High-temperature Extraction Research Articles

Investigation of high-temperature oxide-metal melts during induction melting in a cold crucible

The object of the study is high-temperature oxide-metal melts obtained in furnaces of induction melting in a cold crucible (IMCC). The results of pilot tests in IMCC furnaces at melt temperatures of more than 2200 оC in air, conducted to study the distribution of components between the oxide and metal phases of a two-phase melt with limited miscibility of components, are presented. The results of physicochemical studies of materials obtained by quenching crystallization of a high-temperature melt are presented, confirming the reduction of silicon and the oxidation of iron with the redistribution of these components between the oxide and metal phases. This experimental result contradicts the well-known Ellingham diagrams and thermodynamic calculations, but a similar effect is observed experimentally in the U–O–Fe system. Thus, the IMCC method allows for the inversion of redox processes in a number of oxide-metal systems, which can be used to obtain new materials and create technologies for high-temperature extraction of target components.

Recovery and detection of ignitable liquid residues from the substrates by solid phase microextraction – direct analysis in real time mass spectrometry

In this study, direct analysis in real time mass spectrometry (DART-MS) was coupled to the solid phase microextraction (SPME) to extract and analyze the ignitable liquid residues (ILR) present in the sample matrices. The SPME extraction parameters, such as extraction temperature and extraction time, were optimized using a two-factor central composite design. The SPME-DART-MS setup was utilized to analyze the substrates and fire debris matrices spiked with gasoline. The results indicate that the less volatile marker compounds from gasoline were recovered from the substrates and fire debris, and their profiles matched well with the gasoline liquid samples analyzed directly by DART-MS. As expected, the effective extraction of marker compounds in gasoline required a relatively high temperature, i.e., 150 ℃. In the presence of a matrix, a higher extraction temperature and longer extraction time could benefit the extraction efficiency. The desorption of ILR on SPME fiber was performed by inserting the fiber into the DART-MS helium gas stream at 300 ℃ for 1 min with no carry-over residues being observed between successive samples. The chemical information attained with this method is typically not observed in the current GC/MS-based practice. The SPME-DART-MS was also extended to reanalyze less volatile components of ILR on substrates after the ASTM E1412 activated charcoal method, which indicates its possible application subsequent to the traditional GC/MS ILR analysis. The SPME-DART-MS has shown promise in ILR detection as an important complementary tool.

Survivability of low pathogenic avian influenza virus in aqueous poultry manure fertilizer

Avian influenza has been a growing problem in the United States for decades. Low pathogenic avian influenza (LPAI) virus causes low morbidity, while highly pathogenic avian influenza (HPAI) has a devastating effect on the poultry industry causing high morbidity and mortality worldwide. Manure from large and small poultry operations is spread on crop fields as a fertilizer. During an outbreak of avian influenza in a farm it is critical to adequately process the manure to kill the virus before its use in agriculture. Aqueous extraction of poultry manure at high temperature (55-65°C) is an attractive method for treatment of poultry manure, which extracts the nutrients and kills harmful microbes from the manure. The end product is a nutrient rich liquid that can be safely applied to fields or used in hydroponic operations, with nutrients that are more bioavailable to the plant compared to dry litter. However, we do not know whether aqueous high temperature extraction processes completely kill avian influenza virus present in the manure. Our aim in this study was to determine the competence of the aqueous extraction of poultry manure on avian influenza virus inactivation. We optimized the procedure using a LPAI virus isolate in a biosafety level 2 cabinet. Our data indicated that LPAI virus including the hemagglutinin protein of the virus were completely destroyed when the poultry manure was processed by aqueous extraction at temperatures ≥ 55°C for one hour. Future research will identify the conditions required for inactivating HPAI virus using this optimized procedure by performing the study in a BSL3 facility.

A green extraction method for agar with improved thermal stability and water holding capacity

The conventional agar extraction method has drawbacks such as high energy consumption, low yield, poor quality, and possible residual harmful factors, which greatly limit its application in high-end fields such as biomedicine and high-end materials. This work explored a new freezing-thawing-high-temperature coupling technique for agar extraction. It increased the yield and the strength of agar by 10.6 % and 13.7 %, respectively, as compared to direct high-temperature extraction of agar (HA). The greater molecular weight and lower sulfate content of agar obtained from freeze-thaw cycles combined with high temperature extraction (FA) may be attributed to the desulfurization effect caused by freeze-thaw cycles and the preservation of the molecular chain structure. The reduction in sulfate content decreases the steric hindrance resistance of the polysaccharide chains, enhances their interactions, and promotes the regularity and density of the agar structure, while also improving its water retention and thermal stability. In conclusion, this research can offer a theoretical basis and guidance for the eco-friendly extraction of agar with improved agar characteristics and expended its applications.

