Efficient removal of ethidium bromide from aqueous solutions using chromatin-loaded chitosan polyvinyl alcohol composites.

In this work, a novel chromatin-loaded chitosan polyvinyl alcohol composite was developed as a simple, efficient and environmentally friendly adsorbent for the efficient removal of ethidium bromide (EtBr). SEM images showed that the composites were characterized by dense porous and uniformly distributed morphology. The BET analysis showed the presence of mesopores and macropores in the composites. FTIR and XRD results showed that the chromatin was uniformly dispersed in the chitosan-polyvinyl alcohol carrier through hydrogen bonding. The fluorescence microscopy images showed the change of fluorescence effect before and after the adsorption of the material, which indicated that the chromatin was uniformly distributed in the composites and had a good adsorption effect. The optimal experimental conditions were T = 30℃, t = 120 min, pH = 7.4, m = 0.2 g when the composite with only 5% chromatin content had the ability to adsorb EtBr efficiently (minimum concentration 2 mg·L-1: adsorption rate 99%; maximum concentration 20 mg·L-1: adsorption rate 90%).The adsorption kinetics and thermodynamics showed that the EtBr adsorption kinetics of the composite conformed to the pseudo-second-order kinetic model (0.995 < R2 < 0.999) and the Freundlich isothermal model, and was a spontaneous process (ΔH < 0). This study on the immobilization of chromatin will provide a new way and reference for the application of chromatin in the treatment of EtBr pollutants.

Optimization of aflatoxin B1 removal efficiency of DNA by resonance light scattering spectroscopy.

In this paper, firstly, the resonance light scattering spectra of aflatoxin B1 (AFB1) and DNA were measured by resonance light scattering spectroscopy (RLS), and the DNA binding saturation value (DBSV) of AFB1 was calculated from their spectral results. Then the interaction intensity between DNA and AFB1 and the effects of some external factors on the interaction between DNA and AFB1 were evaluated by corresponding DBSVs, so as to establish and optimize a way for removing AFB1 by DNA. DBSV of AFB1 was 2.04 at 30℃ and pH 7.40. However, after adding sodium ion, calcium ion, vitamin E, vitamin C and D-glucose, DBSV of AFB1 was changed to 2.72, 3.17, 2.67, 1.68 and 1.33 respectively. Correspondingly, the removal efficiency of AFB1 by DNA was changed from 90.05% to 93.25%, 95.48%, 93.08%, 82.36% and 78.90% respectively. These results indicated that the external factors had a significant impact on the interaction between DNA and AFB1. Among them, some factors enhanced the interaction between DNA and AFB1, while some factors weakened the interaction between DNA and AFB1. The change of these external factors led to the corresponding changes in DBSV and the removal efficiency of AFB1. DBSV of AFB1 could really be used as an index to evaluate the intensity of the interaction between DNA and AFB1, and to optimize the removal efficiency of AFB1 by DNA. The experimental data also showed that the adsorption of AFB1 to DNA was consistent with the pseudo-second-order kinetic model and the Freundlich isothermal model, was an exothermic and spontaneous process. All these results will give good references for establishing and optimizing a way of AFB1 removal via DNA intercalation.

Chromatin extracted from common carp testis as an economical and easily available adsorbent for ethidium bromide decontamination.

The waste of ethidium bromide (EtBr) used in the laboratory will bring a great burden to the environment, which need to be solved urgently. In the present paper, an efficient and inexpensive method for EtBr removal using chromatin extracted from common carp testis was investigated. The observation of fluorescence microscopy showed that chromatin had similar property to DNA for selective adsorption of EtBr. The results of batch adsorption showed that the removal efficiency of EtBr by chromatin exceeded 99% at pH 7.4 and 30 °C for 3 min with the EtBr concentration of 2 mg L-1 and the chromatin dosage of 0.5 g L-1, and the maximum adsorption amount of chromatin was 45.73 mg g-1. Further, the analysis of kinetic and isotherm suggested that the adsorption followed Pseudo-second-order kinetics and Langmuir isotherm model, and the calculated maximum theoretical adsorption amount of chromatin to EtBr was 48.08 mg g-1. According to thermodynamic analysis, chromatin adsorption of EtBr was a spontaneous process dominated by hydrogen bonding and van der Waals forces. This work will not only offer an adsorbent for EtBr decontamination, also provide a possibility for EtBr analogs removal.

