Biosynthesis of conjugatable saccharidic moieties of GM2 and GM3 gangliosides by engineered E. coli

Oligosaccharidic moieties of GM(2) and GM(3) gangliosides bearing an allyl or a propargyl aglycon, are efficiently biosynthesized on the gram scale by growing metabolically engineered Escherichia coli cells in the presence of the corresponding lactoside acceptors and sialic acid.     

Non-invasive vibrational SFG spectroscopy reveals that bacterial adhesion can alter the conformation of grafted "brush" chains on SAM

Understanding bacterial adhesion on a surface is a crucial step to design new materials with improved properties or to control biofilm formation and eradication. Sum Frequency Generation (SFG) vibrational spectroscopy has been employed to study in situ the conformational response of a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film to the adhesion of hydrophilic and hydrophobic ovococcoid model bacteria. The present work highlights vibrational SFG spectroscopy as a powerful and unique non-invasive biophysical technique to probe and control bacteria interaction with ordered surfaces. Indeed, the SFG vibrational spectral changes reveal different ODT SAM conformations in air and upon exposure to aqueous solution or bacterial adhesion. Furthermore, this effect depends on the bacterial cell surface properties. The SFG spectral modeling demonstrates that hydrophobic bacteria flatten the ODT SAM alkyl chain terminal part, whereas the hydrophilic ones raise this ODT SAM terminal part. Microorganism-induced alteration of grafted chains can thus affect the desired interfacial functionality, a result that should be considered for the design of new reactive materials.     

Toward Metathesis Reactions on Vinylphosphaalkenes

Abstract

Attempts to utilize C-ethylenic phosphaalkenes in metathesis reactions are discussed. Unprecedented reactivity is observed where the vinylphosphaalkene undergoes the first step of the catalytic cycle and cross-metathesis with the phenylmethylene moiety of Grubbs 2nd generation catalyst. However, homo-metathesis reaction to form 1,6-diphosphahexa-1,3,5-triene is not observed, presumably due to steric constraints.     

Stereoselective Control by Face‐to‐Face Versus Edge‐to‐Face Aromatic Interactions: The Case of C3‐TiIV Amino Trialkolate Sulfoxidation Catalysts

The stereoselective oxidation of differently functionalised benzyl phenyl sulfides has been examined by using enantiopure Ti^IV trialkanolamine complexes. These complexes efficiently catalyse the sulfoxidation with good stereoselectivities. The data highlight the contribution to the stereoselectivity of steric effects and non‐covalent π–π interactions between the aromatic rings of the Ti^IV complex and those pertaining to the substrates. Enantiomeric excesses have been correlated with the electrostatic potential surfaces (EPS) of the reacting sulfides. The overall study leads to a mechanistic interpretation that explains the stereoselectivity of the system and dissects the role of aromatic and steric interactions in the stereoselective process.     

Specific fibre composition and metabolism of the <Emphasis Type=Italic>rectus abdominis</Emphasis> muscle of bovine Charolais cattle

Background  

An important variability of contractile and metabolic properties between muscles has been highlighted. In the literature, the majority of studies on beef sensorial quality concerns M. longissimus thoracis. M. rectus abdominis (RA) is easy to sample without huge carcass depreciation and may appear as an alternative to M. longissimus thoracis for fast and routine physicochemical analysis. It was considered interesting to assess the muscle fibres of M. rectus abdominis in comparison with M. longissimus thoracis (LT) and M. triceps brachii (TB) on the basis of metabolic and contractile properties, area and myosin heavy chain isoforms (MyHC) proportions. Immuno-histochemical, histochemical, histological and enzymological techniques were used. This research concerned two populations of Charolais cattle: RA was compared to TB in a population of 19 steers while RA was compared to LT in a population of 153 heifers.     

Enzyme electrode for glucose determination in whole blood

The development of a glucose sensor suitable for use with whole blood is described. It is based on anodic oxidation at +700 mV of hydrogen peroxide with a platinum electrode covered with a gas permeable membrane. Glucose reacts with glucose oxidase immobilised on the external side of the membrane, and forms hydrogen peroxide which is able to cross the gas permeable membrane due to its high vapour tension, while other electroactive substances that are important interferents are completely blocked. This principle was discovered several years ago but no practical application was presented up to now. Therefore in this work a number of different commercial membranes were tested, in order to obtain a resistant, rapidly responding and interference free sensor to be used in conjunction with a blood gas measurement apparatus. Coimmobilisation of glucose oxidase and catalase was found to be useful for fast response and recovery of the electrode. Using some of the tested membranes, the linearity range is 1-15 mM, CV 5%, response time 90 s, recovery time for the next sample 120 s. The membrane's working life is 2-3 weeks.     

Improving anharmonic infrared spectra using semiclassically prepared molecular dynamics simulations

Classical molecular dynamics is a convenient method for computing anharmonic infrared spectra of polyatomic molecules and condensed phase systems. However it does not perform well for predicting accurate intensities and it lacks nuclear quantization, two deficiencies that are usually accounted for by empirical scaling factors. In this paper we show on the examples of the trans isomer of nitrous acid and naphthalene that both issues can be alleviated by preparing the initial conditions according to semiclassical quantization based on a normal mode representation. The method correctly reproduces fundamental frequencies obtained with quantum mechanical methods. At increasing temperatures, the effective frequencies are found to follow the same trends as path-integral based methods. In the low-temperature limit, the band intensities predicted by the method are also found to agree with quantum mechanical considerations.