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Metal-doped carbon dots (CDs) exhibited promising application in fluorescence and magnetic resonance (MR) imaging, but developing manganese-doped CDs (Mn-CDs) with long wavelength emission and enhanced MR performance is a challenge. Herein, using a one-step solvothermal method, Mn-CDs with redshifted orange emission and enhanced longitudinal relaxation were synthesized for fluorescence and MR imaging. The results indicated that the prepared Mn-CDs had a uniform size distribution, and the average size was 5 nm. Moreover, Mn-CDs possessed a stronger fluorescence performance than Mn-free CDs, and simultaneously, the emission wavelength can redshift from 542 nm (green emission) to 578 nm (orange emission), owing to the increasing N-doping. Because of the movement limit of Mn

Background Hirame novirhabdovirus (HIRRV) can infect a wide range of marine and freshwater fish, causing huge economic losses to aquaculture industry. Vaccine development, especially oral vaccine, has become an effective and convenient way to control aquatic infectious diseases. HIRRV glycoprotein (G), an immunogenic viral protein is a potential vaccine candidate for prevention of the disease. Here, we aimed to construct a recombinant Lactococcus lactis strain expressing HIRRV-G on the cell surface as an oral vaccine to prevent HIRRV. Results Glycoprotein gene of HIRRV was successfully cloned and expressed in L. lactis NZ9000 in a surface-displayed form, yielding Ll:pSLC-G. An approximately 81 kDa recombinant G protein (containing LysM anchoring motif) was confirmed by SDS-PAGE, western blotting and mass spectrometry analysis. The surface-displayed G protein was also verified by immunofluorescence and flow cytometry assays. Furthermore, to evaluate the potential of Ll:pSLC-G as oral vaccine candidate, flounders were continuously fed with commercial diet pellets coated with 1.0 × 109 cfu/g of induced Ll:pSLC-G for 1 week. Four weeks later, booster vaccination was performed with the same procedure. Compared with the controls, Ll:pSLC-G elicited significantly higher levels of specific IgM against HIRRV in flounder gut mucus at the second week and in serum at the fourth week (p

In this study, a novel antibacterial hemp fibre grafted with quaternary ammonium groups (HF–GTA), were prepared by alkalization, oxidation, amination and quaternization multistage reactions. The chemical structure and micromorphology of the fibre were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis and X-ray diffraction. The grafting and reaction mechanism proved to be successful, which indicated that the grafting reaction primarily occurred on the hydroxyl group of cellulose and hemicellulose in the hemp fibre, where it retained good fibrous morphology, thermal stability and hygroscopicity. HF–GTA exhibited the best antibacterial activity, where the antibacterial ratios against Escherichia coli and Staphylococcus aureus were 95.41% and 99.64%, respectively. Even after washing 30 times, the antibacterial activity was retained at 89.78% and 91.12%, indicating that HF–GTA was endowed with good washing resistance. The antibacterial activity was owing to the electrostatic reaction reducing the electrochemical potential on the cell membrane, leading to the release of cytoplasmic substances and the dissolution of cells. This study is significantly important for guaranteeing textile quality and preventing disease transmission.

Backgroud: Heavy metal pollutant, Cadmium (Cd), is an inorganic pollutant in China. Hemp (Cannabis sativa L.) is an important fiber crop to remediate heavy metal-contaminated soils. The MYB family is one of the largest and most important gene families that influences plant growth and produce secondary metabolites. Results: 115 CsMYB genes were identified in the hemp genome. The 1R-MYB subfamily had 17 genes, the 2R-MYB subfamily 88 genes, and the 3R-MYB subfamily 8 genes. The synteny analysis of the CsMYB genes indicated that there were 3 pairs of tandem repeats, 21 pairs of segmental duplication, 6 CsMYB genes present before species differentiation, and 60 genes belonging to the hemp-specific CsMYB genes. 7 CsMYB genes were identified to influence the response to Cd stress by combining the transcriptome data of two hemp species under Cd stress. Based on the changes in the Cannabinoid content of hemp under Cd stress, the expression of different CsMYB genes in hemp with high and low cannabidiol (CBD) contents, and tissue-specific expression, it was inferred that CsMYB024 may be affected by Cd stress and mediate the CBD synthesis pathway.Conclusions: This study provides a comprehensive analysis of the hemp MYB family. These results should be helpful in understanding of their potential functions in Cd-Stress Response and the Regulation of Cannabinoid Biosynthesis in Hemp. In addition, lays the foundation for the further study of biological functions of CsMYBs in hemp.

