Metal Ion Chelating Research Articles

Synthesis of Ni2+-functionalized polydopamine magnetic beads for facilitated purification of histidine-tagged proteins

Facilitated purification of proteins, at a low cost and a short time, is one of the key steps in the industrial production of recombinant proteins. In the current study, polydopamine nanoparticles (PDA-NPs) are considered in the synthesis of magnetic beads for purifying recombinant proteins due to advantages such as biocompatibility/ biodegradability, easy synthesis, as well as the ability to directly chelate metal ions. They were synthesized in Tris buffer (pH: 8:5), then chelated with Fe3+(20 mg) and Ni2+ ions at concentrations of 2, 3, 5, and 7 mg/ml. Prepared nanoparticles were characterized through scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), dynamic light scattering (DLS), Inductively Coupled Plasma (ICP), and vibrating sample magnetometer (VSM). The size distribution of the particles was reported in the narrow range of 120–140 nm and 200 to 220 nm by the SEM image and DLS analysis, respectively. The chelation of ions on the surface of the nanoparticle was confirmed by the ICP technique with a magnetization of 35.42 emu/g. The highest adsorption rate of Ni2+ ions to polydopamine was obtained at a ratio of 1.4. The SDS-PAGE and western blot analysis confirmed the purification of eGFP and Hsp40 by PDA/Fe3+/Ni2+ at 26 and 40 kDa compared to the commercial nickel column. Moreover, the concentration of purified eGFP by PDA/Fe3+/Ni2+ was reported 138.83 µg/ml by the fluorescent signals, which is almost equal to or more than the protein purified by commercial Ni-NTA column (108.28 µg/ ml). The stability of PDA/Fe3+/Ni2+ has also been evaluated by ICP-OES for 10 days, and the result suggested that PDA magnetic beads were stable. Therefore, it can be concluded that PDA/Fe3+/Ni2+ have the ability to purify recombinant proteins in one less step and shorter time.

Neuroprotective Potential of Isoquinoline Alkaloids from Glaucium grandiflorum Boiss. and A. Huet subsp. refractum (Nábelek) Mory: Role of NRF2-KEAP1 Pathway

The extracts of Glaucium grandiflorum have been used to treat neurodegenerative diseases. Nonetheless, no former study has investigated whether the alkaloid extracts of G. grandiflorum have antioxidative effects against oxidative stress. The aim of the present study was to determine the antioxidative effects of the alkaloid extracts of G. grandiflorum with a variety of targets and probable mechanisms. First, we used spectrophotometry to investigate alkaloid extracts with respect to their alkaloid amounts. Then, we determined the alkaloid extracts’ impact on thiol/disulfide homeostasis, total oxidant status/total antioxidant status/oxidative stress index, and antioxidant enzyme activities. Finally, the effects of alkaloid extracts on the genes in the NRF2-KEAP1 pathway were determined via qRT-PCR. We conducted molecular docking analyses to determine the potential binding of isoquinoline alkaloids found within the alkaloid extracts with target proteins. We observed the best results from chloroform alkaloid extract and methanol alkaloid extract. Chloroform alkaloid extract was prominent in DPPH radical scavenging and metal ions chelating, and methanol alkaloid extract showed significant hydroxyl radical scavenging, lipid peroxidation, and superoxide anion radical scavenging activity. Alkaloid extract groups substantially increased in total thiol activity, native thiol activity, disulfide activity, total antioxidant status level, antioxidant enzyme levels, and gene expression levels (GCLC, HO-1, NRF2, and NQO1) compared to the H2O2 group. Also, alkaloid extract groups led to a significant drop in total oxidant status level, oxidative stress index level, and KEAP1 gene expression level relative to the H2O2 group. According to our study results, oxidative stress brought about by H2O2 was regulated by alkaloid extracts. As a result, a phytochemical-based therapeutic that regulates H2O2-induced oxidative stress was brought to the neurochemical field.

