Study on the molecular interactions of hydroxylated polycyclic aromatic hydrocarbons with catalase using multi-spectral methods combined with molecular docking

Investigation on the interaction between catalase and typical phthalates with different side chain lengths

Phthalates (PAEs), a category of plasticizers released from plastic products, have been widely detected in various environmental media and pose potential ecological risks to humans. Although the exposure risks of PAEs to organisms have been studied, the differences in the interactions between PAEs with different side chain lengths and biomolecules remain poorly understood at molecule levels. In this study, three commonly used PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP)) were employed to investigate the influence of their side chain lengths on interactions with catalase (CAT), a key antioxidant enzyme. The effects of PAEs on CAT enzyme activity and their interaction mechanisms were investigated using multi-spectral technique and molecular docking techniques. The results indicate that the order of reduced enzyme activity by PAEs is DMP > DEP > DBP, which inversely correlates with the alkyl chain length of PAEs. Molecular docking analysis reveal that DBP failing to bind to the central cavity of CAT likely contributes to its minimal impact on enzyme activity. The multiple spectrums demonstrate that the binding affinity of PAEs to CAT and the changes of CAT conformational structure align with the observed decline in enzyme activity as alkyl chain length increased. Since enzyme activity ties to its structure, the structural alterations in CAT induced by PAEs would inevitably affect its functional expression in vivo. This study offers a comprehensive assessment on the possible toxicity of PAEs with different side chain lengths at the molecular levels, providing insights into their ecological risks.

Effect of central metal ion on some pharmacological properties of new Schiff base complexes. Anticancer, antioxidant, kinetic/thermodynamic and computational studies

The biological capacities of Schiff Base complexes such as anti-cancer, anti-microbial and anti-oxidant properties have been widely studied in the scientific community. However, the effect of central metal ion in the occurrence of their biological properties should be paid more attention. With this aim, novel 2-(hydroxyimino)-1-phenylpropylidene)benzohydrazide (HIPB) Schiff base ligand, and C1/palladium(II), C2/platinum(II), and C3/zinc(II) complexes derived from it were synthesized and characterized. Theoretical studies showed that C2 is more reactive and also has a higher pharmacological affinity than C1 and C3. Experimental investigations were done to compare some biological properties of the complexes. The anticancer assay showed that C1-C3 have the ability to inhibit the growth of HCT116 colon cancer cell lines, but C2 shows a relatively better effect than other. Antioxidant studies using •DPPH (2,2-diphenyl-1-picrylhydrazyl) assay presented the following trend: C2 > C1 > C3 > HIPB. Considering the importance of the antioxidant enzyme catalase in removing reactive oxygen species (ROS), the interaction of C1-C3 with Bovine Liver Catalase (BLC) was evaluated. Kinetic studies showed that C1-C3 can inhibit the catalytic performance of BLC by a similar mechanism, i.e. mixed-type inhibition. Among them, C1 was the strongest inhibitor (Activity inhibition% = 82.2). The C1-C3 quenched the BLC fluorescence emission with dynamic quenching mechanism. The binding affinity to BLC was higher for C1 and C2 than C3. The most important forces in the interaction of C1-C3 with BLC were hydrophobic interactions, which was strongly confirmed by molecular docking data. Tracking the structural changes of catalase showed that BLC undergoes structural changes in the presence of C1 more than C2 and C3.

Studies of the binding mechanism between liquid smoke from tea tree branches and proteins in dry-cured tenderloin using 4D-DIA proteomics, synergistic multispectral analysis, and molecular docking techniques

This research investigates the impact of various concentrations of tea branch liquid smoke (TLS) on the protein structure of dry cured pork tenderloin using multispectral techniques, molecular docking, and 4D-DIA proteomics. The results reveal that TLS enhances the solubility of myofibrillar protein, with varying effects on tryptophan exposure based on the concentration. Notably, at 5 mL/kg, TLS inhibits myofibrillar protein unfolding. Raman spectroscopy demonstrates that higher TLS concentrations mitigate disruptions in hydrogen bonding and hydrophobicity. Guaiacol and furfural in TLS engage in π-stacking interactions with myosin, heightening myosin interaction with its carrier. 4D-DIA proteomics has revealed that TLS can down-regulate the expression of cytoplasmic and mitochondrial proteins, metabolic enzymes, and ligases, playing pivotal roles in metabolism and genetic information processing. These proteins, featuring membrane linkers and phosphatases, potentially impact peptide and amino acid biosynthesis, thereby affecting meat quality modifications.

