Abstract. Hybrid polymeric networks composed of polyacrylamide and chitosan were developed to determine their swelling and ascorbic acid delivery kinetics at various chitosan concentrations. The hybrid acrylamide/chitosan hydrogels were synthesized in aqueous itaconic acid solution (1% w/w). Young's modulus was also evaluated for the hydrogels, and the results were correlated with the swelling properties. Swelling experiments were carried out using three different pH solutions: acidic (pH 4 buffer solution), neutral (distilled water) and basic (pH 10 buffer solution). The results of the swelling study showed that the swelling properties of the network varied with the changes of the pH in the swelling solution, as well as concentration of chitosan. When chitosan concentration increased, the swelling capacity diminished, and therefore Young's modulus increased. The results indicated that the swelling process followed a second order kinetics. The ascorbic acid diffusion inside the hydrogel follows a Fickian mechanism. The ascorbic acid diffusion coefficients are reported as a function of chitosan concentration.

The n-decanephosphonic acid/water and n-dodecanephosphonic acid/water systems were studied by differential scanning calorimetry, hot stage polarized light microscopy, and FT-IR spectropetry. There is a rich polymorphism:  in both systems there are three liquid crystalline phases (lamellar Lα and Lβ and an inverse cubic phase) plus the isotropic liquid and two solid phases. One of the solids is an ordinary cristalline phase and the other is a waxy crystal in which the polar headgroup network is rigid and ordered but in which the alkyl chains are partially fluid and disordered. The water in these systems exists in two distinct forms:  water bound to the headgroups and water which is effectively free. The polymorphism of the heptyl and octyl analogues has been studied by Klose et al.

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We have identified a membrane-active region in the HCV NS4B protein by studying membrane rupture induced by a NS4B-derived peptide library on model membranes. This segment corresponds to one of two previously predicted amphipathic helix and define it as a new membrane association domain. We report the binding and interaction with model membranes of a peptide patterned after this segment, peptide NS4B(H2), and show that NS4B(H2) strongly partitions into phospholipid membranes, interacts with them, and is located in a shallow position in the membrane. Furthermore, changes in the primary sequence cause the disruption of the hydrophobicity along the structure and prevent the resulting peptide from interacting with the membrane. Our results suggest that the region where the NS4B(H2) is located might have an essential role in the membrane replication and/or assembly of the viral particle through the modulation of the replication complex. Our findings therefore identify an important region in the HCV NS4B protein which might be implicated in the HCV life cycle and possibly in the formation of the membranous web.

In this work we propose a new crosslinking agent and the method to use it for the synthesis of acrylate based hydrogels. The use of this diacrylate of glycerol, synthesized in our laboratory, allows the generation of materials with well defined micro‐structures in the dry state, unique meso‐ and macro‐structures during swelling, and enhanced mechanical properties and swelling capacity in water. These properties depend on the crosslinking agent concentration, as well as synthesis thermal history. Poly(acrylamide‐co‐acrylic acid) hydrogels are commonly crosslinked with N, N′‐methylenebisacrylamide or N‐isopropylacrylamide. Here we obtain and use a new crosslinking agent, obtained from the reaction between glycerol and acrylic acid to produce a Diacrylate of glycerol (DAG). Two synthesis methods at equivalent molar ratio of acrylamide/acrylic acid (AM/AA) were analyzed. The mechanical properties, the swelling capacity, and the morphology at microscale of these hydrogels showed a well defined transition at a critical concentration of crosslinking agent. DAG induces the generation of hydrogels with hierarchichal structure. The micro‐structure surface morphology was investigated by scanning electron microscopy, the meso‐structure by polarized light microscopy and the macro‐structure by CCD imaging. The hydrogels with hierarchical structures showed improved mechanical properties when compared with structureless hydrogels. Control of the microstructure allows the generation of materials for different applications, i.e. templates or smart materials that interact with electromagnetic radiation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2667–2679, 2008