The paper presents novel findings observed during the training process of superelastic, elastocalorically optimized Ni-Ti-based shape memory alloys (SMA). NiTiCuV alloys exhibit large latent heats and a small mechanical hysteresis, which may potentially lead to the development of efficient solid-state-based cooling processes. The paper starts with a brief introduction to the underlying principles of elastocaloric cooling, illustrating the effect by means of a typical thermodynamic cycle. It proceeds with the description of a custom-built testing platform that allows observation of temperature profiles and heat transfer between SMA and heat source/sink during high-loading-rate tensile tests. Similar to other SMA applications, a training process is necessary in order to guarantee stable performance. This well-known mechanical stabilization affects the stress-strain hysteresis and the cycle-dependent evolution of differential scanning calorimetry results. In addition, it can be shown here that the training is also accompanied by a cycle-dependent evolution of temperature profiles on the surface of an SMA ribbon. The applied training leads to local temperature peaks with intensity, number, and distribution of the temperature fronts showing a cycle dependency. The homogeneity of the elastocaloric effect has a significant influence on the efficiency of elastocaloric cooling process and is a key aspect of the specific material characterization.

The chemoselective hydrogenation of carboxylic acids to either alcohols or alkanes is reported, employing a heterogeneous bimetallic catalyst consisting of rhenium and palladium supported on graphite. α-Chiral carboxylic acids were hydrogenated without loss of optical purity. The catalyst displays a reverse order of reactivity upon hydrogenation of different carboxylic functions with esters being less reactive than amides and carboxylic acids. This allows for chemoselective hydrogenation of an acid in the presence of an ester or an amide function.

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An improved procedure was developed for the isolation of pyruvate decarboxylase from wheat germ. Its final step, an electrophoresis of the native apoenzyme in concave pore gradient polyacrylamide gels, followed by superficial activity-staining, produced two bands of different molecular masses and chain compositions. The highmolecular-mass band occurred in low quantity and consisted of, probably eight, apparently identical chains of M , = 33 000, as judged from sodium dodecyl sulfate electrophoreses. The low-molecular-mass band contained two types of chains with MF = 63000-65000 and M! = 61000-62000. The N termini of both chains were threonine, whereas their C-terminal sequences were different:Their amino acid composition was too different to be compatible with our original concept of one chain being produced from the other by proteolytic shortening. Limited proteolysis by Staphylococcus aureus V8 proteinase yielded peptides partly identical size and partly quite different.In all properties investigated, the low-molecular-mass enzyme largely resembled yeast pyruvate decarboxylase; the holoenzyme appeared to possess ( c I~)~ structure, the apoenzyme a/?. SH reagents inactivated the enzyme. Binding and fluorescence of 2-p-toluidinonaphthalene-6-sulfonate indicated a similar lipophilicity of the active site as found earlier for the yeast enzyme. 2-Hydroxy-5-nitrobenzyl modification of exposed tryptophan residues left the holoenzyme intact, but in the apoenzyme it destroyed most of the cofactor-binding ability and hence the activity. The strength of cofactor binding and the maximal specific activity were found somewhat lower than in yeast pyruvate decarboxylase.Pyruvate decarboxylase (PDC) is known to occur in yeasts, several other fungi, many plant materials (review: [l]) and a few bacteria [2, 31. One of the early sources for its preparation has been wheat germ [4]. When our efforts to achieve a detailed chemical analysis of yeast PDC became hampered by uncontrollable actions of contaminating proteinases [5], a practical alternative seemed to be the investigation of PDC from wheat germ, which was expected to contain fewer proteinases. The original method for the preparation of wheat germ PDC [4] has been applied without major alterations in all instances when this enzyme was hitherto needed for a variety of purposes [6 -111. Re-examination of this procedure with modern electrophoresis methods demonstrated that it yields PDC of insufficient chain homogeneity for the requirements of peptide mapping and sequence analysis. Therefore a more efficient isolation scheme was elaborated.

In searching for the gonococcal sialyltransferase gene(s), we cloned a 3.8-kb DNA fragment from gonococcus strain MS11 that hybridized with the oligonucleotide JU07, which was derived from the conserved C terminus of the sialyl motif present in mammalian sialyltransferases. Sequencing of the fragment revealed four putative open reading frames (ORFs), one of which (ORF-1) contained a partial sialyl motif including the amino acid sequence VGSKT, which is highly conserved among sialyltransferases. The gene was flanked by two inverted repeats containing the neisserial DNA uptake sequence and was preceded by a putative 54 promoter. Database searches, however, revealed a high degree of homology between ORF-1 and the N-acetylglucosamine 1-phosphate uridyltransferase (GlmU) of Escherichia coli and Bacillus subtilis and not with any known sialyltransferase. This homology was further established by the successful complementation of an orf-1 mutation by the E. coli glmU gene. Enzyme assays demonstrated that ORF-1 did not possess sialyltransferase activity but mimicked GlmU function catalyzing the conversion of N-acetylglucosamine 1-phosphate into UDP-N-acetylglucosamine, which is a key metabolite in the syntheses of lipopolysaccharide, peptidoglycan, and sialic acids.The lipopolysaccharide (LPS) of the pathogenic Neisseria species is unique in that it can undergo external modification through the addition of sialic acids (for a review, see reference 42). This process involves the covalent transfer of sialic acid from the external substrate cytidine 5Ј-monophospho N-acetylneuraminic acid (CMP-NANA) towards terminal galactose moieties on the LPS. The reaction is catalyzed by a membranebound bacterial sialyltransferase (26). The substrate CMP-NANA is present in human secretions and biological fluids, and LPS sialylation has been demonstrated to occur in vivo during the natural infection (1). The LPS sialylation event seems to have great impact on the virulence of the bacterium. Sialylated gonococci are resistant against killing by antibodies and complement (9,34,41,47) and are poorly ingested by professional phagocytes (16,37). Furthermore, LPS sialylation may reduce the immune response towards the bacterium because of the molecular mimicry of host sialic acids and a masking of bacterial surface antigens (25). The ability of the bacterium to change its LPS structure and switch to a nonsialylated phenotype lacking the acceptor sites for sialic acid provides the bacterium with a flexibility to optimally adapt its surface composition to the changing microenvironment in the host. A nonsialylated bacterial phenotype may be particularly useful at those stages in the infection where intimate bacterium-host cell contact and bacterial entry into host cells are advantageous (41).Despite the apparently important function of bacterial LPS sialyltransferase in the pathogenesis of neisserial disease, our knowledge about this sialyltransferase is still scanty. The enzyme appears to be surface exposed and conserved among meningococcal and go...