Refolding of Aggregation-Prone ScFv Antibody Fragments Assisted by Hydrophobically Modified Poly(sodium acrylate) Derivatives

ScFv antibody fragments are a promising alternative to full-length antibodies for both therapeutic and diagnosis applications. They can be overexpressed in bacteria, which enables easy large scale production. Since scFv are artificial constructs, they are poorly soluble and prone to aggregation, which makes them difficult to manipulate and to refold. Here, stabilization and refolding of scFv fragments from urea-unfolded solutions are reported based on the use of micromolar amounts of polymers playing the role of artificial chaperons. Using fluorescence correlation spectroscopy, the size and aggregation number of complexes of scFv with unmodified or hydrophobically modified poly(sodium acrylate) are determined. The evolution of the secondary structure along the refolding procedure, in the presence or absence of 0.4 m L-arginine at scFv:polymerPeer reviewe

Spent nuclear fuel/water interface behavior: Alpha dose rate profile determination for model surfaces and microcracks by using Monte-Carlo methods

International audienceThis work aims to better understand the nature and evolution of energy deposits at the UO2/water reactional interface subjected to alpha irradiation, through an original approach based on Monte-Carlo-type simulations, using the MCNPX code. Such an approach has the advantage of describing the energy deposit profiles on both sides of the interface (UO2 and water). The calculations have been performed on simple geometries, with data from an irradiated UOX fuel (burnup of 47 GWd.tHM−1 and 15 years of alpha decay). The influence of geometric parameters such as the diameter and the calculation steps at the reactional interface are discussed, and the exponential laws to be used in practice are suggested. The case of cracks with various different apertures (from 5 to 35 μm) has also been examined and these calculations have also enabled new information on the mean range of radiolytic species in cracks, and thus on the local chemistry

Enthalpy of Interaction and Binding Isotherms of Non-ionic Surfactants onto Micellar Amphiphilic Polymers (Amphiphols)

International audienc

DNA bundle formation induced by cationic surfactants

We have evidenced bundle formation in DNA solutions, induced by the addition of a monovalent cationic surfactant to a solution of short DNA rods. The bundles are rod-like, with a large axial ratio ($\sim 10$). Their formation is very likely controlled not only by electrostatic interactions, but also by hydrophobic interactions between surfactant chains, once bound to the DNA. The bundles have diameters and lengths both remarkably well defined and possess internal organisation. The value of the diameter is close to that predicted by a model in which interactions are mediated by condensed counterions; the length might be limited by steric hindrance due to bundle overlapping or by intrinsic chain flexibility

Influence of iron on the alteration of the SON68 nuclear glass in the Callovo-Oxfordian Groundwater

International audienceIn France, the high level radioactive waste, contained in a glassy matrix, is intended for a deep geological disposal. It is then important to understand glass alteration, which depends on the near-field materials and the environmental conditions. The corrosion of the carbon steel overpack (used in the French multi-barrier concept for the disposal of high level radioactive waste) could influence glass alteration by the release of iron in the solution and the formation of iron corrosion products. For a better understanding of these interactions, different experiments were performed at 90 °C using a SON68 glass (non-radioactive surrogate of the R7T7 glass) separated by 80 $\mu$m from a pristine iron foil and immersed in synthetic groundwater. A pre-corroded iron foil and a PTFE foil, replacing the pristine iron foil, were also used. The influence of iron on glass alteration was studied, focusing on two different environments (the confined environment, inside the crack, and the diluted environment, where the faces are exposed to the homogeneous solution) and on the influence of a pre-corrosion of the iron foil. Depending on the previously described conditions, some variations were observed: as a whole, glass alteration increased in the presence of iron due to the precipitation of Fe-silicate minerals and it was also higher in the diluted environment than in the confined environment, indicating that the gel protective properties were different in both cases. This might be related either to differences in the solution composition in contact with the glass or differences in the gel composition, as it was shown that iron can enter the porous gel layer. In the tested conditions, pre-corrosion of an iron foil seemed to have no influence on glass alteration in a confined environment

Presentation of the CETAMA working group 21

International audienceCETAMA network is organized in 13 thematic working groups. The working group number 21 is dedicated to Electron Probe Micro Analysis (EPMA). Its main mission is to listen to participant needs about EPMA practical issues and to propose tools in order to improve the quality of measurement and analysis results

Slow Reorganization of Small Phosphatidylcholine Vesicles upon Adsorption of Amphiphilic Polymers

International audienceStatic or dynamic light scattering measurements were performed in parallel, on dilute mixtures of DPPC/DPPA vesicles (typical radius 60 nm) and hydrophobically modified polymers. This technique gave evidence of the slow kinetics involved in both the reorganization of an adsorbed polymer layer and the membrane breakage. Hours, or sometimes days, were required in order to follow the variation of both the hydrodynamic radius and the scattering intensity at intermediate stages. Images of the intermediate species were collected using freeze-fracture electron microscopy (FFEM). Comparison of different polymers (of varying molecular weight or structure) revealed the prime importance of hydrophobicity on the disruption of membranes. Although the presence of a few percent of pendant alkyl chains along the polymer backbone induced adsorption to membranes, only the association with the more hydrophobic ones (>25 mol% of pendant octyl groups) resulted in small mixed objects of micellar size (radius about 10 nm). The drop of the mean radius of intermediate structures formed upon the vesicle breakage was also sensitive to temperature. A tentative mechanism was proposed on the basis of kinetics and FFEM studies

Determination of alpha dose rate profile at the HLW nuclear glass/water interface h i g h l i g h t s

International audienceThe nuclear glass/water interface is studied. The way the energy of alpha particles is deposited is modeled using MCNPX code. A model giving dose rate profiles at the interface using intrinsic data is proposed. Bulk dose rate is a majoring estimation in alteration layer and in surrounding water. Dose rate is high in small cracks; in larger ones irradiated volume is negligible. a b s t r a c t Alpha irradiation and radiolysis can affect the alteration behavior of High Level Waste (HLW) nuclear glasses. In this study, the way the energy of alpha particles, emitted by a typical HLW glass, is deposited in water at the glass/water interface is investigated, with the aim of better characterizing the dose deposition at the glass/water interface during water-induced leaching mechanisms. A simplified chemical composition was considered for the nuclear glass under study, wherein the dose rate is about 140 Gy/h. The MCNPX calculation code was used to calculate alpha dose rate and alpha particle flux profiles at the glass/water interface in different systems: a single glass grain in water, a glass powder in water and a water-filled ideal crack in a glass package. Dose rate decreases within glass and in water as distance to the center of the grain increases. A general model has been proposed to fit a dose rate profile in water and in glass from values for dose rate in glass bulk, alpha range in water and linear energy transfer considerations. The glass powder simulation showed that there was systematic overlapping of radiation fields for neighboring glass grains, but the water dose rate always remained lower than the bulk value. Finally, for typical ideal cracks in a glass matrix, an overlapping of irradiation fields was observed while the crack aperture was lower than twice the alpha range in water. This led to significant values for the alpha dose rate within the crack volume, as long as the aperture remained lower than 60 lm

Triggering Cell Adhesion, Migration or Shape Change with a Dynamic Surface Coating

There's an APP for that: cell-repellent APP (azido-[polylysine-g-PEG]) is used to create substrates for spatially controlled dynamic cell adhesion. The simple addition of a functional peptide to the culture medium rapidly triggers cell adhesion. This highly accessible yet powerful technique allows diverse applications, demonstrated through tissue motility assays, patterned coculturing and triggered cell shape change