Effect Of Cu Research Articles

Effects of copper and lead on the sorption and desorption behaviors of benzene onto humic acids and black carbons

ABSTRACT Due to rapid urbanization and industrialization, combined pollution caused by BTEX (benzene, toluene, ethylbenzene, and xylene) and heavy metals has become ubiquitous in soils, which would pose serious health risks to humans. However, the effects of heavy metals on the sorption and desorption behaviors of BTEX have not been fully elucidated. In this study, the effects of Cu2+ and Pb2+ ions on the sorption and desorption of benzene onto humic acids and black carbons were investigated. The results showed that Cu2+ and Pb2+ ions significantly reduced the sorption capacity, slowed down the sorption rate, and made the desorption less hysteretic of benzene on both humic acids and black carbons. Furthermore, the inhibitory effects by Pb2+ were significantly stronger than those of Cu2+. By combining the results of Fourier transform infrared spectroscopy and the site energy distribution model, it can be speculated that the hydration shells of Cu2+ and Pb2+ ions partially cover the surface of humic acids and black carbons, blocking their micropores and shielding sorption sites, consequently inhibiting the sorption of benzene. This study highlights that coexisting metal cations can significantly influence the fate of BTEX in soils.

Effect of Cu2+ on the binding of catechins to zein through multi-spectral and in silico analyses

This study aimed to elucidate how Cu2+ influences the interaction between catechins and zein using multi-spectral and molecular modeling techniques. As a result, UV–vis spectra revealed characteristic changes, indicating chelation between catechins and Cu2+ at a 1:1 M ratio. Fluorescence spectra further confirmed interaction through a static quenching mechanism between catechins/catechin-Cu2+ complexes and zein. Catechins induced changes in the microenvironment and hydrophobicity surrounding the binding site of zein, whereas Cu2+ had minimal impact on these aspects. CD spectra underscored catechins' role in altering zein's secondary structure conformation, alongside Cu2+. Various types of interactions (hydrophobic, hydrogen bonding, electrostatic, and van der Waals) contributed to the binding of catechins/catechin-Cu2+ complexes with zein. Molecular modeling elucidated key residues and binding conformations, highlighting the significance of hydrophobic interactions and hydrogen bonding in their association. These findings not only deepen our understanding of catechin-Cu2+-zein interactions but also underscore their potential applications in the food industry.

Smartphone-Assisted and Optical Quantification of Copper and Glucose Using Palm Wine-Tailored Carbon Dots and Their Multiple Logic Gate Application.

In this work, potassium, sulfur, nitrogen, and chlorine self-doped carbon dots (CDs) were hydrothermally synthesized using palm wine as a carbon source. The palm wine-derived CDs (PW-CDs) are amorphous in nature and displayed an average particle size of 4.19 ± 0.89 nm. The as-synthesized CDs are used to fabricate a photoluminescent sensing probe to simultaneously detect Cu2+ and glucose via the "Turn ON-OFF-ON" mechanism. The PL quenching mechanism of PW-CDs enables the selective and sensitive detection of Cu2+ ions with a detection limit (LOD) of 0.8 ppb (4.7 nM). The sensing probe quantified Cu2+ in tap water, drinking water, and e-waste samples to prove its viability. Using CDs to quantify copper in e-waste leachate samples is a novel approach as no prior instances of such application have been reported. The system's performance is considered to be highly reproducible due to the relative standard deviation being <6.64%, along with excellent recoveries within the range of 93.24-109.86%. The quenched PL can be recovered by introducing glucose into the PW-CD + Cu2+ system; this strategy is employed to quantify glucose with a LOD of 0.11 ppm (0.61 μM). The feasibility of this sensor was confirmed by the determination of glucose in actual human plasma specimens of diabetic patients. It is to be noted that these samples were neither diluted nor spiked with glucose. The developed PW-CD + Cu2+ sensing system yields satisfactory recoveries of 93.45-107.37%. This probe was also incorporated into a smartphone-based sensing platform to detect Cu2+ and glucose with desirable recoveries. The proposed smartphone-based sensing platform is flexible, reliable, and accurate, making it suitable for resource-constrained areas. Furthermore, based on the effect of Cu2+ ions and glucose on the PL response and absorbance spectra of PW-CDs, four logic gates (YES, IMPLICATION, NOT, and OR) were designed, and PW-CDs were also used for cell imaging applications.

