Adsorption of arsenic (V) from a water solution onto a surfactant-modified zeolite

In this study a surfactant-modified zeolite (SMZ) was prepared by adsorbing the cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide on a clinoptilolite. The adsorption of the surfactant modified the surface properties of the clinoptilolite and enhanced the anionic capacity of the SMZ. The adsorption equilibrium data of As(V) from the water solution on the SMZ were obtained in a batch adsorber, and the Langmuir isotherm matched the data reasonably well. The As(V) adsorption capacity of the SMZ was 12.5 times greater than that of the clinoptilolite. The adsorption of As(V) on SMZ was mainly due to the interactions between the anionic sites of the SMZ and the As(V) anions in water solution. The adsorption capacity of the SMZ was dependent on the solution pH. The adsorption capacity was increased and decreased by augmenting the pH from 5 to 7 and from 7 to 12, respectively. This unusual behavior was due to the fact that the affinity of the As(V) for the SMZ was dependent on the As(V) species that were present in solution. The adsorption capacity of the SMZ was slightly favored by decreasing the temperature from 25 to 15 °C. The heat of adsorption was estimated to be ΔH _ads=−46.82 KJ/mol, indicating that the adsorption was exothermic and the As(V) was chemisorbed on the SMZ.     

Different Behaviors of Glutathione in Aqueous and DMSO Solutions: Molecular Dynamics Simulation and NMR Experimental Study

An all-atom molecular simulation and NMR experiments have been carried out to investigate the interactions and conformations of glutathione (GSH) in aqueous and DMSO solutions. The simulations started, from different initial conformations, are characterized by intramolecular distance, radius of gyration, root-mean-square deviation, and solvent-accessible surface. Interestingly, different behaviors are found in the two different solutions. GSH is highly flexible in an aqueous solution with transitions to the extended, semifolded, and folded states. However, once GSH reaches the folded state in DMSO, it remains there and becomes difficult to break down. The NMR results show agreement with the MD simulations. The water molecule is small. It is also a good proton donor and a good proton acceptor. Water molecules can easily break down the “folded” conformation. In DMSO solution, the stronger hydrogen bonds and the hydrophobic interactions are more important, which can make the GSH in the folded state stable. Variations in the distribution of conformations and the hydrogen-bonding network may play an important role in its function under physiological conditions.     

In defense of adiabatic ϕ/ψ mapping for cellobiose and other disaccharides

Thorough conformational study of cellobiose requires consideration of numerous arrangements of the exocyclic groups. Therefore, it is customary to prepare a number of structures with different arrangements of hydroxyl and hydroxymethyl groups. These “starting geometries” are then given different values of the glycosidic linkage torsion angles ϕ and ψ. At each increment of ϕ and ψ, the energy is calculated. Usually, the final product is an “adiabatic” contour plot of the lowest energy at each ϕ/ψ point after considering all of the starting geometries. The present paper advocates for adiabatic maps despite the statement by Schnupf and Momany (preceding paper) that adiabatic maps are not of interest because they contain sparse details about the structures at each minimum. Similar information is computed by their method and adiabatic mapping, and comparable details can be provided from adiabatic studies. Although Schnupf and Momany presented maps from calculations in vacuum and in water that considered all of their calculated energies, they favored the presentation of two to four maps for each of 36 individual minima, each with its own zero of relative energy. However, previous work showed that more structures are needed to provide the lowest energies at each point in ϕ/ψ space. Following their preferred strategy would result in even more maps when the added structures are considered. The need to map individual minima can be avoided by starting calculations with the same exocyclic orientations at each ϕ/ψ point instead of using the preceding optimized structure to start the next energy minimization. Using the same orientations at each point allows periodic maps that depict barriers between minima.     

Evaluation of adiabatic runaway reaction of methyl ethyl ketone peroxide by DSC and VSP2

Methyl ethyl ketone peroxide (MEKPO) is generally applied to manufacturing in the polymerization processes. Due to thermal instability and high exothermic behaviors of MEKPO, if any operation is undertaken recklessly or some environmental effect is produced suddenly during the processes, fires and explosions may inevitably occur. In this study, thermal analysis was evaluated for MEKPO by differential scanning calorimetry (DSC) test. Vent sizing package 2 (VSP2) was used to analyze the thermal hazard of MEKPO under various stirring rates in a batch reactor. Thermokinetic and safety parameters, including exothermic onset temperature (T ₀), maximum temperature (T _max), maximum pressure (P _max), self-heating rate (dT dt ⁻¹), pressure rise rate (dP dt ⁻¹), and so on, were discovered to identify the safe handling situation. The stirring rates of reactor were confirmed to affect runaway and thermal hazard characteristics in the batch reactor. If the stirring rate was out of control, it could soon cause a thermal hazard in the reactor.     