Interaction of aflatoxin G1 with free DNA in vitro and possibility of its application in removing aflatoxin G1.

The present study sought to evaluate the interaction between aflatoxin G1 and free DNA in vitro through different analytical techniques. The UV-visible spectra results showed that the structure of DNA might be changed with a new aflatoxin G1-DNA complex forming, which indicated that the interacting mode between them was the intercalating mode. The DNA melting temperature increased by 12.80 °C, suggesting that the DNA double helix structure was more compact and stable through intercalation. The circular dichroism (CD) spectra results indicated that the interaction of aflatoxin G1 with DNA induced the DNA base stacking changes. The results of agarose gel electrophoresis and fluorescence microscope further verified that the interacting mode between aflatoxin G1 and DNA was intercalation mode. According to the fluorescence spectrum data, the binding constant was calculated 6.24 × 104 L·mol-1. The thermodynamic results demonstrated that the reaction of aflatoxin G1 intercalating to DNA was a spontaneous reaction. The elimination results suggested that aflatoxin G1 could be enriched and removed by DNA intercalation through magnetic beads separation, with the removal efficiency of 93.73%. The study results would provide a theoretical basis for establishing a new aflatoxin removal method based on DNA intercalation.

Predicting Protein Surface Property with its Surface Hydrophobicity.

This article reviews and discusses the relationship between surface hydrophobicity and other surface properties of proteins and the possibility of using surface hydrophobicity as a key indicator to predict and evaluate the changes in the surface properties of a protein. Hydrophobicity is the main driving force of protein folding; it affects the structure and functions. Surface hydrophobicity and other surface properties of proteins are controlled by their spatial structures. Due to the hydrophobic interactions, most proteins fold into their globular structures, and they lack sufficient hydrophobic residues on the molecular surface; thus, they do not exhibit excellent surface properties. Surface hydrophobicity is closely related to the changes in the surface property of proteins because it directly reflects the actual distribution of the hydrophobic residues on the surface of a protein. The molecular structure of a protein can be changed or modified to remove the constraints of spatial structures and expose more hydrophobic residues on the molecular surface, which may improve the surface properties of proteins. Therefore, the changes in the surface hydrophobicity caused by changes in the molecular structure can be an ideal key indicator to predict and evaluate the changes in the surface properties of a protein.

Interacting mechanism of benzo(a)pyrene with free DNA in vitro.

Polycyclic aromatic hydrocarbons are environmental pollutants with strong carcinogenicity, indirect teratogenicity, and mutagenicity. This study explored the interaction mechanism of benzo(a)pyrene with free DNA in vitro by using various analytical methods. UV-vis spectra showed that benzo(a)pyrene and DNA formed a new benzo(a)pyrene-DNA complex. The thermal melting temperature of DNA increased by 12.7 °C, showing that the intercalation of benzo(a)pyrene into DNA could promote the stability of the DNA double helix structure. The intercalation of benzo(a)pyrene with DNA in vitro was further confirmed by fluorescence microscopy with magnetic beads. Fluorescence spectra showed that the interaction between DNA and benzo(a)pyrene decreased the fluorescence intensity of benzo(a)pyrene, and the maximum quenching rate was 27.89%. The quenching mode of benzo(a)pyrene was static quenching. Thermodynamic data showed that the main driving forces were van der Waals forces and hydrogen bonds, and the reaction was spontaneous. The results of this study provided a novel insight for the establishment of polycyclic aromatic hydrocarbon capture and elimination through polycyclic aromatic hydrocarbon-DNA intercalation.

Removal of 1,2-benzanthracene via the intercalation of 1,2-benzanthracene with DNA and magnetic bead-based separation.

