A multiwavelength study of the supernova remnant G296.8-0.3

We report XMM-Newton observations of the Galactic supernova remnant G296.8-0.3, together with complementary radio and infrared data. The spatial and spectral properties of the X-ray emission, detected towards G296.8-0.3, was investigated in order to explore the possible evolutionary scenarios and the physical connexion with its unusual morphology detected at radio frequencies. G296.8-0.3 displays diffuse X-ray emission correlated with the peculiar radio morphology detected in the interior of the remnant and with the shell-like radio structure observed to the northwest side of the object. The X-ray emission peaks in the soft/medium energy range (0.5-3.0 keV). The X-ray spectral analysis confirms that the column density is high (NH \sim 0.64 x 10^{22} cm^{-2}) which supports a distant location (d>9 kpc) for the SNR. Its X-ray spectrum can be well represented by a thermal (PSHOCK) model, with kT \sim 0.86 keV, an ionization timescale of 6.1 x 10^{10} cm^{-3} s, and low abundance (0.12 Z_sun). The 24 microns observations show shell-like emission correlated with part of the northwest and southeast boundaries of the SNR. In addition a point-like X-ray source is also detected close to the geometrical center of the radio SNR. The object presents some characteristics of the so-called compact central objects (CCO). Its X-ray spectrum is consistent with those found at other CCOs and the value of NH is consistent with that of G296.8-0.3, which suggests a physical connexion with the SNR.Comment: Accepted for publication in Astrophysics & Space Scienc

Two-site diamond-like point defects as new single-photon emitters

In this small review, we recall two promising candidates for biomarker nanosystems, in which a two-site defect embedded in a diamond-like lattice makes a single-photon source. The two candidates are the silicon-vacancy defect in diamond, and the carbon antisite-vacancy pair in 4H silicon carbide. These defects, which by symmetry resemble to the famous nitrogen-vacancy defect in diamond, bear an exact or nearly exact C3v symmetry, giving them selection rules which lead their important magnetooptical properties. The embedding diamond-like crystal lattice not only determines the symmetry of two-site defects, but also ensure a nontoxic vehicle on which they reside; a definitive requirement against biomarker nanosystems. In the silicon-vacancy case, the size of the biomarker system is also an important feature. Nanoparticles of the embedding crystal do not exceed the size of molecular clusters, in order to be able to aid measuring all types of relevant biomolecular processes

Understanding interactions of functionalized nanoparticles with proteins: A case study on lactate dehydrogenase

Nanomaterials in biological solutions are known to interact with proteins and have been documented to affect protein function, such as enzyme activity. Understanding the interactions of nanoparticles with biological components at the molecular level will allow for rational designs of nanomaterials for use in medical technologies. Here we present the first detailed molecular mechanics model of functionalized gold nanoparticle (NP) interacting with an enzyme (l-lactate dehydrogenase (LDH) enzyme). Molecular dynamics (MD) simulations of the response of LDH to the NP binding demonstrate that although atomic motions (dynamics) of the main chain exhibit only a minor response to the binding, the dynamics of side chains are significantly constrained in all four active sites that predict alteration in kinetic properties of the enzyme. It is also demonstrated that the 5 nm gold NPs cause a decrease in the maximal velocity of the enzyme reaction (Vmax) and a trend towards a reduced affinity (increased Km) for the \u3b2-NAD binding site, while pyruvate enzyme kinetics (Km and Vmax) are not significantly altered in the presence of the gold NPs. These results demonstrate that modeling of NP:protein interactions can be used to understand alterations in protein function. Using molecular dynamic simulations for single, functionalized nanoparticles in solution and a newly developed method of analysis, Stueker and co-workers describe the effects of binding of a mercapto-undecanoic acid functionalized 4.2 nm gold nanoparticle on the structural and dynamic properties of the biological enzyme LDH. The predictions help to explain the experimentally determined alterations in measured LDH enzyme activity when exposed to these particles. \ua9 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Peer reviewed: YesNRC publication: Ye

Mechanistic insights into the effect of nanoparticles on zebrafish hatch

Aquatic organisms are susceptible to waterborne nanoparticles (NP) and there is only limited understanding of the mechanisms by which these emerging contaminants may affect biological processes. This study used silicon (nSi), cadmium selenide (nCdSe), silver (nAg) and zinc NPs (nZnO) as well as single-walled carbon nanotubes (SWCNT) to assess NP effects on zebrafish (Danio rerio) hatch. Exposure of 10 mg/L nAg and nCdSe delayed zebrafish hatch and 100 mg/L of nCdSe as well as 10 and 100 mg/L of uncoated nZnO completely inhibited hatch and the embryos died within the chorion. Both the morphology and the movement of the embryos were not affected, and it was determined that the main mechanism of hatch inhibition by NPs is likely through the interaction of NPs with the zebrafish hatching enzyme. Furthermore, it was concluded that the observed effects arose from the NPs themselves and not their dissolved metal components. \ua9 2014 Informa UK, Ltd.Peer reviewed: YesNRC publication: Ye