No abstract

Silver nanoparticles (AgNPs) containing consumer products have been proliferating in the market due to its unique antimicrobial property, however, lack of in-depth knowledge about their potential effect on human health in a longer run is of great concern. Therefore, we investigated dose-dependent in vivo effect of AgNPs using Drosophila as a model system. Drosophila, a genetically tractable organism with distinct developmental stages, short life cycle and significant homology with human serves as an ideal organism to study nanomaterial-mediated toxicity. Our studies suggest that ingestion of AgNPs in Drosophila during adult stage for short and long duration significantly affects egg laying capability along with impaired growth of ovary. Additionally, dietary intake of AgNPs from larval stage has more deleterious effects that result in reduced survival, longevity, ovary size and egg laying capability at a further lower dosage. Interestingly, the trans-generational effect of AgNPs was also observed without feeding progeny with AgNPs, thereby suggesting its impact from previous generation. Our results strongly imply that higher doses of AgNPs and its administration early during development is detrimental to the reproductive health and survival of Drosophila that follows in generations to come without feeding them to AgNPs.

Articles you may be interested inSurface induced nucleation of a Lennard-Jones system on an implicit surface at sub-freezing temperatures: A comparison with the classical nucleation theoryThe configurational energies, order parameters and normal mode spectra associated with inherent structure, inherent saddle, and instantaneous configurations of the bulk Lennard-Jones system are compared. Instantaneous structures are generated by sampling configurations from an isothermalisobaric ensemble Monte Carlo simulation. Local minimization of the potential, starting from a given instantaneous configuration is used to determine the corresponding inherent structure. The inherent saddles are obtained by local minimization on a pseudo-potential surface defined in terms of the square magnitude of the potential gradient. In the solid phase, no stationary points of order greater than zero are sampled and minimizations of both the potential, as well as of the pseudo-potential, always lead to the same global minimum energy crystalline configuration. The energies of instantaneous configurations of the solid show a clear negative correlation with the second-order bond orientational parameters. The instantaneous normal mode spectrum of the solid close to melting has a fairly prominent imaginary branch and is sufficiently smoothed out by local disorder that it qualitatively resembles the liquid phase INM spectrum. In the liquid phase, the inherent, saddle, and instantaneous structures form distinct sets of configurations. The thermal averages of the saddle energies and force constants lie between that of the instantaneous and inherent structures. The temperature dependence of the mean saddle energy and force constant is essentially parallel to that of the corresponding instantaneous quantities. The fraction of imaginary modes for the saddle configurations is approximately half that of the instantaneous configurations. The most striking similarity between the instantaneous and saddle configurations is the linear relationship between the index density and the configurational energy. The most notable difference between the two sets of configurations is the reduction to zero of the fraction of imaginary modes of the saddle configurations on freezing, making the saddle normal mode spectra qualitatively different in the liquid and solid phases.

Changes in the potential-energy surface as a function of the range and curvature of the pair potential are studied using isothermal-isobaric ensemble Monte Carlo simulations of Morse liquids. The configurational energies of stationary points are found to be linear functions of the fraction of imaginary modes, with slopes that are proportional to the range of the potential. The relative energies of saddles, minima, and instantaneous configurations show qualitatively different behavior for short, long, and intermediate range potentials, which imply corresponding variations in liquid state relaxation dynamics.

No abstract

We revisit a heteropolymer collapse theory originally introduced to explore how the balance between hydrophobic interactions and configurational entropy determines the thermal stability of globular proteins at ambient pressure. We generalize the theory by introducing a basic statistical mechanical treatment for how pressure impacts the solvent-mediated interactions between hydrophobic amino-acid residues. In particular, we estimate the strength of the hydrophobic interactions using a molecular thermodynamic model for the interfacial free energy between liquid water and a curved hydrophobic solute. The model, which also reproduces many of the distinctive thermodynamic properties of aqueous solutions in bulk and interfacial environments, predicts that the water-solute interfacial free energy is significantly reduced by the application of high hydrostatic pressures. This allows water to penetrate into folded heteropolymers at high pressure and break apart their hydrophobic cores, a scenario suggested earlier by information theory calculations. As a result, folded heteropolymers are predicted to display the kind of closed region of stability in the pressure-temperature plane exhibited by native proteins. We compare predictions of the collapse theory with experimental data for several proteins.

No abstract

Among several nanoparticles, silver nanoparticles (AgNPs) are extensively used in a wide variety of consumer products due to its unique antimicrobial property. However, dosage effect of AgNPs on behavior and metabolic activity in an in vivo condition is not well studied. Therefore, to elucidate the impact of AgNPs on behavior and metabolism, systematic and detailed dosages study of AgNPs was performed by rearing Drosophila melanogaster on food without and with AgNPs. We found that dietary intake of AgNPs at early larval stage leads to behavioral abnormalities such as poor crawling and climbing ability of larvae and adults respectively. Interestingly, intake of higher dosage of AgNPs at larval stage significantly altered metabolic activity that includes lipid, carbohydrate and protein levels in adult flies. Further, detailed analysis revealed that AgNPs causes remarkable reduction in the number of lipid droplets (LDs) which are lipid storage organelles in Drosophila. We also observed an increased production of reactive oxygen species (ROS) in AgNPs ingested larval tissues. These results strongly imply that higher dosage of AgNPs ingestion from early larval stage of Drosophila is inimical and thereby draws concern towards the usage of AgNPs in consumer goods.