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Mobility of interacting inorganic nanoparticles

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The mobility of the 110 nm-Fe2O3 particles in a viscous sucrose solution depends on the concentration of the nanoparticles. When the average particle–particle nearest neighbor distance is less than 250 nm, the particle interaction slows down their mobility. When is more than 170 nm, the small mobility of nanoparticles does not depend on their concentration. The critical distance is approximately equal to 2Rh = 260 nm, where Rh is the hydrodynamic radius, determined by the dynamic light scattering (DLS) method.
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Size, shape and secondary structure of calponin.

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The overall size and shape of the chicken gizzard calponin (CaP) h1 molecule was investigated by dynamic light scattering (DLS) measurements. From the DLS experiments, a z-averaged translational diffusion coefficient is derived (5.75 ± 0.3) × 10-7cm2s-1, which corresponds to a hydrodynamic radius of 3.72 nm for calponin. The frictional ratio (1.8 for the unhydrated molecule and 1.5 for the hydrated one) suggests a pronounced anisotropic structure for the molecule. An ellipsoidal model in length 19.4 nm and with a diameter of 2.6 nm used for hydrodynamic calculations was found to reproduce the DLS experimental data. The evaluation of the secondary structure of CaP h1 from the CD spectra by two independent methods has revealed that it contains, on average, 23% helix, 19% β-strand, 18% β-turns and loops, and 40% of remainder structures. These values are in good agreement with those predicted from the amino-acid sequence. Predictions used for CaP h1 were applied to other isoforms of known sequences and revealed that all calponins share a common secondary structure. Moreover, the predicted structure of the calponin CH domain is identical to that found by X-ray studies of the spectrin, fimbrin and utrophin CH domains.
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This review paper focused on the effect of typical phosphorlipid (or lecithin) and enzyme modification on electrokinetic parameters of oil/water emulsion. Physicochemical properties of the systems were investigated taking into account the effective diameter of the droplets as well as the zeta potentials using the dynamic light scattering technique. The effect of phospholipid and phospholipase modification on interfacial properties of o/w emulsion was examined as a function of temperature, pH and ionic strength (effect of Na+ or Ca2+ ions which occur in the physiological fluids). The particular role of Ca2+ ions in the dispersions with zwitterionic phospholipids (the main components of biological membrane) was confirmed.The phospholipids dipalmitoylphosphatidylcholine, DPPC or dioleoylphosphatidylcholine, DOPC having the same headgroup bound to the apolar tail composed of two saturated or unsaturated chains were used as stabilizing agents. The effective diameters do not always correlate with the zeta potentials. A possible reason for such behaviour might a mechanism different from the electrostatic stabilization. Phospholipids and their mixtures (e.g. lecithin) may undergo spontaneous aggregation in aqueous solution and selforganize into liposomes, which possess different sizes and surface affinities. These unique behaviours of phospholipid dispersion can be controlled using the investigated parameters. These findings are expected to increase in importance as phospholipid systems see more use in self-assembly applications.The other aim of the paper was the comparison of the enzyme phospholipase influence on lipid hydrolysis in the o/w emulsion environment. The work is the study which presents the twofold effect of ethanol dipoles on phosholipid hydrolysis. It is believed that the enzyme effect on the phospholipid aggregation behaviour at the oil-water interface will be helpful for understanding differentbiological phenomena.
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