Synthesis of chiral 3,4,5,6-tetrahydro-1,4-thiazin-2-ones (thiamorpholin-2-ones)-novel heterocycles possessing enhanced carbonyl electrophilicity over their oxygen counterparts

We report herein the first synthesis of chiral derivatives possessing the 1,4-thiazinone core. As predicted, the thiolactone is more susceptible to nucleophilic attack than the equivalent lactone system.

Poly(ethylene glycol)-supported nitroxyls: branched catalysts for the selective oxidation of alcohols

Nitroxyl radicals such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) are highly selective oxidation catalysts for the conversion of primary alcohols into the corresponding aldehydes. In this study, direct tethering of TEMPO units onto linear poly(ethylene glycol) (PEG) has afforded macromolecular catalysts that exhibit solubility in both aqueous and organic solvents. Recovery of the dissolved polymer-supported catalyst has been carried out by precipitation with a suitable solvent such as diethyl ether. The high catalyst activities and selectivities associated traditionally with nitroxyl-mediated oxidations of alcohols are retained by the series of "linker-less" linear PEG-TEMPO catalysts in which the TEMPO moiety is coupled directly to the PEG support. Although the selectivity remains unaltered, upon recycling of the linker-less polymer-supported catalysts, extended reaction times are required to maintain high yields of the desired carbonyl compounds. Alternatively, attachment of two nitroxyl radicals onto each functionalized PEG chain terminus via a 5-hydroxyisophthalic acid linker affords branched polymer-supported catalysts. In stark contrast to the linker-less catalysts, these branched nitroxyls exhibit catalytic activities up to five times greater than 4-methoxy-TEMPO alone under similar conditions. In addition, minimal decrease in catalytic activity is observed upon recycling of these branched macromolecular catalysts via solvent-induced precipitation. The high catalytic activities and preservation of activity upon recycling of these branched systems is attributed to enhanced regeneration of the nitroxyl species as a result of intramolecular syn-proportionation.

Synergetic effects of the Cu/Pt{110} surface alloy: enhanced reactivity of water and carbon monoxide

We have used synchrotron-based high-resolution X-ray photoelectron spectroscopy in combination with ab initio density functional theory calculations to investigate the characteristics of water and CO adsorption on the bimetallic Cu/Pt{110}-(2 x 1) surface at a Cu coverage near 0.5 ML. Cu fills the troughs of the reconstructed clean surface forming nanowires, which are stable up to 830 K. Their presence dramatically influences the adsorption of water and CO. Water adsorption changes from intact to partially dissociated while the desorption temperature of CO on this surface increases by up to 27 K with respect to the clean Pt{110} surface. Ab initio calculations and experimental valence band spectra reveal that the Cu 3d-band is narrowed and shifted upward with respect to bulk Cu surfaces. This and electron donation to surface Pt atoms cause the increase in the bond strength between CO and the Pt surface atoms. The pathway for water dissociation occurs via Cu surface atoms. The heat of adsorption of water bonding to Cu surface atoms was calculated to be 0.82 eV, which is significantly higher than on the clean Pt{110} surface; the activation energy for partial dissociation is 0.53 eV (not corrected for zero point energy).

A low-temperature ammonium ylid rearrangement: enhanced reactivity engendered by rigidity

Sigmatropic rearrangement of tetrahydropyridine-derived ammonium is a valuable method for the preparation of substituted prolines. These reaction normally require elevated temperatures to proceed, but bicyclic tetrahydropyridine-like ylid I undergoes rearrangement at -15 degrees C; the extra rigidity of the azabicyclo[3.3.0]octene system preorganizes the transition state and lowers the activation energy for rearrangement.

Monodisperse binary nanocomposite in silica with enhanced magnetization for magnetic separation

The majority of research on magnetic nanoparticles has focused on optical, electrical, and magnetic storage areas. Recently, the application of magnetic nanoparticles as magnetically separable nanovehicles for chemical or biological species has become an area of intensive research but with rather different challenging criteria that are yet to be addressed. For example, the enhancement of intrinsically weak magnetic properties, avoidance of magnetic interactions among particles, and improvement of the stability of the nanoparticles remain key issues. Here, it is demonstrated using sequential nanochemistry preparation techniques that exchange-coupled nanomagnets, such as FePt-Fe3Pt or FePt-Fe3O4 with dramatically enhanced magnetization, can be placed inside a silica nanosphere. The advantages of enhanced magnetization and the provision of protective coating and anchored sites on the silica shell surface render these new coated particles suitable for use in magnetic separation.