Pyrolysis process and formation mechanism of water-based ZrC ceramics studied through a combined experimental and theoretical calculational method

ZrC has an important application in the field of supersonic aircraft, hypersonic spacecrafts and rocket engines. Normally, the toxic metal chelators and toxic organic reagents are used to prepare the ZrC ceramic precursors. In this paper, an environmentally friendly water-based ZrC ceramic precursors were synthesized in aqueous solvent via the combination of metal ion chelator and carbon source. Moreover, the water-based ZrC precursor was prepared by Tartaric Acid (TA) system can obtain high-purity ZrC ceramics. The experiment results indicated that the best Zr/C molar ratio in the precursor was 1:4. The synthetic mechanism of ZrC was Zr atoms reacted in situ to form ZrC. In addition, the effect of metal chelator carbon source assisted glucose carbon source on water-based ZrC precursors can provide a certain experimental basis for subsequent research on water-based carbide precursors.

In Vitro Antioxidant and In Vivo Antigenotoxic Features of a Series of 61 Essential Oils and Quantitative Composition-Activity Relationships Modeled through Machine Learning Algorithms.

The antioxidant activity of essential oils (EOs) is an important and frequently studied property, yet it is not sufficiently understood in terms of the contribution of EOs mixtures' constituents and biological properties. In this study, a series of 61 commercial EOs were first evaluated as antioxidants in vitro, following as closely as possible the cellular pathways of reactive oxygen species (ROS) generation. Hence, EOs were assessed for the ability either to chelate metal ions, thus interfering with ROS generation within the respiratory chain, or to neutralize 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and lipid peroxide radicals (LOO•), thereby halting lipid peroxidation, as well as to neutralize 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid cation radicals (ABTS•+) and hydroxyl radicals (OH•), thereby preventing the ROS species from damaging DNA nucleotides. Showing noteworthy potencies to neutralize all of the radicals at the ng/mL level, the active EOs were also characterized as protectors of DNA double strands from damage induced by peroxyl radicals (ROO•), emerging from 2,2'-azobis-2-methyl-propanimidamide (AAPH) as a source, and OH•, indicating some genome protectivity and antigenotoxicity effectiveness in vitro. The chemical compositions of the EOs associated with the obtained activities were then analyzed by means of machine learning (ML) classification algorithms to generate quantitative composition-activity relationships (QCARs) models (models published in the AI4EssOil database available online). The QCARs models enabled us to highlight the key features (EOSs' chemical compounds) for exerting the redox potencies and to define the partial dependencies of the features, viz. percentages in the mixture required to exert a given potency. The ML-based models explained either the positive or negative contribution of the most important chemical components: limonene, linalool, carvacrol, eucalyptol, α-pinene, thymol, caryophyllene, p-cymene, eugenol, and chrysanthone. Finally, the most potent EOs in vitro, Ylang-ylang (Cananga odorata (Lam.)) and Ceylon cinnamon peel (Cinnamomum verum J. Presl), were promptly administered in vivo to evaluate the rescue ability against redox damage caused by CCl4, thereby verifying their antioxidant and antigenotoxic properties either in the liver or in the kidney.

Emodin derivatives as promising multi-aspect intervention agents for amyloid aggregation: molecular docking/dynamics simulation, bioactivities evaluation, and cytoprotection.

Alzheimer's disease (AD) is a progressive neurodegenerative disease with complex pathogenesis. Despite the pathogenesis is unknown, the misfolding and accumulation of β-amyloid (Aβ) peptide play the important role in the occurrence and development of AD. Hence, multi-aspect intervention of the misfolded Aβ peptides aggregation is a promising therapy for AD. In previous work, we obtained the emodin derivatives (a-d) with multifunctional anti-AD activities, including metal ions chelation, cholinesterase inhibition, and hydroxyl/superoxide anion radical elimination. In this work, we predicted the interaction of emodin derivatives (a-d) with Aβ by combining molecular docking simulation and molecular dynamics simulation, and evaluated the ability to intervene with the self-, Cu2+- and AChE-induced Aβ aggregation via in vitro methods. The results indicated that a-d could act as the potent multi-aspect intervention agents for Aβ aggregation. In addition, a-d could effectively eliminate peroxyl radical, had virtually no neurotoxicity, and protect cells from oxidative and Aβ-induced damage. The prediction results of ADMET properties showed that a-d had suitable pharmacokinetic characteristics. It suggested that a-d could act as the promising multi-targeted directed ligands (MTDLs) for AD. These results may provide meaningful information for the development of the potential MTDLs for AD which are modified from natural-origin scaffolds.

