Monitoring of Gene Expression in Bacteria during Infections Using an Adaptable Set of Bioluminescent, Fluorescent and Colorigenic Fusion Vectors

A family of versatile promoter-probe plasmids for gene expression analysis was developed based on a modular expression plasmid system (pZ). The vectors contain different replicons with exchangeable antibiotic cassettes to allow compatibility and expression analysis on a low-, midi- and high-copy number basis. Suicide vector variants also permit chromosomal integration of the reporter fusion and stable vector derivatives can be used for in vivo or in situ expression studies under non-selective conditions. Transcriptional and translational fusions to the reporter genes gfpmut3.1, amCyan, dsRed2, luxCDABE, phoA or lacZ can be constructed, and presence of identical multiple cloning sites in the vector system facilitates the interchange of promoters or reporter genes between the plasmids of the series. The promoter of the constitutively expressed gapA gene of Escherichia coli was included to obtain fluorescent and bioluminescent expression constructs. A combination of the plasmids allows simultaneous detection and gene expression analysis in individual bacteria, e.g. in bacterial communities or during mouse infections. To test our vector system, we analyzed and quantified expression of Yersinia pseudotuberculosis virulence genes under laboratory conditions, in association with cells and during the infection process

Gold Complexes with Tridentate Cyclometalating and NHC Ligands: A Search for New Photoluminescent Gold(III) Compounds

Many square-planar Pt(II) complexes are strongly photoluminescent, particularly when they contain cyclometalating and/or NHC ligands which produce strong ligand fields. In this work we investigated the possibility of obtaining isoelectronic Au(III) complexes with favorable luminescence properties. Toward this end, the coordination chemistry of gold with three different (potentially) tridentate ligands was explored: 1,3-bis(1-hexyl-2′-benzimidazoyl)benzene (L1H), 2,6-bis(3-butylimidazol-1-ium)pyridine (L2H22+), and 2,6-bis(3-hexylbenzimidazol-1-ium)pyridine (L3H22+). Pt(II) or Pd(II) complexes are known for all of these ligands or closely related analogues, and hence we anticipated that similar Au(III) complexes would be synthetically accessible as well. This turned out to be the case only for L1, despite exploration of different synthetic routes including (i) direct complexation of Au(III), (ii) transmetalation from Ag(I) precursor complexes, and (iii) transmetalation from suitable Hg(II) precursors. Only the mercury procedure was successful (at least in the case of L1); transmetalation from silver or direct complexation yields other reaction products containing Au(I) in most cases. Likewise, with ligands L2 and L3 mainly complexes of Au(I) were obtained: i.e., the propensity of gold for low oxidation states is a major obstacle to obtaining the desired Au(III) compounds. Several new complexes of Au(I) and Au(III) were characterized crystallographically. Our results provide insight into the differences between the coordination chemistry of isoelectronic Pt(II) and Au(III) with tridentate cyclometalating and NHC ligands

Hierarchical MOF-xerogel monolith composites from embedding MIL-100(Fe,Cr) and MIL-101(Cr) in resorcinol-formaldehyde xerogels for water adsorption applications

Shaping of otherwise powdery metal-organic frameworks is recognized as a more-and-more important issue to advance them to the application stage. Monolithic MOF composites were synthesized using micro-to-mesoporous MIL-100(Fe,Cr) and MIL-101(Cr) as thermally and chemically stable MOFs together with a mesoporous resorcinol-formaldehyde based xerogel as binding agent. The monolithic bodies could be loaded with up to 77 wt% of powdery MIL material under retention of the MIL surface area and porosities (from N2 adsorption) by pre-polymerization of the xerogel solution. The obtained monoliths are mechanically stable and adsorb close to the expected water vapor amount according to the MIL weight percentage. There is no loss of BET surface area, porosity and water uptake capacity especially for the MIL-101(Cr) composites. Water vapor adsorption isotherms show that the 77 wt% MIL-101(Cr) loaded composite even features a slightly increased water vapor uptake compared to pure MIL-101(Cr) up to a relative vapor pressure of P · P 0 − 1 = 0.5 . These hydrophilic monolithic composites could be applied for heat transformation application such as thermally driven adsorption chillers or adsorption heat pumps

Brønsted Instead of Lewis Acidity in Functionalized MIL-101Cr MOFs for Efficient Heterogeneous (nano-MOF) Catalysis in the Condensation Reaction of Aldehydes with Alcohols

Porous chromium­(III) 2-nitro-, 2-amino-, and nonfunctionalized terephthalate (MIL-101Cr) metal organic frameworks are heterogeneous catalysts for diacetal formation from benzaldehyde and methanol (B–M reaction) as well as other aldehydes and alcohols. MIL-101Cr-NO₂ obtained by direct reaction between CrO₃ and 2-nitro-terephthalate showed the highest activity with 99% conversion in the B–M reaction in 90 min and turnover numbers of 114. The activity decreased in the order MIL-101Cr-NO₂ > MIL-101Cr > MIL-101Cr-NH₂. Within different samples of nonfunctionalized MIL-101Cr the activity increased with surface area. Methanol gas sorption of the different MIL materials correlates with the BET surface area and pore volume but not with the diacetalization activity. Benzaldehyde adsorption from heptane showed no significant difference for the different MILs. Gas sorption studies of CD₃CN to probe for a higher Lewis acidity in MIL-101Cr-NO₂ remained inconclusive. A high B–M catalytic activity of wet MIL-101Cr-NO₂ excluded significant contributions from coordinatively unsaturated Lewis-acid sites. pH measurements of methanol dispersions of the MIL materials gave the most acidic pH (as low as 1.9) for MIL-101Cr-NO₂, which significantly increased over MIL-101Cr (3.0) to MIL-101Cr-NH₂ (3.3). The increase in acidity is of short range or a surface effect to the heterogeneous MIL particles as protons dissociating from the polarized aqua ligands (Cr–OH₂) have to stay near the insoluble counteranionic framework. The variation in Brønsted acidity of MIL-101Cr-NO₂ <b>></b> MIL-101Cr <b> ≈ </b> MIL-101Cr-NH₂ correlates with the withdrawing effect of NO₂ and the diacetalization activity. The catalytic B–M activity of soluble, substitution-inert, and acidic Cr­(NO₃)₃·9H₂O supports the Brønsted-acid effect of the MIL materials. Filtration and centrifugation experiments with MIL-101Cr-NO₂ revealed that about 2/3 of the catalytic activity comes from nano-MOF particles with a diameter below 200 nm. The MIL-101Cr-NO₂ catalysts can be recycled five times with very little loss in activity. The diacetalization activity of MIL-101Cr-NO₂ decreases with the alcohol chain length from methanol over ethanol, <i>n</i>-propanol, <i>n</i>-butanol, to almost inactive <i>n</i>-pentanol, while conversions for benzaldehyde, paratolylaldehyde, 4-chlorobenzaldehyde, and cyclohexanone all reach 90% or more after 90 min

