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Nganou C.,University of Rochester | Nganou C.,Technion - Israel Institute of Technology | David L.,Technion - Israel Institute of Technology | Meinke R.,TechnischeUniversitat Berlin | And 5 more authors.
Journal of Chemical Physics

We investigated the excitation modes of the light-harvesting protein phycocyanin (PC) from Thermosynechococcus vulcanus in the crystalline state using UV and near-infrared Raman spectroscopy. The spectra revealed the absence of a hydrogen out-of-plane wagging (HOOP) mode in the PC trimer, which suggests that the HOOP mode is activated in the intact PC rod, while it is not active in the PC trimer. Furthermore, in the PC trimer an intense mode at 984 cm -1 is assigned to the C-C stretching vibration while the mode at 454 cm-1 is likely due to ethyl group torsion. In contrast, in the similar chromophore phytochromobilin the C5,10,15-D wag mode at 622 cm-1 does not come from a downshift of the HOOP. Additionally, the absence of modes between 1200 and 1300 cm-1 rules out functional monomerization. A correlation between phycocyanobilin (PCB) and phycoerythrobilin (PEB) suggests that the PCB cofactors of the PC trimer appear in a conformation similar to that of PEB. The conformation of the PC rod is consistent with that of the allophycocyanin (APC) trimer, and thus excitonic flow is facilitated between these two independent light-harvesting compounds. This excitonic flow from the PC rod to APC appears to be modulated by the vibration channels during HOOP wagging, C = C stretching, and the N-H rocking in-plan vibration. © 2014 AIP Publishing LLC. Source

Zhang Y.,Nanjing University of Technology | Zhang Y.,TechnischeUniversitat Berlin | Prigent B.,TechnischeUniversitat Berlin | Geissen S.-U.,TechnischeUniversitat Berlin

Regeneration of loaded adsorbents is a key step for the sustainability of an adsorption process. In this study, ozone was applied to regenerate a synthetic zeolite for the adsorption of trichlorophenol (TCP) as an organic model pollutant. Three initial concentrations of TCP in water phase were used in adsorption tests. After the equilibrium, zeolite loaded different amounts of TCP was dried and then regenerated with ozone gas. It was found that the adsorption capacity of zeolite was increased through three regeneration cycles. However, the adsorption kinetics was compromised after the regeneration with slightly declined 2nd order reaction constants. The ozone demand for the regeneration was highly dependent on the TCP mass loaded onto the zeolite. It was estimated that the mass ratio of ozone to TCP was 1.2 ± 0.3 g O3/g TCP. © 2016 Elsevier Ltd. Source

Ye H.,CAS Institute of Electrical Engineering | Strunz K.,TechnischeUniversitat Berlin | Xia Y.,TechnischeUniversitat Berlin
POWERCON 2014 - 2014 International Conference on Power System Technology: Towards Green, Efficient and Smart Power System, Proceedings

This paper presents three main multi-scale transmission line models that are capable of simulating diverse transients. Such multi-scale simulation is achieved by using the methodology frequency-adaptive simulation of transients (FAST). In addition to the time-step size, a new simulation parameter referred to as shift frequency is introduced. Appropriate adjustment of both shift frequency and time-step size allows the integral simulation of electromagnetic and electromechanical transients within the same study. Based on the simulation concept FAST, three different multi-scale models of transmission lines are developed. These models include multi-scale line model with lumped parameters, multi-scale line model with constant distributed parameters, and multi-scale line model with frequency dependence. Case studies are performed to validate different multi-scale line models in terms of accuracy and efficiency. For studying diverse transients, the multi-scale line model with frequency dependence is the best choice. © 2014 IEEE. Source

David-Henriet X.,TechnischeUniversitat Berlin | David-Henriet X.,Max Planck Institute for Dynamics of Complex Technical Systems | Hardouin L.,University of Angers | Raisch J.,TechnischeUniversitat Berlin | And 2 more authors.
IEEE Transactions on Automatic Control

The trade-off between energy consumption and execution time (i.e., for a given task, the faster it is achieved, the higher its energy consumption is) is investigated for systems modeled by timed event graphs. In this technical note, we aim to increase execution times (and, consequently, lower energy consumption) while preserving input-output and perturbation-output behaviors. Under this condition, the optimal solution is independent of the considered cost functions and is obtained using residuation theory. © 1963-2012 IEEE. Source

Zhou X.,TechnischeUniversitat Berlin | Szeker K.,TechnischeUniversitat Berlin | Jiao L.-Y.,TU Berlin | Oestreich M.,TU Berlin | And 2 more authors.
Advanced Synthesis and Catalysis

The enzymatic transglycosylation of 2,6-dichloropurine (26DCP) and 6-chloro-2-fluoropurine (6C2FP) with uridine, thymidine and 1-(β-D-arabinofuranosyl)-uracil as the pentofuranose donors and recombinant thermostable nucleoside phosphorylases from G. thermoglucosidasius or T. thermophilus as biocatalysts was studied. Selection of 26DCP and 6C2FP as substrates is determined by their higher solubility in aqueous buffer solutions compared to most natural and modified purines and, furthermore, synthesized nucleosides are valuable precursors for the preparation of a large number of biologically important nucleosides. The substrate activity of 26DCP and 6C2FP in the synthesis of their ribo- and 2′-deoxyribo-nucleosides was closely similar to that of related 2-amino- (DAP), 2-chloro- and 2-fluoroadenines; the efficiency of the synthesis of β-D-arabinofuranosides of 26DCP and 6C2FP was lower vs. that of DAP under similar reaction conditions. For a convenient and easier recovery of the biocatalysts, the thermostable enzymes were immobilized on MagReSyn® epoxide beads and the biocatalyst showed high catalytic efficiency in a number of reactions. As an example, 6-chloro-2-fluoro-(β-D-ribofuranosyl)-purine (9), a precursor of various antiviral and antitumour drugs, was synthesized by the immobilized enzymes at 60°C under high substrate concentrations (uridine:purine ratio of 2:1, mol). The synthesis was successfully scaled-up [uridine (2.5 mmol), base (1.25 mmol); reaction mixture 50 mL] to afford 9 in 60% yield. The reaction reveals the great practical potential of this enzymatic method for the efficient production of modified purine nucleosides of pharmaceutical interest. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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