Cholinesterase reactivators and bioscavengers for pre- and post-exposure treatments of organophosphorus poisoning

© 2017 International Society for Neurochemistry.Organophosphorus agents (OPs) irreversibly inhibit acetylcholinesterase (AChE) causing a major cholinergic syndrome. The medical counter-measures of OP poisoning have not evolved for the last 30 years with carbamates for pretreatment, pyridinium oximes-based AChE reactivators, antimuscarinic drugs and neuroprotective benzodiazepines for post-exposure treatment. These drugs ensure protection of peripheral nervous system and mitigate acute effects of OP lethal doses. However, they have significant limitations. Pyridostigmine and oximes do not protect/reactivate central AChE. Oximes poorly reactivate AChE inhibited by phosphoramidates. In addition, current neuroprotectants do not protect the central nervous system shortly after the onset of seizures when brain damage becomes irreversible. New therapeutic approaches for pre- and post-exposure treatments involve detoxification of OP molecules before they reach their molecular targets by administrating catalytic bioscavengers, among them phosphotriesterases are the most promising. Novel generation of broad spectrum reactivators are designed for crossing the blood-brain barrier and reactivate central AChE. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms

Coupling Mars Ground and Orbital Views: Generate Viewsheds of Mastcam Images From the Curiosity Rover, Using ArcGIS® and Public Datasets

The Mastcam (Mast Camera) instrument onboard the NASA Curiosity rover provides an exclusive view of Mars: High‐resolution color images from Mastcam allow users to study Gale crater's geologic terrains along Curiosity's path. These ground observations complement the spatially broader views of Gale crater provided by spacecrafts from orbit. However, for a given Mastcam image, it can be challenging to locate the corresponding terrains on the orbital view. No method for locating Mastcam images onto orbital images had been made publicly available. The procedure presented here allows users to generate Mastcam image viewsheds, using ArcGIS® software, its built‐in Viewshed tool®, and public Mars datasets. This procedure locates onto Mars orbital view the terrains that are observed in a given Mastcam image. Because this procedure uses public datasets, it is applicable to available Mastcam images and to the future ones that will be acquired along the Curiosity rover's path. This procedure can be used by the public to assess scientific questions regarding Martian surface processes and geologic history. In addition, this procedure can be utilized as pedagogic GIS material by the Geosciences or Planetary Sciences communities, for enhancing students' skillsets in GIS and provide students with experience working with datasets from both orbiter and rover Mars missions

Coupling Mars Ground and Orbital Views: Generate Viewsheds of Mastcam Images From the Curiosity Rover, Using ArcGIS® and Public Datasets

The Mastcam (Mast Camera) instrument onboard the NASA Curiosity rover provides an exclusive view of Mars: High‐resolution color images from Mastcam allow users to study Gale crater's geologic terrains along Curiosity's path. These ground observations complement the spatially broader views of Gale crater provided by spacecrafts from orbit. However, for a given Mastcam image, it can be challenging to locate the corresponding terrains on the orbital view. No method for locating Mastcam images onto orbital images had been made publicly available. The procedure presented here allows users to generate Mastcam image viewsheds, using ArcGIS® software, its built‐in Viewshed tool®, and public Mars datasets. This procedure locates onto Mars orbital view the terrains that are observed in a given Mastcam image. Because this procedure uses public datasets, it is applicable to available Mastcam images and to the future ones that will be acquired along the Curiosity rover's path. This procedure can be used by the public to assess scientific questions regarding Martian surface processes and geologic history. In addition, this procedure can be utilized as pedagogic GIS material by the Geosciences or Planetary Sciences communities, for enhancing students' skillsets in GIS and provide students with experience working with datasets from both orbiter and rover Mars missions

Dust from Mars-Analog Plains (Iceland): Physico-Compositional Properties as a Function of Grain-Size Fraction

Dust is a key component of the geological and climatic systems of Earth and Mars. On Mars, dust is ubiquitous. It coats rocks and soils, and, in the atmosphere, it interacts strongly with solar and thermal radiation. Yet, key questions remain about the genesis and fate of martian dust, as well as its sources, composition, and properties. We collected wind-blown dust from basaltic plains in SW Iceland at Skjaldbreiauhraun that represent a geologic Mars-analog environment. Icelandic dust differs from the typical continental sources (e.g. Sahara, Asia) because of its basaltic volcanogenic origin, which is similar to Mars. Dust collection took place in July of 2019 as a complementary project to the SAND-E: Semi-Autonomous Navigation for Detrital Environments project. Here we report preliminary analyses of this Mars-analog dust material, with the goal of understanding the processes that control the physico-chemical proper-ties of the different grain-size fractions

Purification of recombinant human butyrylcholinesterase on Hupresin®

© 2018 Affinity chromatography on procainamide-Sepharose has been an important step in the purification of butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) since its introduction in 1978. The procainamide affinity gel has limitations. In the present report a new affinity gel called Hupresin® was evaluated for its ability to purify truncated, recombinant human butyrylcholinesterase (rHuBChE) expressed in a stably transfected Chinese Hamster Ovary cell line. We present a detailed example of the purification of rHuBChE secreted into 3940 mL of serum-free culture medium. The starting material contained 13,163 units of BChE activity (20.9 mg). rHuBChE was purified to homogeneity in a single step by passage over 82 mL of Hupresin® eluted with 0.1 M tetramethylammonium bromide in 20 mM TrisCl pH 7.5. The fraction with the highest specific activity of 630 units/mg contained 11 mg of BChE. Hupresin® is superior to procainamide-Sepharose for purification of BChE, but is not suitable for purifying native AChE because Hupresin® binds AChE so tightly that AChE is not released with buffers, but is desorbed with denaturing solvents such as 50% acetonitrile or 1% trifluoroacetic acid. Procainamide-Sepharose will continue to be useful for purification of AChE