Gold Complexes with Tridentate Cyclometalating and NHC Ligands: A Search for New Photoluminescent Gold(III) Compounds

Many square-planar Pt­(II) complexes are strongly photoluminescent, particularly when they contain cyclometalating and/or NHC ligands which produce strong ligand fields. In this work we investigated the possibility of obtaining isoelectronic Au­(III) complexes with favorable luminescence properties. Toward this end, the coordination chemistry of gold with three different (potentially) tridentate ligands was explored: 1,3-bis­(1-hexyl-2′-benzimidazoyl)­benzene (L¹H), 2,6-bis­(3-butylimidazol-1-ium)­pyridine (L²H₂²⁺), and 2,6-bis­(3-hexylbenzimidazol-1-ium)­pyridine (L³H₂²⁺). Pt­(II) or Pd­(II) complexes are known for all of these ligands or closely related analogues, and hence we anticipated that similar Au­(III) complexes would be synthetically accessible as well. This turned out to be the case only for L¹, despite exploration of different synthetic routes including (i) direct complexation of Au­(III), (ii) transmetalation from Ag­(I) precursor complexes, and (iii) transmetalation from suitable Hg­(II) precursors. Only the mercury procedure was successful (at least in the case of L¹); transmetalation from silver or direct complexation yields other reaction products containing Au­(I) in most cases. Likewise, with ligands L² and L³ mainly complexes of Au­(I) were obtained: i.e., the propensity of gold for low oxidation states is a major obstacle to obtaining the desired Au­(III) compounds. Several new complexes of Au­(I) and Au­(III) were characterized crystallographically. Our results provide insight into the differences between the coordination chemistry of isoelectronic Pt­(II) and Au­(III) with tridentate cyclometalating and NHC ligands

Gold Complexes with Tridentate Cyclometalating and NHC Ligands: A Search for New Photoluminescent Gold(III) Compounds

Many square-planar Pt­(II) complexes are strongly photoluminescent, particularly when they contain cyclometalating and/or NHC ligands which produce strong ligand fields. In this work we investigated the possibility of obtaining isoelectronic Au­(III) complexes with favorable luminescence properties. Toward this end, the coordination chemistry of gold with three different (potentially) tridentate ligands was explored: 1,3-bis­(1-hexyl-2′-benzimidazoyl)­benzene (L¹H), 2,6-bis­(3-butylimidazol-1-ium)­pyridine (L²H₂²⁺), and 2,6-bis­(3-hexylbenzimidazol-1-ium)­pyridine (L³H₂²⁺). Pt­(II) or Pd­(II) complexes are known for all of these ligands or closely related analogues, and hence we anticipated that similar Au­(III) complexes would be synthetically accessible as well. This turned out to be the case only for L¹, despite exploration of different synthetic routes including (i) direct complexation of Au­(III), (ii) transmetalation from Ag­(I) precursor complexes, and (iii) transmetalation from suitable Hg­(II) precursors. Only the mercury procedure was successful (at least in the case of L¹); transmetalation from silver or direct complexation yields other reaction products containing Au­(I) in most cases. Likewise, with ligands L² and L³ mainly complexes of Au­(I) were obtained: i.e., the propensity of gold for low oxidation states is a major obstacle to obtaining the desired Au­(III) compounds. Several new complexes of Au­(I) and Au­(III) were characterized crystallographically. Our results provide insight into the differences between the coordination chemistry of isoelectronic Pt­(II) and Au­(III) with tridentate cyclometalating and NHC ligands

Ethanol adsorption onto metal organic framework: Theory and experiments

a b s t r a c t This paper presents experimental and theoretical investigations of adsorption characteristics of ethanol onto metal organic framework namely MIL-101Cr. Adsorption isotherms and kinetics of the studied pair have been measured gravimetrically using a magnetic suspension adsorption measurement unit and volumetrically employing a Quantachrome Autosorb iQ MP machine. The present experiments have been conducted within relative pressures between 0.1 and 0.9 and adsorption temperatures ranging from 30 to 70 C, which are suitable for adsorption cooling applications. Adsorption isotherm data exhibit that 1 kg of MIL-101Cr can adsorb as high as 1.1 kg of ethanol at adsorption temperature of 30 C, and the T oth equation has been used to fit the experimentally measured data. As of the experimentally measured adsorption uptake rate data, the Fickian diffusion model is found to be suitable. These data are essential for designing a new generation of adsorption chiller