Self-Assembly of Polyion–Surfactant Ion Complex Salts in Mixtures with Water and n-Alcohols

Phase behavior and structural features were investigated for "complex salts", consisting of the cationic hexadecyltrimethylammonium (CTA) surfactant with polyacrylate (PA(n), n = 30 or 6000) counterions, mixed with water and different n-alcohols (ethanol, butanol, hexanol, octanol, and decanol). The liquid crystalline structures formed were identified by small-angle X-ray scattering measurements, which provided information about the changes in the geometry of the aggregates as functions of the concentration and chain length of the added n-alcohol. The obtained results were compared with a previous work on similar ternary mixtures of the same cationic surfactant but with the monomeric bromide counterion, CTABr (Fontell, K; Khan, A.; Lindstrom, B.; Maciejewska, D.; Puang-Ngem, S. Colloid Polym. Sc., 1991, 269, 727). In general, the same phases were detected in systems with the complex salts CTAPA(n) as in systems with CTABr, but the swelling of the various liquid crystalline phases by water was much more limited in the complex salt systems. An isotropic alcoholic phase was observed with all alcohols and the size of this region of the phase diagram increased for the shorter alcohols, except for ethanol. For mixtures with octanol and ethanol, in particular, the extensions of the disordered isotropic phases were larger for the complex salt with the shorter polyacrylate ions

Surface Deposition and Phase Behavior of Oppositely Charged Polyion–Surfactant Ion Complexes. Delivery of Silicone Oil Emulsions to Hydrophobic and Hydrophilic Surfaces

The adsorption from mixed polyelectrolyte-surfactant solutions at hydrophobized silica surfaces was investigated by in situ null-ellipsometry, and compared to similar measurements for hydrophilic silica surfaces. Three synthetic cationic copolymers of varying hydrophobicity and one cationic hydroxyethyl cellulose were compared in mixtures with the anionic surfactant sodium dodecylsulfate (SDS) in the absence or presence of a dilute silicone oil emulsion. The adsorption behavior was mapped while stepwise increasing the concentration of SDS to a polyelectrolyte solution of constant concentration. The effect on the deposition of dilution of the bulk solution in contact with the surface was also investigated by gradual replacement of the bulk solution with 1 mM aqueous NaCl. An adsorbed layer remained after complete exchange of the polyelectrolyte/surfactant solution for aqueous NaCl. In most cases, there was a codeposition of silicone oil droplets, if such droplets were present in the formulation before dilution. The overall features of the deposition were similar at hydrophobic and hydrophilic surfaces, but there were also notable differences. SDS molecules adsorbed selectively at the hydrophobized silica surface, but not at the hydrophilic silica, which influenced the coadsorption of the cationic polymers. The largest amount of deposited material after dilution was found for hydrophilic silica and for the least-hydrophobic cationic polymers. For the least-hydrophobic polyions, no significant codeposition of silicone oil was detected at hydrophobized silica after dilution if the initial SDS concentration was high

Genomic patterns of malignant peripheral nerve sheath tumor (MPNST) evolution correlate with clinical outcome and are detectable in cell-free DNA

Malignant peripheral nerve sheath tumor (MPNST), an aggressive soft-tissue sarcoma, occurs in people with neurofibromatosis type 1 (NF1) and sporadically. Whole-genome and multiregional exome sequencing, transcriptomic, and methylation profiling of 95 tumor samples revealed the order of genomic events in tumor evolution. Following biallelic inactivation of NF1, loss of CDKN2A or TP53 with or without inactivation of polycomb repressive complex 2 (PRC2) leads to extensive somatic copy-number aberrations (SCNA). Distinct pathways of tumor evolution are associated with inactivation of PRC2 genes and H3K27 trimethylation (H3K27me3) status. Tumors with H3K27me3 loss evolve through extensive chromosomal losses followed by whole-genome doubling and chromosome 8 amplification, and show lower levels of immune cell infiltration. Retention of H3K27me3 leads to extensive genomic instability, but an immune cell-rich phenotype. Specific SCNAs detected in both tumor samples and cell-free DNA (cfDNA) act as a surrogate for H3K27me3 loss and immune infiltration, and predict prognosis

Intraspecific Diversity Regulates Fungal Productivity and Respiration

Individuals and not just species are key components of biodiversity, yet the relationship between intraspecific diversity and ecosystem functioning in microbial systems remains largely untested. This limits our ability to understand and predict the effects of altered genetic diversity in regulating key ecosystem processes and functions. Here, we use a model fungal system to test the hypothesis that intraspecific genotypic richness of Paxillus obscurosporus stimulates biomass and CO2 efflux, but that this is dependent on nitrogen supply. Using controlled experimental microcosms, we show that populations containing several genotypes (maximum 8) of the fungus had greater productivity and produced significantly more CO2 than those with fewer genotypes. Moreover, intraspecific diversity had a much stronger effect than a four-fold manipulation of the carbon:nitrogen ratio of the growth medium. The effects of intraspecific diversity were underpinned by strong roles of individuals, but overall intraspecific diversity increased the propensity of populations to over-yield, indicating that both complementarity and selection effects can operate within species. Our data demonstrate the importance of intraspecific diversity over a range of nitrogen concentrations, and the need to consider fine scale phylogenetic information of microbial communities in understanding their contribution to ecosystem processes

