Affinity Sequence Research Articles

Chromophore‐Assisted Proximity Labeling of DNA Reveals Chromosomal Organization in Living Cells

AbstractThe spatial arrangement of chromosome within the nucleus is linked to genome function and gene expression regulation. Existing genome‐wide mapping methods often rely on chemically crosslinking DNA with protein baits, which raises concerns of artifacts being introduced during cell fixation. By genetically targeting a photosensitizer protein to specific subnuclear locations, we achieved blue‐light‐activated labeling of local DNA with a bioorthogonal functional handle for affinity purification and sequence identification through next‐generation sequencing. When applied to the nuclear lamina in human embryonic kidney 293T cells, it revealed lamina‐associated domains (LADs) that cover 37.6 % of the genome. These LADs overlap with heterochromatin hallmarks and are depleted with CpG islands. This simple labeling method avoids the harsh treatment of chemical crosslinking and is generally applicable to the genome‐wide high‐resolution mapping of the spatial chromosome organization in living cells.

Toxicological effects of microplastics and heavy metals on the Daphnia magna

Microplastics (MPs) are gradually spreading around the world and becoming a ubiquitous environmental contamination in aquatic environments. Due to its unique physicochemical properties, MPs are considered to be strong adsorbents for environmental pollutants and may affect their fate and toxicity in the environment. In this study, the adsorption behaviors of four typical heavy metal ions (Pb2+, Cu2+, Cd2+, and Ni2+) on two sizes of polystyrene MPs (10 μm and 50 μm) were investigated based on batch experiments, and the combined effects of heavy metals and MPs were assessed using Daphnia magna as model. The results showed that smaller MPs (SMPs) exhibited higher adsorption capacities for metal ions (0.261–0.579 mg/g) than that of the larger MPs (LMPs) (0.243–0.525 mg/g), and the affinity sequence of heavy metals on MPs is Pb2+ > Cu2+ > Cd2+ > Ni2+. There are better admirable agreements for pseudo-second-order model and Langmuir model to fit the adsorption kinetics and adsorption isotherms, respectively. Additionally, the combined toxicity of MPs and heavy metals was negatively correlated with the adsorption capacity between them. The combined effects of mixtures toward D. magna changed from antagonism to additive effect with increasing MPs concentrations, and SMPs exhibited higher toxicological risk than LMPs. Our findings compared the accumulative effects of various heavy metals on MPs and can contribute to understanding the combined effects of plastics and heavy metals on biota.

Single and simultaneous adsorption of three sulfonamides in agricultural soils: Effects of pH and organic matter content

Veterinary antibiotics reaching the environment have become a matter of global concern, since they can cause serious negative impacts on human and ecological health. Therefore, a deep understanding of their behavior and fate once they reach the soil environment is of utmost importance to design and implement appropriate measures that could reduce their potential risks. With this aim, batch-type experiments were carried out to study competitive adsorption and desorption for three sulfonamide antibiotics (sulfadiazine –SDZ-, sulfamethazine –SMT-, and sulfachloropyridazine –SCP-) in six crop soils presenting different characteristics. The results obtained showed that sulfonamides have a low retention in soils, with average adsorption percentages of 40% for SDZ, 44% for SMT and 54% for SCP, and with desorption percentages up to 36% for SDZ and SCP and up to 29% for SMT. The retention of sulfonamides was strongly influenced by the soil organic carbon content (SOC), with higher adsorption and less desorption associated to higher SOC contents. In addition, the hydrophobicity of sulfonamides also had an influence, as higher hydrophobicity resulted in higher affinity for soils, showing the affinity sequences: SDZ ~ SMT <SCP in acid soils, and SDZ ~ SCP <SMT in neutral soils. The results obtained in the ternary systems were very similar to those found in simple systems, indicating the absence of substantial competition for adsorption sites among the three sulfonamides. Despite the low competition among them, these antibiotics have high mobility in soils and, therefore, they imply a significant risk of contamination of water bodies, as well as of entering the food chain, generating serious hazards for human and environmental health. Therefore, fertilization of soils with sulfonamide polluted manures should be controlled, implementing new measurements for the pretreatment of manures before their application, thus contributing to a reduction of potential risks.

