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Transfer Complex (transfer + complex)
Kinds of Transfer Complex Selected AbstractsRole of the surface charges D72 and K8 in the function and structural stability of the cytochrome c6 from Nostoc sp.FEBS JOURNAL, Issue 13 2005PCC 711 We investigated the role of electrostatic charges at positions D72 and K8 in the function and structural stability of cytochrome c6 from Nostoc sp. PCC 7119 (cyt c6). A series of mutant forms was generated to span the possible combinations of charge neutralization (by mutation to alanine) and charge inversion (by mutation to lysine and aspartate, respectively) in these positions. All forms of cyt c6 were functionally characterized by laser flash absorption spectroscopy, and their stability was probed by urea-induced folding equilibrium relaxation experiments and differential scanning calorimetry. Neutralization or inversion of the positive charge at position K8 reduced the efficiency of electron transfer to photosystem I. This effect could not be reversed by compensating for the change in global charge that had been introduced by the mutation, indicating a specific role for K8 in the formation of the electron transfer complex between cyt c6 and photosystem I. Replacement of D72 by asparagine or lysine increased the efficiency of electron transfer to photosystem I, but destabilized the protein. D72 apparently participates in electrostatic interactions that stabilize the structure of cyt c6. The destabilizing effect was reduced when aspartate was replaced by the small amino acid alanine. Complementing the mutation D72A with a charge neutralization or inversion at position K8 led to mutant forms of cyt c6 that were more stable than the wild-type under all tested conditions. [source] Novel divinyl monomer for preparation of unsaturated polymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Song Chen Abstract To simplify the preparation of unsaturated polymers, a new type of divinyl monomer was designed in this article. The double bonds of the divinyl monomer are different not only in reactivity but also in electron density. Based on quantum chemistry calculation, (z)-4-(2-(acryloyloxy)ethoxy)-4-oxobut-2-enoic acid (cis -AEOEA) was selected as the nonelectron-donating divinyl monomer in which inactive double bond was electron deficient and can be activated by electron-donating comonomers by forming charge transfer complex (CTC) copolymerization system. So, cis- AEOEA can be used to simplify the preparation of unsaturated polymers and the content of inactive double bonds left in the polymer is controlled by electron-donating ability of comonomers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Dynamic Study of Excited State Hydrogen-bonded Complexes of Harmane in Cyclohexane,Toluene Mixtures,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2002Carmen Carmona ABSTRACT Photoinduced proton transfer reactions of harmane or 1-methyl-9H -pyrido[3,4- b]indole (HN) in the presence of the proton donor hexafluoroisopropanol (HFIP) in cyclohexane,toluene mixtures (CY,TL; 10% vol/vol of TL) have been studied. Three excited state species have been identified: a 1:2 hydrogen-bonded proton transfer complex (PTC), between the pyridinic nitrogen of the substrate and the proton donor, a hydrogen-bonded cationlike exciplex (CL*) with a stoichiometry of at least 1:3 and a zwitterionic exciplex (Z*). Time-resolved fluorescence measurements evidence that upon excitation of ground state PTC, an excited state equilibrium is established between PTC* and the cationlike exciplex, CL*, ,em, 390 nm. This excited state reaction is assisted by another proton donor molecule. Further reaction of CL* with an additional HFIP molecule produces the zwitterionic species, Z*, ,em, 500 nm. From the analysis of the multiexponential decays, measured at different emission wavelengths and as a function of HFIP concentration, the mechanism of these excited state reactions has been established. Thus, three rate constants and three reciprocal lifetimes have been determined. The simultaneous study of 1,9-dimethyl-9H -pyrido[3,4- b]indole (MHN) under the same experimental conditions has helped to understand the excited state kinetics of these processes. [source] Facile synthesis and characterization of star-shaped polystyrene: self-condensing atom transfer radical copolymerization