Biomarker and adverse outcome pathway responses of Tubifex tubifex (sludge worm) exposed to environmentally-relevant levels of acenaphthene: insights from behavioral, physiological, and chemical structure-activity analyses

Polycyclic aromatic hydrocarbons (PAHs), including acenaphthene, pose a significant threat to aquatic ecosystems by harming vital organisms such as benthic invertebrates. This study evaluated the impact of environmentally relevant concentrations of acenaphthene on Tubifex tubifex, focusing on sublethal acute toxicity and subchronic biomarker responses. Key biomarkers assessed included histopathological changes and the modulation of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and malondialdehyde (MDA). Additionally, the study examined structure-activity relationships and species sensitivity distribution (SSD). Concentrations exceeding the solubility threshold of acenaphthene (3.9 mg/L) triggered distinct, concentration-dependent behavioral responses in Tubifex tubifex, such as clumping, mucus secretion, and body wrinkling. Prolonged exposure exacerbated these behavioral dysfunctions, while subchronic exposure resulted in significant histopathological alterations, including epithelial hyperplasia, inflammation, edema, fibrosis, and degenerative changes. The edematic appearance of the body wall suggested a potential immune response to exposure. Furthermore, increased activities of CAT, SOD, and GST indicated oxidative stress in the worms. The study found a 1.5-fold increase in CAT and GST activity, a fivefold increase in SOD, and a striking 100-fold increase in MDA levels compared to controls, signifying an overwhelmed antioxidant defense system and potential cellular disruption. The SSD curve revealed hazard concentrations (HC50 and HC90), indicating that Tubifex tubifex exhibited lower sensitivity to acenaphthene compared to other taxa. In silico analysis and read-across models confirmed the potential of acenaphthene to induce significant oxidative stress upon exposure. The correlation between biomarker responses and structure-activity relationship analysis highlighted the aromatic nature of acenaphthene as a key factor in generating reactive metabolites, inhibiting antioxidant enzymes, and promoting redox cycling, ultimately contributing to adverse outcomes. These findings, coupled with behavioral responses and SSD curve inferences, underscore the importance of the solubility threshold of acenaphthene as a critical benchmark for evaluating its ecological impact in aquatic environments.

Experimental and Theoretical Approaches to Monitor the Behavior of Bovine Liver Catalase in Interaction with a Binuclear Bismuth Complex

Here, the antioxidant potency of a binuclear Bi(III) complex {[Bi2(μ-ox)(dipic)2(H2O)2 (taa)2].H2O, where ox2- = oxalato, dipic2- = pyridine 2,6-dicarboxylato, and taa = thiourea} was evaluated using the •DPPH assay. It was demonstrated that the Bi complex exhibited a high ability to inhibit DPPH free radicals. The binding mechanism of the complex with bovine liver catalase (BLC) was also investigated, revealing structural and activity changes in the enzyme in the presence of the complex. The catalase activity in the decomposition of hydrogen peroxide increased in the presence of the Bi complex, reaching 39.8% higher than its initial activity at a concentration of 7.77 × 10-6 M. The complex exhibited a relatively high affinity for BLC, with K b values of 3.98, 0.13, and 0.09 × 105 M-1 at 303, 310, and 317 K, respectively. The mechanisms involved in the interaction were hydrogen bonding and van der Waals interactions, as validated through molecular docking simulations. Synchronous fluorescence showed that tryptophan was more affected by enzyme-complex interactions than tyrosine. In addition, a cell viability test using the MTT method revealed that at its highest concentration, the Bi complex caused a decrease in the number of cells below 50% compared to the control, while cisplatin showed negative effects at all concentrations. These findings suggest that the Bi complex has the potential to be developed as a promising candidate for BLC-related therapeutic target therapy.

