Internal standardization for the determination of cadmium,cobalt, chromium and manganese in saline produced water from petroleum industry by inductively coupled plasma optical emission spectrometry after cloud point extraction

In the present paper a procedure is proposed for the determination of traces of Cd, Co, Mn and Cr in petroleum industry produced water by inductively coupled plasma optical emission spectrometry. The procedure is based on cloud point extraction of these metals, as their dithizonate complexes, into the surfactant-rich phase of octylphenoxypolyethoxyethanol surfactant (Triton X-114). Extractions were carried out in solutions with salinities between 10‰ and 70‰. Since residual salinity in the surfactant-rich phase caused differences in its transport to the plasma, yttrium was used as an internal standard to correct for this effect. The simultaneous metal extraction procedure was optimized by response surface methodology using a Doehlert design and desirability function. Enhancement factors of 21, 21, 9 and 19, along with limits of quantification of 0.093, 0.20, 0.73 and 1.2 μg L^− 1, and precision expressed as relative standard deviation (n = 8, 20.0 μg L^− 1) of 5.8, 1.2, 1.7 and 5.7% were obtained for Cd, Co, Mn and Cr, respectively. The accuracy was evaluated by spike recovery tests on the high salinity water samples with salinity of 40 and 63‰.     

Effects of processing on the structure of zein/oleic Acid films investigated by x-ray diffraction

Zein films plasticized with oleic acid were formed by solution casting, by the stretching of moldable resins, and by blown film extrusion. The effects of the forming process on film structure were investigated by X-ray diffraction. Wide-angle X-ray scattering (WAXS) patterns showed d-spacings at 4.5 and 10 A, which were attributed to the zein alpha-helix backbone and inter-helix packing, respectively. The 4.5 A d-spacing remained stable under processing while the 10 A d-spacing varied with processing treatment. Small-angle X-ray scattering (SAXS) detected a long-range periodicity for the formed films but not for unprocessed zein, which suggests that the forming process-promoted film structure development is possibly aided by oleic acid. The SAXS d-spacing varied among the samples (130-238 A) according to zein origin and film-forming method. X-ray scattering data suggest that the zein molecular structure resists processing but the zein supramolecular arrangements in the formed films are dependent on processing methods. Structural model for a zein molecular aggregate (based on Matsushima et al.10). Rectangular prisms of individual zein molecules are hexagonally aligned parallel to each other.     

DFT study of polymorphism of the DNA double helix at the level of dinucleoside monophosphates

We apply DFT calculations to deoxydinucleoside monophosphates (dDMPs) which represent minimal fragments of the DNA chain to study the molecular basis of stability of the DNA duplex, the origin of its polymorphism and conformational heterogeneity. In this work, we continue our previous studies of dDMPs where we detected internal energy minima corresponding to the “classical” B conformation (BI‐form), which is the dominant form in the crystals of oligonucleotide duplexes. We obtained BI local energy minima for all existing base sequences of dDMPs. In the present study, we extend our analysis to other families of DNA conformations, successfully identifying A, BI, and BII energy minima for all dDMP sequences. These conformations demonstrate distinct differences in sugar ring puckering, but similar sequence‐dependent base arrangements. Internal energies of BI and BII conformers are close to each other for nearly all the base sequences. The dGpdG, dTpdG, and dCpdA dDMPs slightly favor the BII conformation, which agrees with these sequences being more frequently experimentally encountered in the BII form. We have found BII‐like structures of dDMPs for the base sequences both existing in crystals in BII conformation and those not yet encountered in crystals till now. On the other hand, we failed to obtain dDMP energy minima corresponding to the Z family of DNA conformations, thus giving us the ground to conclude that these conformations are stabilized in both crystals and solutions by external factors, presumably by interactions with various components of the media. Overall the accumulated computational data demonstrate that the A, BI, and BII families of DNA conformations originate from the corresponding local energy minimum conformations of dDMPs, thus determining structural stability of a single DNA strand during the processes of unwinding and rewinding of DNA. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2548–2559, 2010     

Liquid structure of the ionic liquid 1,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]amide

Neutron diffraction has been used to determine the liquid structure of 1,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]amide ([dmim][NTf2]). Significantly smaller charge ordering is found in this liquid compared with analogous chloride and hexafluorophosphate salts due to the diffuse charge density and size of the [NTf2]- anion. This is manifested in a much larger cation-cation and cation-anion separation and an overlap of the cation-cation and cation-anion shells. Comparison of the liquid structure with the crystal structure reported by Holbrey et al. (Dalton Trans. 2004, 2267) indicates little correlation, for example, the [NTf2]- anion adopts a trans orientation predominantly in the liquid whereas a cis orientation is found in the solid phase.     

Formation of zein spheres by evaporation-induced self-assembly

Zein is an amphiphilic protein capable of self-assembly into microspheres. Zein microspheres may form by evaporation-induced self-assembly (EISA) of zein solutions in ethanol/water. The formation of microspheres is of particular interest for the development of delivery systems. Zein solutions in ethanol/water 75?% (v/v) were slowly evaporated to promote self-assembly of microspheres. The ethanol content of the solvent decreased during EISA changing solvent polarity which induced self-assembly of zein particles. The growth of zein spheres was modeled from the hydrophobic and hydrophilic contributions to the interfacial free energy (R ²?=?0.92). The good fit indicated that during EISA zein microspheres increased in size due to hydrophobic interactions between zein molecules. The model may allow the prediction of evaporation time and thus control over microsphere size.     