On the Feasibility of Deep Geothermal Wells Using Numerical Reservoir Simulation

This study examines the geothermal energy extraction potential from the basement rock within the Denver–Julesburg Basin, focusing on the flow performance and heat extraction efficiency of different geothermal well configurations. It specifically compares U-shaped, V-shaped, inclined V-shaped, and pipe-in-pipe configurations against enhanced geothermal system setups. Through numerical modeling, we evaluated the thermal behavior of these systems under various operational scenarios and fracture conditions. The results suggest that while closed-loop systems offer moderate temperature increases, Enhanced geothermal system configurations show substantial potential for high-temperature extraction. This underscores the importance of evaluating well configurations in complex geological settings. The insights from this study aid in strategic geothermal energy planning and development, marking significant advancements in geothermal technology and setting a foundation for future explorations and optimizations.

Evaluation of the Effect of Different Extraction Temperatures on the Synthesis of Silver Nanoparticles from Ocimum basilicum (Basil) Plant

The eco-friendly green synthesis of silver nanoparticles (AgNPs) using Ocimum basilicum (basil) extract at varying extraction temperatures (40°C, 60°C, 80°C, 100°C) was investigated to determine the optimal conditions for nanoparticle formation. Analysis methods such UV-Vis spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and TransmissionElectron Microscopy (TEM) confirmed the crystalline, spherical nature of AgNPs and identified phytochemicals acting as capping and reducing agents. Notably, the extraction temperature was found to influence both the DPPH radical scavenging activity and the structural properties of AgNPs. According to TEM analysis results, it was observed that high extraction temperatures increased the nanoparticle formation efficiency but created a wide size distribution. The crystallite sizes, calculated using the Scherrer equation, for AgNPs synthesized at different extraction temperatures, were determined to be 12.45 nm, 18.77 nm, 17.76 nm, and 16.03 nm, respectively. The hydrodynamic sizes of the AgNPs were found to range between 158.1 and 333.7 nm. The study highlights the critical role of extraction temperature in the synthesis process, suggesting 40°C as the optimal temperature for achieving efficient and environmentally friendly synthesis of AgNPs with enhanced biological activities.

Comparison of Rendement, Viscosity, and Degree of Acidity of Bone Gelatin of Bali Cattle Fed with Lamtoro at Different Extraction Temperatures

The increase in Bali cattle bone waste due to increased slaughter has become a severe societal problem because it will pollute the environment. If Bali cattle bone waste is appropriately processed, it will produce products with high nutritional and economic value, including gelatin. This research aimed to compare the yield, viscosity, and degree of acidity (pH) of bone gelatin from Bali cattle fed with lamtoro at different extraction temperatures. The gelatin from Bali cattle bone was produced under the influence of different extraction temperatures of 50; 60; and 70o C and each was repeated 4 times. The research method used was laboratory experimental. Data were analyzed using a Completely Randomized Design (CRD). The parameters observed were yield, pH, and viscosity. The results show that different extraction temperatures (50, 60, 70o C) had a significant effect (P < 0.05) on viscosity while a very significant effect (P < 0.01) on the degree of acidity (pH) and no significant effect (P > 0.05) to the yield. It can be concluded that a higher extraction temperature (70o C) will be accompanied by an increase in gelatin yield, but the extraction temperature of 60o C showed the maximum viscosity and acidity (pH) values

Comparison on biological activities of Lycium barbarum polysaccharides extracted with five methods