Tracking the binding site of anticancer drug fluxoridin with Fe-related proteins to achieve intelligent drug delivery

In cancer cells that need a lot of iron for growth and metastasis, halo-transferrin (TF-containing iron) enters the cell with the help of the transferrin receptor 1 (TFR1) protein. If the anticancer drug can bind to the iron site by interacting with apo-transferrin (iron-free FT), it can enter the cancer cell by the same mechanism. Two iron-related proteins, Bovine liver catalase (BLC) and apo-Transferrin (TF), that are important in cancer patients were selected and their interaction with the anti-cancer drug Floxuridine (FUDR) was investigated. Here, the protective role of FUDR was evaluated by several variables such as drug concentration, interaction time, and temperature-induced degradation of enzyme function. The results showed that the protective effect of the FUDR is greater in high concentrations (in 5 × 10-5 M:1.78 % and 2.59 % after 24 and 48 h). The interaction of the FUDR with both proteins can reduce the intensity of the fluorescence emission by a static mechanism. The binding strength of the FUDR with both proteins was almost similar and with the order of 104 M-1 (Kb = 3.90 ± 0.41 × 104 M-1 for BLC-FUDR and 5.01 ± 0.36 × 104 M-1 for TF-FUDR at 310 K). The thermodynamic calculations (in agreement with the docking results) indicated that FUDR-protein complex formation was exothermic and the main binding forces in the binding process were van der Waals interactions and hydrogen bonds. Both fluorophores tryptophan (Trp) and tyrosine (Tyr) of both proteins had significant roles in fluorescence quenching and the interaction process, the polarity of their microenvironment changed. CD results showed that the secondary structure changes of TF are slightly more than BLC. Molecular docking showed that the binding of the FUDR to TF is very close to the Fe-specific site and is placed in the cavity among the wrapping domain, N-Terminal arm, and β-barrel in BLC.

A multi-omics approach to unravelling the coupling mechanism of nitrogen metabolism and phenanthrene biodegradation in soil amended with biochar

The presence of polycyclic aromatic hydrocarbons (PAHs) in soil negatively affects the environment and the degradation of these contaminants is influenced by nitrogen metabolism. However, the mechanisms underlying the interrelationships between the functional genes involved in nitrogen metabolism and phenanthrene (PHE) biodegradation, as well as the effects of biochar on these mechanisms, require further study. Therefore, this study utilised metabolomic and metagenomic analysis to investigate primary nitrogen processes, associated functional soil enzymes and functional genes, and differential soil metabolites in PHE-contaminated soil with and without biochar amendment over a 45-day incubation period. Results showed that dissimilatory nitrate reduction to ammonium (DNRA) and denitrification were the dominant nitrogen metabolism processes in PHE-contaminated soil. The addition of biochar enhanced nitrogen modules, exhibiting discernible temporal fluctuations in denitrification and DNRA proportions. Co-occurrence networks and correlation heatmap analysis revealed potential interactions among functional genes and enzymes responsible for PHE biodegradation and nitrogen metabolism. Notably, enzymes associated with denitrification and DNRA displayed significant positive correlation with enzymes involved in downstream phenanthrene degradation. Of particular interest was stronger correlation observed with the addition of biochar. However, biochar amendment inhibited the 9-phenanthrol degradation pathway, resulting in elevated levels of glutathione (GSH) in response to environmental stress. These findings provide new insights into the interactions between nitrogen metabolism and PHE biodegradation in soil and highlight the dual effects of biochar on these processes.

