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101.
Control of the Electronic Ground State on an Electron‐Transfer Copper Site by Second‐Sphere Perturbations
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Marcos N. Morgada Dr. Luciano A. Abriata Ulises Zitare Dr. Damian Alvarez‐Paggi Prof. Daniel H. Murgida Prof. Alejandro J. Vila 《Angewandte Chemie (International ed. in English)》2014,53(24):6188-6192
The CuA center is a dinuclear copper site that serves as an optimized hub for long‐range electron transfer in heme–copper terminal oxidases. Its electronic structure can be described in terms of a σu* ground‐state wavefunction with an alternative, less populated ground state of πu symmetry, which is thermally accessible. It is now shown that second‐sphere mutations in the CuA containing subunit of Thermus thermophilus ba3 oxidase perturb the electronic structure, which leads to a substantial increase in the population of the πu state, as shown by different spectroscopic methods. This perturbation does not affect the redox potential of the metal site, and despite an increase in the reorganization energy, it is not detrimental to the electron‐transfer kinetics. The mutations were achieved by replacing the loops that are involved in protein–protein interactions with cytochrome c, suggesting that transient protein binding could also elicit ground‐state switching in the oxidase, which enables alternative electron‐transfer pathways. 相似文献
102.
Evaluation of tocopherol recovery through simulation of molecular distillation process 总被引:7,自引:0,他引:7
E. B. Moraes C. B. Batistella M. E. Torres Alvarez Rubens Maciel Filho M. R. Wolf Maciel 《Applied biochemistry and biotechnology》2004,114(1-3):689-711
DISMOL simulator was used to determine the best possible operating conditions to guide, in future studies, experimental works.
This simulator needs several physical-chemical properties and often it is very difficult to determine them because of the
complexity of the involved components. Their determinations must be made through correlations and/or predictions, in order
to characterize the system and calculate it. The first try is to have simulation results of a system that later can be validated
with experimental data. To implement, in the simulator, the necessary parameters of complex systems is a difficult task. In
this work, we aimed to determe these properties in order to evaluate the tocopherol (vitamin E) recovery using a DISMOL simulator.
The raw material used was the crude deodorizer distillate of soya oil. With this procedure, it is possible to determine the
best operating conditions for experimental works and to evaluated the process in the separation of new systems, analyzing
the profiles obtained from these simulations for the falling film molecular distillator. 相似文献
103.
Kepka C Rhodin J Lemmens R Tjerneld F Gustavsson PE 《Journal of chromatography. A》2004,1024(1-2):95-104
The primary purification of a 6.1 kilo base pair (kbp) plasmid from a desalted alkaline lysate has been accomplished by a thermoseparating aqueous two-phase system [(50% ethylene oxide-50% propylene oxide)-Dextran T 500]. The partitioning of the different nucleic acids (plasmid DNA, RNA, genomic DNA) in the thermoseparating aqueous two-phase system was followed both qualitatively by agarose gel electrophoresis and quantitatively by analytical chromatography (size exclusion- and anion-exchange mode) and PicoGreen fluorescence analysis. The experimental results showed a complete recovery of the plasmid DNA to the top phase, while 80% of total RNA and 58% of total protein was discarded to the bottom phase. Moreover, a 3.8-fold volume reduction of the plasmid DNA solution was achieved. By using a final thermoseparating step, the EO50PO50 polymer could be efficiently recycled, resulting in plasmid solution containing less than 1% polymer. The developed thermoseparating aqueous two-phase system shows great potential for the large-scale processing of plasmid DNA. 相似文献
104.
Hairy roots of Brugmansia candida produce the tropane alkaloids scopolamine and hyoscyamine. In an attempt to divert the carbon flux from competing pathways
and thus enhance productivity, the polyamine biosynthesis inhibitors cyclohexylamine (CHA) and methylglyoxal-bis-guanylhy,
drazone (MGBG) and the phenylalamine-ammonia-lyase inhibitor cinnamic acid were used. CHA decreased the specific productivity
of both alkaloids but increased significantly the release of scopolamine (approx 500%) when it was added in the mid-exponential
phase. However, when CHA was added for only 48 h during the exponential phase, the specific productivity of both alkaloids
increased (approx 200%), favoring scopolamine. Treatment with MGBG was detrimental to growth but promoted release into the
medium of both alkaloids. However, when it was added for 48 h during the exponential phase, MGBG increased the specific productivity
(approx 200%) and release (250–1800%) of both alkaloids. Cinnamic acid alone also favored release but not specific productivity.