Studying the physicochemical properties and biological activities of Lycium barbarum polysaccharides(LBPs) is of great significance. The previous study had extracted LBPs(LBP-1, LBP-2, LBP-3, LBP-4, and LBP-5) by five different methods(cold water extraction, boiling water reflux extraction of the residue after cold water extraction, ultrasonic extraction with 50% ethanol, ultrasonic extraction with 25% ethanol of the residue after 50% ethanol extraction, and hot water extraction). In this study, the structures of the obtained five LBPs were characterized by UV spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Furthermore, the antioxidant, blood lipid-lowering, nitrosation-inhibting, acetylcholinesterase-inhibiting, and tyrosinase-inhibiting activities of the five LBPs were measured in vitro. The results showed that high-temperature extraction destroyed the polysaccharide structure, while ultrasound-assisted extraction ensured the structural integrity. The thermal stability and degradation behaviors differed among the five LBPs. However, the UV spectroscopic results of the five LBPs did not show significant differences, and all of the five LBPs showed the characteristic absorption peaks of proteins. LBP-3 and LBP-4 exhibited strong antioxidant activity, while LBP-3 had the strongest blood lipid-lowering activity. In addition, LBP-3 outperformed other LBPs in inhibiting nitrosation and acetylcholineste-rase, and LBP-2 showed the strongest inhibitory effect on tyrosinase. This study explored the effects of different extraction methods on the physicochemical properties and biological activities of LBPs, with a view to providing a basis for the selection of suitable extraction methods to obtain LBPs with ideal biological activities.

Biodiesel Production by Biocatalysis using Lipids Extracted from Microalgae Oil of Chlorella vulgaris and Aurantiochytrium sp.

Microalgae are lipid-rich microscopic eukaryotic algae that can be used aiming for more sustainable biodiesel production by employing environmentally sound processes. The present work evaluates biodiesel production using a biocatalyst and two microalgae species as oil feedstock (Chlorella vulgaris and Aurantiochytrium sp.). Lipid extraction was performed using different techniques, namely, Soxhlet extractions (8 h — both species) with different solvents (hexane; hexane:ethanol (1:1 v/v); and chloroform) and room temperature hexane extraction (72 h — Aurantiochytrium sp.). Transesterification occurred for 24 h (150 rpm), using 30 % lipase loading. The results showed that high extraction temperatures cause microalgae oil degradation, focused on unsaturated fatty acids, leading to a lower biodiesel conversion yield. Using Aurantiochytrium sp. oil, it was possible to obtain around 55 %wt. of biodiesel conversion yield using oil extracted at room temperature (6:1 methanol:oil molar ratio), whereas for the oil extracted in the Soxhlet apparatus, the biodiesel conversion yield was around 30 %wt.. The low lipid content (1.0 %wt.) and biodiesel conversion yield (up to 25 %wt.) obtained using C. vulgaris show that the biomass used in the current study has low potential for biodiesel production. However, enzymatic biodiesel production from microalgae represents a promising avenue for sustainable energy generation, offering a renewable and environmentally responsible solution to the world’s energy needs. For that purpose, further studies, such as the optimisation of the extraction and transesterification of Aurantiochytrium sp. oil, should be carried out.

Numerical modeling and evaluation of solid-liquid extraction with pressurized hot water extraction applied to Robinia Pseudoacacia wood

Computational Fluid Dynamics (CFD) simulation was used to study the solid-liquid extraction of Robinia Pseudoacacia wood by pressurized hot water extraction (PHWE). The proposed model couples momentum and mass transfer, including the extraction kinetics. The model is based on transport species and flow in a porous medium. The results show that the extraction of the two main flavonoids, Dihydrorobinetin (DHR) and Robinetin (Rob), increased with increasing temperature up to 120 °C, with values of 46.85±1.44 and 6.84±0.42 mg/gdB, respectively. However, at higher temperatures, these flavonoids degraded. Additionally, the exhaustive extraction cycle, ranging from 80 to 160 °C, was found to be less effective when compared to extraction at 120 °C.The kinetic parameters were included in the CFD simulation. As a result, a good agreement between the results of CFD simulation and experimental data was found with R2 > 0.97. The model predicts the temperature distribution inside the reactor during the pre-heating period, the evolution of the DHR and Rob concentrations at the reactor outlet, and the effect of degradation at high extraction temperatures.

A Rapid and Quantitative Method for Determining Seed Viability Using 2,3,5-Triphenyl Tetrazolium Chloride (TTC): With the Example of Wheat Seed.