Due to the rapid development of industrial society, air pollution is becoming a serious problem which has being a huge threat to human health. Ultrafine particles (UFPs), one of the major air pollutants, are often the culprits of human diseases. At present, most of the toxicological studies of UFPs focus on their biological effects on lung cells and tissues, but there are less researches taking aim at the negative effects on functional proteins within the body. Therefore, we experimentally explored the effects of ultrafine carbon black (UFCB) on the structure and function of trypsin. After a short-term exposure to UFCB, the trypsin aromatic amino acid microenvironment, protein backbone and secondary structure were changed significantly, and the enzyme activity showed a trend that rose at first, then dropped. In addition, UFCB interacts with trypsin in the form of a complex. These studies demonstrated the negative effects of UFCB on trypsin, evidencing potential effects on animals and humans.

The need for an excellent antibacterial material that is sufficiently powerful to never develop bacterial resistance is urgent. In this study, a series of novel polyacrylonitrile-based fibres with chelated Ag ions (referred to as Ag-SH-PANF) were prepared by a two-step chemical modification process: grafting and chelating. The properties of the as-prepared Ag-SH-PANF were characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The antibacterial activities of Ag-SH-PANF were examined against pathogenic bacteria, and an antibacterial mechanism was explicated based on the release of Ag ions from the fibres' surfaces. The results showed that, although chelation occurred between the Ag ions and the grafted amino, sulfhydryl and disulfide groups, Ag-SH-PANF retained its fine microstructure and thermal stability. Moreover, Ag-SH-PANF displayed excellent antibacterial ability against pathogenic bacteria as well as good washing durability. In terms of the antibacterial mechanism, Ag ions are the main bactericidal agents in the role of catalysts and are not consumed in the antibacterial process. Nonetheless, a relatively higher concentration of Ag ions can accelerate the bactericidal process.

Flax (Linum usitatissimum L.) is a common commercial crop that is widely cultivated for fibre, oil and medicinal products globally. To select flax varieties with lead (Pb) tolerance and explore the associated tolerance mechanism under Pb stress, 19 flax varieties were grown using a hydroponic method with added Pb(NO3)2. Our results showed that L. usitatissimum ‘Milas’ displayed the highest tolerance to Pb stress, whereas L. usitatissimum ‘Yuan 2000’ was the most sensitive variety under 1 mM of Pb(NO3)2. ‘Milas’ accumulated lesser Pb than ‘Yuan 2000’. In addition, under Pb stress, the activities of peroxidase (POD) and superoxide dismutase (SOD) were higher in ‘Milas’ than in ‘Yuan 2000’, whereas the malondialdehyde (MDA) content of the aerial part and the root were lower in ‘Milas’ than in ‘Yuan 2000’. The expression levels of heavy metal stress-related genes were higher in ‘Milas’ than in ‘Yuan 2000’. Our results provide information about breeding flax varieties with Pb tolerance and the mechanisms underlying the response to Pb stress.

Alizarin red S (ARS) is a widespread mordant dye derived from alizarin. However, it was reported to be mutagenic and carcinogenic probably because it could induce oxidative damages in organisms. Catalase (CAT) is an important antioxidant enzyme defensing oxidative damages induced by xenobiotics. The underlying mechanisms of ARS interacting with CAT have not been clarified yet. This study is conducted to characterize the functional and conformational changes on CAT by ARS and the binding details to further investigate their interaction mechanisms. Under exposure of ARS at 5 μM, CAT activity was significantly decreased to 76.2%. Inhibition of CAT probably resulted in promotion of intracellular oxidative stress and pro-oxidant property of ARS. The interaction between ARS and CAT was proved to be spontaneous and exothermic. However, limited structural changes were observed according to spectroscopic results. Results showed that ARS prefers to bind with residues buried in the active site and could alter the activity of CAT, which were agree with the molecular docking results. This work proves the adverse effects of ARS on CAT mainly at molecular level and further highlights its potential risks to heath.

