Cr(VI) Adsorption to Magnetic Iron Oxide Nanoparticle-Multi-Walled Carbon Nanotube Adsorbents

  The aim of this study was to investigate the Cr(VI) adsorption to magnetic iron oxide(MIO) nanoparticle- multi-walled carbon nanotubes (MWCNTs) in aqueous solutions using batch experiments. Results show that the maximum adsorption capacity of Cr(VI) to MIO-MWCNTs was 11.256 mg/g. Kinetic model analysis demonstrates that the pseudo-second-order model and Elovich model are suitable for describing the kinetic data. Thermodynamic analysis indicates that Cr(VI) adsorption to MIO-MWCNTs decreased with increasing temperature from 5-60 °C, indicating the spontaneous and exothermic nature of the sorption process. Equilibrium isotherm analysis demonstrates that the Redlich-Peterson model suitably describes the equilibrium data. In the pH experiments, Cr(VI) adsorption to MIO-MWCNTs decreased gradually from 5.70-2.13 mg/g with increasing pH from 3.0-7.3. Sequential extraction indicates that, among the five binding forms of Cr(VI) associated with MIO-MWCNTs, the predominant contributions are the fraction bound to Fe-Mn oxides (57.82%) and the residual (23.38%).

Biosorption of chromium (VI) onto NaOH activated Codium tomentosum biomass

Batch experiments were conducted to examine the efficacy of NaOH activated Codium tomentosum biomass on the sorption of hexavalent chromium. Several influencing parameters like pH, contact time, dosage and initial chromium(VI) concentration was experimented at 20°C. The monolayer sorption capacity was found to be 5.504 ± 0.360 mg g(-1). Langmuir and Freundlich isotherm implied favorable condition of chromium(VI) biosorption, based on R2 values. Dubinin-Radushkevich isotherm showed the best fit linearity and infered that adsorption energy as 4.888 ± 0.129 kJ mol(-1). Pseudo-second order kinetics showed good compliance for the entire data and the rate constant (k2) was found to be 0.0398 ± 0.007 g mg(-1) min. Elovich kinetics exhibited that adsorption occurs on heterogeneous surface. Intraparticle diffusion model specified multi-linearity in adsorption process. Hence, the employed biosorbent was sensible and sorption efficiency was remarkable.

Predicted Role of NAD Utilization in the Control of Circadian Rhythms during DNA Damage Response

The circadian clock is a set of regulatory steps that oscillate with a period of approximately 24 hours influencing many biological processes. These oscillations are robust to external stresses, and in the case of genotoxic stress (i.e. DNA damage), the circadian clock responds through phase shifting with primarily phase advancements. The effect of DNA damage on the circadian clock and the mechanism through which this effect operates remains to be thoroughly investigated. Here we build an in silico model to examine damage-induced circadian phase shifts by investigating a possible mechanism linking circadian rhythms to metabolism. The proposed model involves two DNA damage response proteins, SIRT1 and PARP1, that are each consumers of nicotinamide adenine dinucleotide (NAD), a metabolite involved in oxidation-reduction reactions and in ATP synthesis. This model builds on two key findings: 1) that SIRT1 (a protein deacetylase) is involved in both the positive (i.e. transcriptional activation) and negative (i.e. transcriptional repression) arms of the circadian regulation and 2) that PARP1 is a major consumer of NAD during the DNA damage response. In our simulations, we observe that increased PARP1 activity may be able to trigger SIRT1-induced circadian phase advancements by decreasing SIRT1 activity through competition for NAD supplies. We show how this competitive inhibition may operate through protein acetylation in conjunction with phosphorylation, consistent with reported observations. These findings suggest a possible mechanism through which multiple perturbations, each dominant during different points of the circadian cycle, may result in the phase advancement of the circadian clock seen during DNA damage.

