The surface composition of alumina-supported Pd, Rh, and Pd–Rh catalysts fresh or after high temperature treatments under oxidizing (O2 in N2) or reducing (H2 in N2) mixture has been characterized using various complementary techniques: chemisorption and titration of H2 and O2 probe molecules, 18O2/16O2 isotopic equilibration (OIE), FTIR spectroscopy of adsorbed CO and NO, and electron microscopy with X analysis. From both techniques it is concluded that the surface composition is close to the bulk composition for all the fresh bimetallics, whatever the Rh content. The surface state of the bimetallics treated at 1173 K is strongly dependent on the nature of the gas mixture. There is a relative increase in surface Pd after treatment in an oxidative medium, because of a Rh3+ migration into alumina, and in surface Rh after treatment in a reducing medium. The specific role of alumina can explain these results, in contradiction with thermodynamic models predicting the reverse situation (enrichment in Rh in O2 and in Pd in H2). Activity for propane oxidation at 573 K and for propane steam reforming at 673 K was also determined over fresh and sintered catalysts. Because Pd is more active than Rh in oxidation and Rh is more active than Pd in steam reforming, activity changes with the Rh content, before and after sintering, may reflect modifications of surface composition. The results obtained with the series of Pd–Rh catalysts are in agreement with the measurements made by OIE and FTIR spectroscopy. The hypothesis and the conditions of applications of the methods are discussed.

Les données scientifiques récentes permettent de comprendre la grande variabilité des méthodes de dosage des anticorps antiphospholipides (APA). Ces anticorps réagissent avec les complexes β2-glycoprotéine I (β2GPI)-phospholipides anioniques (PLP). Dans certains cas, ils réagissent aussi avec la β2GPI insolubilisée. Bien qu'il n'y ait que peu de spécificité d'espèce, certains APA réagissent préférentiellement avec les complexes de β2GPI humaine et de PLP.

A 1 wt.-%Pd/γ-Al2O3 catalyst was prepared (38% dispersion) and sintered under a flow of 3 vol.% O2 in N2 at 900°C (9% dispersion). The temperature-programmed oxidation of CO, C3H6, C3H8 and CH4 in substoichiometry of O2 was carried out on the fresh and, in some cases, on the sintered catalyst. The chemical state of palladium in the sintered catalyst was determined by XRD after interruption of the reaction at different temperatures. The temperatures at which a 20% conversion was obtained on the fresh pre-oxidised catalyst were: CO, 210°C < C3H6, 260°C < C3H8, 300°C < CH4, 335°C corresponding to an activity (in mmol h−1 g−1) at 300°C of: CO, 403 > C3H6, 66 > C3H8, 15.3 > CH4, 7.9. Pre-reduction did not change the catalyst activity in CO and in C3H6 oxidation while it decreased the activity by a factor 2.4 for C3H8 and 3.2 for CH4. Except for a definite decrease of activity, the above conclusions remained valid for the sintered catalyst. XRD measurements showed that PdO initially present in the pre-oxidised sample was reduced before the oxidation of CO (< 180°C) and C3H6 (< 210°C) started, which explains why both pre-oxidised and pre-reduced samples had the same activity. In the case of C3H8, the reduction occurred during the reaction and led to a temporary decrease of activity. For CO and C3H8, the Pd° structure was clearly identified while a new structure PdOξ (0 < ξ ≪ 1) was formed with C3H6. This compound has the cfc structure of Pd° with a higher lattice parameter (3.990Åinstead of 3.889Åin Pd°).

Several binds of experiments were carried out to show that oxygen species (OH, O) can be transferred from a Rh/Al2O3 (RhA) catalyst to pure oxides and vice-versa. Ceria physically mixed with RhA increases the catalytic activity of the Rh catalyst for the steam reforming of propane. Conversely, RhA can promote the exchange of (18)O2 with the O-16 Of pure oxides, normally inactive for the O-18/O-16 exchange in the absence of RhA. Moreover, large amounts of steam reforming products (Hz, CO) were obtained by injecting pulses of pure propane over a PtRh/CeO2/Al2O3 catalyst. OH groups stored on the support migrate to the metal particles where the reaction with CHx fragments (issued from the C3H8 activation) can occur.

