A powerful method for In Situ and rapid detection of trace nanoplastics in water-Mie scattering.

The pervasive presence of nanoplastics (NPs) in environmental media has raised significant concerns regarding their implications for environmental safety and human health. However, owing to their tiny size and low level in the environment, there is still a lack of effective methods for measuring the amount of NPs. Leveraging the principles of Mie scattering, a novel approach for rapid in situ quantitative detection of small NPs in low concentrations in water has been developed. A limit of detection of 4.2 µg/L for in situ quantitative detection of polystyrene microspheres as small as 25 nm was achieved, and satisfactory recoveries and relative standard deviations were obtained. The results of three self-ground NPs showed that the method can quantitatively detect the concentration of NPs in a mixture of different particle sizes. The satisfactory recoveries (82.4% to 110.3%) of the self-ground NPs verified the good anti-interference ability of the method. The total concentrations of the NPs in the five brands of commercial bottled water were 0.07 to 0.39 µg/L, which were directly detected by the method. The proposed method presents a potential approach for conducting in situ and real-time environmental risk assessments of NPs on human and ecosystem health in actual water environments.

A novel biomass pyrogenic index and its application coupled with black carbon for improving polycyclic aromatic hydrocarbon source identification.

To accurately subdivide the sources of polycyclic aromatic hydrocarbons (PAHs), the composition characteristics of 36 total polycyclic hydrocarbons (T-PAHs; 16 parent PAHs and 20 alkylated PAHs [A-PAHs]) in biomass-residue samples were analyzed. A novel biomass pyrogenic index (BPI) was defined based on A-PAH-fingerprinting differences between biomass-combustion and petroleum sources of PAHs and the sum of the concentrations of pyrene, fluoranthene, benzo[a]anthracene, and alkylated homologs) divided by the ∑value of EPA PAHs with 2-3 rings. BPIs of < 0.5 and > 0.5 indicated that the PAHs originated mainly from biomass combustion and petroleum, respectively. And the ∑targeted A-PAH pairs influencing the BPI/black carbon (BC) ratio was used to identify PAH sources in surface-sediment samples, using 0.5 as the threshold to distinguish between different sources across the strait. The columnar sediments were used to verify the accuracy of two source-identification methods. The results revealed that the main PAH sources changed since 2005, which is highly consistent with those obtained using positive matrix factors and a changing trend in the main types of local energy use. These results highlight the significance of A-PAHs in accurately identifying PAH sources and suggest that applying compositional differences in BC from different sources for PAH-source identification merits further study.

Occurrence and distribution of lipophilic marine algal toxins in the coastal seawater of Southeast China and the South China Sea.

The composition, levels, and spatial distribution of dissolved lipophilic marine algal toxins (LMATs) including cyclic imines (CIs), yessotoxins (YTXs), okadaic acid (OA) and its derivatives, pectenotoxins (PTXs), azaspiracids (AZAs), and brevetoxins (BTXs) in the coastal waters of Southeast China (Xiamen) and the South China Sea (Hainan Island and Beibu Gulf) were investigated and compared for the first time. Dissolved AZA3 was firstly detected in the coastal seawater of China. OA and PTX2 were widely distributed in the three areas studied. Gymnodimine (GYM), 13-desmethyl spirolide C (SPX1), YTX, and homo-yessotoxins (h-YTX) were found mainly in the South China Sea. The average ∑LMAT concentrations in the coastal waters of Xiamen, Hainan Island, and Beibu Gulf were 10.02 ng/L, 4.21 ng/L, and 44.27 ng/L, respectively. More groups and much higher concentrations of LMATs occurred in the South China Sea than that in the other sea areas of China.

High-Efficiency and Wavelength-Tunable Near-Infrared Emission of Lanthanide Ions Doped Lead-Free Halide Double Perovskite Nanocrystals toward Fluorescence Imaging.