Web services enhanced interoperable construction products catalogue

This paper presents a new approach to achieving interoperability between Web-based construction products catalogues. It first introduces the current development of electronic catalogues of construction products. The common system architecture of Web-based electronic products catalogues is discussed, which is followed by a discussion on construction products information standardization and the latest distributed-systems technologies for the communication and exchange of construction products information. The latter part of this paper presents a model of interoperable Web-based construction products catalogue and an implementation of Web services in E-commerce systems to enable the sharing of construction products information.

Recovery of gallic acid with colloidal gas aphrons (CGA)

In the present paper the potential application of colloidal gas aphrons (CGA) to the recovery of antioxidants from wine-making waste extracts is investigated. CGA were generated by stirring a buffered solution (400 ml) of a cationic surfactant(cetyltrimethylammonium bromide, CTAB) at 8000 rpm for 10 minutes. Trials were carried out on standard solutions (2 ml) of gallic acid (GA) 200 mg/l with varying volumes of colloidal gas aphrons (20-60 ml) generated with varying concentrations of CTAB (2 and 4 mM). Influence of pH, solvent (buffered aqueous solution and ethanol), CTAB to GA molar ratio on recovery were studied. Best recovery (63%) was achieved from an aqueous solution of GA and at a CTAB to GA molar ratio of 16. Separation is mainly driven by electrostatic interactions but pH conditions are to be optimised to preserve the GA antioxidant power.

Mechanisms of probiosis and prebiosis: considerations for enhanced functional foods

The technologies of metagenomics and metabolomics are broadening our knowledge of the roles the human gut microbiota play in health and disease. For many years now, probiotics and prebiotics have been included in foods for their health benefits; however, we have only recently begun to understand their modes of action. This review highlights recent advances in deciphering the mechanisms of probiosis and prebiosis, and describes how this knowledge could be transferred to select for enhancing functional foods targeting different populations. A special focus will be given to the addition of prebiotics and probiotics in functional foods for infants and seniors.

Effects of enhanced consumption of fruit and vegetables on plasma antioxidant status and oxidative resistance of LDL in smokers supplemented with fish oil

Objective: To determine whether consumption of five portions of fruit and vegetables per day reduces the enhancement of oxidative stress induced by consumption of fish oil. Subjects: A total of 18 free-living healthy smoking volunteers, aged 18-63 y, were recruited by posters and e-mail in The University of Reading, and by leaflets in local shops. Design: A prospective study. Setting: Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, Whiteknights PO Box 226, Reading RG6 6AP, UK. Intervention: All subjects consumed a daily supplement of 4 x 1 g fish oil capsules for 9 weeks. After 3 weeks, they consumed an additional five portions of fruits and vegetables per day, and then they returned to their normal diet for the last 3 weeks of the study. Fasting blood samples were taken at the ends of weeks 0, 3, 6 and 9. Results: The plasma concentrations of ascorbic acid, lutein, beta-cryptoxanthin, alpha-carotene and beta-carotene all significantly increased when fruit and vegetable intake was enhanced (P<0.05). Plasma concentrations of α-tocopherol, retinol and uric acid did not change significantly during the period of increased fruit and vegetable consumption. Plasma oxidative stability, assessed by the oxygen radical absorbance capacity (ORAC) assay, also increased from weeks 3-6 (P<0.001) but not in association with increases in measured antioxidants. Lag phase before oxidation of low-density lipoprotein (LDL) significantly decreased in the first 3 weeks of the study, reflecting the incorporation of EPA and DHA into LDL (P<0.0001). Subsequent enhanced fruit and vegetable consumption significantly reduced the susceptibility of LDL to oxidation (P<0.005). Conclusion: Fish oil reduced the oxidative stability of plasma and LDL, but the effects were partially offset by the increased consumption of fruit and vegetables.