HrrSA orchestrates a systemic response to heme and determines prioritization of terminal cytochrome oxidase expression.

Heme is a multifaceted molecule. While serving as a prosthetic group for many important proteins, elevated levels are toxic to cells. The complexity of this stimulus has shaped bacterial network evolution. However, only a small number of targets controlled by heme-responsive regulators have been described to date. Here, we performed chromatin affinity purification and sequencing to provide genome-wide insights into in vivo promoter occupancy of HrrA, the response regulator of the heme-regulated two-component system HrrSA of Corynebacterium glutamicum. Time-resolved profiling revealed dynamic binding of HrrA to more than 200 different genomic targets encoding proteins associated with heme biosynthesis, the respiratory chain, oxidative stress response and cell envelope remodeling. By repression of the extracytoplasmic function sigma factor sigC, which activates the cydABCD operon, HrrA prioritizes the expression of genes encoding the cytochrome bc1-aa3 supercomplex. This is also reflected by a significantly decreased activity of the cytochrome aa3 oxidase in the ΔhrrA mutant. Furthermore, our data reveal that HrrA also integrates the response to heme-induced oxidative stress by activating katA encoding the catalase. These data provide detailed insights in the systemic strategy that bacteria have evolved to respond to the versatile signaling molecule heme.

Fabrication and characterization of polyvinyl chloride mixed matrix membranes containing high aspect ratio anatase titania and hydrous manganese oxide nanoparticle for efficient removal of heavy metal ions: Competitive removal study

AbstractIn this study, novel polyvinyl chloride (PVC) ultrafiltration mixed matrix membranes (MMMs) containing high aspect ratio anatase titania (ANT) and hydrous manganese oxide (HMO) nanoparticles were synthesized in order to decontaminate cadmium and copper metal ions. ANT and HMO nanoparticles with various loadings in a range of 5‐15 were used in the casting solution of MMMs. The characterization of fabricated MMMs was carried out with respect to the structural morphology, hydrophilicity, and composition by scanning electron microscopy (SEM), water contact angle, and Fourier transform infrared spectroscopy (FTIR), respectively. With an increase in the nanoparticle loadings, the change in other membrane characteristics such as mean pore size, pure water flux, and porosity were also evaluated. The results revealed that the mean pore size and water flux increased at a higher loading of ANT and HMO nanoparticles, while the contact angle and porosity of the membranes showed reverse trends. Moreover, the higher flux of pure water was obtained for PVC‐ANT MMMs compared to PVC‐HMO MMMs because of the larger mean pore size, higher porosity, and hydrophilicity of PVC‐ANT MMMs. In this study, the decontamination of cadmium and copper metal ions in single and binary systems of heavy metals was investigated and the effect of Mn2+ (as an interfering ion) was also studied. The evaluation of the metal ion removal data demonstrated that the affinity sequence of both the PVC‐ANT‐15 and PVC‐HMO‐15 MMMs for heavy metal removal was Cu2+ &gt; Cd2+ &gt; Mn2+ in the single and binary systems. It was found through ultrafiltration (UF) experiments that PVC‐ANT MMM was the most efficient membrane in the elimination of heavy metals due to the superior ANT adsorption capacity. However, the overall findings disclosed that both ANT and HMO nanoparticles are suitable candidates for the preparation of MMMs used in cadmium and copper decontamination from aqueous solutions.

Structural biology of telomeres and telomerase.

