The Importance of Therapeutically Targeting the Binary Toxin from Clostridioides difficile

Novel therapeutics are needed to treat pathologies associated with the Clostridioides difficile binary toxin (CDT), particularly when C. difficile infection (CDI) occurs in the elderly or in hospitalized patients having illnesses, in addition to CDI, such as cancer. While therapies are available to block toxicities associated with the large clostridial toxins (TcdA and TcdB) in this nosocomial disease, nothing is available yet to treat toxicities arising from strains of CDI having the binary toxin. Like other binary toxins, the active CDTa catalytic subunit of CDT is delivered into host cells together with an oligomeric assembly of CDTb subunits via host cell receptor-mediated endocytosis. Once CDT arrives in the host cell’s cytoplasm, CDTa catalyzes the ADP-ribosylation of G-actin leading to degradation of the cytoskeleton and rapid cell death. Although a detailed molecular mechanism for CDT entry and host cell toxicity is not yet fully established, structural and functional resemblances to other binary toxins are described. Additionally, unique conformational assemblies of individual CDT components are highlighted herein to refine our mechanistic understanding of this deadly toxin as is needed to develop effective new therapeutic strategies for treating some of the most hypervirulent and lethal strains of CDT-containing strains of CDI.     

Crystal structure of TNF-alpha mutant R31D with greater affinity for receptor R1 compared with R2

Crystal structures have been determined of recombinant human tumor necrosis factor-alpha (TNF-alpha) and its R31D mutant that preferentially binds to TNF receptor R1 with more than seven times the relative affinity of binding to receptor R2. Crystals of the wild-type TNF were of space group P4(1)2(1)2 and had unit cell dimensions of a = b = 94.7 and c = 117.4 A. Refinement of the structure gave an R-factor of 22.3% at 2.5 A resolution. The crystals of TNF R31D mutant diffracted to 2.3 A resolution, and were of identical space group to the wild type with unit cell dimensions of a = b = 95.4 and c = 116.2 A, and the structure was refined to an R-factor of 21.8%. The trimer structures of the wild-type and mutant TNF were similar with a root mean square (r.m.s.) deviation of 0.56 A for Calpha atoms; however, the subunits within each trimer were more variable with an average r.m.s. deviation of 1.00 A on Calpha atoms for pairwise comparison of subunits. Model complexes of TNF with receptors R1 and R2 have been used to predict TNF-receptor interactions. Arg31 in all three subunits of wild-type TNF is predicted to form an ionic interaction with the equivalent glutamic acid in both receptors R1 and R2. Asp31 of the TNF R31D mutant is predicted to interact differently with the two receptors. The side chain of Asp31 in two subunits of the TNF mutant is predicted to form hydrogen bond interactions with Ser59 or Cys70 of R1, while it has no predicted interactions with R2. The loss of three strong ionic interactions of Arg31 and the electrostatic repulsion of Asp31 with Glu in the receptors is consistent with the reduced binding of the R31D mutant to both receptors relative to wild-type TNF. The replacement of these ionic interactions by two weaker hydrogen bond interactions between Asp31 of the R31D mutant and R1, compared with no interactions with R2, is in agreement with the observed preferential binding of the R31D mutant to R1 over R2. Analysis of the structure and function of receptor-discriminating mutants of TNF will help understand the biological role of TNF and facilitate its use as an antitumor agent.      

Untersuchung des einflusses molekularer parameter auf morphologie und eigenschaften von polyethylenen niedriger dichte

Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M?_w = 1.2 ? 390·10⁴ g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M?_w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M?_n, M?_w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal — for specific M?_w-ranges — strong changes and saturation ranges, resp., for the physical and application technological properties.     

Preparation and properties of high molecular weight poly(1-germa-) or poly(1-sila-cis-pent-3-enes)

High molecular weight poly(1,1-dimethyl-1-germa-cis-pent-3-ene), poly(1,1-diphenyl-1-germa-cis-pent-3-ene), poly(1,1-dimethyl-1-sila-cis-pent-3-ene), and poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) have been prepared. The thermal stability of these polymers is found to increase with their molecular weight.     

In situ ellipsometric study of a palladium catalyst during the oxidation of methane

Ellipsometry is used to follow the growth of a PdO layer on the surface of a thick Pd-film catalyst during methane oxidation at 500°C. The oxide layer that develops under rich conditions (excess CH₄) is quite porous and roughens with time. Little CO is formed during this period, but the CO₂ formation rate increases until spontaneous oscillations develop, which correlate with changes in the ellipsometric data. These changes indicate that the porous oxide rapidly converts to a metal-rich state, which has decreased catalytic activity, and then slowly reoxidizes.     

Liquid spouting of pulp fibers in a conical vessel

Pulp fibers can be spouted in water in a conical vessel. The entities which are spouted are fiber flocs rather than individual fibers. Synthetic fibers, which do not flocculate, cannot be spouted. For comparison, rigid spherical particles were spouted with water in the same conical vessel. Liquid spouting of rigid particles was similar to gaseous spouting. For pulp spouting, the minimum spouting velocity is proportional to the mass of fibers in the bed and inversely proportional to the diameter of the inlet. For rigid particles, the minimum spouting velocity is proportional to the height of the bed and inversely proportional to the square of the diameter of the inlet. A model for the minimum spouting velocity was developed for pulp spouting.     