In this study, DNA-functionalize-magnetic beads were investigated as sorbent materials for effective removing 1,2-benzanthracene (BaA) from water. In order to reveal the removal mechanism, the interaction mode between BaA and DNA was evaluated by using various characterization tools such as UV-visible and circular dichroism spectroscopy, fluorescence and resonance scattering spectroscopy, and agarose gel electrophoresis. In the presence of BaA, the melting temperature of DNA increased from 76.2 °C to 82.3 °C, which closely related to the intercalating of BaA. It was found that a part of the ethidium bromide (EB) binding sites to DNA were occupied by BaA in EB competing study. The results indicated that a new complex appeared between hsDNA and BaA, and the number of the binding sites (n) and the binding constants (KA) at different temperatures were obtained. DNA binding saturation value (≈0.80) was obtained by resonance scattering spectra study. BaA could be enriched and removed by DNA-functionalize-magnetic beads via the intercalation, and the removal efficiency was 97.73% when the initial concentration was 2.45 x10-6 mol·L-1 (559.31 µg/L).

Binding characteristics of aflatoxin B1 with free DNA in vitro.

In this paper, the binding characteristics of aflatoxin B1 (AFB1) with the herring sperm deoxyribonucleic acid (DNA) in vitro were investigated through different analytical methods. The ultraviolet-visible spectroscopy (UV-vis), fluorescence, and circular dichroism (CD) spectra results showed that a new AFB1-DNA complex was formed. All the results suggested that AFB1 interacted with free DNA in vitro in an intercalating binding mode. The results of the DNA melting experiments also showed that the melting temperature of DNA increased by about 12.1 °C due to the addition of AFB1, which was supposed to be closely related to the intercalation of AFB1 into DNA. The agar gel electrophoresis experiments further confirmed that the binding mode of AFB1 and free DNA in vitro was indeed intercalation. In addition, the fluorescence quenching induced by adding AFB1 to the ethidium bromide-DNA (EB-DNA) mixture indicated the presence of competitive non-covalent intercalating binding interaction with a competitive binding constant of 5.58 L/mol between AFB1, EB, and DNA. The thermodynamic data demonstrated that the main driving forces of the binding reaction were van der Waals forces and hydrogen bond. The resonance light scattering (RLS) assay results showed that the DNA binding saturation values of AFB1, EB, psoralen (PSO), and angelicin (ANG) were 2.14, 15.59, 0.74, and 0.74, respectively. These results indicated that the DNA binding capacity of AFB1 was weaker than that of EB, but stronger than those of PSO and ANG.

Effect of oxidization and chitosan on the surface activity of soy protein isolate.

The objective of this research was to study the effect of oxidization of performic acid and chitosan on the structure and surface properties of soy protein isolate. As the degree of oxidization increased, the emulsifying capacity and stability of all the oxidized soy protein isolate and chitosan (SPI/CHI) systems increased substantially, which were 29.7%, 31.7%, 34.1%, 31.9% and 31.9% respectively compared. Fluorescent spectrum showed that the fluorescence intensity of SPI/CHI conjugates decreased and the higher the oxidized degree was, the lower the fluorescence intensity. Results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the location of acidic bands of SPI/CHI conjugates moved upwards and broadened. Meanwhile, the basic bands lightened or even disappeared gradually as the oxidization increased. Scanning electron microscope (SEM) showed that the particles became lager as the degree of oxidization increased. Better thermostability of the oxidized SPI/CHI systems was shown in the differential scanning calorimetry (DSC).

Spectroscopic studies on the interaction between anthragallol and DNA using of ethidium bromide as a fluorescence probe.

The interaction of DNA with anthragallol (Ant) was investigated using ethidium bromide (EB) as a fluorescence probe, and the binding mechanism of Ant with DNA was researched via viscosity measurements. The results indicate that there is a complex of Ant and DNA, as confirmed by Ultraviolet visible absorption spectroscopy (UV-vis), Fluorescent and Resonance Light Scattering spectrum (RLS) and viscosity measurements. Ant molecules could intercalate with the base pairs of DNA as evidenced by the hyperchromic effect of absorption spectra, the relative viscosity of DNA and significant increases in the melting temperature. The binding constants of Ant and DNA were obtained by the fluorescence quenching technique. Furthermore, the binding mechanisms of the reaction of Ant with DNA were also investigated. The RLS assay successfully evaluated the saturated value and measured the potential toxicity of Ant. Adriamycin, chrysophanol, rhein, and alizarin can be used as references to build a method based on the mechanism of interactions with DNA and the DNA-saturation binding value to rapidly evaluate the potential toxicity of Ant.