Many physiological processes are regulated by the circadian clock, and we are continuing to learn about the role of the circadian clock in disease. Research in recent years has begun to shed light on the feedback mechanisms that exist between circadian regulation and other processes, including metabolism and the response to DNA damage. A challenge has been to understand the dynamic nature of the protein interactions of these processes, which often involve protein modification as a means of communicating cellular states, such as damaged DNA. Here we have devised a model that simulates an alteration of the circadian clock that is observed during DNA damage response. A novel aspect of this model is the inclusion of SIRT1, a protein that regulates core circadian proteins through modification and helps to repress gene expression. SIRT1 is dependent on a metabolite regulated by the circadian clock and is depleted during DNA damage. In conjunction with a second form of protein modification, our results suggest that multiple forms of protein modification may contribute to the experimentally observed alterations to circadian function.

A new VGLUT-specific potent inhibitor: pharmacophore of Brilliant Yellow

The increased concentration of glutamate in synaptic vesicles, mediated by the vesicular glutamate transporter (VGLUT), is an initial vital step in glutamate synaptic transmission. Evidence indicates that aberrant overexpression of VGLUT is involved in certain pathophysiologies of the central nervous system. VGLUT is subject to inhibition by various types of agents. The most potent VGLUT-specific inhibitor currently known is Trypan Blue, which is highly charged, hence membrane-impermeable. We have sought a potent, VGLUT-specific agent amenable to easy modification to a membrane-permeable analog. We provide evidence that Brilliant Yellow exhibits potent, VGLUT-specific inhibition, with a Ki value of 12 nM. Based upon structure-activity relationship studies and molecular modeling, we have defined the potent inhibitory pharmacophore of Brilliant Yellow. This study provides new insight into development of a membrane-permeable agent to lead to specific blockade, with high potency, of accumulation of glutamate into synaptic vesicles in neurons.

Removal of Pb(II), Cd(II), Cu(II), and Zn(II) by hematite nanoparticles: effect of sorbent concentration, pH, temperature, and exhaustion

Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions (Pb(II), Cd(II), Cu(II), Zn(II)) to nanohematite was examined as a function of sorbent concentration, pH, temperature, and exhaustion. Adsorption experiments were conducted with 0.05, 0.1, and 0.5 g/L nanoparticles in a pH 8 solution and in spiked San Antonio tap water. The adsorption data showed the ability of nanohematite to remove Pb, Cd, Cu, and Zn species from solution with adsorption increasing as the nanoparticle concentration increased. At 0.5 g/L nanohematite, 100 % Pb species adsorbed, 94 % Cd species adsorbed, 89 % Cu species adsorbed and 100 % Zn species adsorbed. Adsorption kinetics for all metals tested was described by a pseudo second-order rate equation with lead having the fastest rate of adsorption. The effect of temperature on adsorption showed that Pb(II), Cu(II), and Cd(II) underwent an endothermic reaction, while Zn(II) underwent an exothermic reaction. The nanoparticles were able to simultaneously remove multiple metals species (Zn, Cd, Pb, and Cu) from both a pH 8 solution and spiked San Antonio tap water. Exhaustion experiments showed that at pH 8, exhaustion did not occur for the nanoparticles but adsorption does decrease for Cd, Cu, and Zn species but not Pb species. The strong adsorption coupled with the ability to simultaneously remove multiple metal ions offers a potential remediation method for the removal of metals from water.

Reduction of dinitrotoluene sulfonates in TNT red water using nanoscale zerovalent iron particles

PURPOSE

This research was designed to investigate the feasibility of converting the dinitrotoluene sulfonates (DNTS) in TNT red water into the corresponding aromatic amino compounds using nanoscale zerovalent iron (NZVI).

METHODS

NZVI particles were simultaneously synthesized and stabilized by sodium borohydride reduction in a nondeoxygenated system. The morphology, elemental content, specific surface area, and crystal properties of the NZVI were characterized before and after the reaction by environmental scanning electron microscope; energy dispersive X-ray; Brunauer, Emmett, and Teller; and X-ray diffraction, respectively. The reduction process was conducted at pH = 6.3 at ambient temperature. The efficiency of the NZVI-mediated DNTS reduction process was monitored by HPLC, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses.