When a combination of CHA or MGBG with cinnamic acid was used, the results obtained were approximately the same as with each
polyamine biosynthesis inhibitor alone, although to a lesser extent. Regarding root morphology, CHA inhibited growth of primary
roots and ramification. However, it had a positive effect on elongation of lateral roots. 相似文献
105.
This paper describes a microfluidics-based sensing system that relies on electrochemical detection and electrogenerated chemiluminescent (ECL) reporting. The important result is that the ECL reporting reaction is chemically decoupled from the electrochemical sensing reaction. That is, the electrochemical sensing reaction does not participate directly in the ECL process, but because electrochemical cells require charge balance, the sensing and ECL reactions are electrically coupled. This provides a convenient and sensitive means for direct photonic readout of electrochemical reactions that do not directly participate in an ECL reaction and thus broadens the spectrum of redox compounds that can be detected by ECL. The approach can be implemented in either a two-electrode or bipolar (single-electrode) configuration. By manipulating the placement and dimensions of the conductors, the photonic response can be enhanced. The system is used to electrochemically detect benzyl viologen present in solution and report its presence via Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) luminescence. 相似文献
106.
107.
Cecilia Devi Wilfred 《合成通讯》2013,43(22):2859-2867
A tandem oxidation reaction has been utilized to prepare ethyl (E)‐4,5‐dioxo‐2‐hexadecenoate, the immediate precusor to the antiviral fungal metabolite podoscyphic acid. 相似文献
108.
109.
Mauricio H. Cornejo Jan Elsen Cecilia Paredes Haci Baykara 《Journal of Thermal Analysis and Calorimetry》2014,115(1):309-321
Two Ecuadorian zeolite-rich tuffs, coded as Zeo1 (Mordenite) and Zeo2 (Clinoptilolite–Heulandite–Mordenite), were treated and used as supplementary cementitious materials (SCM) so as to study the effect of the thermal and mechanical treatments on pozzolanic reaction in mortars. The treatment was carried out by means of thermomechanical process according to a central composite-blocked cube-star experimental design. In this experimental design as independent factors the milling time (48, 60, 90, 120 and 132 min) and the heating temperatures (559, 600, 700, 800 and 841 °C) were used but keeping a constant heating time (5 h), and zeolite-rich tuffs as experimental blocks. The proportion of SCM was kept constant i.e. 15 %. On the other hand, the compressive strength, fixed lime, normalized water in hydrates and mg Ca(OH)2 per mg Cement at 7, 28 and 45 days, as well as hydration products related to dehydration degree of the zeolitic tuffs (DOD) were used as dependent factors. In addition, Quantitative and High-temperature chamber XRD, TG-DSC, particle size distribution and SEM-EDS were also carried out. The most significant factor was calcination leading to increase in the compressive strength compared to control, but just up to 800 °C because of recrystallization. As a conclusion, a meaningful loss of crystal structure of zeolites was not observed; but instead, the treatment could only lead to removing the water in cages and voids, thus improving the reaction with Ca(OH)2, producing more hydrates. In addition, lime was not only fixed by pozzolanic reaction, but also by carbonation. 相似文献
110.
Pierluigi?Contucci Cristian?Giardinà Claudio?GibertiEmail author Giorgio?Parisi Cecilia?Vernia 《Journal of statistical physics》2011,143(1):1-10
We numerically investigate the spin glass energy interface problem in three dimensions. We analyze the energy cost of changing
the overlap from −1 to +1 at one boundary of two coupled systems (in the other boundary the overlap is kept fixed to +1).
We implement a parallel tempering algorithm that simulates finite temperature systems and works with both cubic lattices and
parallelepiped with fixed aspect ratio. We find results consistent with a lower critical dimension D
c
=2.5. The results show a good agreement with the mean field theory predictions. 相似文献