Telomeres are protein-DNA complexes that protect chromosome ends from illicit ligation and resection. Telomerase is a ribonucleoprotein enzyme that synthesizes telomeric DNA to counter telomere shortening. Human telomeres are composed of complexes between telomeric DNA and a six-protein complex known as shelterin. The shelterin proteins TRF1 and TRF2 provide the binding affinity and specificity for double-stranded telomeric DNA, while the POT1-TPP1 shelterin subcomplex coats the single-stranded telomeric G-rich overhang that is characteristic of all our chromosome ends. By capping chromosome ends, shelterin protects telomeric DNA from unwanted degradation and end-to-end fusion events. Structures of the human shelterin proteins reveal a network of constitutive and context-specific interactions. The shelterin protein-DNA structures reveal the basis for both the high affinity and DNA sequence specificity of these interactions, and explain how shelterin efficiently protects chromosome ends from genome instability. Several protein-protein interactions, many provided by the shelterin component TIN2, are critical for upholding the end-protection function of shelterin. A survey of these protein-protein interfaces within shelterin reveals a series of "domain-peptide" interactions that allow for efficient binding and adaptability towards new functions. While the modular nature of shelterin has facilitated its part-by-part structural characterization, the interdependence of subunits within telomerase has made its structural solution more challenging. However, the exploitation of several homologs in combination with recent advancements in cryo-EM capabilities has led to an exponential increase in our knowledge of the structural biology underlying telomerase function. Telomerase homologs from a wide range of eukaryotes show a typical retroviral reverse transcriptase-like protein core reinforced with elements that deliver telomerase-specific functions including recruitment to telomeres and high telomere-repeat addition processivity. In addition to providing the template for reverse transcription, the RNA component of telomerase provides a scaffold for the catalytic and accessory protein subunits, defines the limits of the telomeric repeat sequence, and plays a critical role in RNP assembly, stability, and trafficking. While a high-resolution definition of the human telomerase structure is only beginning to emerge, the quick pace of technical progress forecasts imminent breakthroughs in this area. Here, we review the structural biology surrounding telomeres and telomerase to provide a molecular description of mammalian chromosome end protection and end replication.

Influence of Soil Type on Single and Competitive Retention Behavior of Inorganic Macro Cations in Binary as well as Ternary Solution

Inorganic macro cations (Na+, K+ and Ca+) co-exist in agricultural and municipal landfill sites. The retention behavior of these ions in different soils and combinations (binary and ternary system) has not been fully understood by previous studies. This study seeks to probe into the retention behavior of macro cations (Na+, K+, Ca+2) in six different soils under multiple combinations of ions solution. The retention of common ions was quantified by using Freundlich and Langmuir isotherms. Na+ (single) pollutant-soil interaction was desorbed in most of the soils. The retention of K+ and Ca+2 was much greater than that of Na+. There is no definite trend for retention of Na+ in the presence of K+. For all soils, the retention results of K+ in the presence of Na+ decreased. Affinity for K+ was greater than that for Ca+2 in most of the soils. This study also demonstrated the affinity sequence of the ion retention for each soil and the percentage reduction of ions in competition with respect to single ions. Anomalous trends of the isotherm parameter fitting suggested the limitation of the mathematical models in predicting the experimental data. These results can be helpful in improving accuracy of fate prediction of pollutant fate and thus, design of waste containment facilities for various wastes that contains inorganic ions.

Decoding WW domain tandem-mediated target recognitions in tissue growth and cell polarity.

WW domain tandem-containing proteins such as KIBRA, YAP, and MAGI play critical roles in cell growth and polarity via binding to and positioning target proteins in specific subcellular regions. An immense disparity exists between promiscuity of WW domain-mediated target bindings and specific roles of WW domain proteins in cell growth regulation. Here, we discovered that WW domain tandems of KIBRA and MAGI, but not YAP, bind to specific target proteins with extremely high affinity and exquisite sequence specificity. Via systematic structural biology and biochemistry approaches, we decoded the target binding rules of WW domain tandems from cell growth regulatory proteins and uncovered a list of previously unknown WW tandem binding proteins including β-Dystroglycan, JCAD, and PTPN21. The WW tandem-mediated target recognition mechanisms elucidated here can guide functional studies of WW domain proteins in cell growth and polarity as well as in other cellular processes including neuronal synaptic signaling.

