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Abstract  

Poly(monoitaconates) containing octyl, decyl and dodecyl groups and random monoalkylitaconate-co-vinylpyrrolidone copolymers were studied by thermogravimetric analysis. Copolymers of mono-n-octylitaconate (MOI), mono-n-decylitaconate (MDI), and mono-n-dodecylitaconate (MDoI), respectively, with N-vinyl-2-pyrrolidone (VP) of different compositions were studied by dynamic thermogravimetric analysis. The thermal stability of the copolymers depends on the structure of the monoitaconate comonomer and on the composition of the copolymer The kinetic analysis of the degradation data shows that the thermal decomposition of these copolymers can be described by several kinetic orders depending on the copolymer and on the composition. The relative thermal stability of the copolymers increases as the VP content increases and as the length of the side chain of the itaconate increases, following the same trend as the flexibility of the copolymers in solution.

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Glutathione (g-L-glutamyl-L-cysteinyl-glycine; GSH) shares structural similarities with the b-lactam biosynthetic intermediate ACV-tripeptide {d-(L-a-aminoadipyl)-L-cysteinyl-D-valine}. Not surprisingly, GSH has been reported to inhibit the b-lactam biosynthetic machinery quite effectively and, hence, strategies to decrease the intracellular GSH concentrations without influencing negatively the physiological status of idiophasic mycelia would attract industrial interests. Here we present a detailed map of the GSH metabolic network of P. chrysogenum and show a promising way to keep the GSH pool selectively down under penicillin producing conditions. This procedure includes a well-controlled and transient lowering of pH at the beginning of the production phase, and it relies on the GSH-dependent detoxification of the protonophore penicillin side-chain precursors phenoxyacetic acid (POA) and phenylacetic acid (PA). Encouraging preliminary fed-batch fermentation experiments have been performed to test this technological proposal. Interestingly, the mechanism of the activation of POA and PA to the appropriate CoA derivatives has remained yet to be answered but the involvement of GSH seems to be rather unlikely in this case. Our data also challenge the hypothesis that the formation of different kinds of penicillins would be an alternative to GSH-dependent detoxification processes in P. chrysogenum.

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Journal of Flow Chemistry
Authors: Veronique Maes, Geert Pirotte, Jeroen Brebels, Pieter Verstappen, Laurence Lutsen, Dirk Vanderzande, and Wouter Maes

In this work, the synthesis of N,N’-dialkyl-6,6’-dibromoisoindigo derivatives by continuous-flow chemistry is explored as a means to enhance material availability and structural diversity, in particular toward the application of isoindigo-based semiconductors in high-performance organic photovoltaic devices. The individual steps in the conventional batch synthesis protocol are evaluated and, when needed, adapted to flow reactors. To overcome the low solubility of non-alkylated 6,6’-dibromoisoindigo in common organic solvents, the flow condensation reaction between the 6-bromo-isatin and 6-bromo-oxindole precursors is evaluated in polar aprotic solvents. Dialkylation of 6,6’-dibromoisoindigo is readily performed in flow using a solid-phase reactor packed with potassium carbonate. In an alternative strategy, solubility is ensured by first introducing the N-alkyl side chains on 6-bromo-isatin and 6-bromo-oxindole (accessible via a high-yielding flow reduction of alkylated 6-bromo-isatin), followed by condensation using the conventional method in acetic—hydrochloric acid medium. The N,N’-dialkylated 6,6’-dibromoisoindigo derivatives indeed show enhanced solubility in the hot reaction mixture compared to the non-alkylated material but eventually precipitate when the reaction mixture is cooled down. Nevertheless, the condensation between both alkylated starting materials is achieved in flow without any blockages by keeping the outlet from the reactor heated and as short as possible. The latter strategy allows the preparation of both symmetrically and asymmetrically N-substituted isoindigo compounds.

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Abstract  

Phase transition behaviour of neutral galactomannans, i.e., locust bean gum (LBG), tara gum (Tara-G) and guar gum (GG)-water systems is investigated. In this study, water content {Wc=(gram of water)/(gram of dry sample)} of these systems was varied from 0.2 to 3.6 g g-1. In the DSC heating curves, glass transition (Tg), cold crystallization (Tcc) and melting (Tm) were observed in all three samples. In addition, liquid crystal transition (T*) was observed in GG-water systems at a temperature higher than Tm. Using Tg, Tcc, Tm and T*, phase diagrams of each system were established. From the melting enthalpy of ice in the systems, three types of water, non-freezing water (Wnf), freezing bound water (Wfb) and free water were calculated. The maximum amount of Wnf was observed at Wc=0.7 g g-1, where Tg showed the lowest temperature. The amount of Wnf in LBG and GG is higher than that of Tara-G, whereas the highest amount of Wfb is found in GG. T* was only observed in GG-water systems. It is concluded that frequency of the side chains in the repeating unit of the main chains of these three galactomannan affects the frozen structure of the glassy state in the presence of water.