Near-infrared (NIR) fluorescent materials show unique photophysical properties, which make them widely used in optical communication, night vision imaging, biomedicine, and other applications. However, the development of high-efficiency and wavelength-tunable NIR nanomaterials is still a challenge. Herein, a series of lanthanide ions doped Cs2AgIn0.99Bi0.01Cl6 double perovskite nanocrystals (DPNCs) with wavelength-tunable NIR light emission (800-1600 nm) have been synthesized. The optimal photoluminescence quantum yield (PLQY) of the DPNCs reaches 66.7%, which is a record value for DPNCs. It is mainly attributed to the contribution of NIR emission of lanthanide ions doped into DPNCs. More importantly, the series of NIR emission wavelengths of lanthanide ions doped Cs2AgIn0.99Bi0.01Cl6 DPNCs include not only shorter-wavelength NIR light (≤900 nm) but also longer-wavelength NIR light (>900 nm), which are more appropriate for foodstuff analysis and medical diagnosis applications. Furthermore, 11.2% Nd3+ doped Cs2AgIn0.99Bi0.01Cl6 DPNCs with the optimal PLQY were embedded in a polymethyl methacrylate (PMMA) polymer matrix (DPNCs@PMMA), and the stability of DPNCs modified by PMMA has been greatly improved. Finally, the 11.2% Nd3+ ions doped Cs2AgIn0.99Bi0.01Cl6 DPNCs@PMMA based NIR LEDs have demonstrated good night vision and human tissue penetration. This work indicates that lanthanide ions doped DPNCs have a potential in NIR light applications and could inspire future research to explore novel lanthanide ions doped semiconductor NCs based NIR LEDs.

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. Here, 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 behaviour 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.

Highly efficient and stable red perovskite quantum dots through encapsulation and sensitization of porous CaF2:Ce,Tb nanoarchitectures.

Lead halide perovskite quantum dots (PQDs) are extremely unstable when exposed to oxygen, water and heat, especially red CsPbBrxI3-x (x = 0, 0.5, 1.2) PQDs. This seriously hinders their practical application. Here, red CsPbBrxI3-x (x = 0, 0.5, 1.2) PQDs have been successfully encapsulated in porous CaF2:Ce,Tb hierarchical nanospheres (HNSs), which not only greatly improved the stability of PQDs, benefitting from the protection of the CaF2 shell, but also maintained the high photoluminescence quantum yield (PLQY) of PQDs, benefitting from the sensitization of Tb3+ ions. More importantly, porous CaF2:Ce,Tb nanoarchitectures can prevent aggregation quenching and anion exchange of PQDs. Therefore, the CaF2:Ce,Tb&CsPbBrxI3-x (x = 0, 0.5, 1.2) composite powder can have high PLQY comparable to that of the PQD powder. In view of this, CaF2:Ce,Tb&CsPbBr1.2I1.8 composite based red light-emitting diodes (LEDs) are prepared, and they are very suitable as a supplementary light source for plant lighting. Furthermore, white LEDs are also prepared by coating the CaF2:Ce,Tb&CsPbBr3 and CaF2:Ce,Tb&CsPbBr1.2I1.8 composite on a 450 nm chip. The optimum luminous efficiency is 61.2 lm W-1, and the color rendering index is 91, which are comparable to the current highest values. This shows that the composite composed of PQDs has great potential in LED lighting.

How surfactants affect the depuration of polycyclic aromatic hydrocarbons adsorbed on the mangrove leaf surfaces: insight from an in situ method.

The effects of sodium dodecyl benzene sulfonate (SDBS), polyoxyethylene (20) sorbitan monolaurate (Tween 20), and their mixtures on the depuration of anthracene (Ant) and fluoranthene (Fla) individually adsorbed on the Kandelia obovata (Ko) leaf surfaces were in situ investigated. The Ko original leaf-wax microstructures have been destroyed by SDBS, Tween 20, and their mixtures at or above their critical micelle concentration (CMC). The volatilization rate constants (kV) of the adsorbed PAHs decreased with surfactants at or above their CMC resulting from the plasticizing effect and a decrease in the polarity of the Ko leaf-waxes induced by surfactants. Moreover, the photolysis rate constants (kP) of the adsorbed PAHs decreased with SDBS while increased with Tween 20 and their mixtures at or above their CMC, which can be attributed to effects of surfactants on the light adsorption behavior of Ko leaf-waxes. Overall, the effects of surfactants on the depuration of the adsorbed PAHs were dependent not only on the physical-chemical properties of surfactants but also on the micro-environment of the substrates adsorbed the PAHs. These results are of great significance for further understanding the accumulation of PAHs and could expand our knowledge about the migration mechanism of PAHs from the atmosphere by mangrove leaf surface micro-zones.

The distribution and retained amount of benzo[a]pyrene at the micro-zones of mangrove leaf cuticles: Results from a novel analytical method.