In this work, a facile green hydrothermal method was developed for the synthesis of carbon dots with fluorescent property using pear juice as raw materials. The synthesized carbon dots were characterized by UV-vis, fluorescence and transmission electron microscopic techniques. The synthesized conditions were optimized and the obtained carbon dots exhibited an average size at 10 nm with bright emission centered at 455 nm (blue color) under UV light with the excitation wavelength at 360 nm. The as-prepared carbon dots exhibited quenching effect in the presence of Cu2+ ion and a method for Cu2+ ion detection in water was developed with acceptable selectivity. The synthesized fluorescent carbon dots showed advantages like easy preparation, low cost and environmental friendly. It could be useful in chemical and biochemical detection.

The wide range of applications of copper have caused widespread concern about its toxicity. However, few studies have reported the mechanism of the binding interaction between copper ions and digestive enzymes, which play an important role in physiological health and industrial production. In this study, the effects of copper ions on the conformation and activity of Candida rugosa lipase (CRL) were evaluated by isothermal titration calorimetry (ITC), multiple spectral techniques, molecular simulation and enzyme activity assays. The results showed that copper ions can be combined with lipase, the binding affinity constant (K) was (2.91 ± 0.619) × 10(–3) M(–1), the binding process was a spontaneous process, and the main force was the hydrophobic force. Rather than increasing the hydrophobicity of the amino acid microenvironment of CRL, the spectral methods demonstrated that copper can also make the protein peptide bond structure compact, changing its secondary structure. In addition, molecular simulation results showed that copper ions opened the “lid” of the CRL and entered the active center, which consequently changed the conformation of the CRL molecule. Structural changes may cause changes in enzyme activity. The increased activity of CRL with the addition of copper ions was verified by enzyme activity assay. In summary, copper showed an effect on CRL at the molecular level, which means its toxicity should receive more attention.

Kenaf (Hibiscus cannabinus L.) is a valuable plant with a potential health benefit because of its extensive bioactive compounds. Leaf extracts of 33 kenaf genotypes were investigated for their polysaccharide, total phenolic, and flavonoid content. The antioxidant properties were evaluated by 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric reducing antioxidant potential (FRAP) assays. Antimicrobial capacity was also assessed against Staphylococcus aureus and Escherichia coli using a disc diffusion assay. The polysaccharide content varied from 6.45–16.12 mg glucose per g DW. Total phenolic and flavonoid content ranged from 6.03–21.15 mg GAE/g DW and 1.55–9.24 mg RE/g DW, respectively. Similarly, varied values in the range 20.55–79.99% of inhibition by DPPH, 56.28–88.30% of inhibition by ABTS and 1.26–5.08 mmol Fe2+/g DW by FRAP assays were obtained for antioxidants of the genotype extracts. Extracts from CS4 and CS2 genotypes had the highest antioxidant activities. Kenaf leaves exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli. Strong correlation was found between antioxidant activity with polysaccharide (DPPH, r = 0.893, ABTS, r = 0.819, FRAP, r = 0.864) and total phenolic content (DPPH, r = 0.850, ABTS, r = 0.959, FRAP, r = 0.953). The results suggested that the kenaf leaves could be used as a natural antioxidants and antimicrobial in food industries.