Effect of cycloastragenol and punicalagin on Prp(106–126) and Aβ(25–35) oligomerization and fibrillizaton

Numerous neurological disorders, including prion, Parkinson's, and Alzheimer's disease (AD), are identified as being caused by alterations in protein conformation, aggregation, and metal ion dyshomeostasis. Recent years have seen a significant increase in the exploration and study of natural products (NPs) from plant and microbial sources for their therapeutic potential against several diseases, including cancer, diabetes, cardiovascular disease, and neurodegenerative diseases. In this study, we have examined the effect of two NPs, cycloastragenol (CAG) and punicalagin (PCG), on the metal-induced oligomerization and aggregation of Aβ25–35 and PrP106–126 peptides. The peptide aggregation and inhibitory properties of both NPs were examined by the thioflavin-T (ThT) assay, MALDI-TOF, circular dichroism (CD) spectroscopy, and transmission electron microscopy (TEM). Among the two NPs, PCG significantly binds to the peptides, chelates metal ions (Cu2+ and Zn2+), inhibits peptide aggregation, substantially reduces oxidative stress, and controls the production of reactive oxygen species (ROS). Both NPs exhibited low cytotoxicity and prominently mitigated peptide-mediated cell cytotoxicity in hippocampal neuronal HT-22 cells by covalent bonding and hydrophobic interactions.

Characterization of the structure, antioxidant activity and hypoglycemic activity of soy (Glycine max L.) protein hydrolysates

This study aimed to hydrolyze soy isolate protein (SPI) using five enzymes (alcalase, pepsin, trypsin, papain, and bromelain) in order to obtain five enzymatic hydrolysates and to elucidate the effect of enzymes on structural and biological activities of the resulting hydrolysates. The antioxidant and hypoglycemic activities of the soy protein isolate hydrolysates (SPIEHs) were evaluated through in silico analysis, revealing that the alcalase hydrolysate exhibited the highest potential, followed by the papain and bromelain hydrolysates. Subsequently, the degree of hydrolysis (DH), molecular weight distribution (MWD), amino acid composition, structure, antioxidant activities, and hypoglycemic activity in vitro of SPIEHs were analyzed. After enzymatic treatment, the particle size, polymer dispersity index (PDI), ζ-potentials, β-sheet content and α-helix content of SPIEHs was decreased, and the maximum emission wavelength of all SPIEHs exhibited red-shifted, which all suggesting the structure of SPIEHs was unfolded. More total amino acids (TAAs), aromatic amino acids (AAAs), and hydrophobic amino acids (HAAs) were found in alcalase hydrolysate. For 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, metal ion chelating activity, α-glucosidase inhibitory activity and α-amylase inhibitory activity, alcalase hydrolysate had the lowest IC50; alcalase hydrolysate and papain hydrolysate had the lowest IC50 for hydroxyl radical scavenging activity. Physiological activity of SPIEHs was evaluated thoroughly by 5-Axe cobweb charts, and the results revealed that alcalase hydrolysate exhibited the greatest biological activities.

Novel metallo-β-lactamases inhibitors restore the susceptibility of carbapenems to New Delhi metallo-lactamase-1 (NDM-1)-harbouring bacteria.

