Design of a protective shield for a radiological emergency intervention using Monte Carlo simulation and an anthropomorphic phantom.

Due to the increasing use of radioactive sources, new challenges appear for the protection of humans and the environment against ionizing radiation. Thus, organizations handling these sources must be endowed with plans how to react in case of any radiological emergency situations. Monte Carlo simulations are among the most widely employed methods used for the management and reconstruction of radiological incidents and accidents. In this work, results of a Monte Carlo simulation study with the Geant4 simulation toolkit using a digital anthropomorphic phantom are reported. The investigated scenario included an emergency intervention carried out inside the ionization cell of the National Institute of Agronomic Research (NIAR) of Tangier/Morocco, which houses a 60Co gamma irradiator. In this scenario, a radiological incident was assumed where the source cage of the gamma irradiator is stuck in the guide tube and not completely inserted into its storage container. The objective of this work was to design a radiation shield to protect an operator during the emergency intervention and make sure that any radiation exposure is below the recommended dose limits, taking into account the date of occurrence (which determines the activity of the source at the time of the emergency situation) of the accident and economic aspects of shielding design. In this work, the maximum time available for the operator to accomplish the operation intervention while remaining protected is calculated. The results obtained show that the shielding prototype developed gives the operator a time between 3 and 300 s, depending on shielding design. It is concluded that shielding of the type investigated in the present study will allow any facility to manage the assumed emergency scenario, should it occur.

A Monte Carlo study to investigate the feasibility to use the Moroccan panoramic irradiator in sterile insect technique programs.

Mediterranean fly pest (Ceratitis) is one of the most destructive pests of fruit species in Morocco. The sterile insect technique (SIT) is an environmentally friendly strategy that uses ionizing radiation to sterilize adult insects. Morocco has a panoramic gamma irradiator used to irradiate agri-food products. This irradiator is not dedicated to SIT programs due to its geometry that does not allow to obtain a dose uniformity ratio (DUR) recommended for such applications. This article presents a Monte Carlo study to investigate the feasibility of using the panoramic gamma irradiator at the National Institute for Agronomic Research (NIAR) of Tangier, Morocco, to setting up SIT methods and contributing to Ceratitis control programs. The Monte Carlo method was used to simulate the concrete bunker in which the panoramic gamma irradiator is installed. To obtain a recommended DUR required for SIT programs, two cells similar of the Gammacell-220 irradiator, which is mainly used in the SIT programs around the world, were simulated inside the concrete bunker. The simulation and calculations were performed using the MCNPX-2.7e Monte Carlo simulation code. It is demonstrated that at both investigated positions, the spatial distribution of dose rates in the two modeled irradiation cells, which were similar to a gammacell-220 irradiator cell, are uniform enough that the cells can be used for SIT programs. It is concluded that the panoramic irradiator at NIAR can be used to contribute to the control of Mediterranean fly pest and other insect pests in Morocco.

Gamma irradiation-induced genetic variability and its effects on the phenotypic and agronomic traits of groundnut (Arachis hypogaeaL.).

In order to increase genetic variability for the improvement of groundnut, two varieties, namely Kp29 and Fleur11, were treated with six different gamma irradiation doses. A significant effect of mutagenesis was distinctly observed in the stem lengths, roots, and survival percentage in both varieties. The radio-sensitivity test showed a mean lethal dose of 436.51Gy for Kp29 and 501.18 Gy for Fleur11. Furthermore, this study revealed putative mutants with variable agro-morphological traits. Seven chlorophyll mutants and various seed shape and color mutants were obtained. This study demonstrates the potency of gamma irradiation to induce high genetic variability that led to the emergence of certain mutations of economic importance.

Gamma-irradiation effect on the chemical composition and antibacterial activity of the moroccan tanacetum annuum L. essential oil.