Recovery and purification of surfactin from fermentation broth by a two-step ultrafiltration process

Surfactin is a bacterial lipopeptide produced by Bacillus subtilis and it is a powerful surfactant, having also antiviral, antibacterial and antitumor properties. The recovery and purification of surfactin from complex fermentation broths is a major obstacle to its commercialization; therefore, two-step membrane filtration processes were evaluated using centrifugal and stirred cell devices while the mechanisms of separation were investigated by particle size and surface charge measurements. In a first step of ultrafiltration (UF-1), surfactin was retained effectively by membranes at above its critical micelle concentration (CMC); subsequently in UF-2, the retentate micelles were disrupted by addition of 50% (v/v) methanol solution to allow recovery of surfactin in the permeate. Main protein contaminants were effective]), retained by the membrane in UF-2. Ultrafiltration was carried out either using centrifugal devices with 30 and 10 kDa MWCO regenerated cellulose membranes, or a stirred cell device with 10 kDa MWCO polyethersulfone (PES) and regenerated cellulose (RC) membranes. Total rejection of surfactin was consistently observed in UF-1, while in UF-2 PES membranes had the lowest rejection coefficient of 0.08 +/- 0.04. It was found that disruption of surfactin micelles, aggregation of protein contaminants and electrostatic interactions in UF-2 can further improve the selectivity of the membrane based purification technique. (C) 2007 Elsevier B.V. All rights reserved.

Recovery of lactoferrin and lactoperoxidase from sweet whey using colloidal gas aphrons (CGAs) generated from an anionic surfactant, AOT

The recovery of lactoferrin and lactoperoxidase from sweet whey was studied using colloidal gas aphrons (CGAs), which are surfactant-stabilized microbubbles (10-100 mum). CGAs are generated by intense stirring (8000 rpm for 10 min) of the anionic surfactant AOT (sodium bis-2-ethylhexyl sulfosuccinate). A volume of CGAs (10-30 mL) is mixed with a given volume of whey (1 - 10 mL), and the mixture is allowed to separate into two phases: the aphron (top) phase and the liquid (bottom) phase. Each of the phases is analyzed by SDS-PAGE and surfactant colorimetric assay. A statistical experimental design has been developed to assess the effect of different process parameters including pH, ionic strength, the concentration of surfactant in the CGAs generating solution, the volume of CGAs and the volume of whey on separation efficiency. As expected pH, ionic strength and the volume of whey (i.e. the amount of total protein in the starting material) are the main factors influencing the partitioning of the Lf(.)Lp fraction into the aphron phase. Moreover, it has been demonstrated that best separation performance was achieved at pH = 4 and ionic strength = 0.1 mol/L i.e., with conditions favoring electrostatic interactions between target proteins and CGAs (recovery was 90% and the concentration of lactoferrin and lactoperoxidase in the aphron phase was 25 times higher than that in the liquid phase), whereas conditions favoring hydrophobic interactions (pH close to pI and high ionic strength) led to lower performance. However, under these conditions, as confirmed by zeta potential measurements, the adsorption of both target proteins and contaminant proteins is favored. Thus, low selectivity is achieved at all of the studied conditions. These results confirm the initial hypothesis that CGAs act as ion exchangers and that the selectivity of the process can be manipulated by changing main operating parameters such as type of surfactant, pH and ionic strength.

Recovery of astaxanthin using colloidal gas aphrons (CGA): a mechanistic study

The aim of this study is to investigate the mechanism responsible for the recovery of astaxanthin using Colloidal Gas Aphrons (CGA), which are surfactant stabilised microbubbles. The latter were produced using different surfactant solutions (Cetyl Trimethyl Ammonium Bromide (CTAB)-cationic, Sodium Dodecyl Sulfate (SDS)-anionic, TWEEN 60-non-ionic and mixtures of TWEEN 60-SPAN 80- non-ionic with varying hydrophobicity) at stirring speed 8000 rpm and stirring time 5 min. Experiments were carried out at varying pH and volumetric ratios of astaxanthin to CGA, and with two different astaxanthin standard suspensions: (i) astaxanthin dispersed in aqueous solutions and (ii) astaxanthin dispersed in ethanolic/aqueous solutions with different compositions of ethanol (20/80 (v/v) and 40/60 (v/v)). When astaxanthin is dispersed in aqueous solutions the separation seems to occur mainly by electrostatic interactions. Therefore the recoveries are higher in the case of the cationic surfactant when astaxanthin particles are strongly negatively charged, as shown by the zeta potential measurements. When ethanol is present, highest recoveries are achieved with CGA produced from the non-ionic surfactant, which indicates that, under these conditions, separation is driven mainly by hydrophobic interactions. In experiments with ethanolic/aqueous suspensions, when the hydrophobicity of the surfactant was increased by increasing volumes of SPAN 80, the CGA produced were less stable; thus higher recoveries of astaxanthin under conditions that favour hydrophobic interactions were not observed. (C) 2008 Elsevier B.V All rights reserved.

