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991.
Thomas C. Farmer Corinne L. Carpenter Michael F. Doherty 《American Institute of Chemical Engineers》2016,62(9):3505-3514
This article is motivated by a remarkable observation reported recently by Myerson, Trout, and co‐workers that continuous crystallization is capable of producing metastable polymorphs in stable steady‐state operation. We explain why this phenomenon occurs and give simple design rules for reproducing it in other polymorphic systems. A linear stability analysis gives simple functions of parameters for which one can continuously produce thermodynamically metastable products based only on the relative polymorph dynamics. We demonstrate agreement with two sets of experimental data; L‐glutamic acid grown from aqueous solution and p‐aminobenzoic acid also grown from aqueous solution. For many polymorphic compounds, engineering a process to produce a desired polymorph is as simple as finding a reasonable operating point for the continuous mixed‐suspension mixed‐product removal crystallization process (temperature, residence time, initial supersaturation, etc.) according to the rules reported in this article. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3505–3514, 2016 相似文献
992.
Photoreduction of Shewanella oneidensis Extracellular Cytochromes by Organic Chromophores and Dye‐Sensitized TiO2
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Emma V. Ainsworth Dr. Colin W. J. Lockwood Dr. Gaye F. White Dr. Ee Taek Hwang Dr. Tsubasa Sakai Manuela A. Gross Prof. David J. Richardson Dr. Thomas A. Clarke Dr. Lars J. C. Jeuken Dr. Erwin Reisner Prof. Julea N. Butt 《Chembiochem : a European journal of chemical biology》2016,17(24):2324-2333
The transfer of photoenergized electrons from extracellular photosensitizers across a bacterial cell envelope to drive intracellular chemical transformations represents an attractive way to harness nature's catalytic machinery for solar‐assisted chemical synthesis. In Shewanella oneidensis MR‐1 (MR‐1), trans‐outer‐membrane electron transfer is performed by the extracellular cytochromes MtrC and OmcA acting together with the outer‐membrane‐spanning porin ? cytochrome complex (MtrAB). Here we demonstrate photoreduction of solutions of MtrC, OmcA, and the MtrCAB complex by soluble photosensitizers: namely, eosin Y, fluorescein, proflavine, flavin, and adenine dinucleotide, as well as by riboflavin and flavin mononucleotide, two compounds secreted by MR‐1. We show photoreduction of MtrC and OmcA adsorbed on RuII‐dye‐sensitized TiO2 nanoparticles and that these protein‐coated particles perform photocatalytic reduction of solutions of MtrC, OmcA, and MtrCAB. These findings provide a framework for informed development of strategies for using the outer‐membrane‐associated cytochromes of MR‐1 for solar‐driven microbial synthesis in natural and engineered bacteria. 相似文献
993.
Jean‐Thomas Fonné Ekaterina Burov Emmanuelle Gouillart Sergey Grachev Hervé Montigaud Damien Vandembroucq 《Journal of the American Ceramic Society》2018,101(4):1516-1525
Interdiffusion processes between aluminum enriched PVD‐sputtered silica thin films and industrial float soda‐lime silicate glass substrates are quantitatively studied using SIMS analysis. Heat treatments are performed at temperatures close or above the glass transition temperature of the float glass. Aluminum doping of the film is shown to strongly increase the migration of alkali from the glass substrate to the silica thin film. In particular the final alkali content in the film exhibits a linear scaling with the aluminum concentration. An interdiffusion process is evidenced between bulk alkali ions and protons originating from a significant water content in the as‐deposited silica film. Experimental measurements of sodium concentration are shown to be consistent with a simple thermodynamic model based on the equilibration of the activity of sodium between the film and the glass substrate. 相似文献
994.
New WS9326A Derivatives and One New Annimycin Derivative with Antimalarial Activity are Produced by Streptomyces asterosporus DSM 41452 and Its Mutant
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Songya Zhang Jing Zhu Prof. Dr. David L. Zechel Dr. Claudia Jessen‐Trefzer Dr. Richard T. Eastman Dr. Thomas Paululat Prof. Dr. Andreas Bechthold 《Chembiochem : a European journal of chemical biology》2018,19(3):272-279
In this study, we report that Streptomyces asterosporus DSM 41452 is a producer of new molecules related to the nonribosomal cyclodepsipeptide WS9326A and the polyketide annimycin. S. asterosporus DSM 41452 is shown to produce six cyclodepsipeptides and peptides, WS9326A to G. Notably, the compounds WS9326F and WS9326G have not been described before. The genome of S. asterosporus DSM 41452 was sequenced, and a putative WS9326A gene cluster was identified. Gene‐deletion experiments confirmed that this cluster was responsible for the biosynthesis of WS9326A to G. Additionally, a gene‐deletion experiment demonstrated that sas16 encoding a cytochrome P450 monooxygenase was involved in the synthesis of the novel (E)‐2,3‐dehydrotyrosine residue found in WS9326A and its derivatives. An insertion mutation within the putative annimycin gene cluster led to the production of a new annimycin derivative, annimycin B, which exhibited modest inhibitory activity against Plasmodium falciparum. 相似文献
995.