Synthesis of poly(1-methyl-1-phenyl-1-silapentane) by chemical reduction of poly)1-methyl-1-phenyl-1-sila-cis-pent-3-ene with diimide

Summary Poly(1-methyl-1-phenyl-1-silapentane) (I) has been prepared by the chemical reduction of the carbon-carbon double bonds of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene (cis-II) with diimide, which was generatedin-situ by the thermal decomposition ofp-toluenesulfonhydrazide in refluxing toluene. At lower temperature (100°C),cis-II is isomerized byp-toluenesulfinic acid to lower molecular weight poly(1-methyl-1-phenyl-1-sila-cis andtrans-pent-3-ene) (cis/trans-II). Protodesilation of I with trifluoromethanesulfonic acid yields poly(1-methyl-1-trifluoromethanesulfonyl-1-silapentane) (III). The structures of I andcis/trans-II have been characterized by¹H,¹³C and²⁹Si NMR, GPC, TGA and elemental analysis. The structure of I has been characterized spectroscopically by¹H,¹³C,¹⁹F and²⁹Si NMR.     

A simple method for the objective characterisation of fabric softness. Part 1: Influence of bleaching,dyeing and crosslinking of wool*

A simple method for the characterisation of fabric softness using a conventional tensile tester and a special measurement device has been developed. The method is demonstrated to be especially useful in detecting changes in softness of a given substrate due to different treatments. The results obtained, particularly hysteresis at 75% of the maximum extension, provide a good correlation with subjective ranking for samples that are subjectively distinguishable; they also differentiate well between samples which seem subjectively indistinguishable. Screening tests were carried out, mainly on wool fabrics, to find the effect of different treatments such as oxidative (alkaline and acidic) and reductive (Blankit IN) bleaching, dyeing with acid and a 1:2 metal complex, chrome and (mono and bi)reactive dyes, the effect of the antisetting agent Basolan AS (BASF) and of crosslinking with Irgasol HTW (CGY) on fabric softness.     

Contribution a l'etude des groupements superficiels des noirs de carbone a l'aide de reactifs gazeux: Evolution de l'acidité superficielle du sphéron 6 au cours de traitements thermiques

The Spheron 6 surface acidity has been investigated by adsorption of ammonia at 70°C and microcalorimetry. The carbon samples are degassed at temperatures up to 950°C. The effects of degassing temperature on the adsorption isotherms of ammonia are shown in Fig. 2. Up to 350°C, the isotherms are characterized by a very slight decrease in the total amount adsorbed. On the contrary, these amounts considerably decrease for higher degassing temperatures. The differential heats of adsorption (Fig. 3), which are initially close to 100 kJ/mole, are shown to decrease with the amount of adsorbed ammonia: the higher the degassing temperature, the greater the decrease. By desorption, the adsorption of ammonia is found partly irreversible. By readsorption it is possible to measure the differential heat of the reversible adsorption and to deduce from it the differential heat of the irreversible adsorption (Fig. 4) as well as the amount irreversibly adsorbed, i.e. chemisorbed.The amounts of chemisorbed ammonia are found to be respectively 0.36 ± 0.01 × 10^?6 mole m² at 150°C and 0.29 ± 0.01 × 10^?6 mole m^?2 at 350°C. With the surface covering the differential heat of chemisorption of ammonia slightly decreases from 105 to 88 kJ. mole^?1.These values suggest that carboxyl groups are responsible for irreversible adsorption of ammonia. This assumption has been checked by various experiments: the irreversible uptake of ammonia lies in the same range as the number of carboxyl surface groups determined by chemical analysis of functional groups (Table 1); the evolving of H₂O during the decomposition of the ammonium salt formed by reacting with ammonia has been observed and is probably correlated with the irreversible uptake of ammonia (Fig. 8); moreover it must be pointed out that irreversible adsorption of ammonia disappears after methylation of sample by diazomethane (Figs. 5 and 6). Then, the amounts of carboxyl groups can be determined by measuring the irreversibly adsorbed ammonia.This method has been applied to the study of the thermal stability of functional groups. Carboxyl groups are shown to be quickly decomposed by heat treatment above 500–600°C (Fig. 8).It appears from our experiments that the oxidation at constant temperature followed by a cooling under nitrogen is unable to regenerate functional groups on the surface of carbon after their removal at 950°C. On the contrary, by an oxidation at decreasing temperature it is possible to regenerate functional groups because they are stabilized by the oxidising atmosphere.The groups thus created behave like those initially present on Spheron 6: particularly the graph of the thermal elimination of carbon dioxide presents two peaks (Table 2, Fig. 12). The amount of regenerated carboxyl groups is found to be 0.25 × 10^?6 instead of 0.36 × 10^?6mole m^?2 on untreated Spheron 6.