Fabrication of low-viscosity injectable mineralized hydrogel sensor with redox-activated hybrid nanoparticle structure for cancer detection

A redox-responsive low-viscosity, injectable hydrogel (LVI-gel) sensor with capabilities involving bimodal cancer detection via the incorporation of glutathione (GSH) and reactive oxygen species (ROS)-activated nanoparticles (PD-Cu2+) is proposed and made injectable with varying degrees of mineralization. The PD-Cu2+ complex, in the presence of overexpressed GSH and ROS, undergoes a structural change that causes a regain of fluorescence and a shift in conductivity, accompanied by the variations in the mechanical, and adhesive properties for cancer detection. The release of catechol moieties brought about by the structural change of the PD-Cu2+ complex influences the shift in hydrogen bonding, resulting in increased water uptake, further reducing viscosity (η decreases by 95.14 %) and increasing adhesiveness (360.28 % increase) in the presence of GSH 10 mM. The alterations in mechanical and electrical properties further affect the bending response via LCR (control: ΔR/R0 ∼ 0.55 and GSH 10 mM: ΔR/R0 ∼ 0.89), which was confirmed in vitro via wireless response with HeLa, PC-3, and B16F10 as cancer cells. The effect of Cu2+-catalyzed oxidation of GSH was observed in vivo from the immunohistochemical studies and the downregulation of transcription for GPx1/Rn18s. Additionally, increased superoxide dismutase (SOD2) and catalase (CAT) activity along with the downregulation of the oncogenic NFκβ and TNF gene are observed. Finally, the ex situ sensing activity was monitored by the shift in resistance and the wireless response, demonstrating the ease with which the sensor could diagnose.

Effect of Cu2+ on deposition mechanism and structure of ZrO2-based conversion coatings on AA6060 aluminium alloys and their susceptibility to filiform corrosion

Zirconium oxide-based conversion coatings (CCs) were prepared from hexafluorozirconic acid, H2ZrF6, with and without CuII as an additive. The CCs were prepared on primary and recycled AA6060. The deposition mechanism, structure, electrochemical properties and effectiveness in protection against filiform corrosion (FFC) have been explored. In presence of CuII additives, a two step deposition mechanism is observed, evidenced by open circuit potential measurements and in situ dynamic electrochemical impedance spectroscopy. Copper deposits predominantly as copper(II) hydroxyfluoride on the top surface, and metallic Cu0 at the metal/CC interface, as evidenced by x-ray photoelectron spectroscopy and glow-discharge optical emission spectroscopy. The presence of a CuII additive induces a different distribution of the ZrO2-based products. After deposition of a weak organic model coating, aluminium pretreated with the CuII-containing system shows a 10%–30% lower maximum filament length compared to the CuII-free system in FFC tests, despite a ca. one order of magnitude higher cathodic activity of the former.

Effect of Cu2+ doping on fluorescence of Cs2ZnCl4 powder prepared by solid-state synthesis

Recently Cu-doped all-inorganic zero-dimensional (0D) metal halides Cs2ZnX4 (X = Cl, Br) have attracted many researchers due to their excellent fluorescence (FL) performance and low toxicity compared to lead-based perovskites. Although these 0D metal halides nanocrystals or small-sized single crystals are prepared via solution methods in most of the reports, we used the solid-state synthesis method to get Cu-doped Cs2ZnCl4 powders and characterized their FL properties. The results and analysis indicate that Cu2+ can be doped in Cs2ZnCl4 up to 12 at.%, which enhances the FL of Cs2ZnCl4 powder. The photoluminescence quantum yield (PLQY) at 480 nm rises from 1.11 % (undoped) to 20.06 % (6 at.% Cu doping). A modified triplet self-trapped excitons mechanism is presented to explain the enhanced Cu−doped Cs2ZnCl4 powder.

