Photosynthetic membranes, 21. Immobilization of catalase by photochemically grafted ultrafiltration membranes

Catalase has been immobilized in membranes prepared by photoinduced grafting onto microporous polymeric supports and its catalytic activity on hydrogen peroxide decomposition has been studied under ultrafiltration conditions by means of a recirculation apparatus. The membranes showed a very good catalytic performance and the enzyme reaction took place exclusively within the membrane structure. Initial reaction rates measured in the temperature range 5 – 35°C as a function of both substrate concentration and enzyme amount immobilized per unit membrane surface indicate that the mechanism of action of catalase is not altered after immobilization.     

Thermophiles as Potential Source of Novel Endotoxin Antagonists: the Full Structure and Bioactivity of theLipo‐oligosaccharide from Thermomonas hydrothermalis

Thermomonas hydrothermalis is a Gram‐negative thermophilic bacterium that is able to live at 50 °C. This ability is attributed to chemical modifications, involving those to bacterial cell‐wall components, such as proteins and (glyco)lipids. As the main component of the outer membrane of Gram‐negative bacteria, lipopolysaccharides (LPSs) are exposed to the environment, thus they can undergo structural chemical changes to allow thermophilic bacteria to live at their optimal growth temperature. Furthermore, as one of the major target of the eukaryotic innate immune system, LPS elicits host immune response in a structure‐dependent mode; thus the uncommon chemical features of thermophilic bacterial LPSs might exert a different biological action on the innate immune system—an antagonistic effect, as shown in studies of LPS structure–activity relationship in the ongoing research into antagonist LPS candidates. Here, we report the complete structural and biological activity analysis of the lipo‐oligosaccharide isolated from Thermomonas hydrothermalis, achieved by a multidisciplinary approach (chemical analysis, NMR, MALDI MS and cellular immunology). We demonstrate a tricky and interesting structure combined with a very interesting effect on human innate immunity.     

Hybrid Photopatterned Enzymatic Reaction (HyPER) for in Situ Cell Manipulation

The ability to design artificial extracellular matrices as cell‐instructive scaffolds has opened the door to technologies capable of studying the fate of cells in vitro and to guiding tissue repair in vivo. One main component of the design of artificial extracellular matrices is the incorporation of biochemical cues to guide cell phenotype and multicellular organization. The extracellular matrix (ECM) is composed of a heterogeneous mixture of proteins that present a variety of spatially discrete signals to residing cell populations. In contrast, most engineered ECMs do not mimic this heterogeneity. In recent years, photo‐deprotection has been used to spatially immobilize signals. However, this approach has been limited mostly to small peptides. Here we combine photo‐deprotection with enzymatic reaction to achieve spatially controlled immobilization of active bioactive signals that range from small molecules to large proteins. A peptide substrate for transglutaminase factor XIII (FXIIIa) was caged with a photo‐deprotectable group, which was then immobilized to the bulk of a cell‐compatible hydrogel. With focused light, the substrate can be deprotected and used to immobilize patterned bioactive signals. This approach offers an innovative strategy to immobilize delicate bioactive signals, such as growth factors, without loss of activity and enables in situ cell manipulation of encapsulated cells.     

Bifunctional Squaramide Catalysts with the Same Absolute Chirality for the Diastereodivergent Access to Densely Functionalised Cyclohexanes through Enantioselective Domino Reactions. Synthesis and Mechanistic Studies

We have developed a procedure for the stereoselective and diastereodivergent synthesis of densely functionalised cyclohexanes containing four stereocentres through an asymmetric Michael‐initiated ring closure (MIRC) cascade reaction employing hydrogen‐bond catalysis, which is able to prepare adducts with different absolute configurations starting from the same starting materials. The overall process involves a highly diastereo‐ and enantioselective Michael/Henry cascade reaction between a wide range of nitroalkenes and α‐nitro‐δ‐oxo esters, allowing access to different diastereoisomers of the final adduct by introducing subtle changes in the general (R,R)‐configured bifunctional tertiary amine/squaramide catalyst structure. Moreover, this methodology is also amenable to a three‐component one‐pot procedure, leading to the formation of the same adducts with very good results directly from commercially available reagents, on a multigram scale, and employing a very low catalyst loading. Furthermore, a detailed experimental and computational study is described which shows the origin of the diastereodivergent behaviour of these structurally similar catalysts and the nature of the substrate–catalyst interaction.