Bitterness quantification and simulated taste mechanism of theasinensin A from tea

Theasinensin A is an important quality chemical component in tea, but its taste characteristics and the related mechanism are still unclear. The bitterness quantification and simulated taste mechanism of theasinensin A were researched. The results showed that theasinensin A was significantly correlated with the bitterness of tea. The bitterness threshold of theasinensin A was identified as 65 μmol/L for the first time. The dose-over-threshold (DOT) value of theasinensin A was significantly higher than that of caffeine in black tea soup. The concentration-bitterness curve and time-intensity curve of theasinensin A were constructed. The bitterness contribution of theasinensin A in black tea was higher than in oolong and green tea. Theasinensin A had the highest affinity with bitterness receptor protein TAS2R16, which was compared to TAS2R13 and TAS2R14. Theasinensin A was mainly bound to a half-open cavity at the N-terminal of TAS2R13, TAS2R14, and TAS2R16. The different binding capacity, hydrogen bond, and hydrophobic accumulation effect of theasinensin A and bitterness receptor proteins might be the reason why theasinensin A presented different bitterness senses in human oral cavity.

Hydroxylated polycyclic aromatic hydrocarbons possess inhibitory activity against alpha-glucosidase: An in vitro study using multispectroscopic techniques and molecular docking

Alpha-glucosidase (GAA) activity can be affected by exogenous substances. Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) are typical metabolites of PAHs that can enter the body through various routes. The effects of 1-hydroxynaphthalene (1-OHNap) and 1-hydroxypyrene (1-OHPyr) on GAA activity and the potential mechanisms were investigated viamultispectroscopic methods and molecular docking. First-order derivative synchronous spectrofluorimetry was successfully applied to analyze the fluorescence quenching of GAA in the GAA-1-OHNap and GAA-1-OHPyr systems. 1-OHNap and 1-OHPyr had strong inhibitory effects on GAA activity. GAA could bind with 1-OHNap and 1-OHPyr in 1:1 mode with binding constants of 3.97 × 10⁴ and 9.42 × 10⁴ L/mol at 298 K. Hydrophobic interactions and hydrogen bonds played pivotal roles in the interactions. 1-OHNap was located closer to the active site of GAA than 1-OHPyr. This work suggests that the disturbance of glycometabolism by exogenous pollutants in the human body is worthy of attention and further investigation.

Improvement of Oxidative Stability of Fish Oil-in-Water Emulsions through Partitioning of Sesamol at the Interface

The susceptibility of polyunsaturated fatty acids to oxidation severely limits their application in functional emulsified foods. In this study, the effect of sesamol concentration on the physicochemical properties of WPI-stabilized fish oil emulsions was investigated, focusing on the relationship between sesamol-WPI interactions and interfacial behavior. The results relating to particle size, zeta-potential, microstructure, and appearance showed that 0.09% (w/v) sesamol promoted the formation of small oil droplets and inhibited oil droplet aggregation. Furthermore, the addition of sesamol significantly reduced the formation of hydrogen peroxide, generation of secondary reaction products during storage, and degree of protein oxidation in the emulsions. Molecular docking and isothermal titration calorimetry showed that the interaction between sesamol and β-LG was mainly mediated by hydrogen bonds and hydrophobic interactions. Our results show that sesamol binds to interfacial proteins mainly through hydrogen bonding, and increasing the interfacial sesamol content reduces the interfacial tension and improves the physical and oxidative stability of the emulsion.

Investigation of the binding behavior of bioactive 7-methoxyflavone to human serum albumin by coupling multi-spectroscopic with computational approaches

The natural flavonoids with bioactivity as secondary plant metabolites are mostly found in fruits, vegetables, tea and herbs, the distribution and bioavailability of which in vivo depends on the interaction and successive binding with carrier proteins in the systemic circulation. In this paper, the binding behavior of bioactive 7-methoxyflavone (7-MF) with human serum albumin (HSA) was studied with the aid of the combination of multi-spectroscopic methods, molecular docking and molecular dynamic simulation. The results of multi-spectroscopic experiments revealed that 7-MF interacted with HSA predominantly via fluorescence static quenching and the microenvironment around the fluorophore Trp residues in HSA became more hydrophilicity with the binding of 7-MF. Thermodynamic analysis demonstrated that hydrogen bonds and van der Waals forces played a dominant role in stabilizing the HSA-7-MF complex. Moreover, the docking experiment and molecular dynamic simulation further confirmed that 7-MF could enter the active cavity of HSA and caused more stable conformation and change of secondary structure of HSA through forming hydrogen bond. The exploration of the mechanism of 7-MF binding to HSA lights a new avenue to understand the stability, transport and distribution of 7-MF and 7-MF may hold great potential to be extended as a promising alternative of dietary supplements or pharmaceutical agents.

