1,721,061 research outputs found
Osmotic pressure of aqueous rod-like polyelectrolyte solutions with mono- and di-valent counterions.
No full text
Conformational Changes of Xanthan in Salt-Free Aqueous Solution: A Low-Frequency Electrical Conductivity Study
No full textHigh-frequency dielectric study of side-chain dynamics in poly(lysine) aqueous solutions.
No full textThe high-frequency dielectric properties of poly(lysine) of different chirality in aqueous solutions have been measured in the frequency range from 1 MHz to 1.8 GHz. The dielectric spectra show the existence of relatively small dielectric dispersions at around 100 MHz that have been attributed to internal motion in the polymer chain, due to side-chain polar groups. Our results indicate that the local structure of the chain and its possibility to undergo a conformational transition induced by pH does not modify the main feature of the side-chain dynamics, the dielectric strength being largely proportional to the concentration of charged groups. A similar behavior has been found in poly(alpha-glutamate) and in poly(gamma-glutamate) aqueous solutions, where the dielectric parameters appear to be related to the change in the charge density on the main chain, rather than to the accompanying conformational helix-coil transition
The puzzle of toxicity of gold nanoparticles. The case-study of HeLa cells
No full textBecause of the growing interest of gold nanoparticles in biomedical and biotechnological applications, their toxicity is becoming an increasingly important issue and, in the last few years, there has been continuously expanding research activity in this field. However, due to the intrinsic complexity of the problem, together with the lack in the standardization of the experimental procedures, there is to date a large scattering of the results that still prevents reaching a general consensus of the possible toxic effects of gold nanoparticles in biological systems of increasing complexity (cell membrane, cells, tissues, organs and human body). The strong need to systematize the data suggests employing an appropriate metric, as far as the particle concentration is concerned, that could help in comparing and organizing the available data in a more intelligible scenario. In this note, some recent literature data on the viability of HeLa cells exposed to differently functionalized gold nanoparticles have been analyzed on the basis of a metric based on the numerical particle concentration (number of particles per unit volume of cell culture) that, to a certain extent, takes into account both the size and the shape of nanoparticles. This analysis offers a much more intelligible behavior than the one based on metrics that considers mass concentration (molar concentration) or particle size. At least, in the particular case of HeLa cells, the analysis of the data shows that differently functionalized gold nanoparticles behave similarly and that the different surface coating of the different nanoparticles considered defines the range of particle concentration where toxic effects begin. This kind of analysis could furnish some albeit preliminary suggestions towards an appropriate method to study gold nanoparticle toxicity
Menadione induces changes in the membrane electrical properties associated with down-regulation of insulin receptors in human erythrocytes.
No full textMenadione induces changes in the membrane electrical properties associated with down-regulation of insulin receptors in human erythrocytes.
No full textHeat-Denatured Lysozyme Aggregation and Gelation as Revealed by Combined Dielectric Relaxation Spectroscopy and Light Scattering Measurements
No full textThe dielectric behavior of native and heat-denatured lysozyme in ethanol-water solutions was examined in the frequency range from 1 MHz to 2 GHz, using frequency-domain dielectric relaxation spectroscopy. Because of the conformational changes on unfolding, dielectric methods provide information on the denaturation process of the protein and, at protein concentration high enough, on the subsequent aggregation and gelation. Moreover, the time evolution of the 8 protein aggregation and gelation was monitored measuring, by 2 means of dynamic light scattering methods, the diffusion a coefficient of micro-sized polystyrene particles, deliberately added to the protein solution, which act as a probe of the viscosity of the microenvironment close to the particle surface. All together, our measurements indicate that heat-induced denaturation favors, at high concentrations, a protein aggregation process which evolves up to the full gelation of the system. These findings have a direct support from IR measurements of the absorbance of the amide I band that, because of the unfolding, indicate that proteins entangle each other, producing a network structure which evolves, in long time limit, in the gel
- …