Plant leaf cuticles play a critical role in the accumulation and transport of atmospheric polycyclic aromatic hydrocarbons (PAHs). The relationship between the distribution and retained amount of PAHs on the leaf cuticles and the leaves micro-zone structures is still unclear. In this study, a confocal microscopic fluorescence spectral analysis (CMFSA) system with a spatial resolution of 200 nm was established as a direct and noninvasive means to determine the microscopic distribution and quantify the retained amount of benzo[a]pyrene (B[a]P) at Aegiceras corniculatum (Ac), Kandelia obovata (Ko) and Avicennia marina (Am) leaf cuticle micro-zones (0.096 mm2). The linear ranges for the established method were 10-1900 ng spot-1 for Ac, 15-1700 ng spot-1 for Ko and 30-1800 ng spot-1 for Am, and the detection limits were 0.06 ng spot-1 for Ac, 0.06 ng spot-1 for Ko and 0.07 ng spot-1 for Am. Notably, B[a]P formed clusters and unevenly distributed at the leaf cuticles. On the adaxial cuticles, B[a]P was mainly accumulated unevenly along the epidermis cell wall, and it was also distinctively distributed in the secretory cells around salt glands for Ac and Am. On the abaxial leaf cuticles, B[a]P was concentrated in the salt glands and stomata apart from being unevenly distributed in the epidermis cell wall. Moreover, the amount of B[a]P retained presented a negative correlation with the polarity of leaf cuticles, which resulted in the amount of B[a]P retained on the adaxial leaf cuticles being significantly higher than that on abaxial leaf cuticles. Our results provide a potential in situ method for investigating the distribution and retained amount of PAHs at plant leaf surface micro-zones, which would contribute to further studying and understanding the mechanism of migration and transformation of PAHs by plant leaves from a microscopic perspective.

Metformin attenuates atherosclerosis and plaque vulnerability by upregulating KLF2-mediated autophagy in apoE-/- mice.

Atherosclerosis is a chronic lipid disfunction and inflammatory disease, which is characterized with enriched foam cells and necrotic core underneath the vascular endothelium. Therefore, the inhibition of foam cell formation is a critical step for atherosclerosis treatment. Metformin, a first-line treatment for Type 2 diabetes, is reported to be beneficial to cardiovascular disease. However, the mechanism underlying the antiatherogenic effect of metformin remains unclear. Macrophage autophagy is reported to be a highly anti-atherogenic process that promotes the catabolism of cytosolic lipid to maintain cellular lipid homeostasis. Notably, dysfunctional autophagy in macrophages plays a detrimental role during atherogenesis. Krueppel-like factor 2 (KLF2) is an important transcription factor that functions as a key regulator of the autophagy-lysosome pathway. While the role of KLF2 in foam cell formation during the atherogenesis remains elusive. In this study, we first investigated whether metformin could protect against atherogenesis via enhancing autophagy in high fat diet (HFD)-induced apoE-/- mice. Subsequently, we further determined the molecular mechanism that whether metformin could inhibit foam cell formation by activating KLF2-mediated autophagy. We show that metformin protected against HFD-induced atherosclerosis and enhanced plaque stability in apoE-/- mice. Metformin inhibits foam cell formation and cellular apoptosis partially through enhancing autophagy. Mechanistically, metformin promotes autophagy via modulating KLF2 expression. Taken together, our study demonstrates a novel antiatherogenic mechanism of metformin by upregulating KLF2-mediated autophagy.

Parent and alkylated polycyclic aromatic hydrocarbons in surface sediments of mangrove wetlands across Taiwan Strait, China: Characteristics, sources and ecological risk assessment.

The characteristics, distributions and sources of parent polycyclic aromatic hydrocarbons (PAHs) and alkyl-PAHs (A-PAHs) as well as their ecological risk were explored in six mangrove wetlands across the Taiwan Strait, China. A-PAHs fingerprinting information, combined with PAHs diagnostic ratios and a positive matrix factorization model, were used to identify the sources of PAHs in the mangrove wetland surface sediment samples. The results showed that the total concentration of the 36 PAHs in the sediment samples varied from 186.2 to 2469.2 ng⸱g-1. Furthermore, the total concentration of PAHs would be underestimated about 37.1%-80.6% when only the concentrations of 16 priority PAHs were examined in the sediment samples. Coal combustion (32.7%) and petroleum combustion (24.6%) were identified as important contributing sources in the Yunxiao, Fugong, and Quanzhou mangrove wetlands, whereas the main source was mainly petroleum combustion (49.1%) in the Guandu, Zhuwei and Waziwei mangrove wetlands. In addition, the guidelines for assessing the ecological risk of individual A-PAHs need to be developed due to lack of criteria for most individual A-PAHs.

