Hydrophobic nanoparticles promote lamellar to inverted hexagonal transition in phospholipid mesophases.

This study focuses on how the mesophase transition behaviour of the phospholipid dioleoyl phosphatidylethanolamine (DOPE) is altered by the presence of 10 nm hydrophobic and 14 nm hydrophilic silica nanoparticles (NPs) at different concentrations. The lamellar to inverted hexagonal phase transition (Lα-HII) of phospholipids is energetically analogous to the membrane fusion process, therefore understanding the Lα-HII transition with nanoparticulate additives is relevant to how membrane fusion may be affected by these additives, in this case the silica NPs. The overriding observation is that the HII/Lα boundaries in the DOPE p-T phase diagram were shifted by the presence of NPs: the hydrophobic NPs enlarged the HII phase region and thus encouraged the inverted hexagonal (HII) phase to occur at lower temperatures, whilst hydrophilic NPs appeared to stabilise the Lα phase region.

Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant.

Colloidal suspensions of plate-like particles undergo a variety of phase transitions. The predicted isotropic/nematic transition is often pre-empted by a sol/gel transition, especially in suspensions of the most commonly used natural swelling clay montmorillonite (MMT). A number of factors, including charge interactions, flexibility and salt concentration, may contribute to this competition.

Characterization of nanofibers formed by self-assembly of beta-peptide oligomers using small angle x-ray scattering.

Helical oligomers of beta-peptides represent a particularly promising type of building block for directed assembly of organic nanostructures because the helical secondary structure can be designed to be very stable and because control of the beta-amino acid sequence can lead to precise patterning of chemical functional groups over the helix surfaces. In this paper, we report the use of small angle x-ray scattering measurements (SAXS) to characterize nanostructures formed by the directed assembly of beta-peptide A with sequence H(2)N-beta(3)hTyr-beta(3)hLys-beta(3)hPhe-ACHC-beta(3)hPhe-ACHC-beta(3)hPhe-beta(3)hLys-ACHC-ACHC-beta(3)hPhe-beta(3)hLys-CONH(2). Whereas prior cryo-TEM studies have revealed the presence of nanofibers in aqueous solutions of beta-peptide A, SAXS measurements from the nanofibers were not well-fit by a form factor model describing solid nanofibers.

Characterization of the nanostructure of complexes formed by a redox-active cationic lipid and DNA.

We report characterization of the nanostructures of complexes formed between the redox-active lipid bis(n-ferrocenylundecyl)dimethylammonium bromide (BFDMA) and DNA using small-angle neutron scattering (SANS) and cryogenic transmission electron microscopy (cryo-TEM). A particular focus was directed to the influence of lipid oxidation state (where reduced BFDMA has a net charge of +1 and oxidized BFDMA has a charge of +3) on the nanostructures of the solution aggregates formed. Complexes were characterized over a range of charge ratios of reduced BFDMA to DNA (1.