Current colorimetric methods for quantitative determination of seed viability (SV) with 2,3,5-triphenyl tetrazolium chloride (TTC) have been plagued by issues of being cumbersome and time-consuming during the experimental process, slow in extraction and staining, and exhibiting inconsistent results. In this work, we introduced a new approach that combines TTC-staining with high-temperature extraction using dimethyl sulfoxide (DMSO). The optimization of the germination stage, TTC-staining method, and 1,3,5-triphenylformazan (TTF) extraction method were meticulously carried out as follows: When the majority of wheat seeds had grown the radicle, and the length of radicles was approximately equal to the seed length (24 h-germination), 2 g germinating seeds were placed into a beaker (20 mL) containing 5 mL 10 g·L-1 TTC solution. The seeds were stained with TTC in the dark at 25 °C for 1 h. Following the staining, 1 mL 1 mol·L-1 H2SO4 was added to stop the reaction for 5 min. The H2SO4 solution was then removed, and the seeds were gently rinsed with deionized water. Subsequently, the TTF produced in the seeds was extracted directly with 5 mL DMSO solution at 55 °C for 1 h. The absorbance of the extract was measured at 483 nm, and the index of SV was calculated according to a predetermined TTC calibration curve and expressed by mg TTC·g-1 (seed)·h-1. The new method has been demonstrated to be rapid, stable, and highly sensitive, as evidenced by the accurate measurement of seed viability with different aging degrees.

Storage of High-Strength Steel Flux-Cored Welding Wires in Urbanized Areas

The condition of the consumables is a key factor determining the waste reduction in the welding processes and the quality of the welded joint. The paper presents the results of tests of four types of flux-cored wires dedicated for welding high-strength steels, stored for 1 month and 6 months in Poland in two urbanized areas: in a large seaside city (Gdańsk) and in Warsaw, located in the center of the country. The wires were subjected to macroscopic and microscopic (stereoscopic, SEM) observations, EDS analysis, technological tests assessing elastic properties and targetability. The degree of degradation of the wires was also tested using resistance measurements. In order to assess the effect of storing wires on the weldability of steel, the diffusible hydrogen content in deposited metal was determined by high-temperature extraction. It was found that the storage caused changes in the surface condition of the wires, affected their elasticity and electrical properties, which affects the behavior of the wires during welding. A significant influence of storage conditions on the hydrogenation of deposited metal was found: in the case of three types of wires, the level of low hydrogen processes was exceeded and the maximum result was 15.18 ml/100 g of deposited metal. It was also found that copper-plated wire showed a significantly increased resistance to storage conditions compared to non-copper-plated wires.

A new deep eutectic solvent based on diphenylguanidine for the effective extraction of pertechnetate anion

In this work, for the first time, a new class of deep eutectic solvents has been synthesized and applied for the efficient extraction of pertechnetate anion from imitators of real media from which pertechnetate removal is needed: high-level waste imitator and sea water imitator. Diphenyl guanidine was studied as a hydrogen bond acceptor, which exhibits a high extraction ability for pertechnetate anion separation. Natural fatty acid and natural terpene were studied as hydrogen bond donors. The structure, properties, viscosity and stability of the obtained eutectic solvents were studied. Also, the radiation resistance of the obtained solvents was studied from the point of view of distribution ratio saving. It was shown that the new class of solvents has a high radiation resistance and efficiently extracts pertechnetate anion even from acidic media in high-temperature extraction process and can be the first step platform for solving technological and radiation safety problems.

Elastin Barrier Membranes for Guided Tissue Regeneration Technologies

This article discusses the prospects for the use of new elastin barrier membranes manufactured using adapted technologies for the selective isolation of the elastin component from the extracellular xenogenic matrix of the pericardium ligamentous apparatus: (1) by high-temperature extraction under pressure; (2) cyanogen bromide method. A commercial material, Geistlich Bio–Gide® membrane (BG), was used as a control comparison group. It is shown that the materials of group (1) have a high degree of biocompatibility, exceeding the indicators of the control group BG. Based on the results of an study in a model of subcutaneous heterotopic implantation in rats, it was shown that elastin BM has a chemoattractant effect on the mesenchymal recipient cells and, unlike the control, is able to integrate to a high degree into the surrounding recipient tissues. At the same time, the materials of group (1) had a pronounced proangiogenic effect. Thus, it has been shown that elastin BM groups (1) have a medium-term barrier function and are able to induce full-fledged cellular repopulation and local neoangiogenesis, which can be useful in clinical practice, primarily in GTR technologies (with gingival flap augmentation) or when used together with other BM as an angiogenesis inducer to ensure formation of the vascular bed in GBR technologies of bone tissue.

