Light-Activated Rhenium Complexes with Dual Mode of Action against Bacteria

New antibiotics and innovative approaches to kill drug-resistant bacteria are urgently needed. Metal complexes offer access to alternative modes of action but have only sparingly been investigated in antibacterial drug discovery. We have developed a light-activated rhenium complex with activity against drug-resistant S. aureus and E. coli. The activity profile against mutant strains combined with assessments of cellular uptake and synergy suggest two distinct modes of action.     

Controlling Gas Selectivity in Molecular Porous Liquids by Tuning the Cage Window Size

Control of pore window size is the standard approach for tuning gas selectivity in porous solids. Here, we present the first example where this is translated into a molecular porous liquid formed from organic cage molecules. Reduction of the cage window size by chemical synthesis switches the selectivity from Xe‐selective to CH₄‐selective, which is understood using ¹²⁹Xe, ¹H, and pulsed‐field gradient NMR spectroscopy.     

Absolute structure determination using CRYSTALS

A study of post‐refinement absolute structure determination using previously published data was carried out using the CRYSTALS software package. We show that absolute structure determination may be carried out optimally using the analyses available in CRYSTALS, and that it is not necessary to have the separate procedures absolute structure determination and no interest in absolute structure as proposed by Flack [Chimia (2014), 68 , 26–30].     

Reconstructing bulk isotope ratios from compound‐specific isotope ratios

Carbon isotope analysis by bulk elemental analysis coupled with isotope ratio mass spectrometry has been the mainstay of δ¹³C analyses both at natural abundance and in tracer studies. More recently, compound‐specific isotope analysis (CSIA) has become established, whereby organic constituents are separated online by gas or liquid chromatography before oxidation and analysis of CO₂ for constituent δ¹³C. Theoretically, there should be concordance between bulk δ¹³C measurements and carbon‐weighted δ¹³C measurements of carbon‐containing constituents. To test the concordance between the bulk and CSIA, fish oil was chosen because the majority of carbon in fish oil is in the triacylglycerol form and ～95% of this carbon is amenable to CSIA in the form of fatty acids. Bulk isotope analysis was carried out on aliquots of oil extracted from 55 fish samples and δ¹³C values were obtained. Free fatty acids (FFAs) were produced from the oil samples by saponification and derivatised to fatty acid methyl esters (FAMEs) for CSIA by gas chromatography/combustion/isotope ratio mass spectrometry. A known amount of an internal standard (C15:0 FAME) was added to allow analyte quantitation. This internal standard was also isotopically calibrated in both its FFA (δ¹³C = ?34.30‰) and FAME (δ¹³C = ?34.94‰) form. This allowed reporting of FFA δ¹³C from measured FAME δ¹³C values. The bulk δ¹³C was reconstructed from CSIA data based on each FFA δ¹³C and the relative amount of CO₂ produced by each analyte. The measured bulk mean δ¹³C (SD) was ?23.75‰ (1.57‰) compared with the reconstructed bulk mean δ¹³C of ?23.76 (1.44‰) from CSIA and was not significantly different. Further analysis of the data by the Bland‐Altman method did not show particular bias in the data relative to the magnitude of the measurement. Good agreement between the methods was observed with the mean difference between methods (range) of 0.01‰ (?1.50 to 1.30). Copyright © 2010 John Wiley & Sons, Ltd.     

Non-Uniformity and Generalised Sacks Splitting

We show that there do not exist computable functions f ₁(e, i), f ₂(e, i), g ₁(e, i), g ₂(e, i) such that for all e, i ∈ ω, (1) $ {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)} \leqslant _{{\rm T}} {\left( {W_{e} - W_{i} } \right)}; $ (2) $ {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)} \leqslant _{{\rm T}} {\left( {W_{e} - W_{i} } \right)}; $ (3) $ {\left( {W_{e} - W_{i} } \right)} \not\leqslant _{{\rm T}} {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)} \oplus {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)}; $ (4) $ {\left( {W_{e} - W_{i} } \right)} \not\leqslant _{{\rm T}} {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)}{\text{unless}}{\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\emptyset};{\text{and}} $ (5) $ {\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)}{\text{unless}}{\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\emptyset}. $ It follows that the splitting theorems of Sacks and Cooper cannot be combined uniformly.     

Co-adsorption of surfactants and water at inorganic solid surfaces

Computer simulations of the co-adsorption of water and methanoic acid at a range of surface features of calcite and fluorite minerals have shown that the relative adsorption energies for the two minerals are reversed when solvent effects are included in the calculations, a finding which is important in the search for effective surfactant reagents in flotation techniques, which are used extensively in the mining and pharmaceutical industries and in environmental remediation processes.     

Controlling chemoselectivity in vinyl and allylic C-X bond activation with palladium catalysis: a pK(a)-based electronic switch

It has been demonstrated that the same Pd catalyst can be used to effect allylic substitution or vinylic cross-coupling reactions selectively and interchangeably on polyfunctionalized olefin building blocks despite the differences in reaction mechanism. This was achieved by altering the pK(a) of the conjugate acid of the allylic leaving group while keeping the vinyl coupling partner constant. In the case of 2,3-dibromo-1-propene, Pd-catalyzed allylic ionization with malonate nucleophile proceeded selectively and quantitatively in the presence of the Suzuki reaction components necessary for cross-coupling. Conversely, the bromide of 2-bromo-1-(4-ethylphenoxy)-2-propene could be cross-coupled selectively without activation of the allylic phenoxy substituent. In both reactions, the same catalyst could then be used to complete the sequence, which typically involved heating as the trigger to promote the second, more reluctant reaction. Mechanistic considerations as well as synthetic applications demonstrating the value of this interchangeable catalyzed sequence are presented.