Formation and structure of ionomer complexes from grafted polyelectrolytes

We discuss the structure and formation of Ionomer Complexes formed upon mixing a grafted block copolymer (poly(acrylic acid)-b-poly(acrylate methoxy poly(ethylene oxide)), PAA21-b-PAPEO14) with a linear polyelectrolyte (poly(N-methyl 2-vinyl pyridinium iodide), P2MVPI), called grafted block ionomer complexes (GBICs), and a chemically identical grafted copolymer (poly(acrylic acid)-co-poly(acrylate methoxy poly(ethylene oxide)), PAA28-co-PAPEO22) with a linear polyelectrolyte, called grafted ionomer complexes (GICs). Light scattering measurements show that GBICs are much bigger (~70–100 nm) and GICs are much smaller or comparable in size (6–22 nm) to regular complex coacervate core micelles (C3Ms). The mechanism of GICs formation is different from the formation of regular C3Ms and GBICs, and their size depends on the length of the homopolyelectrolyte. The sizes of GBICs and GICs slightly decrease with temperature increasing from 20 to 65 °C. This effect is stronger for GBICs than for GICs, is reversible for GICs and GBIC-PAPEO14/P2MVPI228, and shows some hysteresis for GBIC-PAPEO14/P2MVPI43. Self-consistent field (SCF) calculations for assembly of a grafted block copolymer (having clearly separated charged and grafted blocks) with an oppositely charged linear polyelectrolyte of length comparable to the charged copolymer block predict formation of relatively small spherical micelles (~6 nm), with a composition close to complete charge neutralization. The formation of micellar assemblies is suppressed if charged and grafted monomers are evenly distributed along the backbone, i.e., in case of a grafted copolymer. The very large difference between the sizes found experimentally for GBICs and the sizes predicted from SCF calculations supports the view that there is some secondary association mechanism. A possible mechanism is discussed

Self-consistent field theory for the interactions between keratin intermediate filaments

Background: Keratins are important structural proteins found in skin, hair and nails. Keratin Intermediate Filaments are major components of corneocytes, nonviable horny cells of the Stratum Corneum, the outermost layer of skin. It is considered that interactions between unstructured domains of Keratin Intermediate Filaments are the key factor in maintaining the elasticity of the skin. Results: We have developed a model for the interactions between keratin intermediate filaments based on self-consistent field theory. The intermediate filaments are represented by charged surfaces, and the disordered terminal domains of the keratins are represented by charged heteropolymers grafted to these surfaces. We estimate the system is close to a charge compensation point where the heteropolymer grafting density is matched to the surface charge density. Using a protein model with amino acid resolution for the terminal domains, we find that the terminal chains can mediate a weak attraction between the keratin surfaces. The origin of the attraction is a combination of bridging and electrostatics. The attraction disappears when the system moves away from the charge compensation point, or when excess small ions and/or NMF-representing free amino acids are added. Conclusions: These results are in concordance with experimental observations, and support the idea that the interaction between keratin filaments, and ultimately in part the elastic properties of the keratin-containing tissue, is controlled by a combination of the physico-chemical properties of the disordered terminal domains and the composition of the medium in the inter-filament region. Keywords: Stratum corneum, Skin keratins, Intermediate filaments, Unstructured terminal domains, Bridging attractio

Quality of life of testicular cancer survivors and the relationship with sociodemographics, cancer-related variables, and life events

Goals of Work: The aim of this study was to (1) assess the quality of life (QoL) of testicular cancer survivors (TCSs) by comparing them to a reference group; (2) investigate the relationship between the QoL of TCSs and sociodemographics, cancer-related variables, and life events; and (3) identify TCSs at risk for an impaired QoL. Patients and methods: Of the TCSs approached, 50% (n=354) participated and completed a generic QoL questionnaire (RAND-36) once. Time since completion of treatment varied from 3 months to 24 years. Main results: (1) TCSs had significantly higher mean scores on the subscales physical functioning (p=0.02) and pain (p=0.001), but lower mean scores on mental health (p=0.04) and vitality (p < 0.001) than a reference group of men. The effect sizes of these differences were small to insignificant. (2) Employment status and chronic disease were the main correlates of the QoL of TCSs. Age, negative life events, type of treatment, and the experience of a second cancer event were moderately associated with some subscales as well. (3) The joint burden of unemployment and a chronic disease was the strongest predictor for an impaired functioning. Conclusion: On a group level, TCSs experience a good QoL, but a small group appeared to be at risk for an impaired functioning, namely, those who were unemployed and had a chronic disease. The variance explained by the variables studied was low, indicating that more important predictors remain to be identified