Folate-targeted optical and magnetic resonance dualmodality PCL-<Emphasis Type="Italic">b</Emphasis>-PEG micelles for tumor imaging

A biodegradable tumor targeting nano-probe based on poly（ε-caprolactone）-b-poly（ethylene glycol）block copolymer（PCL-b-PEG）micelle functionalized with a magnetic resonance imaging（MRI）contrast agent diethylenetriaminepentaacetic acid-gadolinium(DTPA-Gd³⁺)on the shell and a near-infrared（NIR）dye in the core for magnetic resonance and optical dual-modality imaging was prepared.The longitudinal relaxivity（r₁）of the PCL-b-PEG-DTPA -Gd³⁺micelle was 13.4（mmol/L）^-1s^-1,three folds of that of DTPA-Gd³⁺,and higher than that of many polymeric contrast agents with similar structures.The in vivo optical imaging of a nude mouse bearing xenografted breast tumor showed that the dual-modality micelle preferentially accumulated in the tumor via the folic acid-mediated active targeting and the passive accumulation by the enhanced permeability and retention（EPR）effect.The results indicated that the dualmodality micelle is a promising nano-probe for cancer detection and diagnosis.     

Synthesis and photovoltaic properties of alternating conjugated polymers derived from indolo[3,2-<Emphasis Type="Italic">b</Emphasis>]carbazole and thiophene/thieno[3,2-<Emphasis Type="Italic">b</Emphasis>]thiophene-cored benzoselenadiazole

Two alternating narrow band gap (NBG) copolymers derived from 5,11-di(N-9-heptadecanyl)-indolo[3,2-b]carbazole (ICZ) and 4,7-di(thien-2-yl)-2′,1′,3′-benzoselenadiazole (DSeBT) or 4,7-di(thieno[3,2-b]thien-2-yl)-2′,1′,3′-benzoselenadiazole (DTSeBT), were synthesized and named PICZ-DSeBT and PICZ-DTSeBT, respectively. The PICZ-DSeBT shows good solubility in common organic solvent, and the PICZ-DTSeBT is soluble in hot o-dichlorobenzene (ODCB) and not good soluble in chloroform, toluene etc. The chemical structure, molecular weight and fundamental physical properties of the copolymers were characterized by ¹H NMR, gel permeation chromatography (GPC), cyclic voltammetry (CV), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) etc. Potential application of the copolymers to be employed as electron donor material and PC61BM ([6,6]-phenyl-C₆₁ butyric acid methyl ester) for photovoltaic solar cells (PSCs), were investigated. PSCs based on the blends of PICZ-DSeBT/PC₆₁BM (w: w; 1: 2) or PICZ-DTSeBT/PC₆₁BM (w: w; 1: 2) with devices configuration as ITO/PEDOT: PSS/blend/Al, show the power conversion efficiencies (PCEs) of 1.06% and 1.52%, with the open circuit voltage (V _oc) of 0.75 V and 0.70 V, short circuit current densities (J _sc) of 3.45 mA/cm² and 5.30 mA/cm² under an AM1.5 simulator (100 mW/cm²) and the photocurrent response on-set wavelength extending up to 760 nm and 800 nm, respectively. It indicates that the NBG copolymers are viable electron donor materials for PSCs.     