Microwave-ultrasonic technique development coupled with natural deep eutectic solvents in anthocyanin extraction from perilla leaves (Perilla frutescens var. Acuta).

As potent antioxidants, anthocyanins can protect the body from free radicals. However, the traditional solvent extraction method has the disadvantages of requiring a high extraction temperature and long extraction time, so it is necessary to develop an efficient extraction method for anthocyanins. In this study, the technique of natural deep eutectic solvents (DESs) was applied to extract anthocyanins from purple perilla leaves with the aid of microwave-ultrasonic assisted extraction (MUAE). The response surface methodology (RSM), based on the Box-Behnken design (BBD), predicted the maximum extraction yield of anthocyanins to be 619.62 mg (100 g)-1 under the following conditions: x1 (ultrasonic extraction power)=357.25 W, x2 (time)=25.62 min, and x3 (temperature)=57.80 °C. The biological activity of the extract obtained was evaluated by examining its radical-scavenging effect on 1,1-diphenyl-2-picrylhydrazyl, hydroxyl radical, and superoxide anion radicals. Its bacteriostatic impact was investigated on four typical bacteria: Shewanella putrefaciens (S. putrefaciens), Pseudomonas fluorescens (P. fluorescens), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus). The integrated extraction method of DESs with MUAE was efficient, energy-saving, green, and sustainable. © 2022 Society of Chemical Industry.

Zein and Spent Coffee Grounds Extract as a Green Combination for Sustainable Food Active Packaging Production: An Investigation on the Effects of the Production Processes

In this work, the effect of different production techniques was evaluated on the physical and antioxidant properties of bio-based packaging intended to prevent the premature oxidation of packaged foods. Spent coffee ground extract, rich in antioxidant molecules, obtained through high pressure and temperature extraction, was loaded on zein polymeric matrices. The techniques adopted in this work are particularly suitable due to their mild conditions to produce active packaging completely based on natural compounds: electrospinning, solvent casting, and spin coating. The novelty of this work lay in the investigation of the dependance of the properties of active packaging on the adopted production techniques; the results clearly indicated a strong dependence of the features of the films obtained by different production processes. Indeed, spin coated samples exhibited the best oxygen barrier properties, while a higher tensile strength was obtained for the casted samples, and the fastest release of active compounds was provided by electrospun mats. The films produced with different methods had different physical properties and the release of extract bioactive compounds can be tunable by varying the production technique, dependent on the variable to be considered. The products developed offer an alternative to traditional packaging solutions, being more eco-sustainable and promoting waste valorization.

Cosmeceutical Potential of Extracts Derived from Fishery Industry Residues: Sardine Wastes and Codfish Frames.

The fishery industry generates large amounts of waste (20–75% (w/w) of the total caught fish weight). The recovery of bioactive compounds from residues and their incorporation in cosmetics represents a promising market opportunity and may contribute to a sustainable valorisation of the sector. In this work, protein-rich extracts obtained by high-pressure technologies (supercritical CO2 and subcritical water) from sardine (Sardina pilchardus) waste and codfish (Gadus morhua) frames were characterized regarding their cosmeceutical potential. Antioxidant, anti-inflammatory and antibacterial activities were evaluated through chemical (ORAC assay), enzymatic (inhibition of elastase and tyrosinase), antimicrobial susceptibility (Klebsiella pneumoniae, Staphylococcus aureus and Cutibacterium acnes) and cell-based (in keratinocytes-HaCaT) assays. Sardine extracts presented the highest antibacterial activity, and the extract obtained using higher extraction temperatures (250 °C) and without the defatting step demonstrated the lowest minimum inhibitory concentration (MIC) values (1.17; 4.6; 0.59 mg/mL for K. pneumoniae, S. aureus and C. acnes, respectively). Codfish samples extracted at lower temperatures (90 °C) were the most effective anti-inflammatory agents (a concentration of 0.75 mg/mL reduced IL-8 and IL-6 levels by 58% and 47%, respectively, relative to the positive control). Threonine, valine, leucine, arginine and total protein content in the extracts were highlighted to present a high correlation with the reported bioactivities (R2 ≥ 0.7). These results support the potential application of extracts obtained from fishery industry wastes in cosmeceutical products with bioactive activities.

