Effect of counterion structure on rates and diastereoselectivities in α,β-unsaturated iminium-ion Diels-Alder reactions

The use of cyclic α,β-unsaturated iminium-ion dienophiles is documented in two highly diastereoselective Diels-Alder (DA) reactions. The dienophilic counterion was found to have a significant effect on reactivity.     

Observations of shear adhesive force and friction of Blatta orientalis on different surfaces

The shear adhesive force of four non-climbing cockroaches (Blatta orientalis Linnaeus, 1758) was investigated by the use of a centrifugal machine, evaluating the shear safety factor (adhesion force divided by body weight) on six surfaces (steel, aluminium, copper, two sandpapers and a common paper sheet) having different roughness. The adhesive system of Blatta orientalis was characterized by means of a field emission scanning electron microscope and the surface roughness was determined by an atomic force microscope. The cockroach maximum shear safety factor, or apparent friction coefficient, is determined to be 12.1 on the less rough of the two sandpapers, while its minimum value is equal to 1.9 on the steel surface. A two-sample Student t analysis has been conducted in order to evaluate the significance of the differences among the obtained shear safety factors due to both roughness and chemistry. An interesting correlation between cockroach shear adhesion and surface roughness emerges with a threshold mechanism dictated by the competition between claw tip radius and roughness, indicating that the best adhesion is obtained for roughness larger than the claw tip radius.     

Toward the development of a general chiral auxiliary. Enantioselective alkylation and a new catalytic asymmetric addition of silyloxyfurans: application to a total synthesis of (-)-rasfonin

An enantioselective total synthesis of the apoptosis-inducing natural product, (-)-rasfonin, is described. Camphor lactam-mediated asymmetric alkylation reactions enabled the installation of three stereogenic centers with >95:5 diastereoselectivity. A modified Corey-Peterson olefination was employed in the construction of the (E,E)-diene system. A highly diastereoselective, asymmetric vinylogous Mukaiyama aldol addition was conducted using a chiral cationic oxazaborolidine catalyst. The pyranone core of the natural product was prepared via a DBU-promoted rearrangement of a furanol to its corresponding pyranol with concomitant [1,4]-silyl transfer.     

Size dependence of protein diffusion very close to membrane surfaces: measurement by total internal reflection with fluorescence correlation spectroscopy

The diffusion coefficients of nine fluorescently labeled antibodies, antibody fragments, and antibody complexes have been measured in solution very close to supported planar membranes by using total internal reflection with fluorescence correlation spectroscopy (TIR-FCS). The hydrodynamic radii (3-24 nm) of the nine antibody types were determined by comparing literature values with bulk diffusion coefficients measured by spot FCS. The diffusion coefficients very near membranes decreased significantly with molecular size, and the size dependence was greater than that predicted to occur in bulk solution. The observation that membrane surfaces slow the local diffusion coefficient of proteins in a size-dependent manner suggests that the primary effect is hydrodynamic as predicted for simple spheres diffusing close to planar walls. The TIR-FCS data are consistent with predictions derived from hydrodynamic theory. This work illustrates one factor that could contribute to previously observed nonideal ligand-receptor kinetics at model and natural cell membranes.     

Effects of lipopolysaccharide-induced inflammation on expression of growth-associated genes by corticospinal neurons

Background  

Inflammation around cell bodies of primary sensory neurons and retinal ganglion cells enhances expression of neuronal growth-associated genes and stimulates axonal regeneration. We have asked if inflammation would have similar effects on corticospinal neurons, which normally show little response to spinal cord injury. Lipopolysaccharide (LPS) was applied onto the pial surface of the motor cortex of adult rats with or without concomitant injury of the corticospinal tract at C4. Inflammation around corticospinal tract cell bodies in the motor cortex was assessed by immunohistochemistry for OX42 (a microglia and macrophage marker). Expression of growth-associated genes c-jun, ATF3, SCG10 and GAP-43 was investigated by immunohistochemistry or in situ hybridisation.     

Stability and Rheological Properties of Model Low-Fat Salad Dressing Stabilized by Salep

A model low-fat salad dressing including salep as thickening agent was prepared. In order to obtain an stable salad dressing, different variables each one at three levels like salep content (0.5, 2.0, and 3.5% w/w), oil volume fraction (7.50, 16.25, and 25.00% w/w), pH (3, 5, and 7), salt concentration (0.3, 0.9, and 1.5% w/w), and egg yolk content (2, 4, and 6% w/w) were chosen and their effect on the creaming index of salad dressing was studied. It was observed that samples with highest salep content at pH 3 were the most stable during storage time (15 days). The microstructure of some samples was considered. Rheological measurements were performed for stable samples. Oil fraction and salt content increased zero shear viscosity and G′ modulus of samples.      

Correlation between the bath composition and nanoporosity of DC-electrodeposited Ni-Fe alloy

The outstanding mechanical strength of as-deposited DC-electrodeposited nanocrystalline (nc) Ni-Fe alloys has been the subject of numerous researches in view of their scientific and practical interest. However, recent studies have reported a dramatic drop in ductility upon annealing above 350°C, associated with a concomitant abnormal rapid grain growth. The inherent cause has been ascribed to the presence of a detrimental product or by product in the bath, which affects either the microstructure or causes defects in the concentration and/or distribution of the as-deposited films. The present work has been inspired by the observed abnormal behaviour of annealed electrodeposited nc Ni-Fe alloy, which has here been addressed by considering the relationship between the composition of the bath (iron-chloride, nickel-sulphate solution, saccharin and ascorbic acid) and deposition defects (e.g. grain boundary pores) in the case of an nc Ni-Fe (Fe 48 wt%) alloy. The current investigations have included X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) in both as-deposited and post-annealed conditions (300°C–400°C). XPS depth profiling with Ar ion sputtering showed a significant amount of C and O impurities entrapped in the foils during deposition. As such impurities are often overlooked in common analytical techniques, new scenarios may need to be rationalised to explain the observed drop in tensile ductility of the as-deposited Ni-Fe alloys.