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)-ß-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.

Investigation on the interaction differences of algogenic dissolved organic matter released by Prorocentrum donghaiense with phenanthrene and 3-methylphenanthrene using spectroscopy.

Despite the high algogenic dissolved organic matter (A-DOM) content in the marine environment, the impact of A-DOM on the environmental behavior of alkylated polycyclic aromatic hydrocarbons (A-PAHs) has rarely been reported. Thus, this study sought to investigate the changes in A-DOM and its interaction with phenanthrene (Phe) and 3-methylphenanthrene (3-MPhe). The results showed that the spectroscopic characteristics of A-DOM changed dynamically during the entire growth period of Prorocentrum donghaiense. The total proportions of humic-like components in A-DOM, including marine humic-like and longer wavelength humic-like components, increased from 26.30% at the initial phase to 40.42% at the decline phase, but those of protein-like components decreased. Humic-like components showed stronger interaction capabilities with Phe/3-MPhe than that of protein-like components. The interaction characteristics and increased the humic-like components content indicated their prominent role in the interaction of A-DOM and Phe/3-MPhe. 3-MPhe had stronger hydrophobic interactions with the humic-like components and the methyl group increased π-π interactions with A-DOM on day 28. Methyl group also increased the molecular weight and steric hindrance of 3-MPhe, resulting in a lower interaction capability with A-DOM than that of Phe on day 16. The diverse interaction behaviors of A-DOM fluorescent components with Phe and 3-MPhe were largely attributed to dynamic changes in the A-DOM characteristics. Methyl substitution varied the hydrophobicity and molecular weight of Phe and 3-MPhe, and further influenced the interactions with A-DOM fluorescent components. These results highlight the vital impact of dynamic A-DOM on the environmental behavior of PAHs, and the differences in the environmental behavior between parent and alkylated PAHs should also receive additional attention.

Effects of multiwalled carbon nanotubes on the dissolved organic matter released by Prorocentrum donghaiense: Results of spectroscopic studies.

Many reports have investigated the effects of carbon nanotubes (CNTs) on the properties of terrestrial dissolved organic matter (DOM), which could significantly altered its binding affinity for contaminants. However, the effects of CNTs on algogenic DOM are largely unknown. To address this issue, the properties of algogenic DOM released by Prorocentrum donghaiense (P. donghaiense-DOM) under the stress from 0.1 to 10.0 mg/L graphitized multiwalled CNTs were nondestructively characterized by the use of UV-visible absorption and fluorescence excitation-emission matrices with parallel factor analysis. The results showed that the changes in the properties of P. donghaiense-DOM were highly dependent on the CNTs concentration. The properties of P. donghaiense-DOM under 0.1 mg/L CNTs treatment showed no obvious differences compared to the control. The addition of 0.5-10.0 mg/L CNTs changed the release pathways of P. donghaiense-DOM, resulting in significant alterations to the properties of P. donghaiense-DOM. The aromaticity, molecular weight, protein-like and humic-like components were enhanced under stress from 0.5 to 1.0 mg/L CNTs on day 4, which can be ascribed to the overproduction of extracellular DOM (EDOM) that occurred in response to the significant increase in intracellular ROS levels. CNTs at 5.0 and 10.0 mg/L significantly induced membrane damage to P. donghaiense on day 4, which led to the leakage of intracellular DOM (IDOM) and then increased the molecular weight and protein-like components but decreased the aromaticity and humic-like components. After the P. donghaiense recovered to its normal growth under 0.5-10.0 mg/L CNTs treatments, the changes in the properties of P. donghaiense-DOM were attributed to the release pathways of P. donghaiense-DOM that were governed by the production of EDOM and the leakage of IDOM in the stationary and declining phases, respectively.