Glycoprotein is an important immunogenic protein of Hirame novirhabdovirus (HIRRV). In this study, the full-length and N-/C-terminal portions of glycoprotein were recombinantly expressed (rG, rGn and rGc protein), and the induced immune responses were investigated in flounder (Paralichthys olivaceus) model. The results showed that compared to PBS control, rG, rGn and rGc proteins and inactivated HIRRV suspension (iVS) could all stimulate significant increases of flounder CD4-1+, CD4-2+ T lymphocytes and surface IgM positive (sIgM+) B lymphocytes in peripheral blood, spleen and head kidney (p 0.05). iVS could induce the highest mean levels of CD4+ T lymphocytes in peripheral blood and spleen. For sIgM+ B lymphocytes, the average peak percentages in rG and rGc groups were higher than rGn group. Moreover, significant increases of specific serum IgM against HIRRV or rG protein were observed in iVS, rG, rGn and rGc groups, but rG group exhibited the highest mean level. Furthermore, rG protein induced the highest titer of neutralizing antibodies against HIRRV, followed by iVS. Meanwhile, the challenge test showed that the relative percent survival (RPS) of rG, rGn, rGc and iVS groups were 75.0%, 35.7%, 53.6% and 60.7%, respectively. These results revealed that the full-length G protein would be a more effective subunit vaccine candidate against HIRRV infection.

With the wider application of cadmium-containing quantum dots (Cd-QDs) in biomedical fields, it is easier for people to be exposed. Studies have suggested that Cd-QDs could release cadmium ion and induce oxidative effects due to the disruption of redox equilibrium. Antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD), play an important role in organisms to resist the negative impact of exogenous substances. Molecular mechanisms of antioxidant enzymes with Cd-QDs remain unclear, however. In this study, structural and functional changes of CAT and SOD have been investigated under low dose Cd-QDs exposure. Cell viability, malondialdehyde (MDA) level, CAT and SOD activities were influenced by Cd-QDs in hepatocytes of mice. To further investigate the responses of CAT and SOD to Cd-QDs, multiple spectroscopic, calorimetric and activity measurements were carried out. Similar interaction patterns were observed that result in interaction force, structural and functional changes: Cd-QDs combine with CAT and SOD through hydrophobic forces; Intrinsic fluorescence of proteins was statically quenched by Cd-QDs and new complexes were formed; Also, the skeleton and secondary structure (with α-helix decrease) of CAT and SOD was influenced. Taken together, we suggest that Cd-QDs chosen in this study induce oxidative stress effects to hepatocytes but have not caused serious oxidative stress damage at concentrations below 10 μg/mL. MPA-CdSe/ZnS QDs caused the lowest level of oxidative stress which is associated with the induction of antioxidant proteins. This paper presents responses of CAT and SOD to low-dose Cd-QDs, and provides a reference for evaluating health damages caused by Cd-QDs.

Bisphenol A (BPA) and its analogs (bisphenol F, BPF; bisphenol AF, BPAF; bisphenol S, BPS; and tetrabromobisphenol A, TBBPA) are transported by blood and bind estrogen receptors of target organs or cells. They were confirmed to bind human serum albumin (HSA) in blood, and the binding constants of BPA (5.14 × 103 M−1), BPF (1.05 × 104 M−1), and BPS (7.89 × 103 M−1) determined via equilibrium dialysis shows moderate binding ability with multiple binding sites. The HSA-water partition coefficients (log KHW > 3) are greater than their octanol-water distribution coefficients, and may follow the order: TBBPA > BPAF > BPA (3.75) > BPF (3.61) > BPS (3.27). Functional groups and substitutions of bisphenols (BPs) determine the fluorescence quenching of Trp214 in HSA. The effects follow: TBBPA (4.41 × 1014 M−1 s−1) » BPS (4.08 × 1012 M−1 s−1) > BPAF (1.20 × 1012 M−1 s−1) > BPF (3.06 × 1011 M−1 s−1) ≈ BPA (4.47 × 1011 M−1 s−1), which is in line with the molecular docking results. In this process, the enzymatic characteristics of HSA were changed simultaneously, as evidenced by decreased Km and Vmax except for BPS (increased Km and Vmax) and increased catalytic efficiency, which may improve the hydrolysis of other drugs. However, the native conformation of the protein underwent locally adaptive changes due to the reversible binding. Overall, these data provide a mechanistic explanation for the transport of BPs in human blood, which may affect their retention and toxicity.