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Changes in both the morphology and the steroidogenic activity of porcine ovaries denervated surgically on day 12 of the oestrous cycle were studied. Neurectomy of the plexus and the superior ovarian nerves caused a dramatic reduction in the number (or even a disappearance) of dopamine-β-hydroxylase- and/or neuropeptide tyrosine-immunoreactive nerve terminals. On day 20 of the subsequent oestrous cycle, the number of small follicles increased (P < 0.01) and that of large follicles decreased (P < 0.05) in the denervated ovaries, as compared to the controls. Neurectomy led to a decrease in the level of progesterone (P 4 ; P < 0.001) and androstenedione (A 4 ; P < 0.01) in the fluid from small follicles, A 4 (P < 0.001) and testosterone (T; P < 0.05) in the fluid from medium-sized follicles, as well as in the content of all these steroids in the fluid from large-sized follicles (P < 0.001 for P 4 and P < 0.05 for A 4 and T). Denervation also caused a decrease in the content of A 4 (P < 0.01) and T (P < 0.001) in the wall of follicles. Neurectomy resulted in a significant increase in the immunoexpression of cholesterol side-chain cleavage cytochrome P450 in the follicles and a decrease of 3β-hydroxysteroid dehydrogenase. After denervation, plasma levels of LH, P 4 , A 4 , T, oestrone and oestradiol-17β were lower (P < 0.05–0.001) on the particular days of the study than in the control group. Our data revealed that the denervation of ovaries during the middle luteal phase of the oestrous cycle in gilts caused distinct changes in both the morphology and the steroidogenic activity of the organ, confirming an important role of the peripheral nervous system in the control of the gonad in this species.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Mihaela Vlassa, Virginia Coman, Miuţa Filip, Florina Copaciu, Aurora Mocanu, and Maria Tomoaia-Cotişel

The basic of all proteins is constituted by approximately 20 common amino acids that differ only in the structure of their side chain. The purpose of our work was to use the overpressured layer chromatography (OPLC) technique for the separation and identification of the essential and non-essential amino acids from some most common proteins, like hen egg yolk protein, bovine serum albumin (BSA), and Type I Collagen from bovine achilles tendon. In this order, the target proteins were acid-hydrolyzed and derivatized. For the separation of essential amino acids from egg yolk, two successive OPLC developments (normal and overrunning) were performed, followed by direct derivatization with 4-hydroxybenzaldehyde and ninhydrin on the chromatoplate for identification. In the hydrolyzed egg yolk, nine essential amino acids were identified. Between lysine and histidine, a poor separation was obtained. The amino acids from BSA and Type I Collagen were separated and identified as phenylthiohydantoin (PTH) derivatives by OPLC. The supposed identity of the amino acids as PTH derivatives was confirmed by reversed-phase high-performance liquid chromatography (RP-HPLC). Seven essential amino acids (arginine, histidine, threonine, valine, methionine, isoleucine, and leucine) were found in bovine serum albumin (BSA), and six (histidine, threonine, valine, methionine, leucine, and lysine) in Type I Collagen. The same eight non-essential amino acids (cysteine, asparagine, glutamine, glycine, alanine, serine, tyrosine, and proline) were identified in these two proteins. By RP-HPLC, other two non-essential amino acids (aspartic acid and glutamic acid) were found both BSA and Type I Collagen. Cysteic acid was also found in BSA. In our samples, tryptophan was missing due to its destruction during hydrolysis.

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A survey of the possibilities of Thermal Analysis (TA) in the plastics and rubber industry is presented. As well as giving examples from research (liquid crystalline main and side chain polymers) and construction (laminates of carbon fibre reinforced epoxy resin prepregs), the field of quality assurance and material characterization is specially discussed. The correlation between TA-characteristics such as the degree of crystallinity and mechanical properties (e.g. hardness or green strength) is demonstrated. The application of thermogravimetry for a precise compositional analysis of compounded rubbers is shown. In practice, Thermal Analysis is most important for failure analysis and the characterization of processing parameters during the production of moulded parts as TA-methods are usually much faster than traditional standard methods. Moreover, the increasing importance of combining TA-methods with other techniques of instrumental analysis is demonstrated. An example of this combination is the TG-DSC-MS coupling which is invaluable in the area of environmental protection especially in the production, application and recycling of moulded parts from polymeric materials.

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Compounds acting as model biphenyl and phenylcoumarane structural units in the lignin molecule (dehydrodivanillin and dehydrodiisoeugenol) were investigated by thermal analysis. The results were compared with previously obtained data on the thermal degradation of model phenylpropane monomer units of lignin. It was found that the mechanism of thermal degradation of these models and the thermal stabilities of the bonds depend on the structure. The thermal stability of the models increases in the absence of reactive functional groups in the side chain.

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side chains, while cations with LAS values higher than LBS -SO3 − enhance the thermal degradation rate [ 12 ]. Iwai and Yamanishi confirmed that thermal stability improved the most when the Nafion PFSI membrane was exchanged for alkaline ions, followed

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in technical and medical fields. Polymers based on alkyl methacrylates are widely used as construction materials and coatings. Their properties depend particularly on the type of alkyl group in side chain. Chain branching enhances hardness while

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