The production of metallo-β-lactamases is a major mechanisms adopted by bacterial pathogens to resist carbapenems. Repurposing approved drugs to restore the efficacy of carbapenems represents an efficient and cost-effective approach to fight infections caused by carbapenem resistant pathogens. The nitrocefin hydrolysis assay was employed to screen potential New Delhi metallo-lactamase-1 (NDM-1) inhibitors from a commercially available U.S. Food and Drug Administration (FDA) approved drug library. The mechanism of inhibition was clarified by metal restoration, inductively coupled plasma mass spectrometry (ICP-MS) and molecular dynamics simulation. The in vitro synergistic antibacterial effect of the identified inhibitors with meropenem was determined by the checkerboard minimum inhibitory concentration (MIC) assay, time-dependent killing assay and combined disc test. Three mouse infection models were used to further evaluate the in vivo therapeutic efficacy of combined therapy. Twelve FDA-approved compounds were initially screened to inhibit the ability of NDM-1 to hydrolyse nitrocefin. Among these compounds, dexrazoxane, embelin, candesartan cilexetil and nordihydroguaiaretic acid were demonstrated to inhibit all tested metallo-β-lactamases and showed an in vitro synergistic bactericidal effect with meropenem against metallo-β-lactamases-producing bacteria. Dexrazoxane, embelin and candesartan cilexetil are metal ion chelating agents, while the inhibition of NDM-1 by nordihydroguaiaretic acid involves its direct binding to the active region of NDM-1. Furthermore, these four drugs dramatically rescued the treatment efficacy of meropenem in three infection models. Our observations indicated that dexrazoxane, embelin, candesartan cilexetil and nordihydroguaiaretic acid are promising carbapenem adjuvants against metallo-β-lactamases-positive carbapenem resistant bacterial pathogens.

In vitro evaluation of the antiglycation and antioxidant potential of the dietary supplement L-citrulline

Diabetes mellitus (DM) represents a significant global public health concern. It is a metabolic condition characterized by abnormal glucose levels in the bloodstream, known as hyperglycemia. This condition arises due to irregular insulin secretion, defective insulin receptivity, or a combination of both factors. The primary contributors to diabetic complications are protein glycation and oxidative stress resulting from chronic hyperglycemia.
 The aim. The increasing incidence of diabetes mellitus has prompted a quest for a novel, cost-effective, and efficacious medication. The objective of the study generally intends to explore and investigate the antiglycation and antioxidant potential of the dietary supplement L-Citrulline
 Materials and methods. A two-reaction model system was carried out to study and monitor the inhibitory impact of the dietary supplement L-Citrulline against advanced glycation end products (AGEs) formation. This system involved the in vitro glucose bovine serum albumin (BSA-glucose assay) and methylglyoxal bovine serum albumin (BSA-MGO assay). The antioxidant activity of the supplement was assessed by measuring its capacity to chelate metal ions and scavenge reactive oxygen species. The iron chelating activity was evaluated through absorbance measurements, while fluorescence measurements were employed for the remaining assays.
 Results. According to the findings of the antiglycation assays, it was observed that the dietary supplement L-Citrulline demonstrated inhibitory properties against the development of advanced glycation end products (AGEs) in the BSA-Glucose model at a concentration of 100 ppm. The degree of inhibition with respect to glycation was ascertained to be 52.19 ± 0.39 % through observation. The BSA-MGO model has exhibited inhibitory properties with an observed activity of 49.64 ± 0.27 % at 100ppm concentration with respect to glycation. On the other hand, the supplement demonstrates antioxidant characteristics through the chelation of Fe ions, leading to a percentage difference in activity of 68.58 ± 0.45 % compared to the control at 100 ppm. The utilization of Glucolypotoxixity (GLT) media during the reactive oxygen species assay yielded a significant rise of 173.48 ± 9.37 % in the reactive species levels compared to the control, with statistical significance. The addition of 10 mM dietary supplement L-Citrulline resulted in a noteworthy reduction of 98.42 ± 5.04 % in the escalation. Therefore, it can be deduced that utilizing L-Citrulline as a dietary supplement exhibits potential for its therapeutic applications in eliminating reactive oxygen species (ROS) within skeletal muscle cells.
 Conclusion. The study results suggest that the dietary supplement L-Citrulline has demonstrated inhibitory capabilities against glycation at varying concentration levels. Furthermore, it was noted to exhibit significant efficacy in both sets of antioxidant tests. Therefore, the supplement exhibits potential in the treatment of diabetes mellitus