Effects of Endolithic Parasitism on Invasive and Indigenous Mussels in a Variable Physical Environment

Biotic stress may operate in concert with physical environmental conditions to limit or facilitate invasion processes while altering competitive interactions between invaders and native species. Here, we examine how endolithic parasitism of an invasive and an indigenous mussel species acts in synergy with abiotic conditions of the habitat. Our results show that the invasive Mytilus galloprovincialis is more infested than the native Perna perna and this difference is probably due to the greater thickness of the protective outer-layer of the shell of the indigenous species. Higher abrasion due to waves on the open coast could account for dissimilarities in degree of infestation between bays and the more wave-exposed open coast. Also micro-scale variations of light affected the level of endolithic parasitism, which was more intense at non-shaded sites. The higher levels of endolithic parasitism in Mytilus mirrored greater mortality rates attributed to parasitism in this species. Condition index, attachment strength and shell strength of both species were negatively affected by the parasites suggesting an energy trade-off between the need to repair the damaged shell and the other physiological parameters. We suggest that, because it has a lower attachment strength and a thinner shell, the invasiveness of M. galloprovincialis will be limited at sun and wave exposed locations where endolithic activity, shell scouring and risk of dislodgement are high. These results underline the crucial role of physical environment in regulating biotic stress, and how these physical-biological interactions may explain site-to-site variability of competitive balances between invasive and indigenous species

Tuning the polymer release from hydrophilic matrix tablets by mixing short and long matrix polymers

In this work a rotating disc method was developed for studying the dissolution process of "bimodal" polymer tablets, whose dissolution rates have been tuned by mixing low-molecular weight and high-molecular weight samples of poly(ethylene oxide) in various proportions. The tablets were prepared along different routes, by mixing the polymer fractions as powders or by mixing on a molecular level so that the effect of tablet heterogeneity could be assessed, but also by purifying the original powders so the effect of additives could be determined. When the mixed tablet was dominated by the lowmolecular weight fraction, a faster dissolution was observed for the tablet mixed at the powder level. In those cases small gel pieces were released from the tablet during the whole dissolution process. As long as no gel piece erosion was observed, it did not matter if the two polymer fractions were blended on the molecular level or on the powder level, the steady-state dissolution rate was the same. The presence of small amounts of additives in the nonpurified commercial samples had no significant effect on the tablet dissolution within the uncertainty of the experiment. (c) 2005 Wiley-Liss, Inc

A new approach to the phase behavior of oppositely charged polymers and surfactants

The complex salt (ionic surfactant + polymeric counterion) cetyltrimethylammonium polyacrylate (CTAPA) has been synthesized, and its aqueous mixtures with cetyltrimethylammonium bromide (CTABr) have been studied. These mixtures differ from conventional oppositely charged polymer/surfactant mixtures in that the conventional counterion of the polyion (usually sodium, for the polyacrylate) is absent, which simplifies the studies and their interpretation considerably. The phase diagram of the CTAPA/CTABr/water system at > 20 wt % water and at 40 degreesC has been established, representing the first truly ternary phase diagram of an oppositely charged polymer/surfactant pair in water. The two dimensions of the phase diagram may be chosen as the water content (in weight percent) and the fraction of bromide counterions, x(Br) (in units of charge equivalents). The phase diagram is characterized by a large hexagonal phase (at low water contents and for all values of x(Br)), a small cubic phase (at 55 wt % water content and for x(Br) 0.9), and a large multiphase region (at water contents > 50 wt %) containing two or three of the cubic, hexagonal, or isotropic phases in coexistence. The cubic and hexagonal phases are connected to the corresponding phases that separate out from aqueous NaPA/CTABr mixtures. The maximum water uptake of the hexagonal phase is remarkably constant at ca. 50 wt % over a large CTAPA/CTABr composition range (x(Br) < 0.9). The study confirms previous conclusions that the polyacrylate counterions favor a higher aggregate curvature (leading to smaller aggregates) than do the bromide counterions

Phase behavior and rheological properties of DNA-cationic polysaccharide mixtures

Associative aqueous mixtures over a range of concentrations of double- (ds) or single- (ss) stranded DNA with dilute or semidilute solutions of two cationic derivatives of hydroxyethyl cellulose (cat-HEC and cat-HMHEC,(1) the latter carrying grafted hydrophobic groups), were studied. The phase behavior showed an interesting asymmetry: Phase separation occurred immediately when small (sub-stoichiometric) amounts of cationic polyelectrolyte were added to the DNA solution, but redissolution into a single cat-(HM)HEC/DNA/H2O phase occurred already with a modest charge excess of the cationic polyelectrolyte, at a charge ratio approximately independent of the overall polyelectrolyte concentration. Cat-HEC/dsDNA/H2O and cat-HEC/ssDNA/H2O systems presented a considerable difference in the extension of the phase separation region. The one-phase samples with excess cationic polyelectrolyte were studied by rheology. The presence of DNA strengthened the viscoelastic behavior of the solutions of the cationic polyelectrolytes, reflected in an increase in storage modulus and viscosity. Differences in phase behavior and rheology were observed, particularly between systems containing cat-HEC or cat-HMHEC, but also between dsDNA and ssDNA. Thus, these systems allow for the preparation of DNA formulations with widely variable rheology and water uptake. (C) 2012 Elsevier Inc. All rights reserved