RESULTS

The properties of the NZVI particles prepared were found to be similar to those obtained through oxygen-free preparation and inert stabilization processes. Both 2,4-DNT-3-sulfonate (2,220 mg L(-1)) and 2,4-DNT-5-sulfonate (3,270 mg L(-1)) in TNT red water underwent a pseudo-first-order transformation when mixed with NZVI at room temperature and near-neutral pH. Their observed rate constants were 0.11 and 0.30 min(-1), respectively. Within 1 h of processing, more than 99% of DNTS was converted by NZVI-mediated reduction into the corresponding diaminotoluene sulfonates.

CONCLUSIONS

NZVI can be simultaneously prepared and stabilized in a nondeoxygenated system. NZVI reduction is a highly efficient method for the conversion of DNTS into the corresponding diaminotoluene sulfonates under near-neutral pH conditions. Therefore, NZVI reduction may be useful in the treatment of TNT red water and subsequent recovery of diaminotoluene from explosive wastewater.

Synthesis, properties and application research of atrazine Fe₃O₄@SiO₂ magnetic molecularly imprinted polymer

INTRODUCTION

Magnetic Fe3O4 nanoparticles were prepared by coprecipitation and then were coated with SiO2 on the surface.

MATERIALS AND METHODS

Fe3O4@SiO2 composite microspheres were modified by KH570. Using molecular imprinting technology, atrazine magnetic molecularly imprinted polymer was prepared by using atrazine as template molecule, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linkers. The morphology, composition and magnetic properties of magnetic nanoparticles were characterized. The recognition selectivity of polymer was studied for template molecule and simulation by UV spectrophotometry. The adsorption properties and selectivity ability were analyzed by Scatchard analysis.

RESULTS

Scatchard linear regression analysis indicated that there are two binding sites of the target molecules. The magnetic molecularly imprinted polymer has been applied to the analysis of atrazine in real samples.

CONCLUSION

The results show that: the recovery rates and the relative standard deviation were 94.0∼98.7% and 2.1∼4.0% in corn, the recovery rates and the relative standard deviation were 88.7∼93.5% and 2.8∼7.2% in water.

Evaluation of adsorption characteristics of an anionic azo dye Brilliant Yellow onto hen feathers in aqueous solutions

PURPOSE AND AIM: Removal of an anionic azo dye Brilliant Yellow has been carried out from its aqueous solutions by using hen feathers as potential adsorbent.

MATERIALS AND METHODS

Hen feathers procured from local poultry were cut, washed, and activated. Detailed chemical and physical analysis of hen feathers and its characterization through scanning electron microscopy, X-ray diffraction, and infrared measurements have been made. Procured dye has been adsorbed over under batch measurements and adsorption process is monitored using UV spectrophotometer.

RESULTS

Optimum parameters for the adsorption of Brilliant Yellow over hen feathers have been determined by studying the effect of pH, temperature, concentration of dye, and amount of adsorbent. On the basis of Langmuir adsorption, isotherms feasibility of the ongoing adsorption has been ascertained and thermodynamic parameters have been calculated. Attempts have also been made to verify Freundlich, Tempkin, and Dubinin–Radushkevich adsorption isotherm models. It is found that during adsorption, uniform distribution of binding energy takes place due to interaction of the dye molecules and the ongoing adsorption process is chemisorptions. The kinetic measurements indicate dominance of pseudo-second-order process during the adsorption. The mathematical treatment on the kinetic data reveals the rate-determining step to be governed through particle diffusion at 8 × 10−5 M and involvement of film diffusion mechanism at higher concentration at temperatures at all the temperatures.

CONCLUSIONS

The developed process is highly efficient and it can be firmly concluded that hen feather exhibits excellent adsorption capacity towards hazardous azo dye Brilliant Yellow.

