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By using modifiers in platinum catalysts it is possible to modulate the hydrogenation selectivity in α , β -unsaturated aldehydes carbonyl bond with regard to olefinic bond hydrogenation. The challenge is to find an emergent catalytic material able to produce 100% unsaturated alcohol. In this field, 1% Pt/ZnO catalysts were tested in hydrogenation of crotonaldehyde, in gas phase, at atmospheric pressure. The catalysts were prepared by impregnation of ZnO from two different precursors, H 2 PtCl 6 and Pt(NH 3 ) 4 (NO 3 ) 2 , followed by calcination at 673 K and tested after reduction at different temperatures, 473–773 K. The ex-nitrate and ex-chloride catalysts showed quite different catalytic behaviors. The ex-chloride was much more active and selective; in certain conditions 90% crotyl alcohol selectivity was reached. Different techniques (TPR, XRD, TEM, XPS, FTIR) were used to characterize both types of catalysts and to correlate the structure and the reactivity. The Lewis acidity of ZnO after the reduction treatment and the formation of PtZn alloy were found to be the key factors leading to high crotyl alcohol yield. It was proposed that modification of the electronic properties of platinum both by alloying to zinc and by Lewis acidity of the support reinforced by chlorine changes the adsorption mode of crotonaldehyde by favoring the binding of the terminal oxygen of the molecule to the electronically modified platinum atom.

Surface properties of unsupported MoS 2 have been studied by means of IR spectroscopy of a wide range of adsorbed molecules. After contact with air, surface of MoS 2 is partially oxidised and contains adsorbed water, MoO groups, sulphate and thiosulphate-like anions. These species are removable by treatment in vacuum or in H 2 S–H 2 mixture. On MoS 2 , only molecular adsorption was established for SO 2 , CO 2 , COS and CH 3 SH showing weak basicity of surface sulphur ions. Unsupported MoS 2 presents also very weak acidic properties, as revealed by pyridine, 2,6-dimethylpyridine and ethylene adsorption. However, ammonia could be protonated or coordinately bound to MoS 2 surface. CO and NO interact with the coordinately unsaturated Mo sites of the sulphide, providing evidence for an important back donation effect. Comparison with surface properties of supported MoS 2 points to the lower acidic and higher metallic character of Mo sites of the unsupported sulphide.

The lipase from the Antarctic psychrophilic bacterium Psychrobacter immobilis B10 shows a very limited thermal stability when compared to the lipase from a mesophilic strain of Pseudomonas aeruginosa . The thermal dependence of its activity is shifted by at least 30 °C towards low temperatures and its activation energy is reduced by a factor of 2. The three-dimensional model of the P. immobilis lipase reveals several features typical of cold-adapted enzymes: a very low proportion of arginine residues as compared to lysines, a low content in proline residues, a small hydrophobic core, a very small number of salt bridges and of aromatic-aromatic interactions. All these properties should confer on the enzyme a more flexible structure, in accord with its low activation energy and its low thermal stability.

FT i.r. spectroscopy has been applied in studying the reaction between methanol and hydrogen sulfide on NaX and NaY zeolites. Hydrogen-bonded methanol and methoxy and carbonate species were found on both of the zeolites after methanol adsorption. Pyrrole and pyridine preadsorption experiments have shown that methanol is chemisorbed on basic and/or cationic sites on the zeolites used. H 2 S is adsorbed on the same sites. In the reaction between methanol and hydrogen sulfide on sodium zeolites methoxy species or HS − ions are involved. Carbonate species can also react with H 2 S producing hydrogenthiocarbonates or thiocarbonates. However, this reaction does not play any role in the interaction between CH 3 OH and H 2 S under the conditions used.

The catalytic properties of six "natural" mutants of the TEM-1 beta-lactamase have been studied in detail, with special emphasis on their activity versus third-generation cephalosporins. On the basis of the recently determined high-resolution structure of the wild-type enzyme, and of the substrates' structures optimized by the AMI quantum chemistry method, we have attempted to explain the influences of the mutations on the substrate profiles of the enzymes. Some of the kinetic results have thus received a satisfactory, semi-quantitative interpretation, especially in the case of single mutations. Analysis of the double mutants proved more hazardous. Extending the comparison to some other class A beta-lactamases showed that similar properties could result from different sequences, supplying an interesting example of convergent evolution within a generally diverging family.

Oxidation of benzisothiazole by hydrogen peroxide leads to saccharine, but the same reaction with benzisoselenazole does not lead to selenosaccharine. The product of this oxidation is the ammonium o-carboxybenzeneselenonate monohydrate. Crystals are triclinic, P1, with a =6.243, b =7.598 and c =12.457 A, α =142.38, β = 104.98 and γ = 85.47°, and Z = 2. The refinement led to a final R-value of 0.056. The ammonium ion and water molecule coordinations are discussed in terms of hydrogen bonds. The coordination of the selenium atom is also described.

From the roots of Strychnos icaja Baill. an unsymmetrical dimeric alkaloid has been isolated and called sungucine. Its original structure has been established by X-Ray diffraction; UV, IR, MS and NMR data are also given.