‘Fixed charge’ chemical derivatization and data dependant multistage tandem mass spectrometry for mapping protein surface residue accessibility

Protein surface accessible residues play an important role in protein folding, protein-protein interactions and protein-ligand binding. However, a common problem associated with the use of selective chemical labeling methods for mapping protein solvent accessible residues is that when a complicated peptide mixture resulting from a large protein or protein complex is analyzed, the modified peptides may be difficult to identify and characterize amongst the largely unmodified peptide population (i.e., the ‘needle in a haystack’ problem). To address this challenge, we describe here the development of a strategy involving the synthesis and application of a novel ‘fixed charge’ sulfonium ion containing lysine-specific protein modification reagent, S,S′-dimethylthiobutanoylhydroxysuccinimide ester (DMBNHS), coupled with capillary HPLC-ESI-MS, automated CID-MS/MS, and data-dependant neutral loss mode MS³ in an ion trap mass spectrometer, to map the surface accessible lysine residues in a small model protein, cellular retinoic acid binding protein II (CRABP II). After reaction with different reagent:protein ratios and digestion with Glu-C, modified peptides are selectively identified and the number of modifications within each peptide are determined by CID-MS/MS, via the exclusive neutral loss(es) of dimethylsulfide, independently of the amino acid composition and precursor ion charge state (i.e., proton mobility) of the peptide. The observation of these characteristic neutral losses are then used to automatically ‘trigger’ the acquisition of an MS³ spectrum to allow the peptide sequence and the site(s) of modification to be characterized. Using this approach, the experimentally determined relative solvent accessibilities of the lysine residues were found to show good agreement with the known solution structure of CRABP II.     

Biosynthesis of Indigo Dye by Newly Isolated Naphthalene-Degrading Strain <Emphasis Type="Italic">Pseudomonas s</Emphasis>p. HOB1 and its Application in Dyeing Cotton Fabric

Indigo is one of the oldest dyes manufactured chemically and is mostly used in textile, food, and pharmaceutical industries. However, owing to the environmental hazards posed by the chemical production, the present scenario in the field stipulates a biosynthesis alternative for indigo production. The present study describes an indigenously isolated naphthalene-degrading strain Pseudomonas sp. HOB1 producing a blue pigment when indole was added in the growth medium. This blue pigment was analyzed by high-pressure thin-layer chromatography and other spectroscopic techniques which revealed it to be the indigo dye. Pseudomonas sp. HOB1 showed ability to produce 246 mg indigo liter⁻¹ of the medium. The K _m for the enzyme naphthalene dioxygenase which is involved in indigo formation is 0.3 mM, and V _max was as high as 50 nmol min⁻¹ mg dry biomass⁻¹. The bacterial indigo dye was further successfully applied for dyeing cotton fabrics. The high indigo productivity of Pseudomonas sp. HOB1 using naphthalene as growth substrate and its applicability on cotton fabrics, therefore, stems the probability of using this culture for commercial indigo production.     

Optically transparent superhydrophobic TEOS-derived silica films by surface silylation method

Optically transparent silica films were prepared at room temperature (~27°C) by keeping the molar ratio of TEOS:MeOH:H₂O (0.001 M NH₄F) constant at 1:19.29:6.20, respectively. A surface chemical modification of the films was done with alkylchlorosilanes at different concentrations from 0 to 1 vol. % and aging times varied from half to 2 h. The DMCS and TMCS surface modified silica films showed the static water contact angle of 146° and 162°, respectively. When the DMCS and TMCS modified films were cured at temperatures higher than 240 and 275°C, respectively, the films became superhydrophilic. Further, the humidity study was carried out at a relative humidity of 90% at 30°C temperature over 60 days. We characterized the water repellent silica films by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, % of optical transmission, humidity tests and contact angle measurements.     

Single-Chain Fv Antibody Fragments Retain Binding Properties of the Monoclonal Antibody Raised Against Peptide P1 of the Human Prion Protein

Prion diseases are incurable neurodegenerative diseases that affect both humans and animals. The infectious agent is a pathogenic form of the prion protein that accumulates in brain as amyloids. Currently, there is neither cure nor reliable preclinical diagnostics on the market available. The growing number of reports shows that passive immunisation is one of the most promising strategies for prion disease therapy, where antibodies against prions may prevent and even cure the infection. Since antibodies are large molecules and, thus, might not be suitable for the therapy, different antibody fragments are a good alternative. Therefore, we have designed and prepared single-chain antibody fragments (scFvs) derived from the PrP^Sc-specific murine monoclonal antibody V5B2. Using a new expression vector pMD204, we produced scFvs in two opposing chain orientations in the periplasm of Escherichia coli. Both recombinant antibody fragments retained the specificity of the parent antibody and one of these exhibited binding properties comparable to the corresponding murine Fab fragments with the affinity in nM range. Our monovalent antibody fragments are of special interest in view of possible therapeutic reagents for prion diseases as well as for development of a new generation of diagnostics.