Glutathione peroxidases (Gpxs) play vital roles in elimination of hydroperoxide and other reactive oxygen species through catalyzing reduced glutathione to protect from oxidative stress caused by heavy metals such as lead. Among the family of Gpxs, Gpx3 is the only extracellular enzyme synthesized in the kidney and actively secreted into the plasma. This study investigated mechanisms of lead-induced GPx3 inactivation both at the animal and molecular levels. Six-week-old mice were randomly divided into 4 groups, and exposed to different lead concentrations (0, 1, 2 and 4 g/L) in their drinking water for 4 weeks. Contents of GPx3 in blood serum were tested by enzyme-linked immunosorbent assay (ELISA) and the mRNA levels of Gpx3 in mice nephrocytes were determined by quantitative real-time PCR (qPCR), both of which showed significantly inhibited at higher lead concentrations accompanied by the decreased Gpx3 activities and the elevated levels of malondialdehyde (MDA) in nephrocytes, which indicated that lead could induce strongly oxidative stress through affecting Gpx3 function. So we further investigated molecular mechanisms of GPx3 inactivation caused by lead with multiple spectroscopic techniques, isothermal titration calorimetry (ITC) and molecular docking studies in vitro. Results showed that lead statically quenched GPx3 fluorescence by tightly binding to the structural domain of GPx3 in a 3:1 ratio with high binding affinity (K = 3.1(±0.087) × 107 mol−1). Further investigation of the conformation of GPx3 by UV–visible spectroscopy and circular dichroism (CD) spectroscopy indicated that lead changed the secondary structure of GPx3 by loosening the GPx3 skeleton and decreasing the hydrophobicity around tryptophan residues. This work proved in vivo and in vitro experiments that lead could induce oxidative stress in mice nephrocytes by interacting with GPx3.

Cadmium-quantum dots (Cd-QDs) possess unique properties as optoelectronic devices for sensitive detection in food and biomedicine fields. However, the toxic effects of Cd-QDs to single cells is still controversial, due to the release mechanism of QDs to Cd2+in situ and the cytotoxic effects of QDs and Cd2+ respectively are still unclear. In this paper, the release rule of Cd2+ from CdTe QDs within single cells was investigated in situ by using flow cytometry method and the dose-response relationships were explored. Besides, an all-inclusive microscopy system was optimized for live cell imaging to observe the real-time entry process of CdTe QDs into cells. We found that intracellular CdTe QDs and Cd2+ contents were increased based on the dosage and exposing time. A dissociated saturation of Cd2+ from CdTe QDs was exist within cells. CdTe QDs induced more serious cytotoxicity on kidney cells than hepatocytes. The toxicity of oxidative stress, cell apoptosis effects induced by CdTe QDs and Cd2+ are also in consistent with this result. This research develops analytical method to quantify the uptake and release of Cd-QDs to primary cells in situ and can provide technical support in studying the cytotoxicity portion contributed by nanoparticles (NPs) and metal ions.

As a heavy metal generally considered to be toxic, lead displays the destruction of the antioxidant system and causes oxidative damage through animal, cellular and molecular evidences. Selenium exists in the form of selenocysteine (Sec) upon its incorporation into selenoproteins and plays vital roles in protection from oxidative stress caused by toxic materials such as lead. This study investigated mechanisms of lead-induced changes of selenium status both at the animal and molecular levels. Total selenium concentrations in blood plasma, contents of glutathione peroxidase 3 (Gpx3) and selenoprotein P (SelP) in blood plasma and mRNA levels of key selenoproteins in mice livers were significantly inhibited after lead exposure, and indicators of oxidative damages in mice livers caused by lead also presented significantly higher, including levels of reactive oxygen species, malonaldehyde concentration and TNF-α levels. To further confirm the hypothesis that lead may disturb selenium status through affecting SelP function, we investigated molecular mechanisms of lead on SelP in vitro. Results indicated that lead changed secondary structure of SelP by loosening and destruction its skeleton. This work presents molecular mechanisms changes of selenium status in mice livers caused by lead combined in vivo and in vitro studies, and contributes to a better understanding of lead toxicity on human health.

