SDS (sodium dodecyl sulfate) effect on the autoxidation of the Glossoscolex paulistus giant extracellular hemoglobin: kinetic studies at pH 7.0 and 9.0

The effect of the anionic surfactant sodium dodecyl sulfate (SDS) on the autoxidation process of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) is addressed in the present work. The complex oligomeric assembly of hemoglobin subunits may influence the autoxidation rate and the exponential decay behavior. Kinetic studies were developed using UV-vis measurements at 415 nm. These spectroscopic measurements are analyzed at two pH values, 7.0 and 9.0, where the hemoglobin presents different oligomeric assembly. At pH 7.0 a high stability of the native form of the oxy-hemoglobin is observed, while at pH 9.0 an intense dissociation of the oligomer is promoted by alkalization. This difference is evident by comparison of the rate constants in the absence of surfactant: at pH 7.0 the kinetics presents a mono-exponential behavior with a rate constant of 0.27 x 10(-4)s(-1) while at pH 9.0 a bi-exponential behavior was observed with rate constant increase to 7 x 10(-4)s(-1) (fast process) and 1 x 10(-4)s(-1) (slow process). In the autoxidation induced by SDS two factors affect significantly the process rate, namely, the oligomeric arrangement of the hemoglobin and the strength of the interaction between SDS and HbGp. At pH 7.0, for SDS concentrations up to 0.3mM, a mono-exponential behavior was observed, showing rate constants around 0.4 x 10(-4)s(-1), which suggest that the hemoglobin still maintains the more compact structure observed at this pH for the native protein. In the SDS concentration range 0.75-1.0mM, the mono-exponential process changes into a bi-exponential behavior with rate constants varying from 48 x 10(-4) up to 99 x 10(-4)s(-1) for the fast process and from 1.7 x 10(-4) up to 3.7 x 10(-4)s(-1) for the slow process, suggesting hemoglobin dissociation. At pH 9.0, a bi-exponential decay is observed for all studied SDS concentration range, presenting rate constants from 11.0 x 10(-4) up to 179 x 10(-4)s(-1) for the fast process and from 1.0 x 10(-4) up to 8 x 10(4)s(-1) for the slow process probably due to hemoglobin dissociation, which is already present in the absence of surfactant. At pH 7.0, the highly packed native protein structure should inhibit the autoxidation process, but the SDS/HbGp interaction is more intense as compared to pH 9.0, due to the acid pI value, promoting oligomeric dissociation. So, the autoxidation process is regulated at pH 7.0 by the interaction with SDS, which triggers oligomeric dissociation and increase of autoxidation rate. At pH 9.0, the autoxidation process should be very fast, probably due to the oligomeric dissociation, which is already present in the absence of surfactant. At alkaline pH, the interaction with SDS seems be weaker than at pH 7.0. This behavior at pH 7.0 can be observed through the higher autoxidation rate for the faster chains and it is associated to the acid pI of the giant extracellular hemoglobins.     

Novel copoly(amide-thioamide), synthesis,characterization and behavior in metal ions adsorption

Copoly(amide-thioamide)s synthesized by polycondensation of bis(thioamide-amine)s and terephthaloyl dichloride in N-methyl pyrrolidone with moderate yields, possess inherent viscosity around 0.70 dL/g, and could be easily dissolved in amide-type polar aprotic solvent. The corresponding polythioamide was amorphous and showed a good thermal stability with glass transition temperature of 177°C in nitrogen atmosphere. The synthesized polymers were characterized by ¹H and ¹³C NMR and X-ray diffraction and were used as sorbents for the treatment of waste water containing heavy metals. Various factors affecting the uptake behavior such as concentration and pH were investigated.     

A one-dimensional model for dispersive wave turbulence

Summary A family of one-dimensional nonlinear dispersive wave equations is introduced as a model for assessing the validity of weak turbulence theory for random waves in an unambiguous and transparent fashion. These models have an explicitly solvable weak turbulence theory which is developed here, with Kolmogorov-type wave number spectra exhibiting interesting dependence on parameters in the equations. These predictions of weak turbulence theory are compared with numerical solutions with damping and driving that exhibit a statistical inertial scaling range over as much as two decades in wave number. It is established that the quasi-Gaussian random phase hypothesis of weak turbulence theory is an excellent approximation in the numerical statistical steady state. Nevertheless, the predictions of weak turbulence theory fail and yield a much flatter (|k|^−1/3) spectrum compared with the steeper (|k|^−3/4) spectrum observed in the numerical statistical steady state. The reasons for the failure of weak turbulence theory in this context are elucidated here. Finally, an inertial range closure and scaling theory is developed which successfully predicts the inertial range exponents observed in the numerical statistical steady states.     