Preparation of Lipid Nanodisks Containing Apolipoprotein E-Derived Synthetic Peptides for Biocompatible Delivery Vehicles Targeting Low-Density Lipoprotein Receptor

High-density lipoprotein (HDL) particles that are formed in vivo adopt a disk-shaped structure, in which the periphery of the discoidal phospholipid bilayer is surrounded by apolipoprotein. Such discoidal nanoparticles can be reconstituted with certain apolipoproteins and phospholipids and are commonly called lipid nanodisks. Apolipoprotein E (apoE), one of the HDL constituent proteins, serves as a ligand for the low-density lipoprotein (LDL) receptor. Thus, it is considered that biocompatible delivery vehicles targeting LDL receptors could be prepared by incorporating apoE as the protein component of lipid nanodisks. To enhance targeting efficiency, we designed lipid nanodisks with a large number of ligands using a peptide with the LDL receptor-binding region of apoE combined with a high lipid affinity sequence (LpA peptide). In our study, the LpA peptide spontaneously formed discoidal complexes (LpA nanodisks) of approximately 10 nm in size, equivalent to native HDL. LpA peptides on nanodisks adopted highly α-helical structures, a competent conformation capable of interacting with LDL receptors. As anticipated, the uptake of LpA nanodisks into LDL receptor-expressing cells (HepG2) was higher than that of apoE nanodisks, suggesting an enhanced targeting efficiency via the enrichment of LDL receptor-binding regions on the particle. Biodistribution studies using 111In-labeled LpA nanodisks showed little splenic accumulation and prolonged retention in blood circulation, reflecting the biocompatibility of LpA nanodisks. High accumulation of 111In-labeled LpA nanodisks was observed in the liver as well as in implanted tumors, which abundantly express LDL receptors. Thus, LpA nanodisks are potential biocompatible delivery vehicles targeting LDL receptors.

New ACE-inhibitory peptides derived from α-lactalbumin produced by hydrolysis with Bromelia antiacantha peptidases

Abstract Angiotensin converting enzyme (ACE) plays a key role in regulating blood pressure and ACE inhibitors are first-line drugs for treating hypertension. Food protein-derived peptides with ACE inhibitory activity are natural and safe alternatives for both prevention and treatment of hypertension. The second most abundant whey protein, α-lactalbumin (ALA) was hydrolysed with proteases from Bromelia antiacantha Bertol., a native plant. Two new peptides with potent ACE-inhibitory activity: TTFHTSGY (IC50 = 142 μM) and GYDTQAIVQ (IC50 = 1.0 mM) were purified by affinity chromatography and sequences were determined by mass spectrometry. In silico analysis indicated that neither of these peptides was toxic (ToxinPred). Inhibition kinetic analysis showed that TTFHTSGY was a fully functional ACE competitive inhibitor, whereas GYDTQAIVQ caused only partial ACE inhibition. Our results indicate that cysteine peptidases from B. antiacantha hydrolyse ALA to produce novel ACE inhibitory peptides that could be useful even as functional food ingredients.

Study on the affinity sequence between inhibitor ions and chloride ions in Mg[sbnd]Al layer double hydroxides and their effects on corrosion protection for carbon steel

A simple method was proposed to investigate the affinity sequence between inhibitor ions and chloride ions based on the pH values of filtrate after reconstruction of calcined layered double hydroxides (CLDH) in the corresponding salt solution with the following results: CrO42− > C6H5COO– > Cl− > NO2− > NO3−. The relationship between pH values and affinity sequence was further discussed by a conceptual model. Another common method was also performed for comparison and the same results verified the feasibility and accuracy of the above method. Electrochemical tests revealed the LDH loaded with inhibitors could provide effective corrosion protection for carbon steel in the simulated concrete pore (SCP) solution with following inhibition efficiency sequence: NO2-LDH > NO3-LDH > C6H5COO-LDH > CrO4-LDH. Long-term immersion experiment showed the NO2-LDH had the best anticorrosion effect in a long period. Therefore, NO2− can be an excellent candidate for inserting into LDH interlayer to exert LDH's dual effects of releasing inhibitor anions and immobilizing chloride ions.

