Little green molecules.
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ABSTRACT: To determine the effectiveness of tert-butyl hydroperoxide (tBHP) plus the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) and a tetra-amido macrocyclic ligand (TAML) activator in killing spores of Bacillus subtilis and the mechanisms of spore resistance to and killing by this reagent. Killing of spores of B. subtilis by tBHP was greatly stimulated by the optimum ratio of concentrations of a TAML activator (1.7 micromol l(-1)) to tBHP (4.4%, vol/vol) plus a low level (270 mg l(-1)) of CTAB. Rates of killing of spores lacking most DNA protective alpha/beta-type small, acid-soluble spore proteins (alpha(-)beta(-) spores) or the major DNA repair protein, RecA, by tBHP plus CTAB and a TAML activator were essentially identical to that of wild-type spore killing. Survivors of wild-type and alpha(-)beta(-) spores treated with tBHP plus CTAB and a TAML activator also exhibited no increase in mutations. Spores lacking much coat protein either because of mutation or chemical decoating were much more sensitive to this reagent than were wild-type spores, but were more resistant than growing cells. Wild-type spores killed with this reagent retained their large pool of dipicolinic acid (DPA), and the survivors of spores treated with this reagent were sensitized to wet heat. The tBHP plus CTAB and TAML activator-killed spores germinated with nutrients, albeit more slowly than untreated spores, but germinated faster than untreated spores with dodecylamine. The killed spores were also germinated by application of 150 and 500 megaPascals of pressure for 15 min and by lysozyme treatment in hypertonic medium, but these spores lysed shortly after their germination. The combination of tBHP plus CTAB and a TAML activator is effective in killing B. subtilis spores. The spore coat is a major factor in spore resistance to this reagent system, which does not kill spores by DNA damage or by inactivating some component needed for spore germination. Rather, this reagent system appears to kill spores by damaging the spore's inner membrane in some fashion. This work demonstrates that tBHP plus CTAB and a TAML activator is an effective and mild decontaminant for spores of Bacillus species. Evidence has also been obtained on the mechanisms of spore resistance to and killing by this reagent system.Journal of Applied Microbiology 05/2007; 102(4):954-62. DOI:10.1111/j.1365-2672.2006.03162.x · 2.39 Impact Factor
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ABSTRACT: Zr-doped titania of anatase structure type has been prepared by a combined sol–gel and chemical vapour deposition (CVD) process. The material has been characterized by XRD, TEM and chemical analysis. The photocatalytic performance has been investigated in the oxidative decomposition of the pharmaceutical ibuprofen (IBP) down to low ppm concentrations. The change of the composition of the reaction solution after photocatalytic treatment was followed by UV–Vis spectroscopy and GC/MS. Formation of reaction intermediates was studied by HPLC coupled electrospray ionization time-of-flight mass spectrometry ESI-TOF-MS. The catalytic performance has been studied by varying the catalyst and substrate concentration as well as changing the catalyst-to-substrate ratio. The influence of pH, adsorption and re-use of the catalyst has been tested. The results confirm the high catalytic activity of Zr-doped titania compared to pure titania at low catalyst loading. The material shows the improved textural mesoporosity. However, more reaction intermediates were formed, leading to faster deactivation of the photocatalyst. ESI-TOF-MS measurements point to the formation of a couple of reaction intermediates, which poison the catalyst.Journal of Photochemistry and Photobiology A Chemistry 01/2014; 274:108–116. DOI:10.1016/j.jphotochem.2013.08.018 · 2.29 Impact Factor
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ABSTRACT: Reacting rationally: During the 1e oxidation of ferrocyanide by the catalytic TAML activator/H(2) O(2) , four Fe(IV) tetra-amido macrocyclic ligand (TAML) intermediates were detected that are involved in a fast acid-base equilibrium. The counterintuitive reactivity pattern is explained by the overall free-energy change during the reduction of Fe(IV) to Fe(III) TAML complexes, with competing contributions from electronic- and solvation energy changes.Chemistry - A European Journal 08/2012; 18(33):10244-9. DOI:10.1002/chem.201201665 · 5.70 Impact Factor