Characterization and pillaring of a Turkish bentonite (Resadiye)

The shifts of the SiOSi stretching and the SiOAl and SiOSi bending modes, as well as the free silica peak in the IR spectra and the strengthening of the XRD reflections due to the quartz and alpha-cristobalite components of the Al-pillared bentonites (Wyoming and Resadiye), are ascribed to the formation of new SiOAl groups of covalent character. The mass losses in the temperature range 150-700 degrees C correspond to the dehydration and dehydroxylation processes. The total mass losses of the Al-pillared bentonites (Wyoming and Resadiye) are close to each other at an OH/Al ratio of 2.2, but calcination from 400 to 600 degrees C causes the surface area of the latter composite to decrease by 13%.     

Researches on pyrazoles

Alkyl and aryl pyrazoles are acylated at position 4 by the chloroanhydrides and anhydrides of the lowest fatty and aromatic acids in the presence of catalytic amounts of sulfuric acid. Reaction is readily effected because it is the neutral pyrazole molecule which is being acylated. In individual cases 1, 3, 5-trimethylpyrazole can be alkylated at position 4 by the Friedel-Crafts reaction.For Part IL see [6].     

Researches on pyrazoles

The dissociation constants (pK _a ) of isomeric hydroxy, amino, and carboxy substituted 1-phenylpyrazoles are determined. From the results certain conclusions are drawn regarding the distribution of electron density in the 1-phenylpyrazole ring, and regarding the effect (ortho effect) of substituents at position 5 on the basicities and acidities of these compounds.For Part LIV see [19].     

Crystallization and preliminary structural analysis of the giant haemoglobin from Glossoscolex paulistus at 3.2 Å

Glossoscolex paulistus is a free-living earthworm encountered in south-east Brazil. Its oxygen transport requirements are undertaken by a giant extracellular haemoglobin, or erythrocruorin (HbGp), which has an approximate molecular mass of 3.6 MDa and, by analogy with its homologue from Lumbricus terrestris (HbLt), is believed to be composed of a total of 180 polypeptide chains. In the present work the full 3.6 MDa particle in its cyanomet state was purified and crystallized using sodium citrate or PEG8000 as precipitant. The crystals contain one-quarter of the full particle in the asymmetric unit of the I222 cell and have parameters of a = 270.8 ?, b = 320.3 ? and c = 332.4 ?. Diffraction data were collected to 3.15 ? using synchrotron radiation on beamline X29A at the Brookhaven National Laboratory and represent the highest resolution data described to date for similar erythrocruorins. The structure was solved by molecular replacement using a search model corresponding to one-twelfth of its homologue from HbLt. This revealed that HbGp belongs to the type I class of erythrocruorins and provided an interpretable initial electron density map in which many features including the haem groups and disulfide bonds could be identified.     

A Family of Nonparametric Density Estimation Algorithms

A new methodology for density estimation is proposed. The methodology, which builds on the one developed by Tabak and Vanden‐Eijnden, normalizes the data points through the composition of simple maps. The parameters of each map are determined through the maximization of a local quadratic approximation to the log‐likelihood. Various candidates for the elementary maps of each step are proposed; criteria for choosing one includes robustness, computational simplicity, and good behavior in high‐dimensional settings. A good choice is that of localized radial expansions, which depend on a single parameter: all the complexity of arbitrary, possibly convoluted probability densities can be built through the composition of such simple maps. © 2012 Wiley Periodicals, Inc.     

Structural analysis of reactive dye species retained by the basic alumina surface

The alumina-dye composites were prepared by treating the basic alumina with the water solutions of Reactive Red 120 (RR 120) and Reactive Blue 15 (RB 15) dyes. The bands of low intensities in the 1400–1600 cm⁻¹ region and at 783 cm⁻¹ in the IR spectra of these composites point out that the dye species is bound weakly to the surface. In the case of mechanochemical adsorption of dye molecules, the asymmetric and symmetric S(=O)₂ and the S-O-C stretching bands together with the vibrations of aromatic ring revealed that dye types under dry conditions interacted effectively with alumina surface. After the heating of the alumina dye complexes in the temperature range 150–350°C, the intensities of the IR and XRD peaks for adsorbed types decreased. The endothermic peaks over 200°C and the bigger total mass losses for the alumina-dye composites can be ascribed to the decomposition of dye species retained by the alumina surface. The mass losses on TG curves of the alumina-dye complexes up to ∼800°C exhibit the removal of black residues occurred by decomposition of first adsorbed products. The thermal analysis data also point out that the water molecules bonded strongly to the alumina surface and dye types compete to accommodate at the surface active sites.