Onium salts as catalysts in the liquid-phase oxidation of cyclohexene or tetraline by N2O

The liquid-phase oxidation of cyclohexene or tetraline with N2O was studied in various solvents in the presence of onium salts or without them. The onium salts exerted significant promoting effect on the reactions. The activation of the oxidant was studied by IR spectroscopy. It was found that the interactions of the ions in the onium salts and the polarised N–O bond further enhanced polarisation leading to an activation of the oxidant, thus, increasing the rate of oxidation

Nagyszelektivitású katalizátorrendszerek kifejlesztése = Towards 100% selectivity - development of highly selective catalytic systems

Kezdetben Cu-Tyr és Cu-His komplexek kovalens immobilizálására került sor, ahol C- illetve N-védett aminosavakat használtunk. A hordozók klórpropilezett szilikagél és Merrifield gyanta voltak. A komplexek kialakítására a védőcsoport eltávolítása után került sor. A későbbiekben Cu-, Co-, Fe- és Ni-aminosav komplexeket készítettünk a fenti hordozókon úgy, hogy a C- vagy N-védett aminosavakat (hisztidin, tirozin, cisztein, cisztin) a hordozóra kovalensen rögzítettük, majd kialakítottuk ki a fémkomplexeket. Az anyagokat szerkezetileg jellemeztük, és teszteltük SOD aktivitásukat. A védőcsoportot tartalmazó felületi komplexek aktívabbak, mint a védőcsoport nélküliek, a ligandumszegény környezetben szintetizáltak aktívabbak, mint a ligandumban gazdag környezetben készítettek, a fehérjevázhoz hasonlónak gondolt gyanta nem növelte a katalitikus aktivitást, és a Cu(II) ion geometriája a felületi komplexben torzult tetraéderes. A továbbiakban felületre kovalensen kötött vegyes ligandumú komplexeket készítettünk. Kidolgoztunk háromféle szintézismódszert, amely nagyszámú katalizátort eredményezett. A központi ionok Cu(II), Co(II), Fe(III) és Ni(II), a ligandumpárok C- vagy N-védett hisztidin és tirozin, vagy hisztidin és cisztein, vagy hisztidin és cisztin vagy cisztein és cisztin voltak az eddigi hordozókon. Sokféle koordinációs módot láttunk, és azt tapasztaltuk, hogy a felületi komplexek szerkezete a készítésmódtól is erősen függ. Sok esetben jelentős SOD aktivitást mértünk. | We started with the synthesis of covalently grafted Cu-Tyr and Cu-His complexes using C- or N-protected amino acids. Chloropropylated silica gel or Merrifield's resin was the support. The complexes were made after deprotecting the amino acid ligands. Later, surface-anchored Cu-, Co-, Fe- és Ni-amino acid complexes were prepared on the same supports using C- or N-protected histidine, tyrosine, cysteine and cystine and covalent bonding. The substances were structurally characterised and their SOD activities were tested. Surface complexes with protected amino acid ligands were more active than with deprotected ligands, those made under ligand poor conditions were more active than those made under ligand-excess conditions, the resin, thought to be similar to the proteomic skeleton, did not increase activity, and the geometry of the Cu(II) ion is distorted tetrahedron. In further work surface-anchored mixed amino acid complexes were prepared. Three synthesis methods were elaborated giving a large number of catalysts. The central ions were Cu(II), Co(II), Fe(III) and Ni(II), the ligands were C- or N-protected histidine and tyrosine, or histidine and cysteine, or histidine and cystine or cysteine and cystine and the supports were the same as before. Many coordination modes were observed and it was found that the catalytic activities of the substances largely depended on the method of preparation as well. In many cases substantial SOD activity could be measured

A Tudománypolitikai Bizottság részére készült tájékoztató a rendszerelemzés, mint a döntés előkészítés korszerű módszere alkalmazásának és terjesztésének helyzetéről

A hazai rendszerszemléletű, komplex munkák áttekintése, különösen az oktatás, kutatás, intézmények tekintetében

Covalently immobilized, silica gel or resin-supported C-protected cysteine or cystine Fe and Ni complexes - synthesis and structural characterization with FT-IR spectroscopy

In this work the syntheses of covalently grafted C-protected Fe(III)− or Ni(II)−L-cysteine and Fe(III)− or Ni(II)−L-cystine complexes onto a surface-modified silica gel or Merrifield’s resin are described. Conditions of the syntheses were varied and the obtained structures were studied by classical analytical (titration) as well as spectroscopic (infrared, atomic absorption) methods. It was found that the sulphur atoms in the molecules acted as primary coordination sites, while the other coordinating groups varied depending on whether the complexes were formed under ligand-poor or ligand-excess conditions

Diurnal and seasonal changes in stem radius increment and sap flow density indicate different responses of two co-existing oak species to environmental stress

Using continuous monitoring of stem radius combined with sap flow measurements we assessed the effects of environmental conditions on tree radial growth and water status of two co- existing oak species ( Quercus petraea and Quercus cerris ) at high resolution time in growing seasons of 2008 and 2009. The forest (95–100 yr) is situated in a xeric site in the transition zone between forested and forest-steppe regions in north -eastern Hungary, Bükk mountains (47 o 90’N, 20 o 46’E, elevation 320–340 m a.s.l.). Weather conditio ns in the growing season of 2008 (total rainfall 354 mm, mean daily temperature 17.0 o C) was less extreme than in 2009 (total rainfall 299 mm, temperature 17.9 o C). Rainfall strongly determined the course of radi al growth increment in trees. Radial growth of trees was limited in 200 9 due to the drought in spring. The maximum radial increment of both species was achieved three weeks earlier (4 th week of June) than in 2008 (4 th week of July). We used dendrometer monitoring data for estimation of stem (tree) water deficit ( ∆ W) by measuring water-related changes in stem radiu s (Zweifel et al. 2005). The magnitude of tree water deficit variation ( ∆ W) was always smaller in Q. cerris than in Q. petraea. In contrast, Quercus cerris always exhibited larger daytime averages and maxima of sap flow density. In August of 2009 when drought became seve re there were larger increases in tree water deficit ( ∆ W) (50–55 %) in both species compared to July as it could be expected from the extent of decreases in sap flow density (24–28%). Our data suggested that due to the low SWC the transpiration was supported mainly from the inner w ater storage of trees during prolonged drought which resulted in high stem water deficit ( ∆ W)

