Comparative study of azobenzene and stilbene bridged crown ether p-tert-butylcalix[4]arene

Photo-switchable calixarenes consisting of a stilbene or azobenzene bridge, spanning the narrow rim as a switching unit, were synthesized through reductive coupling of o-, m- and p-bis-benzaldehyde and bis-nitrobenzene-substituted calix[4]arenes. Both cis- and trans-stilbenes were produced from the reductive coupling of the o- and m-bis-benzaldehyde with the cis isomer being predominant for both regioisomers, whilst the coupling of p-bis-benzaldehyde gave only cis product. On the other hand, the only isolable product obtained from the reductive coupling of bis-o- and bis-m-nitrobenzene was the corresponding trans-azobenzene and the coupling product from bis-p-nitrobenzene was not stable. Each of the synthesized compounds showed a photostationary state in their cis-trans isomerization. The complexation of alkali metal ions was observed for only the o-azobenzene derivative suggesting that the lone pair of N-atom in the azo bridge participates in this process.     

Mixed-Isotope Labeling with LC-IMS-MS for Characterization of Protein–Protein Interactions by Chemical Cross-Linking

Chemical cross-linking of proteins followed by proteolysis and mass spectrometric analysis of the resulting cross-linked peptides provides powerful insight into the quaternary structure of protein complexes. Mixed-isotope cross-linking (a method for distinguishing intermolecular cross-links) was coupled with liquid chromatography, ion mobility spectrometry and mass spectrometry (LC-IMS-MS) to provide an additional separation dimension to the traditional cross-linking approach. This method produced multiplet m/z peaks that are aligned in the IMS drift time dimension and serve as signatures of intermolecular cross-linked peptides. We developed an informatics tool to use the amino acid sequence information inherent in the multiplet spacing for accurate identification of the cross-linked peptides. Because of the separation of cross-linked and non-cross-linked peptides in drift time, our LC-IMS-MS approach was able to confidently detect more intermolecular cross-linked peptides than LC-MS alone.      

Exploring the performance of small- and medium-sized enterprises through the credit crunch

Small- and medium-sized enterprises (SMEs) are major contributors to most western economies. They are often supported by government policies, and in the UK the government encourages banks to lend to them. It is generally believed that the credit crunch has had an impact on the performance of SMEs. This study looks at the impact of the crunch using large samples from 2007 through to 2010. It looks at performance by region, age and industrial sector (SIC code). It then proceeds to explore the modelling of default over the years, with a focus on young businesses. It was found that there is a degree of stability within the models, though the level of default varies across years. Young businesses, as has been found before, are shown to be more vulnerable.     

The mixing properties of hexafluorobenzene with carbon tetrachloride and with perfluoromethylcyclohexane

Excess thermodynamic functions (free energies, enthalpies and entropies of mixing) have been obtained from measurements of vapour pressures, together with excess volumes of mixing, for mixtures of hexafluorobenzene with carbon tetrachloride and with perfluoromethyl-cyclohexane (tetradecafluoromethylcyclohexane). Deviations from thermodynamic ideality are large, although the systems are completely miscible. Critical temperatures of the mixtures are also reported. A correlation between the data, anticipated from a simple model for mixtures of asymmetric molecules, does not obtain.