Insights into the Binding Interaction of Catechol 1,2-Dioxygenase with Catechol in Achromobacter xylosoxidans DN002

Microbial remediation has become one of the promising ways to eliminate polycyclic aromatic hydrocarbons (PAHs) pollution due to its efficient enzyme metabolism system. Catechol 1,2-dioxygenase (C12O) is a crucial rate-limiting enzyme in the degradation pathway of PAHs in Achromobacter xylosoxidans DN002 that opens the benzene ring through the ortho-cleavage pathway. However, little attention has been given to explore the interaction mechanism of relevant enzyme-substrate. This study aims to investigate the binding interaction between C12O of strain DN002 and catechol by means of a molecular biological approach combined with homology modeling, molecular docking, and multiple spectroscopies. The removal rate of catechol in the mutant strain of cat A deletion was only 12.03%, compared to the wild-type strain (54.21%). A Ramachandran plot of active site regions of the primary amino acid sequences in the native enzyme showed that 93.5% sequences were in the most favored regions on account of the results of homology modeling, while an additional 6.2% amino acid sequences were found in conditionally allowed regions, and 0.4% in generously allowed regions. The binding pocket of C12O with catechol was analyzed to obtain that the catalytic trimeric group of Tyr164-His224-His226 was proven to be great vital for the ring-opening reaction of catechol by molecular docking. In the native enzyme, binding complexes were spontaneously formed by hydrophobic interactions. Binding constants and thermodynamic potentials from fluorescence spectra indicated that catechol effectively quenched the intrinsic fluorescence of C12O in the C12O/catechol complex via conventional static and dynamic quenching mechanisms of C12O. The results of ultraviolet and visible (UV) spectra, synchronous fluorescence, and circular dichroism (CD) spectra revealed conspicuous changes in the local conformation, and site-directed mutagenesis confirmed the role of predicted key residues during catalysis, wherein His₂₂₆ had a significant effect on catechol utilization by C12O. This is the first report to reveal interactions of C12O with substrate from the molecular docking results, providing the mechanistic understanding of representative dioxygenases involved in aromatic compound degradation, and a solid foundation for further site modifications as well as strategies for the directed evolution of this enzyme.

Interactions between hydroxylated polycyclic aromatic hydrocarbons and serum albumins: Multispectral and molecular docking analyses

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) can bind to serum albumin and influence their distribution and elimination in organisms. Herein, multispectral analysis and molecular docking methods were used to investigate the binding mechanism of two OH-PAHs, 1-hydroxyphenanthrene (1-OHPhe) and 9-hydroxyphenanthrene (9-OHPhe), with two homologous serum albumins, human serum albumin (HSA) and bovine serum albumin (BSA). The quenching constants of HSA with 1-OHPhe and 9-OHPhe were much larger than those for BSA. Energy transfer from the tryptophan (Trp) residues in HSA to 1-OHPhe and 9-OHPhe was more probable than from Trp in BSA. The interactions of 1-OHPhe and 9-OHPhe with Trp in HSA and BSA altered the microenvironment of Trp. Molecular docking results revealed that the binding modes and binding forces of 1-OHPhe and 9-OHPhe with HSA and BSA were different. The two OH-PAHs were used as fluorescent probes to analyze the microenvironmental hydrophobicities of HSA and BSA, which were distinctly different. The structural difference between HSA and BSA induced significant variations in their binding behavior with 1-OHPhe and 9-OHPhe. Moreover, HSA was more susceptible to 1-OHPhe and 9-OHPhe than BSA. This work suggests that the differences between the two serum albumins should be considered in related studies.