Several neotropical leaf-beetles of the genus Platyphora ingest and specifically metabolize plant acquired pyrrolizidine alkaloids (PAs) of the lycopsamine type (e.g., rinderine or intermedine) and enrich the processed alkaloids in their exocrine defensive secretions. In contrast to the related palaearctic leaf beetles of the genus Oreina, which absorb and store only the non-toxic alkaloid N-oxides, Platyphora sequesters PAs exclusively as protoxic tertiary amines. In this study, the ability of P. boucardi larvae to accumulate PAs was investigated. Tracer studies with [14C]rinderine and its N-oxide revealed that P. boucardi larvae, like adult beetles, utilize the two alkaloidal forms with the same efficiency, but accumulate the alkaloid as a tertiary amine exclusively. Ingested rinderine is rapidly epimerized to intermedine, which is localized in the hemolymph and all other tissues; it is also detected on the larval surface. Like adults, larvae are able to synthesize their own alkaloid esters (beetle PAs) from orally administered [14C]retronecine and endogenous aliphatic 2-hydroxy acids. These retronecine esters show the same tissue distribution as intermedine. A long-term feeding experiment lasting for almost four months revealed that retronecine esters synthesized from [14C]retronecine in the larvae are transferred from larvae via pupae into the exocrine glands of adult beetles. Pupae contain ca. 45% of the labeled retronecine originally ingested, metabolized, and stored by larvae; ca. 12% of larval radioactivity could be recovered from the defensive secretions of adults sampled successively over two and a half months. Almost all of this radioactivity is found in the insect-made retronecine esters that are highly enriched in the defensive secretions, i.e., more than 200-fold higher concentration compared to pupae. 相似文献
996.
De novo synthesis and mitochondrial elongation of fatty acids have been demonstrated in subcellular fractions from hog and human
aorta. Microsomal fatty acid elongation has been shown in hog aorta. The activity catalyzing the formation of fatty acids
from acetyl and malonyl CoA was associated with a high molecular weight complex in the 6×106g×min supernatant fraction. The principal product was palmitic acid. Some myristic and stearic acids were also formed. One
elongation system was associated with protein which sedimented between 4500 g×min and 150,000 g×min. It used acetyl CoA but
not malonyl CoA, and NADH was the preferred reducing agent. Radioactivity from acetyl CoA was incorporated into many fatty
acids. In hog aorta a second elongation system was found associated with protein which sedimented at 6×106 g×min. It used malonyl CoA preferentially as substrate and either NADH or NADPH as reducing agent. 相似文献
997.
The hydrogenation/dehydrogenation catalytic activity of minerals commonly present in coal was investigated. The extent of reaction undergone by the model hydrogen-transfer system tetralin/1,2-dihydronaphthalene/naphthalene at 400 °C in the presence of these minerals was used to measure the catalytic activity. For the four most active minerals, the order of catalytic activity per gram of mineral, for a given range of particle size, is limonites > pyrites > diaspore > magnetites. The pure chemical analog of the limonites, Fe2O3, was found to have catalytic activity similar to that of the limonites. Heating the minerals at 400 °C before running the reaction was found to decrease these catalytic activities, despite the surface-area increases resulting from the annealing process. The catalytic activity per unit area of mineral was determined and used as an index of the catalytic activity of the reactive sites for these heterogeneous systems. The order of decreasing site catalytic activity for the more active minerals is pyrites > magnetites > diaspore > limonites. The observed mineral/ chemical compound catalytic activities indicate that the more reactive mineral hydrogenation/ dehydrogenation catalytic sites are composed of iron compounds. 相似文献
998.
The problem of predicting adhesive bond performance for both surface preparation and undercure defects has been studied using an ultrasonic, experimental test bed system. This experimental test bed incorporates the ultrasonic and computer equipment necessary to acquire and process data from various types of adhesively bonded test specimens. The computer hardware and software has been developed to allow the design of reliable pattern recognition algorithms for the evaluation of surface preparation and bond cure. The specific problem studied is the inspection of the adhesive bond in an aluminum to aluminum step-lap joint whose strength could be affected by improper surface preparation or undercure. A set of 154 bond specimens was used to design an algorithm that is 91% reliable for separating the specimens into a good class, those bonds with no defects, or a weak class, bonds with poor surface preparation or undercured adhesive layer. A Fisher Linear Discriminant function was selected by the test bed as the best pattern recognition routine for this classification problem. 相似文献
999.
Three types of pulverized coal were burned in a laboratory furnace under various combustion configurations. Pulverized samples of Utah bituminous, Beulah (North Dakota) lignite, and Texas lignite coals were burned at a rate of 2.5 kg/hr in a laboratory furnace. Aerosol size distributions were measured at various positions within the convection section, and temperature and gas compositions were measured throughout. The evolution of the submicron particle size distribution within the convection section for the three coals was similar, although the location of the initial particle mode at the convection section inlet varied with coal type. While staged combustion of Utah bituminous coal had a variable effect on the volume of submicron aerosol produced, staged combustion of the lignites caused a definite increase in the submicron aerosol volume. Vapor enhancement due to a localized reducing atmosphere, which would effect coals of higher ash volatility, is thought to explain this behavior. 相似文献