Copper Ions Reduced Toxicity of Sodium Azide and Lipopolysaccharide on Cultured Cerebellar Granule Neurons

Introduction. Copper ions (Cu2+) are structural elements of proteins such as cytochrome с oxidase (Complex IV), an enzyme that catalyzes the final step of electron transfer to oxygen during oxidative phosphorylation in the mitochondria. With Cu2+ homeostasis being of utmost importance, its disturbances in the central nervous system are involved in the mechanisms of many neurodegenerative and other brain disorders.&#x0D; This study aimed to assess the effects of non-toxic copper ion levels on death of cerebellar granule neurons associated with lipopolysaccharide (LPS; in vitro inflammation model) or azide sodium (NaN3; cytochrome с oxidase inhibitor).&#x0D; Materials and methods. LPS (10 μg/mL) or NaN3 (250 μM) was added on day 7 to 8 to the culture medium with rat cerebellar cells for 24 hours in vitro. Nitrite concentrations were measured in the culture medium by Griess assay; absorbance was recorded with a spectrophotometer at 540 nm, and morphologically intact cells were counted as survived neurons.&#x0D; Results. Added to the culture medium, LPS or NaN3 reduced neuron survival to 15 ± 2% or 20 ± 3% vs. control, respectively. Cu2+ (0.5 to 5.0 μM) increased neuron survival in a dose-dependent manner to 78 ± 4% with toxic levels of LPS and to 86 ± 6% with NaN3 with 5 μM Cu2+. The concentration of nitrites in the control culture medium was 2.0 ± 0.2 μM. Added to the cell cultures, LPS increased the concentration of nitrites to 8.5 ± 0.5 μM. Cu2+ 5 μM did not show any significant effects on nitrite accumulation in the culture medium.&#x0D; Conclusions. We showed that copper ions can exert protective effects on neurons against LPS-induced or NaN3-induced toxicity. This protection is likely to be associated rather with Cu2+ interaction with Complex IV of the electron transfer chain in the mitochondria than with inhibition of NO production. Effects of Cu2+ on apoptosis pathway proteins also cannot be ruled out.

Corrosion inhibition of 8-HQ for AA5052 in 3 wt% NaCl solution in presence of trace Cu2+ ions: Electrochemical/surface studies, DFT/MD modeling

In this paper, the effect of Cu2+ ions on corrosion inhibition of 8-hydroxyquinoline (8-HQ) for AA5052 aluminum alloy in the simulated seawater solution has been studied by weight loss experiments, electrochemical measurements and surface analysis. 8-HQ inhibits the corrosion of AA5052 aluminum alloy in 3 wt% NaCl solutions very well, resulting in a positive shift in corrosion potential. The 0.01 mg/L of Cu2+ ions can deteriorate the corrosion inhibition of 8-HQ at low concentrations. This behavior is interpreted on the basis of deposition of copper by displacement on the defects of the corrosion inhibition film of 8-HQ. When the concentration of 8-HQ reached 5 mg/L, the presence of 0.01 mg/L Cu2+ ions increase the corrosion inhibition efficiency of 8-HQ by 6.27%. 8-HQ shows efficient inhibition at a relative high concentration, suggesting that the chelate formed by Cu2+ ions and 8-HQ can repair the defects of the 8-HQ inhibitive film on aluminum surface. The complex film would suppress the partial cathodic reaction and lead to the improved corrosion inhibition.

(Digital Presentation) Coffee Extract Assisted Synthesis of Cu2+-Doped NiFe2O4 and Influence on Corrosion for Steel in Acidic Environment

Due to the great importance of looking for new alternatives for the use of agroindustrial waste, it is intended to synthesizeCu2+-doped NiFe2O4 nanoparticles in an environmentally friendly way from extract of the agroindustrial waste coffee pulp, characterizing its structural and anticorrosive properties. A preliminary study of the effect of the concentration of Ni, Cu and Fe on the corrosion of steel in 1M sulfuric acid was developed, using various advanced electrochemical tools such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD). The effect of Cu2+-doped NiFe2O4 on corrosion for steel in acidic environment is promising and of great importance for the industry.

Investigation on the effect of Cu2+, Mn2+ and Fe3+ on biotreatment of Cr(VI) by Shewanella oneidensis and Bacillus subtilis in bimetallic system

Coexistence of chromium and iron, manganese and copper in industries is common, which may affect the microbial treating efficiency and toxicity to microorganisms, thus restricting the application of microbial treatment technology. In this research, Cu2+ promoted the reduction of Cr(VI) and the fixation of total chromium in bimetallic systems for both Shewanella oneidensis MR-1 and Bacillus subtilis, while Mn2+ and Fe3+ exhibited inhibition effects. Generally, groups with coexisting heavy metal of 0.1 mM were most affected, no matter promotive or inhibitive. Toxicity analysis revealed that high concentration of heavy metal ions led to damage to the cell membranes and reduction of their survival rate. To clarify the optimal condition for microbial treatment, response surface methodology was used to investigate the influencing factors of Cr(VI) reduction by S. oneidensis. The total chromium concentration in the supernatant was correlated with three factors, and the significant order of influence was: culture time > culture temperature > pH.