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

To reveal the potential effects of hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) on catalase (CAT), the interactions of 1-hydroxynaphthalene (1-OHNap), 9-hydroxyphenanthrene (9-OHPhe) and 1-hydroxypyrene (1-OHPyr) with CAT were investigated using multi-spectroscopic and molecular docking techniques. Fluorescence analysis showed that 1-OHNap, 9-OHPhe and 1-OHPyr can form 1:1 complex with CAT, with the binding constant of 6.31 × 103, 1.03 × 104 and 2.96 × 105 L mol-1 at 17 °C. Thermodynamic and docking parameters demonstrated that van der Waals' force, hydrogen bonds and hydrophobic interactions dominated the three binding processes. Molecular docking also revealed the specific binding mode of OH-PAHs with CAT. Synchronous fluorescence and circular dichroism spectral results indicated that the three OH-PAHs induced varied structural changes of CAT. Furthermore, CAT activity was promoted by 9-OHPhe, but inhibited by either 1-OHNap or 1-OHPyr. Under the maximum experimental concentration of OH-PAHs, the percent change of CAT activity induced by 1-OHNap, 9-OHPhe and 1-OHPyr were 8.42%, 4.26% and 13.21%.

Neurodevelopmental toxicity assessments of alkyl phenanthrene and Dechlorane Plus co-exposure in zebrafish.

Alkyl phenanthrene (A-Phen) and Dechlorane Plus (DP) are ubiquitous environmental pollutants that widely co-exist in the environment. It has been established that both A-Phen and DP elicit neurotoxicity, but the potential interactive toxicity of these contaminants is not well-known. To determine whether a mixture of A-Phen and DP would exhibit interactive effects on neurodevelopment, we co-exposed 3-methylphenanthrene (3-MP), a representative of A-Phen, with DP. Our results illustrated that exposure to 5 or 20 µg/L 3-MP alone or in combination with 60 µg/L DP caused neurobehavioral anomalies in zebrafish. In accordance with the behavioral deficits, 3-MP alone or co-exposed with DP significantly decreased axonal growth of secondary motoneurons, altered intracellular Ca2+ homeostasis and induced cell apoptosis in the muscle of zebrafish. Additionally, 3-MP alone or co-exposed with DP significantly increased reactive oxygen species (ROS) and the mRNA levels of apoptosis-related genes. These findings indicate that 3-MP alone or co-exposed with DP induces neurobehavioral deficits through the combined effects on neuronal connectivity and muscle function. Chemical analysis revealed significant increases in 3-MP and DP bioaccumulation in zebrafish co-exposed with 3-MP and DP. Elevated bioaccumulation resulting from mixture exposure may represent a significant contribution of the synergistic effects observed in combined chemical exposure.

Simultaneous determination of dissolved phenanthrene and its metabolites by derivative synchronous fluorescence spectrometry with double scans method in aqueous solution.

A simple and sensitive derivative synchronous fluorescence spectrometry with double scans (DS-DSFS) method was developed for simultaneous determination of dissolved Phenanthrene (Phe) and its metabolites 1-hydroxy-2-naphthoic acid (1H2NA) and salicylic acid (SA) in aqueous solution. The value of 69 nm was selected as the optimal Δλ conditions for Phe and 1H2NA, and the Δλ value of 55 nm was selected for SA. The overlapping fluorescence emission spectra of Phe, 1H2NA and SA were resolved by DS-DSFS. The signals detected at wavelength of 296 nm for Phe, 352 nm for 1H2NA and 307 nm for SA vary linearly when the concentrations in the range of 4.0-1.0 × 103 µg L-1, 4.0-1.2 × 103 µg L-1 and 4.0-8.0 × 102 µg L-1, respectively. The detection limits were 0.08, 0.07 and 0.88 µg L-1 for Phe, 1H2NA and SA, with the relatively standard deviations less than 5.0%. The established method was successfully applied in the determination of Phe and the metabolites during the biodegradation of dissolved Phe in the lab. It was evidenced that the method has potential for the in situ investigation of PAH biodegradation.

Data on the fluorescence quenching analysis of BSA induced by pyrene and/or 1-hydroxypyrene in binary and ternary systems.

This article present data related to the publication entitled "Interactions of pyrene and/or 1-hydroxypyrene with bovine serum albumin based on EEM-PARAFAC combined with molecular docking" (Zhang et al., 2018) [1]. The excitation-emission matrix (EEM) fluorescence spectral parameters of pyrene, 1-hydroxypyrene, bovine serum albumin (BSA), and their mixtures were presented in this article. Combined EEM - parallel factor analysis with fluorescence quenching analysis, some data related to the binding affinity of pyrene and/or 1-hydroxypyrene with BSA in the binary and ternary systems were obtained.