A major user of carbon black is the pigment and dyes industry, where carbon black is incorporated into paints, inks, printers, and plastics. However, little is known about the mechanism underlying the toxicity of carbon black to antioxidant proteins. Carbon black can cause oxidative stress to organisms after they invade into the body. Antioxidant proteins play a key role in keeping the organism from nanoparticle-induced oxidative damage and tend to bind with nanoparticles immediately after their invading into the biological environment, so it is meaningful to elucidate the toxicity of nanoparticles on the antioxidant proteins. In this study, the toxicity of carbon black (SB100) on three different antioxidant proteins (TF (transferrin), SOD (superoxide dismutase), and LYZ (lysozyme)) were investigated. The multi-spectra studies indicated that SB100 interacted with these three proteins and changed their structure in different ways. SB100 changed the microenvironment of fluorophores in SOD and LYZ by quenching the fluorescence spectra of the two enzymes, while changed that of TF by increasing the fluorescence intensity of TF. SB100 changed the secondary structure of these three proteins by decreasing the α-helix content of TF and increasing that of SOD and LYZ. Moreover, SB100 changed the hydrophobicity of the three proteins in different ways as well. And SOD exhibits a more severe activity inhibition than LYZ after exposed to SB100. In summary, SB100 caused different structural and functional changes to these three antioxidant enzymes.

The toxic mechanism of cadmium-quantum dots (Cd-QDs) to organisms is still debating. In this paper, it was found that Cd-QDs could induce adverse effects to kidney by entering into cells in a time and dose manner and disturbing the redox balance in vivo. As a selenium containing protein, glutathione peroxidase3 (Gpx3) plays a crucial role in maintaining the balance of redox system. The decrease in Gpx3 activity might be related to the imbalance of redox system. Similar to the animal results, it was demonstrated that Gpx3 activity is also inhibited by Cd-QDs in vitro. To investigate the underlying mechanism of Cd-QDs on conformational and functional changes of Gpx3, systematical measurements including calorimetric, multispectroscopic studies, and molecular model studies were carried out on molecular level. Results showed that Cd-QDs binds to Gpx3 via Van der Waals' force and hydrogen bonds, resulting in structural changes with increasing contents of α-helix. By interacting with Glu136 in the cavity of Gpx3 as well as Phe132, Pro130, and Van129 surrounded, Cd-QDs changes the microenvironment of fluorophore and further reduce the activity of Gpx3.

Maltol, a food additive, is extensively used in our daily life. To date, its biological safety is still debated. In this article, binding interaction of maltol with bovine hemoglobin (BHb), an important functional protein, was studied by molecular docking research and spectroscopic and calorimetric measurements. We found that maltol could cause structural changes of BHb. By interacting with Glu 101 (1.27 A) and Lys 104 (2.49 A) residues, maltol changed the cavity structure and induced a microenvironment change around tryptophan (Trp) residue. Thermodynamic parameters obtained from isothermal titration calorimetry (ITC) measurement showed that hydrophobic forces were the main forces existing in this system. The association constant of K (8.0 ± 3.4 × 104 M-1 ) shows the mild ligand-protein binding for maltol with BHb. The α-helix amount in BHb increased (59.6-62.6%) with different concentrations of maltol and the intrinsic fluorescence intensity was quenched by maltol, indicating the conformation changes and denaturation of BHb. This work presents the interactions of maltol with BHb at the molecular level and obtains evidence that maltol induces adverse effects to proteins in vitro.

Drought is the main environmental factor impairing hemp growth and yield. In order to decipher the molecular responses of hemp to drought stress, transcriptome changes of drought-stressed hemp (DS1 and DS2), compared to well-watered control hemp (CK1 and CK2), were studied with RNA-Seq technology. RNA-Seq generated 9.83, 11.30, 11.66, and 11.31 M clean reads in the CK1, CK2, DS1, and DS2 libraries, respectively. A total of 1292 differentially expressed genes (DEGs), including 409 (31.66%) upregulated and 883 (68.34%) downregulated genes, were identified. The expression patterns of 12 selected genes were validated by qRT-PCR, and the results were accordant with Illumina analysis. Gene Ontology (GO) and KEGG analysis illuminated particular important biological processes and pathways, which enriched many candidate genes such as NAC, B3, peroxidase, expansin, and inositol oxygenase that may play important roles in hemp tolerance to drought. Eleven KEGG pathways were significantly influenced, the most influenced being the plant hormone signal transduction pathway with 15 differentially expressed genes. A similar expression pattern of genes involved in the abscisic acid (ABA) pathway under drought, and ABA induction, suggested that ABA is important in the drought stress response of hemp. These findings provide useful insights into the drought stress regulatory mechanism in hemp.

