Interaction of cationic surfactant and anionic polyelectrolytes in mixed aqueous solutions

Surfactant–polymer interactions in aqueous solutions have been studied using dynamic surface tension, polyelectrolyte titration, nephelometric turbidity, and dynamic light scattering. For the preparation of complexes, a technical cationic surfactant was used in combination with two poly(maleic acid-co-polymers) of similar structure but different hydrophobicity. The dynamic surface tensions of mixed solutions as functions of surfactant concentration at constant polyelectrolyte content, as well as changes in the surface activity due to the influence of polyanion at constant surfactant concentration are discussed in terms of a complex or aggregate formation in the bulk phase. The interaction of the surfactant with poly(maleic acid-alt-propene) (P-MS-P) and poly(maleic acid-alt--methylstyrene) (P-MS-MeSty), respectively, is strong in both cases and results in the formation of nanoparticles with properties depending on the composition of the corresponding mixture.     

Bis-morpholine-substituted perylene bisimides: impact of isomeric arrangement on electrochemical and spectroelectrochemical properties

The synthesis and separation of the 1,6- and 1,7- isomers of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide are reported. Investigations of the electrochemical and spectroscopic, in particular, spectroelectrochemical, properties of the two isomers reveal a sequence of electrochemically and chemically reversible redox processes for both isomers. Importantly, the 1,7-isomer of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide was observed to undergo a two-electron oxidation process, which contrasts with the behavior of both the corresponding 1,6-isomer and other related amino-substituted perylene bis-imide species.     

Activation detection in event-related fMRI data based on spatio-temporal properties.

Template-based activation detection methods, such as cross-correlation, could be difficult to apply in event-related functional MRI data because accurate a priori knowledge about the activation signal patterns is often not available. As a result, several categories of template-free data analysis techniques have been introduced in the fMRI literature. One previously described template-free activation detection technique is based on the feature that activated voxels yield reproducible time course patterns as the subject undergoes the same simulation in repeated epochs. In this paper, spatial information is incorporated as a second feature and a combined univariate measure is formed. The resulting method is shown to offer measurable improvement in detecting activation regions in simulated data in a highly computationally efficient manner. Its practical utility is demonstrated with an experimental data set obtained with a visually guided motor paradigm.     

Quantitation of intracellular purine intermediates in different Corynebacteria using electrospray LC-MS/MS

Intermediates of the purine biosynthesis pathway play key roles in cellular metabolism including nucleic acid synthesis and signal mediation. In addition, they are also of major interest to the biotechnological industry as several intermediates either possess flavor-enhancing characteristics or are applied in medical therapy. In this study, we have developed an analytical method for quantitation of 12 intermediates from the purine biosynthesis pathway including important nucleotides and their corresponding nucleosides and nucleobases. The approach comprised a single-step acidic extraction/quenching procedure, followed by quantitative electrospray LC-MS/MS analysis. The assay was validated in terms of accuracy, precision, reproducibility, and applicability for complex biological matrices. The method was subsequently applied for determination of free intracellular pool sizes of purine biosynthetic pathway intermediates in the two Gram-positive bacteria Corynebacterium glutamicum and Corynebacterium ammoniagenes. Importantly, no ion pair reagents were applied in this approach as usually required for liquid chromatography analysis of large classes of diverse metabolites.     

Structure and dynamics of cellular systems

This review addresses recent progress in the analysis and modelling of disordered cell structures. It focuses on planar systems, for which most research has been performed. The subject is approached from a general viewpoint rather than focusing on the specific evolution of certain systems. To this end, results of studies performed in completely different disciplines, ranging from applied sciences, biology and physics to mathematics, are gathered and discussed systematically. Special emphasis is laid on common properties of the different structures, including a critical discussion of the information contained in typically measured quantities. Efficient techniques for the simulation of typical disordered cell structures are summarized, and novel theoretical approaches to the modelling of dynamical cell structures are presented. Here, special attention is paid to the application of the methods of statistical mechanics and the resulting implications. In several systems, a breakdown of order induced by variation of an external control parameter can be observed. Its diagnostics in Voronoi tessellations is presented focusing on the connection with the underlying physics. The discussion of planar cell structures is concluded with a presentation of the peculiar properties of exceptional systems, characterized by the coexistence of two different length scales or by scale invariance. This review concludes with a presentation of recent developments in the research on three-dimensional cell structures.     

Impact of Various Parameters Over the Adsorption of Polyvinylpyrrolidone onto Kaolin

The adsorption of water-soluble polymer, polyvinylpyrrolidone having molecular mass 9.1 ± 1.43 × 10³Kg mole^?1 on kaolin has been investigated. The effect of different parameters like pH, molecular mass of polymer and pre-heat treatment on the adsorption of PVP has been deliberated. The 20.7% decrease in adsorption in pH ranging from 2–10 have been found, which was an indication of the fact that with the increase in pH the kaolin surfaces sites charge amount and ultimately sign changes. Maximum adsorption was observed at pH 5.6 that was also molecular mass dependent. By increasing the pretreatment temperature, the amount of polymer adsorbed was also increased. However, above the specific temperature adsorption of PVP was decreased and attributed to decrease in specific surface area of kaolin.