Immobilization and Evaluation of Penicillin G Acylase on Hydroxy and Aldehyde Functionalized Magnetic α-Fe2O3/Fe3O4 Heterostructure Nanosheets

Magnetic α-Fe2O3/Fe3O4 heterostructure nanosheets were fabricated via hydrothermal calcination. The activity of penicillin G acylase (PGA), which was covalently immobilized onto silica-decorated heterostructure nanosheets, achieved the highest activity of 387.03 IU/g after 18 h of incubation with 0.1 ml of PGA. In contrast, the activity of free PGA reached the highest level when the temperature was 45°C with a pH of 8.0. However, the activity of free PGA changed more dramatically than immobilized PGA as the relative conditions changed. Moreover, the Michaelis-Menten constant (Km) and reusability of immobilized PGA were also explored. The results showed that free PGA Km and maximum rate (Vmax) were 0.0274 M and 1.167 μl/min, respectively. Km and Vmax values of immobilized PGA were 0.1082 M and 1.294 μl/min, respectively. After 12 cycles of repetitive use, immobilized PGA remained approximately 66% of its initial activity, indicating that the PGA immobilized onto the heterostructure nanosheets showed better stability and reusability than free PGA.

Dose-response relationships between polycyclic aromatic hydrocarbon exposure and blood cell counts among coke oven workers: a sex-stratified analysis

OBJECTIVES

To explore sex differences and dose-response relationships between nine urinary polycyclic aromatic hydrocarbon (PAH) metabolites and neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR) and complete blood counts among coke oven workers.

DESIGN AND SETTING

A cross-sectional study with stratified sex was conducted in Shanxi, China.

PARTICIPANTS

A total of 458 male workers and 226 female workers were selected.

PRIMARY AND SECONDARY OUTCOME MEASURES

General linear models, p values for trend tests and natural cubic spline models were used to explore the dose-response relationships between nine urinary PAH metabolites and NLR, PLR and complete blood counts.

RESULT

Compared with male workers, female workers had lower exposure level of PAH (0.95 ng/mL vs 1.38 ng/mL). Only among female workers did we observe that a 1-unit increase in lg(1-OHPyr) was related to a 0.149 (95% CI: 0.055 to 0.242; p for trend=0.041) and 0.103 (95% CI: 0.025 to 0.181; p for trend=0.007) increase in lg(NLR) and lg(PLR), and a 0.116 (95% CI: -0.179 to -0.054; p for trend=0.007) decrease in lg(lymphocyte counts (LYMs)). A 1-unit increase in lg(2-OHNap) was related to a 0.045 (95% CI: 0.003 to 0.086; p for trend=0.037) increase in lg(PLR) and a 0.029 (95% CI: -0.056 to -0.002; p for trend=0.030) and 0.016 (95% CI: -0.029 to -0.003; p for trend=0.010) decrease in lg(white blood cell counts (WBCs)) and lg(haemoglobin (HGB)).

CONCLUSION

Female workers' NLR, PLR, WBCs, HGB and LYMs may be more susceptible than those of male workers when affected by PAH.

Molybdenum Selenide/Porous Carbon Nanomaterial Heterostructures with Remarkably Enhanced Light-Boosting Peroxidase-like Activities

Nanozymes have emerged as a fascinating nanomaterial with enzyme-like characteristics for addressing the limitations of natural enzymes. Nevertheless, how to improve the relatively low catalytic activity still remains challenging. Herein, a facile recrystallizing salt template-assisted chemical vapor deposition method was utilized to synthesize MoSe₂/PCN heterostructures. This heterostructure displays remarkably enhanced light boosting peroxidase-like activities. Notably, the maximal reaction velocity of this heterostructure attains 17.81 and 86.89 μM min^-1 [for o-phenylenediamine (OPD) and 3,3'5,5'-tetramethylbenzidine (TMB), respectively]. Moreover, various characterization means were performed to explore the mechanism deeply. It is worth mentioning that the photoinduced electrons generated by the heterostructure directly react with H₂O₂ to yield plentiful ^•OH for the effective oxidation of OPD and TMB. Therefore, this work offers a promising approach for improving peroxidase-like activity by light stimulation and actuating the development of enzyme-based applications.