Advances in Chelated Metal Electrolyte for Aqueous Flow Batteries

Flow battery electrolyte containing chelated metal ions can support high voltage, high power, and high efficiency battery cycling in pH-neutral conditions. In this talk the coordination behavior and flow battery performance of chelated metal ions including vanadium, chromium, iron, and cerium will be presented. Key to enabling this approach is the fundamental understanding of the coordination properties of the chelating agent to specific metal ions and oxidation states. Techno-economic analyses suggest that the performance advantages of chelation more than offsets the cost of the chelating agents. Finally, strategies towards high concentration (> 2 M) cycling of these electrolytes will be presented, and the implications of energy density on overall system footprint will be discussed.

Discovery of New Hydrazone-Thiazole Polyphenolic Antioxidants through Computer-Aided Design and In Vitro Experimental Validation.

Oxidative stress is linked to a series of diseases; therefore, the development of efficient antioxidants might be beneficial in preventing or ameliorating these conditions. Based on the structure of a previously reported compound with good antioxidant properties and on computational studies, we designed several catechol derivatives with enhanced antioxidant potential. The compounds were synthesized and physicochemically characterized, and their antioxidant activity was assessed through different antiradical, electron transfer and metal ions chelation assays, their electrochemical behavior and cytotoxicity were studied. The results obtained in the in vitro experiments correlated very well with the in silico studies; all final compounds presented very good antioxidant properties, generally superior to those of the reference compounds used. Similarly, the results obtained from studying the compounds' electrochemical behavior were in good agreement with the results of the antioxidant activity evaluation assays. Regarding the compounds' cytotoxicity, compound 7b had a dose-dependent inhibitory effect against all cell lines. In conclusion, through computer-aided design, we developed several catechol thiazolyl-hydrazones with excellent antioxidant properties, of which compound 7b, with two catechol moieties in its structure, exhibited the best antioxidant activity.

Constructing Ultrastable Metallo-Cages via In Situ Deprotonation/Oxidation of Dynamic Supramolecular Assemblies.

Coordination-driven self-assembly enables the spontaneous construction of metallo-supramolecules with high precision, facilitated by dynamic and reversible metal-ligand interactions. The dynamic nature of coordination, however, results in structural lability in many metallo-supramolecular assembly systems. Consequently, it remains a formidable challenge to achieve self-assembly reversibility and structural stability simultaneously in metallo-supramolecular systems. To tackle this issue, herein, we incorporate an acid-/base-responsive tridentate ligand into multitopic building blocks to precisely construct a series of metallo-supramolecular cages through coordination-driven self-assembly. These dynamic cagelike assemblies can be transformed to their static states through mild in situ deprotonation/oxidation, leading to ultrastable skeletons that can withstand high temperatures, metal ion chelators, and strong acid/base conditions. This in situ transformation provides a reliable and powerful approach to manipulate the kinetic features and stability of metallo-supramolecules and allows for modulation of encapsulation and release behaviors of metallo-cages when utilizing nanoscale quantum dots (QDs) as guest molecules.

A lignin-derived material improves plant nutrient bioavailability and growth through its metal chelating capacity

The lignocellulosic biorefinery industry can be an important contributor to achieving global carbon net zero goals. However, low valorization of the waste lignin severely limits the sustainability of biorefineries. Using a hydrothermal reaction, we have converted sulfuric acid lignin (SAL) into a water-soluble hydrothermal SAL (HSAL). Here, we show the improvement of HSAL on plant nutrient bioavailability and growth through its metal chelating capacity. We characterize HSAL’s high ratio of phenolic hydroxyl groups to methoxy groups and its capacity to chelate metal ions. Application of HSAL significantly promotes root length and plant growth of both monocot and dicot plant species due to improving nutrient bioavailability. The HSAL-mediated increase in iron bioavailability is comparable to the well-known metal chelator ethylenediaminetetraacetic acid. Therefore, HSAL promises to be a sustainable nutrient chelator to provide an attractive avenue for sustainable utilization of the waste lignin from the biorefinery industry.