Distributions, influencing factors, and risk assessment of Dechlorane Plus and related compounds in surficial water and sediment from the Jiulong River Estuary, Southeast China.

Dechloranes, a type of additive polychlorinated flame retardant, which include Dechlorane (Dec) Plus (DP), Dec 602, Dec 603, and Dec 604, were detected in surficial water and sediment from the Jiulong River Estuary (JRE). The total concentration of dechloranes in the water and sediments ranged from 1.4 to 4.1 ng/L and 9.3 to 36.2 ng/g dry weight, respectively. The distribution patterns of dechloranes in the water and sediments were both dominated by DP. The average values of the anti-DP fractional abundances (fanti) in the water and sediment samples both were fell in the range of commercial DP mixtures. The relationships of DP in the water with suspended particulate matter (SPM), total organic carbon (TOC), and tides indicated that the combined actions of these environmental factors influenced the distribution of DP in the JRE. The deleterious risk associated with exposure to dechloranes via the water for adults was very low, suggesting that exposure of the local population of dechloranes via water is relatively safe in the JRE.

Interactions of pyrene and/or 1-hydroxypyrene with bovine serum albumin based on EEM-PARAFAC combined with molecular docking.

The interactions of pyrene (Pyr) and/or 1-hydroxypyrene (1-OHPyr) with bovine serum albumin (BSA) in binary and ternary systems were investigated using the excitation-emission matrix (EEM)-parallel factor analysis (PARAFAC) method combined with fluorescence quenching analysis and the molecular docking method. The results showed that the PARAFAC approach could be used to decompose the EEM spectra of Pyr, 1-OHPyr, and BSA in the binary and ternary systems. The binding constants of Pyr and 1-OHPyr with BSA increased from 1.01 × 106 and 1.62 × 106 L mol-1 to 2.09 × 106 and 1.86 × 107 L mol-1 in the ternary systems compared with the binary systems, respectively. Molecular docking revealed that in both binary and ternary systems, Pyr was bound between II A and III A regions of BSA, whereas 1-OHPyr was located in the I B region. Van der Waals forces dominated the formation of the BSA-Pyr complexes; however, for BSA-1-OHPyr complexes, in addition to Van der Waals forces, hydrogen bonds also played an important role in their binding as a hydrogen bond formed between 1-OHP and the amino residue of BSA. Moreover, the coexistence of Pyr and 1-OHPyr aggravated the conformation changes of BSA and led to a prominent decrease in the hydrophobicity of the micro-environment around tryptophan (TRP) residues. 1-OHPyr has a more severe influence on BSA conformation than Pyr in the ternary systems. This study will help to understand the combined effects of PAHs and their hydroxyl metabolites on proteins at the molecular level.

Insight into the heterogeneous adsorption of humic acid fluorescent components on multi-walled carbon nanotubes by excitation-emission matrix and parallel factor analysis.

The heterogeneous adsorption behavior of commercial humic acid (HA) on pristine and functionalized multi-walled carbon nanotubes (MWCNTs) was investigated by fluorescence excitation-emission matrix and parallel factor (EEM- PARAFAC) analysis. The kinetics, isotherms, thermodynamics and mechanisms of adsorption of HA fluorescent components onto MWCNTs were the focus of the present study. Three humic-like fluorescent components were distinguished, including one carboxylic-like fluorophore C1 (λex/λem= (250, 310) nm/428nm), and two phenolic-like fluorophores, C2 (λex/λem= (300, 460) nm/552nm) and C3 (λex/λem= (270, 375) nm/520nm). The Lagergren pseudo-second-order model can be used to describe the adsorption kinetics of the HA fluorescent components. In addition, both the Freundlich and Langmuir models can be suitably employed to describe the adsorption of the HA fluorescent components onto MWCNTs with significantly high correlation coefficients (R2> 0.94, P< 0.05). The dissimilarity in the adsorption affinity (Kd) and nonlinear adsorption degree from the HA fluorescent components to MWCNTs was clearly observed. The adsorption mechanism suggested that the π-π electron donor-acceptor (EDA) interaction played an important role in the interaction between HA fluorescent components and the three MWCNTs. Furthermore, the values of the thermodynamic parameters, including the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), showed that the adsorption of the HA fluorescent components on MWCNTs was spontaneous and exothermic.