Enhanced dielectric properties and improved thermal stability in TiO2-based ceramics by Cu and Nb co-doping

TiO2-based ceramics have application potential in multilayer ceramic capacitors because of its large dielectric constant and low dielectric loss. In this work, Cu2+, Nb5+ co-doped TiO2 ceramics (CNTO) with colossal permittivity and low loss were designed and prepared via an oxide mixed method, and the effect of Cu2+, Nb5+ co-doped amount on dielectric properties were systematically investigated. Remarkably, the compositions of (Cu1/3Nb2/3)0.005Ti0.995O2 and (Cu1/3Nb2/3)0.01Ti0.99O2 exhibit large dielectric permittivity (εr) of ∼27,060 and ∼41,200 accompanied with low dielectric loss (tan δ) of ∼0.011 and ∼0.032 at 1 kHz, respectively. Based on dielectric properties, relaxation behavior assessments and X-ray photoelectron spectroscopy analysis, we confirmed that the high dielectric permittivity of CNTO ceramics mainly originates from the electron-pinned defect-dipole (EPDD) effect. Moreover, the temperature stability value of εr keeps stable of ±7.5% at 1 kHz from −200 to 200 °C for (Cu1/3Nb2/3)0.005Ti0.995O2 and from 10 to 200 °C for (Cu1/3Nb2/3)0.01Ti0.99O2 ceramics, which separately meet the X9F and Z9F capacitor requirements, respectively. The findings presented in this work might have important strategic significance for promoting the miniaturization of electronic components.

Corrosion behavior of AA5052 aluminum alloy in the presence of heavy metal ions in 3.5 % NaCl solution under negative pressure

Aluminum alloy heat exchange tube is attractive for the Low Temperature-Multi Effect Distillation (LT-MED) desalination device, for its low cost and excellent mechanical property. However, it is prone to galvanic coupling corrosion in presence of heavy metal ions. In this paper, the effect of Cu2+ and Fe3+ ions on the corrosion of aluminum alloy in 3.5 wt% NaCl solution under negative pressure is investigated by the weight-loss method and the electrochemical measurements. It shows that the operation pressure affects significantly the corrosion behavior of AA5052 aluminum alloy in presence of heavy metal ions. As the pressure decreases, the resistance of the aluminum alloy to corrosion increases markedly. The corrosion products formed under different operation pressure are detected by SEM, XRD analysis. It is found that the diffusion process of corrosion products from the aluminum alloy surface into the solution is prevented as the decrease of pressure, resulting in the formation of the passivation layer on the aluminum alloy surface. The decrease of pressure can effectively restrain the heavy metal ions to be adsorbed on the defects of the oxide layer and mitigate the corrosion of aluminum during the LT-MED desalination process.

Effect of Cu2+ and Cr3+ doping on structural, morphological, optical and electrical properties of zinc sulfide nanoparticles for optoelectronic applications

Effect of Cu2+ and Cr3+ doping on structural, morphological, optical and electrical properties of zinc sulfide nanoparticles for optoelectronic applications

The Effect of Cu2+ and Pb2+ in the Feed Solution on the Water and Reverse Solute Fluxes in the Forward Osmosis (FO) Process Using Nanofiltration (NF) Membranes

The application of nanofiltration (NF) membranes in the forward osmosis (FO) process to remove heavy metal ions from wastewater is an emerging concept. Unlike NF, FO does not require an external driving force. Although the product, a dilute draw solution, must further be processed by NF to produce pure water and reconcentrate a draw solution, the feed to that NF process is “clean”, which minimizes membrane fouling. This paper examines the role of Cu2+ and Pb2+ in the feed solution on the water and the reverse solute fluxes in FO process using novel thin film nanocomposite (TFN) NF membranes. The TFN membranes were fabricated by in situ interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride (TMC) containing different amounts of dispersed halloysite nanotubes (HNTs) nanoparticles functionalized with the first generation of poly(amidoamine) (PAMAM) dendrimers. The presence of Cu2+ and Pb2+ in the feed solution decreased the reverse flux of MgCl2 by at least 2.5 times compared to the experiments with pure water as a feed. Simultaneously, the water flux also increased. The corresponding rejections of Cu2+ and Pb2+ in the FO process ranged from 94.5% to 98.1%.