Phospholipid dependent antibodies are usually measured with assays for antiphospholipid/anticardiolipin antibodies (aPLA) or for lupus anticoagulant (LA) activity. Most of them are targeted to complexes of beta 2-glycoprotein I (beta 2-GPI) and anionic phospholipids (PLP) or to prothrombin for some LA. New understandings allow a better standardisation and optimisation of assays' reactivity. Antigenic targets of phospholipid dependent antibodies were studied on plasmas from 38 patients with the antiphospholipid syndrome (APS) and presenting aPLA and/or LA. Using human beta 2-GPI-PLP complexes as solid phase antigen offers the highest sensitivity for measuring aPLA. Many aPLA, but not all, also react with beta 2-GPI coated on solid phase, however there is no evidence until now that this latter reactivity shows a closest association with the clinical context. Most of the patients with LA present an immunological reactivity to beta 2-GPI alone or to prothrombin, when these proteins are coated on solid phase. In two cases there was a reactivity to only beta 2-GPI-PLP complexes. For the various immunoassays, using NUNC type I plates offers a good binding capacity for coating antigens. They are then present at enough density on solid phase for insuring an efficient binding of autoantibodies. This is an important factor for assay sensitivity and reproducibility. Interestingly, in 1 case with LA, autoantibodies were reactive with coated beta 2-GPI alone but not with its PLP-complexes. In another case reactivity to beta 2-GPI was much higher than that to beta 2-GPI-PLP.

A 1% Pd catalyst (38% dispersion) was prepared by impregnating a γ-alumina with palladium acetylacetonate dissolved in acetone. The behaviour of this catalyst in oxidation and steam reforming (SR) of propane was investigated. Temperature-programmed reactions of C3H8 with O2 or with O2 + H2O were carried out with different stoichiometric ratios S(S =[O2]/5[C3H8]). The conversion profiles of C3H8 for the reaction carried out in substoichiometry of O2 (S < 1) showed two discrete domains of conversion: oxidation at temperatures below 350°C and SR at temperatures above 350°C. The presence of steam in the inlet gases is not necessary for SR to occur: there is sufficient water produced in the oxidation to form H2 and carbon oxides by this reaction. Contrary to what was observed with Pt, an apparent deactivation between 310 and 385°C could be observed with Pd in oxidation. This is due to a reduction of PdOx into Pd0, which is much less active than the oxide in propane oxidation. Steam added to the reactants inhibits oxidation while it prevents the reduction of PdOx into Pd0. Compared to Pt and to Rh, Pd has a higher thermal resistance: no deactivation occurred after treatment up to 700°C and limited deactivation after treatment up to 900°C, provided that the catalyst is maintained in an oxygen-rich atmosphere during the cooling.

In vivo localization of a mouse monoclonal antibody (F2-10.23 IgM) binding leukemic L 1210 cells was studied in DBA/2 mice bearing an L 1210 tumor. F(ab′)2 fragments were prepared and their specific binding to L 1210 cells was analyzed by flow cytofluorometry. Radiolocalization studies were performed by using 125I- or 131I-labeled IgM monoclonal antibody or its F(ab')2 fragments to ascertain their capacity to visualize the L 1210 tumor. F(ab′)2 fragments were cleared more rapidly than the whole IgM; the clearance was as fast in healthy as in tumor-bearing mice. The tumor-to-muscle ratio observed 24 h after injection of 125I-radiolabeled F(ab′)2 fragments and 125I-radiolabeled IgM was 10; the radioactivity level in the blood with F(ab′)2 fragments was lower than with IgM, and so γ-camera imaging was workable with F(ab′)2 fragments without background substraction. The tumor localization was studied over a period of 5 days by recording the distribution of the iodinated fragments in the tumor-bearing leg compared with that in the normal leg, and by computer analysis of the region of interest. F(ab′)2 fragments gave better results than intact IgM in tumor visualization. Nevertheless, the rapid clearance of this antibody or its F(ab′)2 fragments make them hardly suitable as carriers of toxic drugs.

A fluorogenic substrate for plasmin, CBZ‐Gly—Pro—Arg‐AEC, has been synthesized and used to develop a new sensitive photometric and fluorometric assay of plasminogen activator activity. The fluorescence intensity of free AEC at 460 nm is about 3 orders of magnitude higher than that of acyl‐AEC. The release of AEC from the peptidyl derivative was monitored fluorometrically after extraction of free AEC in ethylacetate. Under such conditions, theKmwas 0.16 mM. This method was used to monitor the activity of plasminogen activator synthetized by fibroblastic cells (BHK 21 C 13) either released in the supernantants or cell‐associated.

A new sensitive fluorimetric assay has been developed using peptidyl-3-amino-9-ethyl-carbazole as substrate. The fluorescence intensity of free 3-amino-9-ethyl-carbazole (AEC) at 460 nm is between two and three orders of magnitude higher than the fluorescence intensity of acyl-AEC. The release of AEC from a peptidyl derivative by proteases may be monitored continuously during the hydrolysis step or may be quantified upon addition of a general inhibitor such as benzamidinium chloride. Using N-benzoyl-arginyl-AEC as substrate, as little as 1 ng trypsin may be detected. Using t-butyloxycarbonyl-Val-Leu-Gly-Arg-AEC and the amoebocyte lysate of Limulus polyphemus, as little as 1 pg lipopolysaccharide can be detected. This fluorimetric method allows detection of trace amounts of lipopolysaccharide (endotoxins) in various biological materials, including sera.