Self-Assembly in Monoelaidin Aqueous Dispersions: Direct Vesicles to Cubosomes Transition

Background: In the present study, synchrotron small-angle X-ray scattering (SAXS) and Cryo-TEM were used to characterize the temperature-induced structural transitions of monoelaidin (ME) aqueous dispersion in the presence of the polymeric stabilizer F127. We prove that the direct transition from vesicles to cubosomes by heating this dispersion is possible. The obtained results were compared with the fully hydrated bulk ME phase. Methodology/principal findings: Our results indicate the formation of ME dispersion, which is less stable than that based on the congener monoolein (MO). In addition, the temperature-dependence behavior significantly differs from the fully hydrated bulk phase. SAXS findings indicate a direct L(alpha)-V(2) internal transition in the dispersion. While the transition temperature is conserved in the dispersion, the formed cubosomes with internal Im3m symmetry clearly contain more water and this ordered interior is retained over a wider temperature range as compared to its fully hydrated bulk system. At 25 degrees C, Cryo-TEM observations reveal the formation of most likely closely packed onion-like vesicles. Above the lamellar to non-lamellar phase transition at 65 degrees C, flattened cubosomes with an internal nanostructure are observed. However, they have only arbitrary shapes and thus, their morphology is significantly different from that of the well-shaped analogous MO cubosome and hexosome particles. Conclusions/significance: Our study reveals a direct liposomes-cubosomes transition in ME dispersion. The obtained results suggest that the polymeric stabilizer F127 especially plays a significant role in the membrane fusion processes. F127 incorporates in considerable amount into the internal nanostructure and leads to the formation of a highly swollen Im3m phase

Shepsi, the Oldest Dolmen with Port-Hole Slab in the Western Caucasus

The dolmen known as Shepsi was accidentally discovered on the Black Sea coast (Tuapse region, Russia). Radiocarbon dates show that the classic trapezoidal construction of the Caucasian dolmens with a port-hole appeared in the region as early as 3250 BC. The distinctive structural characteristic for dolmens of that time was a floor slab laid between the side slabs, which were embedded in the ground. The material complex and C-14 dates show that this type of dolmen coexisted with the Novosvobodnaya-type of the Maikop culture, located on the northern slope of the main Caucasus ridge. This leads to a new hypothesis concerning the regional origin and further development of the megalithic structures in the western Caucasus

Crowding effects on amyloid aggregation kinetics

Biological protein self-assembly occurs in the cellular milieu, densely occupied by other macromolecules which do not participate directly in the aggregation process. Excluded volume effects arising in such a crowded environment deeply affect the thermodynamics and kinetics of biological processes, like protein folding, ligand binding, and protein aggregation. Here, Langevin dynamics simulations of a simplified model of an amphipathic polypeptide are used to investigate how macromolecular crowding influences the amyloid aggregation kinetics. The simulations show that the net influence of macromolecular crowding on the self-assembly process is the result of two competing effects: oligomer stabilization and solution viscosity increase. Notably, the net effect crucially depends on the aggregation propensity and pathways. Therefore, comparative studies of concentration and crowding effects on the kinetics of amyloid aggregation could shed light on the underlying self-assembly mechanism