Dynamics of human acetylcholinesterase bound to non-covalent and covalent inhibitors shedding light on changes to the water network structure

© 2016 the Owner Societies.We investigated the effects of non-covalent reversible and covalent irreversible inhibitors on human acetylcholinesterase and human butyrylcholinesterase. Remarkably a non-covalent inhibitor, Huperzine A, has almost no effect on the molecular dynamics of the protein, whereas the covalently binding nerve agent soman renders the molecular structure stiffer in its aged form. The modified movements were studied by incoherent neutron scattering on different time scales and they indicate a stabilization and stiffening of aged human acetylcholinesterase. It is not straightforward to understand the forces leading to this strong effect. In addition to the specific interactions of the adduct within the protein, some indications point towards an extensive water structure change for the aged conjugate as water Bragg peaks appeared at cryogenic temperature despite an identical initial hydration state for all samples. Such a change associated to an apparent increase in free water volume upon aging suggests higher ordering of the hydration shell that leads to the stiffening of protein. Thus, several additive contributions seem responsible for the improved flexibility or stiffening effect of the inhibitors rather than a single interaction

In situ detection of boron by ChemCam on Mars

We report the first in situ detection of boron on Mars. Boron has been detected in Gale crater at levels Curiosity rover ChemCam instrument in calcium-sulfate-filled fractures, which formed in a late-stage groundwater circulating mainly in phyllosilicate-rich bedrock interpreted as lacustrine in origin. We consider two main groundwater-driven hypotheses to explain the presence of boron in the veins: leaching of borates out of bedrock or the redistribution of borate by dissolution of borate-bearing evaporite deposits. Our results suggest that an evaporation mechanism is most likely, implying that Gale groundwaters were mildly alkaline. On Earth, boron may be a necessary component for the origin of life; on Mars, its presence suggests that subsurface groundwater conditions could have supported prebiotic chemical reactions if organics were also present and provides additional support for the past habitability of Gale crater

Large sulfur isotope fractionations in Martian sediments at Gale crater

Variability in the sulfur isotopic composition in sediments can reflect atmospheric, geologic and biological processes. Evidence for ancient fluvio-lacustrine environments at Gale crater on Mars and a lack of efficient crustal recycling mechanisms on the planet suggests a surface environment that was once warm enough to allow the presence of liquid water, at least for discrete periods of time, and implies a greenhouse effect that may have been influenced by sulfur-bearing volcanic gases. Here we report in situ analyses of the sulfur isotopic compositions of SO2 volatilized from ten sediment samples acquired by NASA’s Curiosity rover along a 13 km traverse of Gale crater. We find large variations in sulfur isotopic composition that exceed those measured for Martian meteorites and show both depletion and enrichment in 34S. Measured values of δ34S range from −47 ± 14‰ to 28 ± 7‰, similar to the range typical of terrestrial environments. Although limited geochronological constraints on the stratigraphy traversed by Curiosity are available, we propose that the observed sulfur isotopic signatures at Gale crater can be explained by equilibrium fractionation between sulfate and sulfide in an impact-driven hydrothermal system and atmospheric processing of sulfur-bearing gases during transient warm periods

Pressure-induced molten globule state of human acetylcholinesterase: Structural and dynamical changes monitored by neutron scattering

© the Owner Societies 2015. We used small-angle neutron scattering (SANS) to study the effects of high hydrostatic pressure on the structure of human acetylcholinesterase (hAChE). At atmospheric pressure, our SANS results obtained on D11 at ILL (Grenoble, France) give a radius of gyration close to that calculated for a mixture of monomers, dimers and tetramers of the enzyme, suggesting a good agreement between hAChE crystal structure and its conformation in solution. Applying high pressure to the sample we found a global compression of about 11% of the enzyme up to a pressure of 900 bar and then again an extension up to 2.1 kbar indicating unfolding of the tertiary structure due to a molten globule (MG) state. On the other hand, we studied the influence of pressure up to 6 kbar on the dynamics of this enzyme, on the backscattering spectrometer IN13 at ILL. For the first time, we used elastic incoherent neutron scattering (EINS) to probe the differences between hAChE in its folded state (N), its high-pressure induced MG state and its unfolded state (U). Especially around the MG state at 1750 bar we found a significant increase in the dynamics, indicating a partial unfolding. A four-step-model is suggested to describe the changes in the protein

A Novel System for the Efficient Generation of Antibodies Following Immunization of Unique Knockout Mouse Strains

International audienceBACKGROUND: We wished to develop alternate production strategies to generate antibodies against traditionally problematic antigens. As a model we chose butyrylcholinesterase (BChE), involved in termination of cholinergic signaling, and widely considered as a poor immunogen. METHODOLOGY/PRINCIPAL FINDINGS: Jettisoning traditional laborious in silico searching methods to define putative epitopes, we simply immunized available BChE knock-out mice with full-length recombinant BChE protein (having been produced for crystallographic analysis). Immunization with BChE, in practically any form (recombinant human or mouse BChE, BChE purified from human serum, native or denatured), resulted in strong immune responses. Native BChE produced antibodies that favored ELISA and immunostaining detection. Denatured and reduced BChE were more selective for antibodies specific in Western blots. Two especially sensitive monoclonal antibodies were found capable of detecting 0.25 ng of BChE within one min by ELISA. One is specific for human BChE; the other cross-reacts with mouse and rat BChE. Immunization of wild-type mice served as negative controls. CONCLUSIONS/SIGNIFICANCE: We examined a simple, fast, and highly efficient strategy to produce antibodies by mining two expanding databases: namely those of knock-out mice and 3D crystallographic protein-structure analysis. We conclude that the immunization of knock-out mice should be a strategy of choice for antibody production