The promoter of Rv0560c is induced by salicylate and structurally-related compounds in Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a major global health threat. During infection, bacteria are believed to encounter adverse conditions such as iron depletion. Mycobacteria synthesize iron-sequestering mycobactins, which are essential for survival in the host, via the intermediate salicylate. Salicylate is a ubiquitous compound which is known to induce a mild antibiotic resistance phenotype. In M. tuberculosis salicylate highly induces the expression of Rv0560c, a putative methyltransferase. We identified and characterized the promoter and regulatory elements of Rv0560c. P_Rv0560c activity was highly inducible by salicylate in a dose-dependent manner. The induction kinetics of P_Rv0560c were slow, taking several days to reach maximal activity, which was sustained over several weeks. Promoter activity could also be induced by compounds structurally related to salicylate, such as aspirin or para-aminosalicylic acid, but not by benzoate, indicating that induction is specific to a structural motif. The −10 and −35 promoter elements were identified and residues involved in regulation of promoter activity were identified in close proximity to an inverted repeat spanning the −35 promoter element. We conclude that Rv0560c expression is controlled by a yet unknown repressor via a highly-inducible promoter.

Individual actin filaments in a microfluidic flow reveal the mechanism of ATP hydrolysis and give insight into the properties of profilin

A novel microfluidic approach allows the analysis of the dynamics of individual actin filaments, revealing both their local ADP/ADP-Pi-actin composition and that Pi release is a random mechanism.

The hydrolysis of ATP associated with actin and profilin-actin polymerization is pivotal in cell motility. It is at the origin of treadmilling of actin filaments and controls their dynamics and mechanical properties, as well as their interactions with regulatory proteins. The slow release of inorganic phosphate (Pi) that follows rapid cleavage of ATP gamma phosphate is linked to an increase in the rate of filament disassembly. The mechanism of Pi release in actin filaments has remained elusive for over 20 years. Here, we developed a microfluidic setup to accurately monitor the depolymerization of individual filaments and determine their local ADP-Pi content. We demonstrate that Pi release in the filament is not a vectorial but a random process with a half-time of 102 seconds, irrespective of whether the filament is assembled from actin or profilin-actin. Pi release from the depolymerizing barbed end is faster (half-time of 0.39 seconds) and further accelerated by profilin. Profilin accelerates the depolymerization of both ADP- and ADP-Pi-F-actin. Altogether, our data show that during elongation from profilin-actin, the dissociation of profilin from the growing barbed end is not coupled to Pi release or to ATP cleavage on the terminal subunit. These results emphasize the potential of microfluidics in elucidating actin regulation at the scale of individual filaments.

Actin proteins assemble into microfilaments that control cell shape and movement by polymerizing or depolymerizing. These actin monomers can bind ATP or ADP molecules. The incorporation of an ATP-actin monomer into a growing filament results in rapid cleavage of ATP into ADP and inorganic phosphate (Pi), followed by a slower release of Pi. As a consequence, actin filaments are composed mainly of ADP- and ADP-Pi-actin subunits, which have different depolymerization kinetics and mechanical properties, and can be targeted specifically by regulatory proteins that affect filament function. Hence, the understanding of many cellular processes requires a knowledge of the ADP/ADP-Pi composition of actin filaments at a molecular scale. This has so far remained elusive because traditional studies rely on measuring an average over many filaments in solution. To address this issue, we developed a microfluidics setup to monitor individual filaments with light microscopy while rapidly changing their chemical environment. We find that depolymerization accelerates progressively and corresponds to an exponential ADP-Pi-actin profile in the filament, meaning that each subunit releases its Pi with the same rate. Our method also provides novel insight into the function of profilin, a protein important for regulation of actin dynamics in cells, thus demonstrating the method's potential in the functional analysis of actin regulators.

Absorption spectroscopy

Absorption spectroscopy is one of the most widely used techniques employed for determining the concentrations of absorbing species (chromophores) in solutions. It is a nondestructive technique which biologists and biochemists and now systems biologists use to quantify the cellular components and characteristic parameters of functional molecules. This quantification is most relevant in the context of systems biology. For creating a quantitative depiction of a metabolic pathway, a number of parameters and variables are important and these need to be determined experimentally. This chapter describes the UV-visible absorption spectroscopy used to produce experimental data for bottom-up modeling approaches of systems biology which uses concentrations and kinetic parameters (K(m) and V(max)) of enzymes of metabolic/signaling pathways, intracellular concentrations of metabolites and fluxes. It also briefly describes the application of this technique for quantification of biomolecules and investigating biomolecular interactions.