of N -[4-(,-bromoisobutyryloxy)phenyl]maleimide and styrenePOLYMER INTERNATIONAL, Issue 10 2008Yun Cao Abstract BACKGROUND: Generation of stars around in situ formed cores provides a facile approach to star-shaped polymers. Therefore the self-condensing atom transfer radical copolymerization (SCATRCP) of N -[4-(,-bromoisobutyryloxy)phenyl]maleimide (BiBPM) and a large excess of styrene (St) was investigated. RESULTS: BiBPM and St formed a charge transfer complex (CTC), which underwent the SCATRCP, leading to the branched core initiating the atom transfer radical polymerization of St, finally giving star-shaped polystyrene (PS). Kinetic and structural study showed that a higher dosage of BiBPM resulted in an enhanced polymerization rate, a higher degree of branching and a larger number of short PS arms. Differential scanning calorimetry suggested that the glass transition temperature of the star-shaped PS decreased with molecular weight. Melt rheometry showed that even a slightly branched architecture of the PS led to a significantly lower viscosity; both the melt flow index and the activation energy increased with the degree of branching. CONCLUSION: Due to the preferential consumption of BiBPM and formation of a CTC, even a very low dosage of BiBPM could lead to star-shaped PS, which, in comparison with linear analogues, could possess much better melt fluidity. Copyright © 2008 Society of Chemical Industry [source] Research on synthesis and conductivity of ferrocenyl Schiff base and its saltAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2007Wei-Jun Liu Abstract Ferrocenyl Schiff base was synthesized through the condensation of ferrocenecarboxaldehyde and p -phenylenediamine under neutral conditions, and then a new interesting category of organometallic charge transfer complex was obtained by the doping of ferrocenyl Schiff base with Fe3+, Al3+ and Ti3+ salts. The effects of the dosage of doping agent and doping temperature on the room-temperature electric conductivity of samples were discussed; in addition, the temperature dependence of the electric conductivity of samples was studied, their structures and compositions were characterized by 1H-NMR spectra, infrared spectra, ultraviolet spectra and an electron probe X-ray microanalyser. The results showed that the electric conductivity of sample can increase 4,5 orders of magnitude after doping with a metallic salt, and the electric conductivity has a positive temperature coefficient effect. The electrical activation energies of the complexes in the range 0.09,1.54 eV were calculated from Arrhenius plots, indicating their favourable semiconducting behaviour. Copyright © 2006 John Wiley & Sons, Ltd. [source] Photolysis of oxygen saturated ethers in the presence of Sn(II) or Cu(II) saltsCHINESE JOURNAL OF CHEMISTRY, Issue 6 2000Min Shi Abstract Photolysis of diethyl ether-oxygen charge transfer complex in the presence of Sn(II) or Cu(II) salts gave higher yields of the oxidation products, ethyl acetate, acetaldehyde, ethanol, ethyl formate and methanol compared with those without the salts. In addition, the photolysis of an oxygen saturated tetrahydrofuran (THF) or dibutyl ether solution gave ,-butyrolactone or butanol and butyl butyrate as major products with small amounts of undetermined compounds, respectively. Their yields were also affected by the addition of Cu(II) or Sn(II) salts. [source] Role of the Charge Transfer State in Organic Donor,Acceptor Solar CellsADVANCED MATERIALS, Issue 37 2010Carsten Deibel Charge transfer complexes are interfacial charge pairs residing at the donor,acceptor heterointerface in organic solar cell. Experimental evidence shows that it is crucial for the photovoltaic performance, as both photocurrent and open circuit voltage directly depend on it. For charge photogeneration, charge transfer complexes represent the intermediate but essential step between exciton dissotiation and charge extraction. Recombination of free charges to the ground state is via the bound charge transfer state before being lost to the ground state. In terms of the open circuit voltage, its maximum achievable value is determined by the energy of the charge transfer state. An important question is whether or not maximum photocurrent and maximum open circuit voltage can be achieved simultaneously. The impact of increasing the CT energy,in order to