Structural and functional changes of catalase through interaction with Erlotinib hydrochloride. Use of Chou's 5-steps rule to study mechanisms

Erlotinib hydrochloride (Erlo) is used in the treatment of non-small cell lung cancer, pancreatic cancer and other types of cancer. Interaction of small molecules with bio-macromolecules can lead to changes in the structure and function of them which is one of the possible side effects of the drugs. In this study, the interaction of Erlo with bovine liver catalase (BLC) using spectroscopic and computational methods is presented in detail. The enzymatic function of BLC decreased to 58.7% when the concentration of the Erlo was 0.5 × 10^-7 M. Fluorescence results revealed that the combination of BLC with Erlo undergoes static quenching mechanism (K_b = 1.15 × 10⁴ M^-1 at 300 K). The interaction process was spontaneous, exothermic and enthalpy-driven and Van der Waals and hydrogen bonds forces played major roles in the this process. UV-Vis, CD, 3D, and synchronous fluorescence measurements indicated the changes in the microenvironment residues and α-helix contents of BLC in the presence of Erlo. Docking and molecular dynamics presented a stable binding configuration and their results were perfectly consistent with the spectroscopic results. Theoretical calculations and experimental analysis help to fully understand of drug interaction with important biological molecules such as enzymes.

Mucin corona delays intracellular trafficking and alleviates cytotoxicity of nanoplastic-benzopyrene combined contaminant

Nanoplastics have recently become a worldwide concern as newly emerging airborne pollutants, which can associate with polycyclic aromatic hydrocarbons (PAHs) and form combined contaminant nanoparticles (CCNPs). After being inhaled in the respiratory system, the CCNPs would first encounter the mucous gel layer being rich in mucin. Herein, polystyrene-benzopyrene (PS@Bap) NPs were prepared as CCNPs model and their interaction with mucin and the resultant biological responses were studied. It was observed that mucin corona stably attached to the CCNPs surface, which significantly altered the fate of the CCNPs in lung epithelial cells (A 549 cell line). The mucin corona would 1) stably adsorbed on PS@Bap at the early stages of endocytosis until degraded during the lysosomal transport and maturation process, 2) delay intracellular trafficking of PS@Bap and the progress of Bap detached from PS, 3) enhance uptake of PS@Bap but reduce the cytotoxicity elicited by PS@Bap, as indicated by cell viability, generation of reactive oxygen species, impairment on mitochondrial function, and further cell apoptosis. In addition, in vivo study also verified the enhanced effect of PS on the development of an acute lung inflammatory response induced by Bap. This study highlights the significance of incorporating the effects of mucin for precisely assessing the respiratory system toxicity of nanoplastics based CCNPs in atmospheric environments.

Toxic mechanism of pyrene to catalase and protective effects of vitamin C: Studies at the molecular and cell levels

Polycyclic aromatic hydrocarbons, distributing extensively in the soil, would potentially threaten the soil organisms (Eisenia fetida) by triggering oxidative stress. As a ubiquitous antioxidant enzyme, catalase can protect organisms from oxidative damage. To reveal the potential impact of polycyclic aromatic hydrocarbon pyrene (Pyr) on catalase (CAT) and the possible protective effect of Ascorbic acid (vitamin C), multi-spectral and molecular docking techniques were used to investigate the influence of structure and function of catalase by pyrene. Fluorescence and circular dichroism analysis showed that pyrene would induce the microenvironmental changes of CAT amino acid residues and increase the α-helix in the secondary structure. Molecular simulation results indicated that the main binding force of pyrene around the active center of CAT is hydrogen bonding force. Furthermore, pyrene inhibited catalase activity to 69.9% compared with the blank group, but the degree of inhibition was significantly weakened after vitamin C added into the research group. Cell level experiments showed that pyrene can increase the level of ROS in the body cavity cell of earthworms, and put the cells under the threat of potential oxidative damage. Antioxidants-vitamin C has a protective effect on catalase and maintains the stability of intracellular ROS levels to a certain extent.