     

Experimentation with a water tank including a PCM module

Storage of heat is seen as a major issue for the development of solar energy for house heating and cooling under all climates. Most of the storage systems available on the market use water as the storage medium. The idea studied here was to add a phase change material (PCM) module at the top of a hot-water storage tank with stratification. An experimental solar pilot plant was constructed to test the PCM behaviour in real conditions. The PCM module geometry adopted was to use several cylinders. A granular PCM–graphite compound was chosen as the PCM for the experiments presented here.     

Experimental features affecting the transparency of YAG ceramics

This article focuses on the importance of the ceramic production process for the final transparency and overall optical quality of materials to be used as laser hosts. YAG-based ceramics are prepared starting from commercial powders. The materials are prepared by reactive sintering in a clean atmosphere and under high vacuum. Nd or Yb are selected as active elements as the more appropriate for high energy and high peak power lasers. The powder type and treatment and the solvent removal technique are described in detail as well as the experimental conditions adopted during shaping. The influence of the pre-sintering and sintering cycles on the reaction among the involved oxides and on the microstructure after sintering is shown. The optical characterization is also reported.     

Proportioning of reinforced concrete column sections

Relatively simplistic recommendations are widely available for the preliminary sizing of reinforced concrete columns. A simple, more precise approach is developed herein. The neutral axis depth and reinforcement required to provide a desired resistance to axial load and moment was determined analytically for the common case of symmetrically distributed reinforcement. Readily available solver routines are used to determine section dimensions required to provide the desired axial and flexural strength, for a desired reinforcement ratio. The approach is illustrated for two examples, including a case in which independent load combinations cause bending about each principal axis of the section.     

Effect of ripening stage of grapes on the low molecular weight phenolic compounds of red wines

Different red wines were elaborated to study the effect of the date of the grape harvest on the levels of individual low molecular weight phenolic compounds, which are chiefly responsible for the wine color. Two red grape varieties and two consecutive years were studied at three different harvesting stages of grapes, and the changes during the 18 months of wine aging (12 months in oak barrels and 6 months in the bottle) were also followed. The results showed that the wines made from grapes harvested 1 week later than the usual date generally had higher contents of some simple phenols, which can act as cofactors that can maintain the color intensity and violet tonalities in aged wines. Besides, these wines had lower levels of caftaric and coutaric acids, which are two of the main substrates for oxidation and browning processes.     

Preparation and Characterization of NTC Thermistors: Nickel Manganites Doped with Lithium

Oxides of the form Ni_xMn_3-x O₄ present properties that make them useful as NTC thermistors. Nickel manganites doped with lithium were synthesized by two methods: insertion with n -BuLi and reaction of nickel-manganese formates with lithium formate. XPS and XRD studies showed that both procedures led to oxides with spinel structure, although with different cation distributions. Dilatometry established that a cationic reordering took place on manganites doped by insertion with n -BuLi during sintering. SEM mapping studies showed that a segregation on grain boundaries took place, leading to an increase in Mn content and a decrease in nickel on the particle surface. Finally, electrical studies showed the nickel manganites doped with lithium, Ni_xMn_3-x-yLi_yO₄, had similar resistivities and sensitivity indexes to nickel manganites, Ni_xMn_3-xO₄, but higher electrical stability.     

Solid phase microextraction (SPME) applied to honey quality control

The assessment of the botanical origin of unifloral honeys is an important application in food control. The current official methods mainly use pollen analysis. The aim of this paper is to present an SPME analytical approach to the study of honey volatiles. Honey samples (40) obtained from hive sites in different regions of Italy were analysed. The samples had six different botanical origins: citrus (five), chestnut (10), eucalyptus (eight), lime tree (11), thyme (two) and dandelion (four). Melissopalynological analysis was also performed. Identification of volatile compounds was carried out by SPME/GC/MS analysis, and quantitative evaluation was done by SPME/GC/FID analysis for compounds with well‐resolved peaks. Using the SPME method, all samples with the same botanical origin gave remarkably similar GC profiles. Some volatile compounds were found only in specific floral source honey samples and thus could be interesting for use as markers. Copyright © 2003 Society of Chemical Industry