The primary objective of the present inquiry was to assess the impact of gamma irradiation on the chemical composition and antibacterial potential of the essential oil extracted from the aerial parts of Moroccan Tanacetum annuum L. to this end, two distinct irradiation doses of 5 kGy and 10 kGy were administered to the essential oil, and the resultant effects were evaluated via analysis of the oil's chemical composition and antibacterial activity. The study findings have revealed that irradiation technology possesses the remarkable ability to modulate the concentrations of specific chemical constituents in a manner that effectively amplifies the antibacterial activity of the essential oil. Moreover, the technology has evinced the generation of novel compounds while also demonstrating the eradication of certain pre-existing ones upon the oil's exposure to irradiation. These discoveries have emphasized the potential of irradiation technology for augmenting the chemical profile of essential oils, thereby mitigating the risk of contamination via microbiological, physical, or chemical means, ultimately enhancing the therapeutic efficacy of the plant and its essential oil. Furthermore, the results of this study signify the possibility of harnessing irradiation technology in the production of various natural products and essential oils. The present research has thus broadened the horizons for the application of irradiation technology in advancing the potency and safety of essential oils, paving the way for a diverse range of applications in different fields, such as medicine.

Solution nuclear magnetic resonance spectroscopy of bacterial outer membrane proteins in natively excreted vesicles using engineered Escherichia coli.

Gaining structural information on membrane proteins in their native lipid environment is a long-standing challenge in molecular biology. Instead, it is common to employ membrane mimetics, which has been shown to affect protein structure, dynamics, and function severely. Here, we describe the incorporation of a bacterial outer membrane protein (OmpW) into natively excreted membrane vesicles for solution nuclear magnetic resonance (NMR) spectroscopy using a mutant Escherichia coli strain with a high outer membrane vesicle (OMV) production rate. We collected NMR spectra from both vesicles containing overexpressed OmpW and vesicles from a control strain to account for the presence of physiologically relevant outer membrane proteins in vesicles and observed distinct resonance signals from OmpW. Due to the increased production of OMVs and the use of non-uniform sampling techniques we were able to obtain high-resolution 2D (HSQC) and 3D (HNCO) NMR spectra of our target protein inside its native lipid environment. While this workflow is not yet sufficient to achieve in situ structure determination, our results pave the way for further research on vesicle-based solution NMR spectroscopy.

Carbon nanotube uptake in cyanobacteria for near-infrared imaging and enhanced bioelectricity generation in living photovoltaics.

The distinctive properties of single-walled carbon nanotubes (SWCNTs) have inspired the development of many novel applications in the field of cell nanobiotechnology. However, studies thus far have not explored the effect of SWCNT functionalization on transport across the cell walls of prokaryotes. We explore the uptake of SWCNTs in Gram-negative cyanobacteria and demonstrate a passive length-dependent and selective internalization of SWCNTs decorated with positively charged biomolecules. We show that lysozyme-coated SWCNTs spontaneously penetrate the cell walls of a unicellular strain and a multicellular strain. A custom-built spinning-disc confocal microscope was used to image the distinct near-infrared SWCNT fluorescence within the autofluorescent cells, revealing a highly inhomogeneous distribution of SWCNTs. Real-time near-infrared monitoring of cell growth and division reveal that the SWCNTs are inherited by daughter cells. Moreover, these nanobionic living cells retained photosynthetic activity and showed an improved photo-exoelectrogenicity when incorporated into bioelectrochemical devices.

Influence of Detergent and Lipid Composition on Reconstituted Membrane Proteins for Structural Studies.

Membrane proteins are frequently reconstituted in different detergents as a prerequisite to create a phospholipid environment reminiscent of their native environment. Different detergent characteristics such as their chain length and bond types could affect the structure and function of proteins. Yet, they are seldom taken into account when choosing a detergent for structural studies. Here, we explore the effect of different detergents and lipids with varying degrees of double- or single-bond composition on 1H-15N transverse relaxation optimized spectroscopy spectra of the outer membrane protein W (OmpW). We observed changes in nuclear magnetic resonance chemical shifts for OmpW reconstituted in micelles, bicelles, and nanodiscs, depending on their detergent/lipid composition. These results suggest that a careful evaluation of detergents is necessary, so as not to jeopardize the structure and function of the protein.