Design, Synthesis, and Proof of Concept of Balanced Dual Inhibitors of Butyrylcholinesterase (BChE) and Histone Deacetylase 6 (HDAC6) for the Treatment of Alzheimer's Disease.

Concomitant inhibition of butyrylcholinesterase (BChE) and histone deacetylase 6 (HDAC6) is supposed to be effective in the treatment of Alzheimer's disease (AD). Inspired by our previous efforts in designing BChE inhibitors, herein, selective BChE and HDAC6 dual inhibitors were successfully identified through the fusion of the core pharmacophoric moiety of BChE and HDAC6 inhibitors. After the structure-activity relationship (SAR) studies, two compounds (24g and 29a) were confirmed to have superior inhibitory activity against BChE (the IC50 against hBChE are 4.0 and 1.8 nM, respectively) and HDAC6 (the IC50 against HDAC6 are 8.9 and 71.0 nM, respectively). These two compounds showed prominently neuroprotective effects in vitro, potent reactive oxygen species (ROS) scavenging effects, and effective metal ion (Fe2+ and Cu2+) chelation. In addition, they exhibited pronounced inhibition of phosphorylated tau and a moderate immunomodulatory effect, with a lack of neurotoxicity at the cellular level. In vivo studies showed that both 24g and 29a ameliorated the cognitive impairment in an Aβ1-42-induced mouse model at a low dosage (2.5 mg/kg). Our data demonstrated that BChE/HDAC6 dual inhibitors could establish the basis for a potential new symptomatic and disease-modifying strategy to treat AD.

Biochemical Mechanisms of Beneficial Effects of Beta-Alanine Supplements on Cognition.

Using nutritional interventions to cure and manage psychiatric disorders is a promising tool. In this regard, accumulating documents support strong relationships between the diet and brain health throughout the lifespan. Evidence from animal and human studies demonstrated that β-alanine (Beta-alanine; BA), a natural amino acid, provides several benefits in fight against cognitive decline promoting mental health. This review summarizes and reports state-of-the-art evidence on how BA affects cognitive health and argues existence of potential unrevealed biochemical mechanisms and signaling cascades. There is a growing body of evidence showing that BA supplement has a significant role in mental health mediating increase of the cell carnosine and brain-derived neurotrophic factor (BDNF) content. BDNF is one of the most studied neurotrophins in the mammalian brain, which activates several downstream functional cascades via the tropomyosin-related kinase receptor type B (TrkB). Activation of TrkB induces diverse processes, such as programmed cell death and neuronal viability, dendritic branching growth, dendritic spine formation and stabilization, synaptic development, cognitive-related processes, and synaptic plasticity. Carnosine exerts its main effect via its antioxidant properties. This critical antioxidant also scavenges hypochlorous acid (HOCl), another toxic species produced in mammalian cells. Carnosine regulates transcription of hundreds of genes related to antioxidant mechanisms by increasing expression of the nuclear erythroid 2-related factor 2 (Nrf2) and translocating Nrf2 to the nucleus. Another major protective effect of carnosine on the central nervous system (CNS) is related to its anti-glycating, anti-aggregate activities, anti-inflammatory, metal ion chelator activity, and regulation of pro-inflammatory cytokine secretion. These effects could be associated with the carnosine ability to form complexes with metal ions, particularly with zinc (Zn2+). Thus, it seems that BA via BDNF and carnosine mechanisms may improve brain health and cognitive function over the entire human lifespan.

Structural Characterization of Zinc-Sucrose Complex and Its Ability to Promote Zinc Absorption in Caco-2 Monolayer Cells and Mice.