To research the mechanism of dimercaptosuccinic acid coated-superparamagnetic iron oxide nanoparticles (SPION) with human serum albumin (HSA), the methods of spectroscopy, molecular modeling calculation, and calorimetry were used in this paper. The inner filter effect of the fluorescence intensity was corrected to obtain the accurate results. Ultraviolet-visible absorption and circular dichroism spectra reflect that SPION changed the secondary structure with a loss of α-helix and loosened the protein skeleton of HSA; the activity of the protein was also affected by the increasing exposure of SPION. Fluorescence lifetime measurement indicates that the quenching mechanism type of this system was static quenching. The isothermal titration calorimetry measurement and molecular docking calculations prove that the predominant force of this system was the combination of Van der Waals' force and hydrogen bonds.

In this study, xanthine oxidase immobilized silica coated Fe3O4 nanoparticles (Fe3O4@SiO2-XO) were successfully prepared and characterized by transmission electron microscope, X-ray powder diffraction, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The average diameter of the Fe3O4 nanoparticles was about 300 nm to 350 nm with a shell thickness of 60 nm. The maximum saturation magnetization of the Fe3O4@SiO2-XO nanoparticles was 44.9 emu/g, which ensured the separation from the medium within one minute by using an ordinary magnet. A xanthine oxidase (XO) inhibitor screening method using Fe3O4@SiO2-XO nanoparticles was established and utilized in the extract of Clerodendranthus spicatus. Under the optimized conditions, two compounds were screened out and identified as gardenin B and eupatorin. The half maximal inhibitory concentration (IC50) values of these two compounds were 1.488 μg/mL and 11.197 μg/mL, respectively. The interactions between these two compounds and XO were investigated by the fluorescence spectroscopic method. The results suggested that the quenching effects of gardenin B and eupatorin were due to a static quenching mechanism. Furthermore, gardenin B showed stronger binding capacity than that of eupatorin. In conclusion, this screening method exhibited efficiency and reusability in screening, identification and analysis of enzyme inhibitors from complex mixtures.

As a promising biolabeling biomaterials, quantum dots (QDs) present a great potential. However, the toxicity of QDs to organisms has attracted wide attention. In our research, we introduced an in vitro method to study the molecular mechanisms for the structure and activity alterations of Candida rugosa lipase (CRL) with the binding of 3-mercaptopropionic acid-capped CdTe QDs. Multiple spectroscopic methods, isothermal titration calorimetry, and enzyme activity measurements were used in this paper. QDs statically quenched the intrinsic fluorescence of CRL with the quenching constant decreases from 2.46 × 1013 to 1.64 × 1013 L mol-1 second-1 (298 to 310 K). It binds to CRL through hydrophobic force with 1 binding site, unfolding and loosening the skeleton and changed its secondary structure. Rather than aggregating on the surface, it enters the pocket of the CRL to interact with Ser-209 (2.43 A) and the residues surrounding Ser-209, making the catalytic triad more exposed. Furthermore, the activity of CRL was inhibited by approximately 15%. This work demonstrates that 3-mercaptopropionic acid-capped CdTe QDs may cause negative effects to CRL and obtains a molecular mechanism on QD-induced toxicity to proteins in vitro.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have effects on human health by inducing oxidative stress and catalase (CAT) is a vital enzyme involved in protection against oxidative damage. The interactions of PFOA and PFOS with CAT were investigated by using biophysical methods including spectroscopic techniques, molecular docking and enzyme activity measurements. UV–visible, circular dichroism (CD) and resonance light scattering (RLS) spectroscopy results showed that the structure and conformation of CAT were changed by PFOA and PFOS. PFOA could loosen and unfold the skeleton of CAT but PFOS affected the microenvironment around the aromatic amino acid residues and heme groups. Both PFOA and PFOS altered the secondary structure of CAT by decreasing α-helix and increasing β-sheet content. The size of CAT was smaller and CAT became dispersed when it was bound by perfluorinated compounds (PFCs). Furthermore, enzyme activity test showed that PFOS decreased the activity of CAT because the binding site of PFOS was close to the active center of CAT, but PFOA had little effect on the activity because PFOA bound at the surface of the enzyme. These results indicated that PFCs could damage the structures and conformations of CAT but the changes were not always related to the activity and function of CAT.