The Effect of Cu2+ Exposure on the Nrf2 Signaling Pathway of Tilapia Hepatocyte, Base on Experiments In Vitro

Copper is a common component of industrial heavy metal waste and a major component of some fish medicines, which can cause oxidative stress and damage the health of farmed fish. The Nrf2 signaling pathway is an important pathway related to the oxidative stress on vertebrates. Exploring the effect of copper on the Nrf2 signaling pathway in fish hepatocytes would help improve the understanding of the molecular mechanism of antioxidants in fish hepatocytes and provide theoretical data for relevant toxicological research. Adult tilapia were cultured under properly controlled conditions for two weeks to adapt to laboratory culture conditions. Primary tilapia hepatocytes were obtained by cell culture. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay was used to detect the effect of copper ions on the viability of tilapia hepatocytes. The lipid peroxidation level (MDA) and antioxidant ability of tilapia hepatocytes (SOD and CAT activity) were detected. Quantitative PCR (qPCR) was used to detect the differential expression of each gene (Nrf2, Keap1a, Keap1b, CuZnSOD, MnSOD, HO-1, and GSTA) in the Nrf2 signaling pathway. The results suggested that after treatment with 100 μM copper ions for 4 h, 8 h, and 24 h, the viability of hepatocytes significantly decreased (p &lt; 0.05). LDH and MDA after 8 h and 24 h treatment were significantly higher than those in the control group (p &lt; 0.05). CAT activity significantly decreased after 4 h (p &lt; 0.05), and SOD activity significantly decreased after 8 h and 24 h (p &lt; 0.05). The results of qPCR showed that the expression of MnSOD significantly increased after a treatment with copper ions for 4 h, and the expression of Nrf2, Keap1a, CuZnSOD, HO-1 as well as GSTA significantly increased after a treatment with copper ions for 8 h, compared with the control group (p &lt; 0.05). After being treated with copper ions for 24 h, the expression of Nrf2 and CuZnSOD significantly increased compared with the control group (p &lt; 0.05). There was no significant difference in the expression of Keap1b or CAT at each time point. In conclusion, with copper ions exposure, the viability of tilapia hepatocytes was reduced, causing lipid peroxidation, a reduction in the antioxidant capacity of cells, the activation of the Nrf2 signaling pathway, and the increase in the expression of most genes in this pathway, which are defensive responses of hepatocytes to oxidative stress caused by copper ions. This study can provide theoretical data for related toxicological research.

The photoactivity of complexation of DOM and copper in aquatic system: Implication on the photodegradation of TBBPA

The photoactivity of dissolved organic matter (DOM) has a great impact on the photodegradation of organic pollutants in natural waters. In this study, the photodegradation of TBBPA was investigated under simulated sunlight irradiation in the presence of copper ion (Cu2+), dissolved organic matter (DOM) and Cu-DOM complexation (Cu-DOM) to illustrate the effect of Cu2+ on photoactivity of DOM. The rate of photodegradation of TBBPA in the presence of Cu-DOM complex was 3.2 times higher than that in pure water. The effects of Cu2+, DOM and Cu-DOM on the photodegradation of TBBPA were highly pH dependent and hydroxyl radical(·OH) responded for the acceleration effect. Spectral and radical experiments indicated that Cu2+ had high affinity to fluorescence components of DOM, and acted as both the cation bridge and electron shuttle, resulting the aggregation of DOM and increasing of steady-state concentration of ·OH (·OHss). Simultaneously, Cu2+ also inhibited intramolecular energy transfer leading to the decrease of steady-state concentration singlet oxygen (1O2ss) and triplet of DOM (3DOM⁎ss). The interaction between Cu2+ and DOM followed the order of conjugated carbonyl CO, COO− or CO stretching in phenolic groups and carbohydrate or alcoholic CO groups. With these results, a comprehensive investigation on the photodegradation of TBBPA in the presence of Cu-DOM was conducted, and the effect of Cu2+ on the photoactivity of DOM was illustrated. These findings helped to understanding the potential mechanism of interaction among metal cation, DOM and organic pollutants in sunlit surface water, especially for the DOM-induced photodegradation of organic pollutants.