Adaptive behaviour of the spinal cord in the transition from quiet stance to walking

Background

Parkinson??s disease is characterized by a continuous loss of neurons within the substantia nigra (SN) leading to a depletion of dopamine. Within the adult SN as a non-neurogenic region, cells with mainly oligodendrocytic precursor characteristics, expressing the neuro-glial antigen-2 (NG2) are continuously generated. Proliferation of these cells is altered in animal models of Parkinson??s disease (PD). Exercise and environmental enrichment re-increase proliferation of NG2⁺ cells in PD models, however, a possible mechanistic role of dopamine for this increase is not completely understood. NG2⁺ cells can differentiate into oligodendrocytes but also into microglia and neurons as observed in vitro suggesting a possible hint for endogenous regenerative capacity of the SN. We investigated the role of dopamine in NG2-generation and differentiation in the adult SN stimulated by physical activity and environmental enrichment.

Results

We used the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-model for dopamine depletion and analysed newborn cells in the SN at different maturation stages and time points depending on voluntary physical activity, enriched environment and levodopa-treatment. We describe an activity- induced increase of new NG2-positive cells and also mature oligodendrocytes in the SN of healthy mice. Running and enriched environment refused to stimulate NG2-generation and oligodendrogenesis in MPTP-mice, an effect which could be reversed by pharmacological levodopa-induced rescue.

Conclusion

We suggest dopamine being a key regulator for activity-induced generation of NG2-cells and oliogodendrocytes in the SN as a potentially relevant mechanism in endogenous nigral cellular plasticity.     

Porous Ionic Liquids or Liquid Metal–Organic Frameworks?

Porous liquids can be prepared from the dispersion metal–organic frameworks (MOFs) in ionic liquids (ILs). Porous liquids prepared from 5 % of ZIF‐8 in a phosphonium‐based ionic liquid are capable of absorbing reversibly up to 150 % more nitrogen and 100 % more methane than the pure ionic liquid.     

Assessment of cardiac iron by MRI susceptometry and R2* in patients with thalassemia

A magnetic resonance imaging cardiac magnetic susceptometry (MRI-CS) technique for assessing cardiac tissue iron concentration based on phase mapping was developed. Normal control subjects (n=9) and thalassemia patients (n=13) receiving long-term blood transfusion therapy underwent MRI-CS and MRI measurements of the cardiac relaxation rate R2*. Using MRI-CS, subepicardium and subendocardium iron concentrations were quantified exploiting the hemosiderin/ferritin iron specific magnetic susceptibility. The average of subepicardium and subendocardium iron concentrations and R2* of the septum were found to be strongly correlated (r=0.96, P<.0001), and linear regression analysis yielded CIC (μg Fe/g_{wet tissue})=(6.4±0.4)·R2* _septum (s⁻¹) − (120±40). The results demonstrated that septal R2* indeed measures cardiac iron level.     

Galactomannans as a sieving matrix in capillary electrophoresis

Purification of galactomannans including guaran, tara gum, and locust bean gum is described as well as their use as a sieving matrix in DNA sequencing by capillary electrophoresis (CE). Three methods of galactomannan purification were developed and tested using guaran. The first method is based on hydrolysis of proteins using alkali treatment and precipitation of guaran with acetone. The second method uses ion-exchange resins QAE Sephadex A-25 and SP Sephadex C-25 together with acetone precipitation. The third method is similar to the second one, except that it uses ion-exchange resins based on polystyrene, Source 30Q and Source 30S. Capillary zone electrophoresis of acetonitrile extracts from guaran revealed 4-5 characteristic major peaks and several minor peaks. Guar gum from different suppliers differed in the content of proteins. In purified guaran, protein peaks were detectable only using a 300-fold concentrate of extract. The content of proteins in the guaran purified using the third method was 0.001% m/m as determined by CE. The weight average molecular mass of purified guaran can be as large as 2.2 x 10(6). The purified galactomannans were used as a sieving matrix in DNA sequencing by CE. M13 DNA was sequenced to read lengths of about 600 bases in less than 90 min. Separation efficiencies exceeded 1 million theoretical plates for DNA fragments shorter than about 600 bases.     

Robustness of virus removal by protein A chromatography is independent of media lifetime

The robustness of virus clearance with respect to protein A media reuse was demonstrated using media with four matrix chemistries: Protein A immobilized ProSep A, Poros A50, Protein A ceramic Hyper DF and MabSelect SuRe, an alkali resistant protein A ligand. Endogenous retrovirus clearance, step yield, impurity clearance and other performance parameters were evaluated periodically in media cycled up to 300 times. Media lifetime was generally limited by either declining step yield or media fouling. However, clearance of endogenous retrovirus remained in an acceptable range, either increasing or remaining constant. Multiply cycled media were tested for clearance of three viruses (SV40, X-MuLV, and MMV); clearance was comparable to na?ve media. Overall, virus clearance by protein A chromatography appears to be extremely robust with respect to media age.