Synthesis and application of chloroacetamides in pyridinium based ionic liquid for high temperature extraction of uranyl ion: A novel and 'green' approach for extractive mass transfer at elevated temperature

Two different chloroacetamides viz 2-chloro-N-methyl-N-phenylacetamide (MACA) and 2-chloro-N-(3-methylpyridin-2-yl)acetamide (AMPCA) have been synthesized and applied for the extraction of uranyl ions from acidic feed. 1-Ethyl-2-methylpyridinium bis(trifluoromethylsulfonyl)imide ionic liquid (IL) has been used at elevated temperature for liquid–liquid biphasic mass transfer. An effort has also been made to study the mechanism of extraction, kinetics, thermodynamics, speciation, radiolytic stability and elution behavior of UO22+. The investigation revealed the predominance of ‘cation exchange’ mechanism. The D values in 2-chloro-N-methyl-N-phenylacetamide (MACA) were found to be more than that of 2-chloro-N-(3-methylpyridin-2-yl)acetamide (AMPCA). The species were found to be[(UO2(NO3)(MACA)2]+ and [(UO2(NO3)(AMPCA)2]+. Back extraction studies using aqueous solution of oxalic acid and sodium carbonate revealed that, the stripping of uranyl ion from AMPCA in ionic liquid was better than that of MACA. However, MACA exhibited better radiolytic stability as compared to AMPCA in ionic liquid. To understand the complexation of UO22+ with MACA and AMPCA, theoretical calculations were carried out.

Reuse of Abandoned oil and gas wells for Power generation in Western Dessert and Gulf of Suez fields of Egypt

This study investigates the capable outcome of using existing abandoned oil and gas wells as a geothermal energy source in Egypt. Geothermal resources of Egypt are mainly located along the Gulf of Suez and Red Sea in addition to some additional spots with lower potential in the Western Desert of Egypt. In Gulf of Suez the geothermal potential identified data and parameters dignified from oil and gas wells under the regulation of the Egyptian General Petroleum Corporation. Using abandoned oil and gas well which already lost their economic value would save drilling time and cost which would decrease the ROR of the investment. In this paper a simulation model cycle has been made by ASPEN HYSYS software to show the reliability of using the abandoned oil and gas wells outlet fluid as a source geothermal energy in Egypt by mapping the geothermal favorability locations with the oil and gas field area. Mapping shows that in Egypt there is potential of extracting low, medium and high temperature extractions from wells according to the location. Results demonstrates that the output power for the simulation geothermal power plant in different locations of Egypt and at various temperatures. Showing that in western desert the maximum output power that can be generated from the modified binary cycle is 3.063 MW at output temperature of 125 °C. Whereas in the Gulf of Suez proposed maximum output is 44.6 MW that can be produced from modified Flash steam cycle at an output temperature of 300 °C.

A Preparative Method for the Isolation of Calponin from Molluscan Catch Muscle.

We describe the development of a preparative method to isolate molluscan catch muscle, calponin. This method is based on the ability of calponin to interact with actin in a temperature-dependent manner. After extracting thin filaments, as previously described, the extract was ultracentrifuged at 2 °C. While other surface proteins of thin filaments co-precipitated with actin, calponin, along with some minor contaminants, remained in the supernatant. Calponin was purified through cation-exchange chromatography. The yield of pure protein was four-fold higher than that achieved through high-temperature extraction. To evaluate functionally isolated proteins, we determined the effect of calponin on Mg2+-ATPase activity of hybrid and non-hybrid actomyosin. The degree of ATPase inhibition was consistent with previously published data but strongly dependent on the environmental conditions and source of actin and myosin used. Furthermore, at low concentrations, calponin could induce the ATPase activity of hybrid actomyosin. This result was consistent with data indicating that calponin can modulate actin conformation to increase the relative content of “switched on” actin monomers in thin filaments. We assume that calponin obtained by the isolation method proposed herein is a fully functional protein that can both inhibit and induce the ATPase activity.