The MarR-Type Regulator MalR Is Involved in Stress-Responsive Cell Envelope Remodeling in Corynebacterium glutamicum.

It is the enormous adaptive capacity of microorganisms, which is key to their competitive success in nature, but also challenges antibiotic treatment of human diseases. To deal with a diverse set of stresses, bacteria are able to reprogram gene expression using a wide variety of transcription factors. Here, we focused on the MarR-type regulator MalR conserved in the Corynebacterineae, including the prominent pathogens Corynebacterium diphtheriae and Mycobacterium tuberculosis. In several corynebacterial species, the malR gene forms an operon with a gene encoding a universal stress protein (uspA). Chromatin affinity purification and sequencing (ChAP-Seq) analysis revealed that MalR binds more than 60 target promoters in the C. glutamicum genome as well as in the large cryptic prophage CGP3. Overproduction of MalR caused severe growth defects and an elongated cell morphology. ChAP-Seq data combined with a global transcriptome analysis of the malR overexpression strain emphasized a central role of MalR in cell envelope remodeling in response to environmental stresses. For example, prominent MalR targets are involved in peptidoglycan biosynthesis and synthesis of branched-chain fatty acids. Phenotypic microarrays suggested an altered sensitivity of a ΔmalR mutant toward several β-lactam antibiotics. Furthermore, we revealed MalR as a repressor of several prophage genes, suggesting that MalR may be involved in the control of stress-responsive induction of the large CGP3 element. In conclusion, our results emphasize MalR as a regulator involved in stress-responsive remodeling of the cell envelope of C. glutamicum and suggest a link between cell envelope stress and the control of phage gene expression.

Efficient Screening of Combinatorial Peptide Libraries by Spatially Ordered Beads Immobilized on Conventional Glass Slides.

Screening of one-bead-one-compound (OBOC) libraries is a proven procedure for the identification of protein-binding ligands. The demand for binders with high affinity and specificity towards various targets has surged in the biomedical and pharmaceutical field in recent years. The traditional peptide screening involves tedious steps such as affinity selection, bead picking, sequencing, and characterization. Herein, we present a high-throughput “all-on-one chip” system to avoid slow and technically complex bead picking steps. On a traditional glass slide provided with an electrically conductive tape, beads of a combinatorial peptide library are aligned and immobilized by application of a precision sieve. Subsequently, the chip is incubated with a fluorophore-labeled target protein. In a fluorescence scan followed by matrix-assisted laser desorption/ionization (MALDI)-time of flight (TOF) mass spectrometry, high-affinity binders are directly and unambiguously sequenced with high accuracy without picking of the positive beads. The use of an optimized ladder sequencing approach improved the accuracy of the de-novo sequencing step to nearly 100%. The new technique was validated by employing a FLAG-based model system, identifying new peptide binders for the monoclonal M2 anti-FLAG antibody, and was finally utilized to search for IgG-binding peptides. In the present format, more than 30,000 beads can be screened on one slide.

Affinity selection and sequencing.

Powerful combinatorial peptide library methods allow the discovery of peptide leads from diverse libraries. A new platform based on tandem mass spectrometry peptide sequencing coupled with high-performance size-exclusion chromatography enables identification of high-affinity peptidic ligands from focused libraries.

Bentonites with grafted aminogroups: Synthesis, protolytic properties and assessing Cu(II), Cd(II) and Pb(II) adsorption capacity

