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Based on small angle neutron-scattering data from a nanocomposite composed of fullerene C60 (16.5 wt %) in an isotactic polypropylene matrix, we receive information on the clusterization of nanoparticles and define their geometric parameters and dimensionality. This study proposes an interpretation of the aggregation of particles with surface fractal properties in the size range up to 80 nm, as observed in a small-angle-neutron-scattering experiment. Based on well-known theories about the defect structure of the fullerene C60 molecule in non-Euclidean metrics, specifically disclinations and monopoles in the two-dimensional spherical space of Gödel type, we formulate a lattice version of the monopole gas model. Within this framework, we use the Monte Carlo method on a lattice with the Abelian projection to estimate the energies of monopole currents at various monopole concentrations. The proposed model enables the calculation of the fractal properties of C60 nanoparticles in a polymer composite, as well as the interpretation of the evolution of disclinations. [ABSTRACT FROM AUTHOR]

Recently, the fabrication of ferrite nanoparticles in controlled varied shape and ferrofluids obtained with their help has become another requirement of interest for researchers. The present article reports the structural features of a new ferrofluid containing large, rod-like CuFe2O4 particles stabilized by a double layer of triple surfactant. Depending on the experimental method used, i.e., neutrons or X-rays, and, accordingly, the properties of the solvent (H2O, D2O), several peculiarities of the system, such as the morphology and particle dimensions, and the sizes of the surfactant coatings have been obtained. [ABSTRACT FROM AUTHOR]

Combining small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and densitometric measurements, we have studied the interactions of the divalent cations Ca 2+ and Mg 2+ with the lipid vesicles prepared of a mixed-chain palmitoyl-oleoyl-phosphatidylcholine (POPC) at 25°C. The structural parameters of the POPC bilayer, such as the bilayer thickness, lateral area, and volume per lipid, displayed no changes upon the ion addition at concentrations up to 30 mM and minor changes at > 30 mM Ca 2+ and Mg 2+ , while some decrease in the vesicle radius was observed over the entire concentration range studied. This examination allows us to validate the concept of lipid-ion interactions governed by the area per lipid suggested previously and to propose the mixed mode of those interactions that emerge in the POPC vesicles. We speculate that the average area per POPC lipid that corresponds to the cutoff length of lipid-ion interactions generates an equal but opposite impact on ion bridges and separate lipid-ion pairs. As a result of the dynamic equilibrium, the overall structural properties of bilayers are not affected. As the molecular mechanism proposed is affected by the structural properties of a particular lipid, it might help us to understand the fundamentals of processes occurring in complex multicomponent membrane systems., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Kurakin, Ivankov, Skoi, Kuklin, Uhríková and Kučerka.)

The structure and dynamics of membranes depend on many external and internal factors that in turn determine their biological functions. One of the widely accepted and studied characteristics of biomembranes is their fluidity. We research a simple system with variable fluidity tweakable via its composition. The addition of cholesterol is employed to increase the order of lipid chains, thus decreasing the membrane fluidity, while melatonin is shown to elevate the chain disorder, thus also the membrane fluidity. We utilize the densitometric measurements to show a shift of studied systems closer or further from the gel-to-fluid phase transition. The structural changes represented by changes to membrane thickness are evaluated from small angle neutron scattering. Finally, we look at the ability of the two additives to control the interactions between membrane and amyloid-beta peptides. Our results suggest that fluidizing effect of melatonin can promote an insertion of peptide within the membrane interior. Intriguingly, the latter structure relates possibly to an Alzheimer's disease preventing mechanism postulated in the case of melatonin.