Molybdenum oxide catalysts (1 wt %) supported on SiO 2 (L-90, 95 m 2 /g), SiO 2 (EH-5, 350 m 2 /g), Al 2 O 3 (96 m 2 /g), and TiO 2 (52 m 2 /g) were characterized using Raman spectroscopy and near-edge and extended X-ray absorption fine structure (NEXAFS and EXAFS, respectively) spectroscopies. The structural possibilities (tetrahedral and distorted octahedral) for the Mo active center were explored using ab initio calculations through the Hartree-Fock method using a 3-21G(d) basis set. The Raman vibrational frequencies and bond lengths obtained from EXAFS were compared to ab initio calculations to arrive at the likely structures for the isolated Mo centers on each support. The studies revealed a mixture of tetrahedral Mo sites along with crystalline MoO 3 for the MoO 3 /SiO 2 (L-90) catalyst. The Mo sites for the MoO 3 /SiO 2 (EH-5) catalyst were found to be a mixture of isolated, tetrahedral, and distorted octahedral sites. The MoO 3 /Al 2 O 3 catalyst was found to have isolated, tetrahedral sites. Finally, the MoO 3 /TiO 2 catalyst was found to have distorted octahedral Mo active centers. Complementary information from Raman, NEXAFS, and EXAFS spectra and ab initio calculations were required to arrive at the structural assignments for the Mo centers in the present study. Importantly, however, the calculations indicate the possible existence of other stable geometries and help explain the many diverging conclusions in the literature concerning the structure of supported molybdenum oxide catalysts.

The mechanism of methanol oxidation over highly dispersed 1% MoO3/SiO2 was studied using a combination of steady state and transient kinetic measurements together with in situ Fourier transform infrared (FTIR) observations of surface-adsorbed species. The main reactive intermediates were methoxide species formed on surface Mo centers. Deuterium substitution experiments showed that these species decomposed through a rate-determining C−H bond-breaking step to form the primary product of reaction, formaldehyde. The steady state data gave an apparent activation energy of 89 kJ/mol, while the oxidation rate of the surface intermediate gave an activation energy for the rate-determining step of 108 kJ/mol. The difference in these gives a heat of adsorption of −19 kJ/mol. Although the oxidation reaction occurred on the Mo centers, the methoxide species were found to migrate to the silica support by reversibly displacing mobile silica OH groups. Two kinds of methoxide species were distinguished, spectators and active intermediates. Only the active intermediates could be oxidized at temperatures lower than 300 °C, and these were the actual participants in the reaction. Quantitative FTIR measurements indicated that the number of methoxide species on the silica support was about six times larger than the number of Mo centers. Thus, the silica surface, which was otherwise inert, participated in a noninnocent manner, holding a substantial population of the reactive intermediates.

Oxidation of organic substrates on metal oxide catalysts can be viewed as entailing a transfer of electrons from the organic moeity to the catalytic center, and is expected to involve the electron-accepting levels in the metal center. This investigation deals with the study of the electron-transfer processes associated with the C-H bond breaking reaction in adsorbed methoxide species in the course of methanol oxidation on supported MoO 3 . It is shown that the activity of a series of catalysts duly correlates with the unoccupied density of electronic states of the parent metal oxides. The unoccupied levels are probed with near-edge X-ray absorption spectroscopy (NEXAFS). The particular system chosen for study is that of methanol oxidation on supported molybdenum oxide, a reaction in which C-H bond breaking is rate-determining. The findings of this study are in good agreement with the known facts about the reaction and allow a deeper understanding of various reported effects. For example, the positive relationships between the catalytic activity and the decreasing electronegativity of the support ion, the increasing reducibility of the dispersed molybdenum centers, and the increasing size of the molybdenum ensembles can all be explained by the increasing ease of accommodation of charge by the metal centers. The findings in this study should be of importance in understanding other C-H bond breaking reactions and multicomponent catalyst systems.

The resistance to antibiotics and the distribution of virulence factors in enterococci isolated from traditional Slovak sheep cheese bryndza was compared with strains from human infections. The occurrence of 4 enterococcal species was observed in 117 bryndza-cheese isolates. The majority of strains were identified as E. faecium (76 %) and E. faecalis (23 %). Several strains of E. durans and 1 strain of E. hirae were also present. More than 90 % of strains isolated from 109 clinical enterococci were E. faecalis, the rest belonged to E. faecium. The resistance to 6 antimicrobial substances (ampicillin, ciprofloxacin, higher concentration of gentamicin, nitrofurantoin, tetracycline and vancomycin) was tested in clinical and food enterococci. A higher level of resistance was found in clinical than in food strains and E. faecium had a higher resistance than E. faecalis; no resistance to vancomycin was detected. The occurrence of 3 virulence-associated genes, cylA (coding for hemolysin), gelE (coding for gelatinase) and esp (coding for surface protein) was monitored. Differences were found in the distribution of cylA gene between clinical and bryndza-cheese E. faecalis strains; in contrast to clinical strains (45 %), cylA gene was detected in 22 % of food isolates. The distribution of 2 other virulence factors, gelE and esp, was not significantly different in the two groups of E. faecalis strains. cylA and gelE genes were not detected in E. faecium but more than 70 % of clinical E. faecium were positive for esp, even thought none of the 79 E. faecium cheese isolates contained this gene.

A set of reference strains and a group of previously unidentified enterococci were analysed by rep-PCR with the (GTG)(5) primer to evaluate the discriminatory power and suitability of this method for typing and identification of enterococcal species. A total of 49 strains representing all validly described species were obtained from bacterial collections. For more extensive evaluation of this identification approach 112 well-defined and identified enterococci isolated from bryndza cheese were tested. The (GTG)(5)-PCR fingerprinting assigned all strains into well-differentiated clusters representing individual species. Subsequently, a group including 44 unidentified enterococci isolated from surface waters was analysed to evaluate this method for identification of unknown isolates. Obtained band patterns allowed us to identify all the strains clearly to the species level. This study proved that rep-PCR with (GTG)(5) primer is a reliable and fast method for species identification of enterococci.

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The Gould-Jacobs reaction of all position isomeric 2-aminonitrobenzothiazoles II with diethyl ethoxy- methylenemalonate has been studied. The structure of substitution (IV) and cyclization (VI) products and of the corresponding acids (VIII) was confirmed by elemental analysis, IR, UV, 1H and 13C NMR spectra. Analogous derivatives III, V and VII, derived from the unsubstituted 2-aminobenzothiazole I, were used as standards in interpretation of the spectra. The synthesized derivatives I - VIII were tested for antimicrobial activity.

Alcohol adsorption on MoO3/SiO2 resulted in formation of two types of alkoxide, spectator and participant for selective oxidation, which exist on SiO2 consuming silanol groups through spillover and migration from MoO3 to SiO2 support.