Cadmium(Cd) is a widespread and one of the most toxic heavy metals, threatening human health. As a pioneer fiber crop, hemp (Cannabis sativa L.) has a great potential in Cd-polluted soil repair, but molecular mechanisams of hemp supporting the process of soil decontamination are still unknown. In this study, the key factors for differential Cd tolerance in two contrasting hemp cultivars (Cd-tolerant: Ym, Cd-sensitive: Nx) were investigated. Ym has a stronger transport and accumulation capacity than Nx. Furthermore, Cd detoxification in Ym is stronger than in Nx. Phenotype and 3,3′-diaminobenzidine(DAB) staining observation indicated that Ym was more tolerant to cadmium stress than Nx, as well as malondialdehyde(MDA) contents, superoxide dismutase(SOD) and peroxidase(POD) activities showed Ym has a stronger detoxification ability than Nx. Compared the transcriptome analysis between Ym and Nx, many genes involved in heavy metal transport and oxidation-reduction progress were identified between the two varieties. A schematic representation of main processes about differential Cd transport and detoxification was described, based on these results, which suggested that the higher Cd tolerance in Ym due to the key genes encoding some specific Cd transporter, defense system, special proteins that have a high expression in Ym.

Bisphenol A is widely used in the manufacture of food packaging and beverage containers and can invade our food and cause contamination. Candida rugose lipase has been a versatile enzyme for biocatalysis and biotransformations to produce useful materials for food, pharmaceutical and flavor. The interactions between bisphenol A and Candida rugosa lipase in vitro were studied by UV–vis, steady-state fluorescence, circular dichroism, synchronous fluorescence, light scattering spectra, molecular docking and enzyme activity assay to better understand the toxicity and toxic mechanisms of bisphenol A. The intrinsic fluorescence of the tryptophan amino acid residue and the secondary structure of the globular protein candida rugose lipase were made use of to thoroughly investigate the structural changes caused by bisphenol A. The results of the fluorescence indicated that bisphenol A interacted with candida rugose lipase and made tryptophan be exposed to a hydrophobic environment. Multi-spectroscopic measurements showed that the addition of bisphenol A increased the intrinsic fluorescence of Candida rugosa lipase, loosened its skeleton structure and changed its secondary structure. Also, the increased activity of Candida rugosa lipase revealed that the position or the structure of the catalytic triad of Candida rugosa lipase may be changed. The molecular docking results showed that bisphenol A bound with the residue Serine 209 which could be another reason for the increased activity of Candida rugosa lipase. Moreover, as can be seen from the results of resonance light scattering and dynamic light scattering, the volume of the Candida rugosa lipase was decreased and the lid may be stripped.

The effect of 3-mercaptopropionic acid (MPA)-capped CdTe quantum dots (QDs) on lysozyme was systematically investigated by spectroscopic methods, enzyme activity assay, and calorimetry techniques. Results show that the MPA-capped CdTe QDs binded to lysozyme through van der Walls forces and hydrogen bondings, causing the decrement of α-helical content (∼7%) and increment of β-sheet content (∼11%) of lysozyme. The binding caused static quenching of the fluorescence, while the microenvironment of aromatic amino acid residues did not show any significant alteration. The lysozyme activity was affected by the increasing exposure of QDs, it was inhibited to 53.77% under a 6 × 10−7 M exposure compared with the control group. This work will provide direct evidence about enzyme toxicity of QDs to lysozyme in vitro.