Expansion of orderly stacked metakaolinite layers and order destruction using a kaolinite-tetraphenylphosphonium chloride intercalation compound

Metakaolinite layers were expanded via the heat treatment of a kaolinite-tetraphenylphosphonium chloride intercalation compound and the obtained metakaolinite stacking order was destroyed upon manual grinding.

Comparison of ReO4− and TcO4− in solvent extraction systems

The suitability of perrhenate (Re(VII)) to act as an analog for pertechnetate (Tc(VII)) was tested using solvent extraction and the carrier/tracer systems 99Tc(VII)/99mTc(VII) and 185/187Re/186/188Re(VII). Perrhenate is often used as a non-radioactive analogue of pertechnetate, but scarce data is available for the comparison of these metals for liquid-liquid extraction applications. Results show that neither Tc(VII) nor Re(VII) extraction is influenced by pH in the 2–8 range. The anion extractant also separates electrolyte anions, with increasing extraction following the order Cl− < NO3− ≪ ClO4−, resulting in a decreased Tc(VII) and Re(VII) extraction in presence of salt. In particular, the extraction of Re and Tc is suppressed in presence of NaCl at concentrations higher than 1 mM. While Tc extraction is larger than that of Re in absence of electrolyte, they are statistically identical in presence of enough electrolyte. Furthermore, tetraphenylphosphonium chloride (Ph4PCl) is a stronger extractant than iodonitrotetrazolium chloride (INT).

Dehydrochlorination of 1,2-dichloroethane over a tetraphenylphosphonium chloride-supported carbon catalyst

An activated carbon-supported tetraphenylphosphonium chloride (TPPC/AC) catalyst shows excellent catalytic activity and stability for dehydrochlorination of 1,2-dichloroethane.

Listeria monocytogenes Strains Selected on Ciprofloxacin or the Disinfectant Benzalkonium Chloride Exhibit Reduced Susceptibility to Ciprofloxacin, Gentamicin, Benzalkonium Chloride, and Other Toxic Compounds

ABSTRACTListeria monocytogenesis a leading agent for severe food-borne illness and death in the United States and other nations. Even though drug resistance has not yet threatened therapeutic interventions for listeriosis, selective pressure associated with exposure to antibiotics and disinfectants may result in reduced susceptibility to these agents. In this study, selection of severalL. monocytogenesstrains on either ciprofloxacin (2 μg/ml) or the quaternary ammonium disinfectant benzalkonium chloride (BC; 10 μg/ml) led to derivatives with increased MICs not only to these agents but also to several other toxic compounds, including gentamicin, the dye ethidium bromide, and the chemotherapeutic drug tetraphenylphosphonium chloride. The spectrum of compounds to which these derivatives exhibited reduced susceptibility was the same regardless of whether they were selected on ciprofloxacin or on BC. Inclusion of strains harboring the large plasmid pLM80 revealed that MICs to ciprofloxacin and gentamicin did not differ between the parental and plasmid-cured strains. However, ciprofloxacin-selected derivatives of pLM80-harboring strains had higher MICs than those derived from the plasmid-cured strains. Susceptibility to the antimicrobials was partially restored in the presence of the potent efflux inhibitor reserpine. Taken together, these data suggest that mutations in efflux systems are responsible for the multidrug resistance phenotype of strains selected on ciprofloxacin or BC.

Optimized Nile Red Efflux Assay of AcrAB-TolC Multidrug Efflux System Shows Competition between Substrates

ABSTRACT AcrAB-TolC is the major constitutively expressed efflux pump system that provides resistance to a variety of antimicrobial agents and dyes in Escherichia coli. However, no systematically optimized real-time dye efflux assay has been published for the measurement of its activity and for detection of possible competition between substrates. Here, we report on the development of such an assay using a lipophilic dye, Nile Red. Energy-depleted cells were loaded with the dye in the presence of low (10 μM or less) concentrations of the proton conductor carbonyl cyanide m-chlorophenylhydrazone (CCCP). The CCCP was then removed, and efflux was triggered by energization with glucose. Various known efflux pump inhibitors and antimicrobials were checked for the ability to slow down Nile Red efflux, presumably through competition. Besides the known inhibitors Phe-Arg-β-naphthylamide and 1-naphthyl-methylpiperazine, several tetracyclic compounds (doxorubicin, minocycline, chlortetracycline, doxycycline, and tetracycline) and tetraphenylphosphonium chloride were found to interfere with dye efflux. This inhibition could not be explained by the depletion of proton motive force. None of the other tested antimicrobials, including macrolides, fluoroquinolones, and β-lactams, had any impact on Nile Red efflux, even at concentrations of up to 1 mM.