Slowing bacterial translation speed enhances eukaryotic protein folding efficiency

The mechanisms for de novo protein folding differ significantly between bacteria and eukaryotes, as evidenced by the often observed poor yields of native eukaryotic proteins upon recombinant production in bacterial systems. Polypeptide synthesis rates are faster in bacteria than in eukaryotes, but the effects of general variations in translation rates on protein folding efficiency have remained largely unexplored. By employing Escherichia coli cells with mutant ribosomes whose translation speed can be modulated, we show here that reducing polypeptide elongation rates leads to enhanced folding of diverse proteins of eukaryotic origin. These results suggest that in eukaryotes, protein folding necessitates slow translation rates. In contrast, folding in bacteria appears to be uncoupled from protein synthesis, explaining our findings that a generalized reduction in translation speed does not adversely impact the folding of the endogenous bacterial proteome. Utilization of this strategy has allowed the production of a native eukaryotic multidomain protein that has been previously unattainable in bacterial systems and may constitute a general alternative to the production of aggregation-prone recombinant proteins.

Thermoperiodic growth control by gibberellin does not involve changes in photosynthetic or respiratory capacities in pea

Active gibberellin (GA(1)) is an important mediator of thermoperiodic growth in pea. Plants grown under lower day than night temperature (negative DIF) elongate less and have reduced levels of GA(1) compared with plants grown at higher day than night temperature (positive DIF). By comparing the wild type (WT) and the elongated DELLA mutant la cry(s), this study has examined the effect of impaired GA signalling on thermoperiodic growth, photosynthesis, and respiration in pea. In the WT a negative DIF treatment reduced stem mass ratio and increased both root mass ratio and leaf mass ratio (dry weight of specific tissue related to total plant dry weight). Leaf, root and stem mass ratios of la cry(s) were not affected by DIF. Under negative DIF, specific leaf area (projected leaf area per unit leaf dry mass), biomass, and chlorophyll content of WT and la cry(s) plants were reduced. Young, expanding leaves of plants grown under negative DIF had reduced leaf area-based photosynthetic capacity. However, the highest photosynthetic electron transport rate was found in fully expanded leaves of WT plants grown under negative DIF. Negative DIF increased night respiration and was similar for both genotypes. It is concluded that GA signalling is not a major determinant of leaf area-based photosynthesis or respiration and that reduced dry weight of plants grown under negative DIF is caused by a GA-mediated reduction of photosynthetic stem and leaf tissue, reduced photosynthesis of young, expanding leaves, and reduced growth caused by low temperature in the photoperiod.

Dissolved organic matter enhances transport of PAHs to aquatic organisms

In this study, the uptake of pyrene and benzo[b]fluoranthene by an aquatic worm (Lumbriculus variegatus) and a poly(dimethylsiloxane) coated glass fiber was studied at different humic acid concentrations. The accumulation of pyrene was not affected by the presence of the humic matrix. However, the accumulation rate of benzo[b]fluoranthene increased a factor of 3 for the fiber and a factor of 4 when 55 mg L(-1) dissolved organic carbon was added in the form of humic acid. The difference between the two chemicals can be explained by the higher affinity of benzo[b]fluoranthene for the dissolved humic material. A comparison of modeled transport enhancement of benzo[b]fluoranthene by humic acid and the experimental results suggested that the benzo[b]fluoranthene complexed with the humic phase was not completely labile.

Apraxia, metaphor and mirror neurons

Ideomotor apraxia is a cognitive disorder in which the patient loses the ability to accurately perform learned, skilled actions. This is despite normal limb power and coordination. It has long been known that left supramarginal gyrus lesions cause bilateral upper limb apraxia and it was proposed that this area stored a visual-kinaesthetic image of the skilled action, which was translated elsewhere in the brain into the pre-requisite movement formula. We hypothesise that, rather than these two functions occurring separately, both are complementary functions of chains of "mirror neurons" within the left inferior parietal lobe. We go on to propose that this neural mechanism in the supramarginal gyrus and its projection zones, which originally evolved to allow the creation of a direct map between vision and movement, was subsequently exapted to allow other sorts of cross-domain mapping and in particular those sorts of abstract re-conceptualisation, such as metaphor, that make mankind unique.