The use of colloidal gas aphrons as novel downstream processing for the recovery of astaxanthin from cells of Phaffia rhodozyma

BACKGROUND: There is an increasing interest in obtaining natural products with bioactive properties, using fermentation technology. However, the downstream processing consisting of multiple steps can be complicated, leading to increase in the final cost of the product. Therefore there is a need for integrated, cost-effective and scalable separation processes. RESULTS: The present study investigates the use of colloidal gas aphrons (CGA), which are surfactant-stabilized microbubbles, as a novel method for downstream processing. More particularly, their application for the recovery of astaxanthin from the cells of Phaffia rhodozyma is explored. Research carried out with standard solutions of astaxanthin and CGA generated from the cationic surfactant hexadecyl. trimethyl ammonium bromide (CTAB) showed that up to 90% recovery can be achieved under optimum conditions, i.e., pH 11 with NaOH 0.2 mol L-1. In the case of the cells' suspension from the fermentation broth, three different approaches were investigated: (a) the conventional integrated approach where CGA were applied directly; (b) CGA were applied to the clarified suspension of cells; and finally (c) the in situ approach, where CGA are generated within the clarified suspension of cells. Interestingly, in the case of the whole suspension (approach a) highest recoveries (78%) were achieved under the same conditions found to be optimal for the standard solutions. In addition, up to 97% recovery of total carotenoids could be achieved from the clarified suspension after pretreatment with NaOH. This pretreatment led to maximum cell disruption as well as optimum conditioning for subsequent CGA separation. CONCLUSIONS: These results demonstrate the potential of CGA for the recovery of bioactive components from complex feedstock. (c) 2008 Society of Chemical Industry.

Recovery of norbixin from a raw extraction solution of annatto pigments using colloidal gas aphrons (CGAs)

Annatto dyes are widely used in food and are finding increasing interest also for their application in the pharmaceutical and cosmetics industry. Bixin is the main pigment extracted from annatto seeds and accounts for 80% of the carotenoids in the outer coat of the seeds; norbixin being the water-soluble form of the bixin. Typically annatto dyes are extracted from the seeds by mechanical means or solutions of alkali, edible oil or organic solvents, or a combination of the two depending on the desired final product. In this work CGAs are investigated as an alternative separation method for the recovery of norbixin from a raw extraction solution of annatto pigments in KOH. A volume of CGAs generated from a cationic surfactant (CTAB) solution is mixed with a volume of annatto solution and when the mixture is allowed to settle it separates into the top aphron phase and the bottom liquid phase. Potassium norbixinate presented in the annatto solution will interact with the surfactant in the aphron phase, which results in the effective separation of norbixin. Recovery= 94% was achieved at a CTAB to norbixin molar ratio of 3.3. In addition a mechanism of separation is proposed here based on the separation results with the cationic surfactant and an anionic surfactant (bis-2-ethyl hexyl sulfosuccinate, AOT) and measurements of surfactant to norbixin ratio in the aphron phase; electrostatic interactions between the surfactant and norbixin molecules result in the fort-nation of a coloured complex and effective separation of norbixin. (c) 2005 Elsevier B.V. All rights reserved.

Heat-inactivated peroxidases and the role of calcium abstraction as a cause of their enhanced lipid oxidation activity: potential effects on the flavour quality of heat-processed vegetables

Cationic swede and anionic turnip peroxidases were partially purified by ion-exchange and gel-filtration chromatography, respectively. Heat treatment of these enzymes and of a commercial high purity horseradish peroxidase (HRP) caused a loss of enzyme activity and a corresponding increase in linoleic acid hydroperoxide formation activity. The hydroperoxide levels in model systems increased only in the early stages of the oxidation reaction and then declined as degradation became more significant. The presence of a dialysed blend of cooked swede markedly lowered the hydroperoxide level formed. Analysis of volatile compounds formed showed that hexanal predominated in a buffer system and in a blend of cooked turnip. In dialysed blends of cooked swede, hexanol was the primary volatile compound generated. After inactivation under mild conditions in the presence of EDTA, the peroxidases showed hydroperoxide formation activity and patterns of volatile compounds from linoleic acid that were similar to those found on heat-inactivation. This suggested that calcium abstraction from the peroxidases was critical for the enhancement of lipid oxidation activity. (C) 2002 Elsevier Science Ltd. All rights reserved.