Bentonites with grafted methylaminopropyl (NHCH3-Bent), aminopropyl (NH2-Bent), ethylenediaminopropyl (En-Bent) and diethylenetriaminopropyl (Dien-Bent) groups were synthesized by silylation procedure. The successful covalent grafting of silylating agents on the bentonite was confirmed by 29Si NMR, FTIR and thermal analysis. The effects of polar (ethanol) and non-polar (dioxane) solvents on grafting process were compared. The samples prepared in ethanol showed the increase of d001 value from initial 1.44 nm to 1.63–2.05 nm proportionally to the loading amount of grafted silane. However, an almost constant value of d001 (1.96–2.10 nm) was observed for all samples obtained in dioxane, which may be related to more efficient intercalation of the nonpolar solvent. High concentration of grafted aminogroups (0.7–1.6 mmol g−1) resulted in almost four times increase of adsorption capacity of Cu(II), Pb(II) and Cd (II) ions (1.35–0.91 mmol g−1) compared to the initial bentonite (0.23–0.25 mmol g−1). The modification with aminosilanes shifted the affinity sequence of the initial bentonite Pb(II) > Cd(II) > Cu(II) to Cu(II) > Pb(II) > Cd(II).

Genomic Characterization of the Zinc Transcriptional Regulatory Element Reveals Potential Functional Roles of ZNF658.

The zinc transcriptional regulatory element (ZTRE) is a newly reported binding motif for human zinc finger protein ZNF658, which alters gene expression in response to cellular zinc. The ZTRE has two nucleotide components-the palindromic flanking pairs and the bridging "N" bases between these flanks that range in number from 0 to 100. There are 12 pairs of ZTRE flanks (designated A-L). Three thousand five hundred twenty-five genes contain one or more ZTREs - 1000 to + 200bp from their transcriptional start site (TSS). ZTRE-E is observed at a greater frequency, and ZTRE containing 25 bridging bases are less frequent, within - 200bp from the TSS. The genes with ZTREs in this range are enriched in processes that may compensate zinc deficiency, while other genes with ZTREs outside this range are enriched in transcriptional activation processes. The division of ZTREs into two groups may imply a dual role of ZNF658, similar to the homologous yeast protein Zap1, via binding to low or high affinity sequences dependent upon cellular zinc. The KLF/Sp1-family binding motif is prevalent within the ZTRE "N" bridging bases, suggesting ZNF658 may compete with Sp1-like transactivators to suppress transcription.

Partition of Cd, Cu, Pb and Zn among mineral particles during their sorption in soils

Heterogeneity of soil mineral particles may lead to the misinterpretation of bulk sorption data on their role in metal sorption, which may be resolved through the direct observation of metal distribution among the soil particles after the sorption. Analytical transmission electron microscopy was used to study metal (Cd, Cu, Pb, Zn) sorption characteristics of clay minerals, Fe-oxyhydroxides and their natural assemblages in soils with contrasting pH under single element and competitive situations. Iron-oxyhydroxides sorbed higher metal amounts than clay mineral particles mostly, and the sorption capacity of the latter phases were more affected by competition. Iron-oxyhydroxide particles acted as effective metal sorbents in soils not only as individual particles but also as coatings on other mineral particles, and the structural Fe in clay minerals may also resulted in higher metal sorption in some cases. Besides the direct observation of metal sorption onto soil mineral particles, metal precipitates could be identified directly, and the role of organic surfaces in metal sorption could be inferred indirectly in certain cases. Comparison of metal affinity sequences and their partition characteristics between the bulk soil and different mineral particles were found to be an effective tool to specify the most active mineral components in metal sorption at given soil and sorption condition.

Modeling arsenic (V) removal from water by micellar enhanced ultrafiltration in the presence of competing anions