Potential ability of different types of cyclodextrins to modulate the interaction between bovine serum albumin and 1-hydroxypyrene

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) can bind with functional biomacromolecules and thus cause toxic effects in vivo. Four types of cyclodextrins (CDs) were selected to explore their potential ability to regulate the bindings between 1-hydroxypyrene (1-OHPyr) and bovine serum albumin (BSA) using multi-spectroscopic methods combined with molecular docking. The results showed that the four CDs caused varied modulating effects on the binding of BSA with 1-OHPyr, and the effects of γ-CD and (2-hydroxypropyl)-β-CD (HPCD) are the most significant. Specifically, γ-CD and HPCD could significantly reduce the binding affinity between 1-OHPyr and BSA, inhibit the micro-environmental changes of tryptophan residues, and slightly recover the helicity of BSA. The interactions and inclusion behavior of CDs with 1-OHPyr was the main reason why CDs could affect the binding of 1-OHPyr to BSA. The results indicated that γ-CD and HPCD might have potential application value in regulating the toxic effects of OH-PAHs.

Probing the Interaction between Human Serum Albumin and 9-Hydroxyphenanthrene: A Spectroscopic and Molecular Docking Study

9-Hydroxyphenanthrene (9-OHPhe), the representative hydroxyl metabolite of phenanthrene, has generated increasing concern as it is potentially hazardous to organisms. Herein, multispectroscopic and molecular docking techniques were applied to investigate the molecular interaction of human serum albumin (HSA) with 9-hydroxyphenanthrene (9-OHPhe) under simulated physiological conditions. Steady-state fluorescence and time-resolved fluorescence spectral analysis showed that 9-OHPhe quenched HSA fluorescence through a mixed static and dynamic process. HSA can bind with 9-OHPhe to form a 1:1 complex, with binding constants of 1.28 × 10⁵, 1.36 × 10⁵, and 1.26 × 10⁵ L·mol^-1 at 298.15, 303.15, and 308.15 K, respectively. The strong binding between HSA and 9-OHPhe is spontaneous and entropy-driven. Molecular docking indicated that the optimal binding site of 9-OHPhe with HSA was located in the IA subdomain of HSA. Thermodynamic analysis and molecular docking results suggested that hydrophobic interactions and hydrogen bond force dominated the binding process of HSA with 9-OHPhe. Specifically, 9-OHPhe formed hydrophobic interactions with LEU134, LEU139, ILE142, LEU154, PHE157, ALA158, and TYR161 and formed a 1.86 Å hydrogen bond with LEU135. Circular dichroism spectral analysis showed that the α-helical content of HSA decreased from 52.3 to 50.9% after adding 9-OHPhe with a ratio of 1:1. The obtained results are hoped to provide basic data for understanding the potential effects of the hydroxyl metabolites of PAHs on functional biomacromolecules.

Immobilization and characterization of cellulase on hydroxy and aldehyde functionalized magnetic Fe2O3/Fe3O4 nanocomposites prepared via a novel rapid combustion process

In this work, magnetic Fe₂O₃/Fe₃O₄ nanocomposites were prepared via a novel rapid combustion process. The silica was precipitated on the surface of Fe₂O₃/Fe₃O₄ nanocomposites. The silica-coated magnetic nanocomposites were cross-linked with glutaraldehyde, on which cellulase was covalently immobilized. The morphology, composition, and property of the prepared nanomaterials were characterized by the scanning electron microscopy (SEM), the energy dispersive spectrometry (EDS), the X-ray diffraction (XRD), the vibrating sample magnetometer (VSM), and the Fourier transform infrared (FTIR) spectroscopy. The immobilization conditions were optimized by varying operating parameters and determined to be 0.05 mL of 0.5% cellulase solution for 2 h. The catalytic stabilities of the immobilized cellulase were evaluated. The results showed that the immobilized cellulases performed higher apparent activity at pH 4.5 and exhibited good thermal stability compared with their free counterparts. The Michaelis-Menten equation showed that K_m and V_max of free cellulase were 3.46 mol·L^-1 and 0.53 mol·min^-1, respectively. The immobilized cellulase had higher K_m and V_max (18.99 mol·L^-1 and 0.59 mol·min^-1). The retained activity of the immobilized cellulase maintained over 71% of the initial activity after being used for five cycles.