Sucrose emerges as a metal-ion chelating agent with excellent stability that may increase metal-ion absorption. This study aimed to characterize the structure of zinc-sucrose complex and investigate its ability to promote zinc absorption in Caco-2 monolayer cells and mice. Based on the results of the inductively coupled plasma emission spectrometer (ICP-ES), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared spectroscopy (FT-IR), it can be inferred that zinc and sucrose were chelated at a 1:1 ratio, with the hydroxyl groups playing a significant role. The Caco-2 monolayer cell model revealed that zinc-sucrose complex increased the amount of zinc uptake, retention, and transport in a dose- and time-dependent manner. Through the upregulation of genes and proteins for ZIP4, MT1, and DMT1, treatment with zinc-sucrose complex improved the proportion of absorbed zinc utilized for transport compared to ZnCl2 (26.21 ± 4.96 versus 8.50 ± 1.51%). Pharmacokinetic analysis of mice confirmed the zinc absorption-promoting effect of zinc-sucrose complex, as indicated by the considerably higher serum zinc level (4.16 ± 0.53 versus 2.56 ± 0.45 mg/L) and intestinal ZIP4, MT1, and DMT1 gene expression than ZnCl2. Further treatment of different zinc channel inhibitors and CETSA demonstrated the direct interaction of zinc-sucrose complex with ZIP4 protein and ZIP4-mediated cellular transport of zinc-sucrose complex. These findings provide a novel insight into the zinc absorption-promoting mechanism of zinc-sucrose complex, which could be used as an ingredient in functional foods to treat zinc deficiency.

Comprehensive analysis of the effect of reservoir key parameters on the efficacy of DTPA chelating agent in minimizing interfacial tension and enhanced oil recovery

Chelating agents reduce the salinity of seawater (SW) and mimic low salinity water (LSW) by binding metal ions in the solution and on the rock surface. This process decreases SW dilution costs and prevents scale formation while improving oil recovery without damaging the reservoir. This study investigates the impact of Diethylenetriaminepentaacetic acid (DTPA) chelating agent on the reduction of interfacial tension (IFT) between oil and SW, without the use of additional chemicals. For the first time, we comprehensively analyzed how reservoir key parameters (concentration, salinity, temperature, and pH) affect the performance of DTPA in reducing IFT. Additionally, rock wettability alteration and sand pack flooding experiments were conducted to evaluate the effect of DTPA on rock wettability and oil recovery. The results revealed that increasing the temperature to 75 °C and the concentration of DTPA to 5 wt% resulted in an IFT reduction to less than 1 mN/m, making the oil miscible in the DTPA solution. Salinity studies demonstrated that by increasing the solution salinity up to the optimal level, the IFT of oil/brine decreased. Furthermore, using 5 wt% DTPA solution altered the rock/oil contact angle from 143° (oil-wet) to 23° (strongly water-wet), highlighting the effect of DTPA on rock wettability alteration. Based on these findings, 5 wt% DTPA was selected as the optimal concentration, resulting in an increase in oil recovery up to 20.3% of original oil in place (OOIP) after SW injection. Elemental analysis of DTPA flooding effluent also confirmed the chelation of metal ions from rock and solution.

Improving functional properties of rice protein isolates by hydrolysis using alcalase enzyme and assessing bioactivities of hydrolysates