Metallic Nanoparticles in Heterogeneous Catalysis

Heterogeneous catalysis is a chemical process achieved at solid–gas or solid–liquid interfaces. Many factors including the particle size, shape and metal-support interfaces can have significant influences on the catalytic properties of metal catalysts. The recent progress in the synthesis techniques and advanced characterization tools allow to understand the catalytic mechanisms at molecular level. In this Review, the size and shape dependent catalytic chemistry of metal nanoparticles and their electronic properties will be discussed. Then the unique catalytic chemistry at the metal-support interfaces will be discussed in details. Furthermore, the challenges of bimetallic nanoparticle catalytic chemistry will be discussed

Phosphorus-loaded alumina supported nickel catalysts for CO2 hydrogenation: Ni2P/Ni5P12 drives activity

A series of 5 wt% NiO-xP-Al2O3 with different phosphorus loading contents (x = 0, 5, 15 and 20 wt%) were prepared by a modified sol-gel method. A significant promotional effect of phosphorus on NiO-Al2O3 in CO2 hydrogenation is observed. All the catalysts reach the highest conversion at 600 °C with 61.54 %, 62.89 %, 63.88 % and 66.13 % respectively for 5 wt% NiO-Al2O3, 5 wt% NiO-5P-Al2O3, 5 wt% NiO-15P-Al2O3 and 5 wt% NiO20P-Al2O3 catalysts. Ni/NiO/Ni2P/Ni5P12/AlPO4 interfacial species were detected on the surface as active species on the used catalysts by X-ray photoelectron spectroscopy. The formation ratio of the metal-phosphide is relatively low ∼3−5 %, and this atomic concentration is decreasing with the rising of the phosphate content. However, the nickel enrichment in the surface layer presumable in Ni2P/Ni5P12 form is very likely according to the P 2p spectra and the authors assume that could be responsible for the enhanced catalytic activity

Mobile genomic islands : the key role of extrachromosomal and integrative mobile elements in horizontal gene transfer

The plasticity of bacterial genomes enables the rapid adaptation to the changing environmental conditions. Horizontal gene transfer (HGT), by which bacteria can acquire and disseminate many beneficial traits, is mainly responsible for this plasticity. Conjugative elements such as plasmids, some genomic islands (GIs) and transposons have a key role in HGT since their mobility can lead to the rapid acquisition of virulence, pathogenicity or resistance factors and/or complete metabolic pathways of bacteria. Recent investigations of bacterial genomes put the mobile GIs in the spotlight of scientific interest. Mobile GIs are classified into two groups: integrative/conjugative elements (ICEs) and mobilizable genomic islands (MGIs). Unlike ICEs, MGIs are not self-transferable, so they require helper elements (ICEs or conjugative plasmids) that can provide the missing conjugative functions. GIs are stable part of the bacterial chromosome. They can not maintain extrachromosomally, but can be excised by site-specific recombination, transferred to other bacteria by conjugation and integrated into the chromosome of the recipient cell. These maintenance and transfer functions are encoded by the “backbone” of GIs, while another group of genes coding for antibiotic resistance, pathogenicity, catabolic pathways etc. confers adaptive functions to the host. The structure of mobile GIs shows remarkable flexibility: they evolve by acquisition, deletion and exchange of genes or gene clusters via homologous and/or site-specific recombination or transposition. One of the most studied MGIs is the Salmonella genomic island 1 (SGI1), which contains several antibiotic resistance genes embedded in the complex In104 integron segment. Prototype of SGI was detected in multiresistant Salmonella enterica serovar Typhimurium DT104 isolates, but its variants have also been identified in many other Salmonella serovars and in Proteus mirabilis isolates. Interestingly, SGI1 has never been found in natural Escherichia coli isolates even though it can easily be transferred into E. coli under laboratory conditions. SGI1 is a typical MGI, which is mobilized exclusively by the conjugative helper plasmids of IncA/C family. The first step of SGI1 transfer is the excision from the bacterial chromosome, which is carried out by the SGI1-encoded site-specific recombinase Int and Xis. The induction of excision and the transfer process also requires helper plasmid-encoded functions. Beside the conjugation apparatus (T4SS) of IncA/C plasmids, SGI1 also exploits regulatory functions of the helper plasmid. The plasmid-encoded FlhDC-family master regulator controls all conjugation genes of the plasmid including the relaxase, a key factor in the transfer initiation step, the operons of pilus assembly and perhaps some other functions. The master regulator triggers the excision of SGI1, i.e. signals the presence of a helper plasmid for SGI1, thus SGI1 hijacks both the regulation and the conjugation apparatus of IncA/C plasmids for its horizontal transfer. On the contrary, only SGI1 encoded functions are required for the integration into the recipient chromosome. SGI1 represents a good example how MGIs ensure their vertical transmission in absence of a helper and how they can exploit their helpers for horizontal spread