With increasing arsenic (As) contamination incidents reported around the world, better processes for As removal from industrial wastewater and other contaminated waters are required to protect drinking water sources. Complexation of As with cetylpyridinium chloride (CPC) cationic surfactant micelles, coupled with ultrafiltration (UF), has the potential to improve As removal, but competition from other anions could be a limiting factor. Using a binary-system ion-exchange model, the selectivity coefficients for binding of the monovalent and divalent forms of arsenate (As (V)) to cationic cetylpyridinium (CP+) micelles, relative to Cl−, were determined to be 0.55 for H2AsO4− and 0.047 mol L−1 for HAsO42−, respectively. The affinity sequence for binding of commonly occurring monovalent anions by CP+ micelles was found to be NO3− > Cl− > HCO3− > H2AsO4−, and for divalent anions, SO42− > HAsO42−. Distribution of As (V) between the micellar and aqueous phases was explored using ion exchange isotherms, with higher pH and lower concentrations of competing anions increasing rejection of As (V) across UF membranes. A model accounting for these effects, based on mass balances across UF membranes and selectivity coefficients for binding of anions to the CP+ micelles, was used to predict As (V) removal during micellar-enhanced ultrafiltration (MEUF) of mixtures of competing anions. Model predictions agreed well with experiment results for both artificial and spiked natural river water samples. Arsenic (≈0.1 mM) removals of 91% and 84% were achieved from artificial waters and spiked natural river waters, respectively, by adding 20 mM CPC prior to UF.

Heavy Metal Removal from Aqueous Solution Using Biosurfactants Produced by &lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; with Corn Oil as Substrate

The batch removal of Cu(II), Cd(II) and Pb(II) from individual heavy metal ion aqueous synthetic solution using biosurfactants produced by Pseudomonas aeruginosa with corn oil as substrate was investigated. The metal ion removal process of crude preparation biosurfactants (CPB) was established to be dependent on the initial pH and contact time. The optimum metal removal was observed at pH 6.0 of the initial metal solution and 10 min of contact time. The affinity sequence for metal ion removal was Pb(II)&gt;Cd(II)&gt;Cu(II). The removal capacity value of biosurfactant for Cu(II), Cd(II) and Pb(II) from single metal ions solution were 0.169, 0.276 and 0.323 mg/g, respectively. The removal capacity value of biosurfactant for Cu(II), Cd(II) and Pb(II) from multi metal ions solution were 0.064, 0.215 and 0.275 mg/g, respectively. The removal capacity of individual metal ion was diminished by the presence of other metal ions in multi metal ions from synthetic aqueous solution. The removal capacity value of biosurfactant for Cu(II), Cd(II) and Pb(II) from silver industry wastewater were 0.027, 0.055 and 0.291 mg/g, respectively. The results indicated that biosurfactants have potential to be used in the remediation of heavy metals in industrial wastewater.

Competitive sorption of lead and methylene blue onto black soil and their interaction with dissolved organic matter using two-dimensional correlation analyses

This study investigated the competitive sorption of black soil to adsorb Pb(II) and methylene blue (MB) from multi-contaminated soils. According to the experimental data, the process of adsorption can be clearly explained by pseudo-second-order kinetic equation. Both single and binary systems of the adsorption isotherms had a good fit with Langmuir models. The maximal adsorption abilities of Pb(II) and MB acquired from binary systems sorption were attenuated compared to those from the single system (Pb(II): 77.70 > 65.96 mg g−1; MB: 242.31 > 222.36 mg g−1). Pb(II) and MB can inhibit each other's sorption ability. A combination of three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence spectra as well as two-dimensional correlation spectroscopy (2D-COS) were employed to determine the binding of dissolved organic matter (DOM) for Pb(II) and MB during soil sorption process. As a result, 3D-EEM implicated that the two main composes of DOM were humic acid-like substances and the fluorescence of DOM specimens were gradually diminished with increasing concentrations of Pb(II) and MB. According to synchronous fluorescence spectra, static quenching of Pb(II) and MB mainly led to fluorescence quenching. Specifically, fluorescence-2D-COS implicated that Pb(II) and MB bound to fluorescence in the following sequence: the earlier occurrence of the humic-like fraction compared to that of protein-like fraction. FTIR-2D-COS results concluded that the structural change sequence of DOM by Pb(II) binding followed the order: 1700＞863＞1332＞1529＞1200＞1086 cm−1 and the sequence of the MB binding affinities followed the order: 1520＞1399＞1345＞1152＞1602＞993＞881 cm−1. These findings would be beneficial to understand the mechanism of adsorb multi-component systems and have the potential to contribute significance to the interaction mechanism of multi-component with soil DOM at the molecular level.