valuable laccase, designated ThLacc-S, purified from white rot fungus Trametes hirsuta. ThLacc-S is a monomeric protein in nature with a molecular weight of 57.0 kDa and can efficiently metabolize endocrine disrupting chemicals. The enzyme was successfully purified to homogeneity via three consecutive steps consisting of salt precipitation and column chromatography, resulting in a 20.76-fold increase in purity and 46.79% yield, with specific activity of 22.111 U/mg protein. ThLacc-S was deciphered as a novel member of the laccase family and is a rare metalloenzyme that contains cysteine, serine, histidine, and tyrosine residues in its catalytic site, and follows Michaelis-Menten kinetic behavior with a Km and a kcat/Km of 87.466 μM and 1.479 s–1μM–1, respectively. ThLacc-S exerted excellent thermo-alkali stability, since it was markedly active after a 2-h incubation at temperatures ranging from 20 to 70°C and retained more than 50% of its activity after incubation for 72 h in a broad pH range of 5.0–10.0. Enzymatic activities of ThLacc-S were enhanced and preserved when exposed to metallic ions, surfactants, and organic solvents, rendering this novel enzyme of interest as a green catalyst for versatile biotechnological and industrial applications that require these singularities of laccases, particularly biodegradation and bioremediation of environmental pollutants.

scholarly journals ENHANCED ENZYMATIC ACTIVITY OF STREPTOMYCES GRISEOPLANUS L-ASPARGINASE VIA ITS INCORPORATION IN AN OIL-BASED NANOCARRIER

2020 ◽  
pp. 203-210
Author(s):  
ABEER A. EL-HADI ◽  
HANAN MOSTAFA AHMED ◽  
RANIA A. ZAKI ◽  
AMIRA MOHAMED MOHSEN
Keyword(s):  
Thermal Stability ◽  
Oleic Acid ◽  
Enzymatic Activity ◽  
Specific Activity ◽  
Residual Activity ◽  
Tween 80 ◽  
Biochemical Properties ◽  
Lymphocytic Leukemia ◽  
Tween 20 ◽  
Ph Range

Objective: L-asparaginase (L-asp) is a vital enzyme used as a therapeutic agent in combination with other drugs in the treatment of acute lymphoma, melanosarcoma and lymphocytic leukemia. Immobilization of enzymes through loading on nanoemulsion (NE) results in some advantages such as enhancing their stability and increasing their resistance to proteases. Aim of the present study is to formulate L-asp loaded nanoemulsion to enhance its efficiency and thermal stability. Methods: Nanoemulsion loaded with L-asp crude extract (specific activity 13.23U/mg protein) was prepared employing oleic acid as oil, tween 20/tween 80 as surfactants and propylene glycol (PG) as co-surfactant. L-asp loaded NE underwent several thermodynamic stability studies and the optimized formulae were further examined for their biochemical properties and thermal stability. Results The developed formulations were spherical in shape and their sizes were in the nanometric dimensions with negatively charged zeta potential values. Upon comparing the enzyme activity of L-asp loaded NE employing tween 20 (F1) or tween80 (F4) at different concentrations, the results revealed that F4 NE showed higher enzymatic activity [323 U/ml] compared to F1 NE [197 U/ml] at the same concentration. The nanosized immobilized L-asp was more stable in the pH range from 8 to 8.5 as compared to free L-asp. The immobilized enzyme preserved about 59.11% of its residual activity at 50 °C; while free L-asp preserved about 33.84%. Conclusion: In the view of these results, NE composed of oleic acid, tween 80 and PG represents a promising dosage form for enhancing the activity and stability of Streptomyces griseoplanus L-asp.

scholarly journals Production and Characterization of Esterase in Lantinus tigrinus for Degradation of Polystyrene

2013 ◽  
Vol 62 (1) ◽  
pp. 101-108 ◽  
Author(s):  
LUBNA TAHIR ◽  
MUHAMMAD ISHTIAQ ALI ◽  
MUHAMMAD ZIA ◽  
NAIMA ATIQ ◽  
FARIHA HASAN ◽  
...  
Keyword(s):  
Acidic Medium ◽  
Specific Activity ◽  
Mineral Salt Medium ◽  
Tween 80 ◽  
Synthetic Polymers ◽  
Ftir Analysis ◽  
Polystyrene Film ◽  
Biological Degradation ◽  
Ph Range

Polystyrene is considered stable to biological degradation. Lantinus tigrinus isolated from wood sample produced esterase in growth medium under normal conditions. However, acidic medium, 37 degrees C temperature, presence of tween 80; and urea and yeast extract in mineral salt medium enhance the production of esterase and specific activity. Purified esterase was active at broad pH range and 45 degrees C. FTIR analysis confirmed that esterase produced by Lantinus tigrinus effectively degraded polystyrene film and broke macromolecules down to non-toxic molecules. This study concludes that the presence of Lantinus tigrinus at dumping sites can be exploited for waste management containing high molecular weight synthetic polymers.

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