Rapid single- and multiple-scattering EXAFS Debye-Waller factor calculations on active sites of metalloproteins

This paper describes recent results using our approach to calculating self-consistently single (SS) and multiple-scattering (MS) Debye- Waller factors (DWF) on active sites of metalloproteins. The calculation of MS DWF, together with the Feff7 program allows us to simulate ab-initio EXAFS spectra for a given temperature systems with no adjustable parameters. In our latest report (Dimakis N., and Bunker G., 1998) we calculate, using density functional and semiempirical approaches, the SS and MS DWF for small molecules and compared them to Raman, infrared and EXAFS spectra. In this report calculation of DWFs is done for tetrahedral Zn imidazole, a complex containing thirty two atoms that is similar in certain respects to active sites of many metalloproteins. Ab-initio calculation, although it is a more accurate and reliable scheme, it is not at present practical on desktop computers; computation times are weeks. Therefore as an alternative we have tried the semiempirical MNDO Hamiltonian, which is at least three orders of magnitude faster than ab-initio, and can be expected to be of reasonable accuracy because it is parameterized for organic compounds. Our approaches take advantage of commercially available molecular orbital programs. We have written additional programs which, using normal mode calculations, calculate the MS paths, and transparently interface with Fef-f\u27/to produce the EXAFS spectra. Results are in very good agreement with experimental data tested

NiO-nanofillers embedded in graphite/PVA-polymer matrix for efficient electromagnetic radiation shielding

In this study, we report on the preparation of NiO/graphite sheets nanofillers in PVA-polymer matrix using a simple cost-effective hydrothermal process for EM shielding effectiveness applications. The careful optimization of the growth conditions and NiO/G/PVA relative ratios have resulted in NiO nanoparticles formation with homogeneous density. In this nanocomposite, the NiO nanoparticles and graphite sheets were incorporated into a polymer to enhance the electromagnetic shielding effectiveness. The morphological, structural, and chemical analysis have been conducted by SEM, EDX and XRD techniques. EDX and XRD analysis confirmed the exact chemical composition with high purity. SEM images showed the best morphology with homogenous NiO-nanoparticles distribution on graphite sheets for 15 wt% NiO relative ratio NiO/G/PVA nanocomposite. The nanocomposite was tested in different environments and shielding chambers that contained relatively high-level exposure to electromagnetic radiation. The shielding effectiveness (SE) measurements of NiO/G/PVA showed a significant increase of shielding effectiveness of about 17 dB compared to the commercial shielding paint. This can be ascribed to the homogenous distribution of NiO-NPs over the entire graphite sheets and the strong interaction of the incident electromagnetic radiation with the magnetic and electric dipoles in the nanocomposite. These finding is promising for enhanced flexible and cost-effective EMI shielding applications

Role of interface quality in iron oxide core/shell nanoparticles on heating efficiency and transverse relaxivity

Core/shell Fe3O4/gamma-Fe2O3 nanoparticles have been designed as a promising agent for magnetic hyperthermia and contrast agents for MRI imaging applications, because of their high magnetic moment and biocompatibility. Three sets of core/shell nanoparticles with the same core diameter of 8 nm and shell thicknesses of 1, 3 and 5 nm were synthesized by chemical coprecipitation. The nanoparticles were coated with PEG and the specific absorption rate for the nanoparticles was determined by applying 3.6 kA/m alternating magnetic field with 236 kHz frequency. The biocompatibility of the nanoparticles was confirmed by MTT assay. Three sets of nanoparticles presented in the study have shown the ability to kill 80-85% HeLa cells upon exposure to alternating magnetic field for 10 minutes in the presence of the nanoparticles. The transverse relaxivity of water protons for the three sets of the nanoparticles were obtained using 400 MHz Bruker NMR. The core/shell interface structure is found to be of poor quality because of interface defects which results in interface spin glass structures. The existence of the spin glass clusters suppresses the interface exchange coupling which leads to weak interface magnetic anisotropy. The insignificant role of core/shell structure on the heating efficiency is attributed to the insignificant contribution of the interface structure towards the effective anisotropy

Artificial semi-rigid tissue sensitized with natural pigments: Effect of photon radiations

Background: A new approach for evaluating the optical penetration depth and testing its validity with Monte Carlo simulations and Kubelka-Munk theory is used for artificial semi-rigid tissue sensitized with natural pigments. Photodynamic therapy is a promising cancer treatment in which a photosensitizing drug concentrates in malignant cells and is activated by visible light at certain wavelength. Materials and Methods: Cheap artificial semi-rigid tissue incorporated with scattering and absorbing materials along with some other composites comparable to normal human tissue has been performed. The optical parameters as measured with different conditions and calculated with various techniques are investigated. Results: The probability of interaction of light with tissue is very high when exposed to light in presence of Cichorium pumilum and RBCs followed by photohemolysis or/and photodegradation. The optical penetration depth calculated by linear absorption coefficient ranges from 0.63 to 2.85 mm is found to be comparable to those calculated using Kubelka-Munk theory or Monte Carlo simulation (range from 0.78 to 2.42 mm). The ratio of absorption to the scattering is independent of thickness and decreases with increasing irradiation time. Moreover, the optical parameters as well as their ratios are in very good agreement in the two approaches of calculation. The values of absorption and scattering coefficients are independent of thickness. Furthermore, the average photon ranges in the samples containing no scattering and absorbing materials are about three times greater than those samples containing scattering materials. Conclusion: Our results suggest that light propagation with optical properties presented in this work could be applicable in diagnostic and therapeutic of the human biological tissue for photodynamic therapy

Magnetic nanoparticles sensitize MCF-7 breast cancer cells to doxorubicin-induced apoptosis

<p>Abstract</p> <p>Background</p> <p>Resistance of breast cancer cells to the available chemotherapeutics is a major obstacle to successful treatment. Recent studies have shown that magnetic nanoparticles might have significant application in different medical fields including cancer treatment. The goal of this study is to verify the ability of magnetic nanoparticles to sensitize cancer cells to the clinically available chemotherapy.</p> <p>Methods</p> <p>The role of iron oxide nanoparticles, static magnetic field, or a combination in the enhancement of the apoptotic potential of doxorubicin against the resistant breast cancer cells, MCF-7 was evaluated using the MTT assay and the propidium iodide method.</p> <p>Results</p> <p>In the present study, results revealed that pre-incubation of MCF-7 cells with iron oxide nanoparticles before the addition of doxorubicin did not enhance doxorubicin-induced growth inhibition. Pre-incubation of MCF-7 cells with iron oxide nanoparticles followed by a static magnetic field exposure significantly (<it>P</it> < 0.05) increased doxorubicin-induced cytotoxicity. Sensitization with pre-exposure to the magnetic field was dose-dependent where the highest cytotoxicity was seen at 1 tesla. Further experiments revealed that the anti-proliferative effect of this treatment procedure is due to induction of apoptotic cell death.</p> <p>Conclusions</p> <p>These results might point to the importance of combining magnetic nanoparticles with a static magnetic field in treatment of doxorubicin-refractory breast cancer cells.</p