Cu2−x Se nanoparticles suppress cell proliferation and migration in hepatocellular carcinoma by impairing mitochondrial respiration

Cu2−x Se nanoparticles (Cu2−x Se NPs) as a new therapeutic drug platform is widely used in disease treatment due to their strong near-infrared optical absorption. In recent years, with their continuous expansion of applications in different fields, their own biological effects have received increasing attention. However, little is known about the effect of Cu2−x Se NPs on cancer cell. In this research, we found that Cu2−x Se NPs inhibited proliferation of HepG2 cells (IC50: 15.91 μM) and SMMC-7721 cells (IC50: 43.15 μM) and they mainly induced cell cycle arrest at the G2/M phase. Moreover, Cu2−x Se NPs inhibited HepG2 and SMMC-7721 cell migration and lamellopodia formation. Further studies indicated that Cu2−x Se NPs impaired mitochondrial respiration by inhibiting electron transport chain complex activity, thus reducing adenosine triphosphate levels. The insufficient energy supply subsequently impaired actin cytoskeleton assembly, ultimately inhibiting HepG2 and SMMC-7721 cell proliferation and migration. These findings suggest that Cu2−x Se NPs may have potentially antitumor activity, which might provide new insights of NPs into specific cancer treatment.

Metallothionein-3 attenuates the effect of Cu2+ ions on actin filaments

Metallothionein 3 (MT-3) is a cysteine-rich metal-binding protein that is expressed in the mammalian central nervous system and kidney. Various reports have posited a role for MT-3 in regulating the actin cytoskeleton by promoting the assembly of actin filaments. We generated purified, recombinant mouse MT-3 of known metal compositions, either with zinc (Zn), lead (Pb), or copper/zinc (Cu/Zn) bound. None of these forms of MT-3 accelerated actin filament polymerization in vitro, either with or without the actin binding protein profilin. Furthermore, using a co-sedimentation assay, we did not observe Zn-bound MT-3 in complex with actin filaments. Cu2+ ions on their own induced rapid actin polymerization, an effect that we attribute to filament fragmentation. This effect of Cu2+ is reversed by adding either EGTA or Zn-bound MT-3, indicating that either molecule can chelate Cu2+ from actin. Altogether, our data indicate that purified recombinant MT-3 does not directly bind actin but it does attenuate the Cu-induced fragmentation of actin filaments.

Repeated fluctuation of Cu2+ concentration during photocatalytic purification of SMZ-Cu2+ combined pollution: Behavior, mechanism and application

Although the effect of Cu2+ on antibiotic removal during photocatalytic reaction has been studied in depth, there is less known about the effect of antibiotics on Cu2+ removal. In this study, we report for the first time that, during the photocatalytic purification of sulfamerazine (SMZ) and Cu2+ combined pollution, Cu2+ concentration showed an obvious five-stage fluctuation, which was completely different from the simple promotion or inhibition reported in previous studies. By employing HPLC-MS analysis and density functional theory (DFT) calculation, the repeated fluctuation of Cu2+ concentration was found to be closely related to the SMZ degradation process, mainly resulting from solution pH drop and formation of Cu-containing intermediates which acted as sacrificial agents for Cu2+ reduction. In addition, compared with the SMZ-free system, the presence of SMZ can greatly enhance the deep removal of Cu2+ (minimum Cu2+ concentration was only 0.17 mg/L vs. 1.28 mg/L without SMZ), and there was a wide time interval to ensure the efficient recovery of Cu metal. More interestingly, the in-situ obtained Cu-decorated TiO2 photocatalyst performed well in water splitting, nitrogen fixation and bacterial sterilization. Results of this study confirmed the great potential of photocatalytic technology in purifying antibiotic-heavy metal combined pollution.

Effect of Cu2+ and Al3+ on the interaction of chlorogenic acid and caffeic acid with serum albumin

Despite the phenolic acids' health benefits, their interactions with proteins are still unclear. In this study, the interactions of Bovine Serum Albumin (BSA) with chlorogenic acid (CHA), caffeic acid (CA), and their Al3+, Cu2+ complexes were studied by using circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and UV/Vis spectroscopy. It was found that esterification of carboxyl group of CA with quinic acid increased the binding affinities for BSA. After chelating with Cu2+ and Al3+, both CHA and CA exhibited high binding affinities for BSA. CHA could form CHA-Cu2 and CHA-Al2 complex with Cu2+ and Al3+. The result of CD spectroscopy demonstrated that the binding of CHA and Al3+ with BSA contributed to the folding of BSA secondary structure. In addition, with the presence of CHA, binding with Al3+ could also induce changes in BSA conformation. The binding sites of both CHA and CA were closed to Trp213.