Interaction between Sulfated Zirconia and Alkanes: Prerequisites for Active Sites – Formation and Stability of Reaction Intermediates

Two sulfated zirconia catalysts were prepared via sulfation and calcination at 873 K of zirconium hydroxide aged at room temperature for 1 h (SZ-1) or aged at 373 K for 24 h (SZ-2). SZ-1 was active for n-butane isomerisation at 373 K; SZ-2 reached similar performance only at 473 K. Both materials contained about 9 wt% sulfate and were tetragonal. Due to a BET lower surface area (105 m2/g vs. 148 m2/g) SZ-1 featured a higher sulfate density, and XRD and EXAFS analysis showed larger (ca. 10 nm) and more well ordered crystals than for SZ-2. n-Butane TPD on SZ-1 showed a butene desorption peak at low temperature, whereas, no obvious butene desorption was observed with SZ-2, suggesting that SZ-1 has a higher oxidizing power at low temperature than SZ-2. The number of sites capable of dehydrogenation are less than 5 µmol/g, because the differential heats of n-butane adsorption as measured by microcalorimetry were 45–60 kJ/mol for higher coverages, indicating weak and reversible interaction. TAP experiments describe the adsorption and desorption behavior of n-butane at different activity states and are the basis for a simple adsorption model. Reactant pulses and purge experiments show that the active species, presumably formed in an oxidative dehydrogenation step, are stable at the surface under reaction conditions

The solid-state photo-CIDNP effect

Solid state NMR/Biophysical Organic Chemistr

Matrix Polysaccharides and SiaD Diguanylate Cyclase Alter Community Structure and Competitiveness of Pseudomonas aeruginosa during Dual-Species Biofilm Development with Staphylococcus aureus

Copyright © 2018 Chew et al. Mixed-species biofilms display a number of emergent properties, including enhanced antimicrobial tolerance and communal metabolism. These properties may depend on interspecies relationships and the structure of the biofilm. However, the contribution of specific matrix components to emergent properties of mixed-species biofilms remains poorly understood. Using a dual-species biofilm community formed by the opportunistic pathogens Pseudomonas aeruginosa and Staphylococcus aureus, we found that whilst neither Pel nor Psl polysaccharides, produced by P. aeruginosa, affect relative species abundance in mature P. aeruginosa and S. aureus biofilms, Psl production is associated with increased P. aeruginosa abundance and reduced S. aureus aggregation in the early stages of biofilm formation. Our data suggest that the competitive effect of Psl is not associated with its structural role in cross-linking the matrix and adhering to P. aeruginosa cells but is instead mediated through the activation of the diguanylate cyclase SiaD. This regulatory control was also found to be independent of the siderophore pyoverdine and Pseudomonas quinolone signal, which have previously been proposed to reduce S. aureus viability by inducing lactic acid fermentation-based growth. In contrast to the effect mediated by Psl, Pel reduced the effective crosslinking of the biofilm matrix and facilitated superdiffusivity in microcolony regions. These changes in matrix cross-linking enhance biofilm surface spreading and expansion of microcolonies in the later stages of biofilm development, improving overall dual-species biofilm growth and increasing biovolume severalfold. Thus, the biofilm matrix and regulators associated with matrix production play essential roles in mixed-species biofilm interactions.IMPORTANCE Bacteria in natural and engineered environments form biofilms that include many different species. Microorganisms rely on a number of different strategies to manage social interactions with other species and to access resources, build biofilm consortia, and optimize growth. For example, Pseudomonasaeruginosa and Staphylococcus aureus are biofilm-forming bacteria that coinfect the lungs of cystic fibrosis patients and diabetic and chronic wounds. P. aeruginosa is known to antagonize S. aureus growth. However, many of the factors responsible for mixed-species interactions and outcomes such as infections are poorly understood. Biofilm bacteria are encased in a self-produced extracellular matrix that facilitates interspecies behavior and biofilm development. In this study, we examined the poorly understood roles of the major matrix biopolymers and their regulators in mixed-species biofilm interactions and development

Signals in solid-state photochemically induced dynamic nuclear polarization recover faster than signals obtained with the longitudinal relaxation time

Biological and Soft Matter PhysicsSolid state NMR/Biophysical Organic Chemistr

Ozone-based eye drops activity on ocular epithelial cells and potential pathogens infecting the front of the eye

Confirmation of the biological effectiveness of new ophthalmic preparations introduced in the market is an important element in maintaining the safety of using this type of medications. This study aimed to investigate the activity of Ozodrop® on human corneal and conjunctival epithelial cells, as well as its antibacterial and antifungal activity. Cytotoxicity analyses of ocular surface epithelial cells were performed in vitro by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) and Neutral Red uptake assays. The level of nitric oxide released by the cells was assessed by the Griess method. The reduction of the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical by the tested formulation was analyzed. Microbiological tests were also performed. It was found that the Ozodrop® preparation exhibited biological activity, but was less active than the reference antibiotics and the anti-yeast agent. The cytotoxic activity of the Ozodrop® formulation was dependent on the time of cell exposure to it. No toxic effect was observed in the short-term, for up to 3 h. It appeared after 24 h of exposure of the cells to the preparation. The drops showed antioxidant activity in the specified concentration range. They also stimulated the release of nitric oxide, mainly by corneal epithelial cells. The Ozodrop® formulation exhibits biological activity that can be considered useful in the treatment of infections in the front part of the eye

Nanosecond-Flash N-15 Photo-CIDNP MAS NMR on reaction centers of Rhodobacter sphaeroides R26

Solid state NMR/Biophysical Organic ChemistryBiological and Soft Matter Physic

15N photo-CIDNP MAS NMR analysis of a bacterial photosynthetic reaction center of rhodobacter sphaeroides wildtype

Solid state NMR/Biophysical Organic Chemistr

Magnetic field dependence of photo-CIDNP MAS NMR on photosynthetic reaction centers of Rhodobacter sphaeroides WT

Biological and Soft Matter Physic

Photo-CIDNP MAS NMR in intact cells of Rhodobacter sphaeroides R26: molecular and atomic resolution at nanomolar concentration?

Biological and Soft Matter Physic

Observation of the solid-state photo-CIDNP effect in entire cells of cyanobacteria Synechocystis

Cyanobacteria are widely used as model organism of oxygenic photosynthesis due to being the simplest photosynthetic organisms containing both photosystem I and II (PSI and PSII). Photochemically induced dynamic nuclear polarization (photo-CIDNP) 13C magic-angle spinning (MAS) NMR is a powerful tool in understanding the photosynthesis machinery down to atomic level. Combined with selective isotope enrichment this technique has now opened the door to study primary charge separation in whole living cells. Here, we present the first photo-CIDNP observed in whole cells of the cyanobacterium Synechocystis