AbstractBackgroundDeveloping value‐added products from rice grains is becoming increasingly significant to enhance productivity from excess rice grains. Therefore, the objective of this study was to improve the functional properties of rice protein from four rice varieties, namely, RRF‐127, RRF‐105, Swarna, and Protezin by enzymatic hydrolysis, and also to evaluate bioactivities like antioxidant, ACE, and DPP‐IV inhibitory activities of the hydrolysates.ResultsThe alcalase hydrolysis increased protein solubility to >80% in the pH range of 4–10. The foaming capacity and stability of rice protein hydrolysates (RPHs) improved with the increase in pH. The hydrolysis significantly improved the emulsification activity index (EAI) in the pH range of 5–9. The hydrolysates showed antioxidant activity, namely, ABTS•+radical scavenging, reducing power, and metal ion chelation. RRF‐105 was found to possess the most potent antioxidant capacity among the hydrolysates. RPH could alleviate oxidative damage in erythrocytes, and their protective effects were concentration‐dependent. The hydrolysates had stronger inhibition of ACE and DPP‐IV enzymes. Protezin exhibited the highest ACE inhibition (63%), while Swarna demonstrated the most effective DPP‐IV inhibition (66%).ConclusionHydrolysis with alcalase improved the functional and bioactive properties of rice proteins, indicating that RPH could serve as a source of bioactive peptides or as a functional ingredient with potential properties.

Improving the functionality and biological properties of Iranian date palm (Phoenix dactylifera L) seeds protein with different proteases

In this study, date seeds as a major agricultural by-product were utilized for production of antioxidant peptides with techno-functional properties. Date seeds protein (DSP) was extracted and hydrolyzed by different enzymes (Alcalase, trypsin, pancreatin and pepsin). Then, the degree of hydrolysis (DH), amino acid composition, functional characteristics (e.g., solubility, and water- and oil-holding capacity), free radical inhibiting activity, reducing power, total antioxidant activity (TAA) and metal ion chelating activity of the hydrolysates (DSPHs) were examined. Chemical analysis of the obtained protein concentrate (∼ 65 %) indicated the presence of amide A and B regions. Also, amide I to III regions and secondary structures (α-helix, β-sheet, β-tern and random coils) were observed in the extracted DSP-protein. The DH and essential amino acids content of DSPHs were affected by enzyme type. The hydrolysis treatments resulted in a significant increase in the solubility of DSP, particularly in acidic pH levels and around its isoelectric point. In comparison to DSP, DSPHs also exhibited higher inhibitory activity against free radicals such as DPPH (72.5 %), ABTS (92.5 %), OH (64.5 %), and NO (57.9 %). Furthermore, DSPHs demonstrated greater reducing power (1.84), TAA (2.3), and enhanced chelating activity towards iron (73.2 %) and copper (40.1 %) transition ions. Various factors, including DH and the composition of amino acids, especially the amount of charged, hydrophobic, and antioxidant types, have played a crucial role in these outcomes. With their significant nutritive, functional, antioxidant, and metal ion chelating activities, DSPHs can serve as a natural additive to enhance the nutritional value and stability of various food products.

Experimental Study of New Antioxidant to Inhibit Spontaneous Combustion of Coal

ABSTRACT Free radicals and metal ions are key factors causing coal spontaneous combustion. In order to effectively suppress coal spontaneous combustion, experiments were conducted using luteolin as an inhibitor, luteolin is abbreviated as LUT. The influence of different concentrations of LUT on the spontaneous combustion heat characteristics of coal was tested using a C600 high-precision microcalorimeter, and the inhibition mechanism was inferred by FTIR. The experimental results show that LUT is an effective coal oxygen inhibitor, under the same action conditions, different concentrations of LUT can absorb heat to different degrees, delay the initial exothermic temperature of coal, prolong the heat absorption phase of coal. Compared with raw coal, 6 wt% LUT absorbs the most heat, the starting exothermic temperature is delayed by 46°C, and the activation energy is increased by 47.89 kJ/mol, the functional group -OH content decreased by 43.4%, -CH3 decreased by 32.1%, -CH2-decreased by 37.76%. Based on this, the mechanism of inhibition is inferred, LUT not only removes free radicals (ROO•) during the chain initiation stage and captures free radicals (•OH) in the reaction chain but also chelates metal ions to inhibit the catalytic effect of metal ions during the free radical reaction, which can play a dual role in preventing free radical generation and interrupting the free radical chain reaction. The results of the study can provide a novel, environmentally friendly and effective way to prevent the spontaneous combustion of coal.