raise the open circuit voltage, but lowering the kinetic excess energy of the CT complexes at the same time,on the charge photogeneration will accordingly be discussed. Clearly, the fundamental understanding of the processes involving the charge transfer state is essential for an optimisation of the performance of organic solar cells. [source] Catalytic synthesis of styryl-capped isotactic polypropylenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2010Huahua Huang Abstract Bis-styrenic molecules, 1,4-divinylbenzene (DVB) and 1,2-bis(4-vinylphenyl)ethane (BVPE), were successfully combined with hydrogen (H2) to form consecutive chain transfer complexes in propylene polymerization mediated by an isospecific metallocene catalyst (i.e., rac -dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride, I) activated with methylaluminoxane (MAO), rendering a catalytic access to styryl-capped isotactic polypropylenes (i -PP). The chain transfer reaction took place in a unique way where prior to the ultimate chain transfer DVB/H2 or BVPE/H2 caused a copolymerization-like reaction leading to the formation of main chain benzene rings. A preemptive polymer chain reinsertion was deduced after the consecutive actions of DVB/H2 or BVPE/H2, which gave the styryl-terminated polymer chain alongside a metal-hydride active species. It was confirmed that the chain reinsertion occurred in a regio-irregular 1,2-fashion, which contrasted with a normal 2,1-insertion of styrene monomer and ensured subsequent continuous propylene insertions, directing the polymerization to repeated DVB or BVPE incorporations inside polymer chain. Only as a competitive reaction, the insertion of propylene into metal-hydride site broke the chain propagation resumption process while completed the chain transfer process by releasing the styryl-terminated polymer chain. BVPE was found with much higher chain transfer efficiency than DVB, which was attributed to its non-conjugated structure with much divided styrene moieties resulting in higher polymerization reactivity but lower chain reinsertion tendency. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3709,3713, 2010 [source] Hyperbranched macromolecules through donor-acceptor type copolymerization of allyl,vinylene bifunctional monomers,POLYMER INTERNATIONAL, Issue 10 2002O Rzaev, Zakir M Abstract Present review is an attempt to generalize and systematize the results accumulated in synthesis of cyclolinear and hyperbranched reactive macromolecules via radical alternating copolymerization of various bifunctional monomers containing donor and acceptor type double bonds. Synthesis of hyperbranched reactive macromolecules was carried out using complex-radical cyclocopolymerization of donor-acceptor type bifunctional monomers such as monoallyl ester of maleic acid (MAM), allyl acrylate (AA), allyl methacrylate (AM), allyl trans -cinnamate (AC), methylallylmaleate (MeAM), methylallylfumarate (MAF) and allyl-,-(N-maleimido)acetate (AMI), and maleic anhydride (MA) and styrene (St) as typical acceptor and donor comonomers, respectively. The kinetic parameters of these reactions, constants of cyclization, complex-formation and copolymerization, as well as the ratios of chain growth rates for the participation of monomeric charge transfer complexes and free monomers, were all determined. It was demonstrated that in the studied systems, copolymerizations predominantly proceed according to alternating mechanism with formation of macromolecules having cyclolinear structure in the steady-state and hyperbranched structure in the high conversion conditions. It was shown that formation of linear and hyperbranched macromolecules containing allyl or vinylene groups in the side chain occurs selectively carry out and depends on the nature of used comonomer. General schemes and proposed mechanism of hyperbranching and crosslinking reactions were also described. Some useful properties of synthesized reactive copolymers were discussed. © 2002 Society of Chemical Industry. [source] RNA-containing adenovirus/polyethylenimine transfer complexes effectively transduce dendritic cells and induce antigen-specific T cell responsesTHE JOURNAL OF GENE MEDICINE, Issue 4 2004Tatjana C. Gust Abstract Background Dendritic cells (DCs) are the most potent antigen-presenting cells in initiating primary immune responses. Given the unique properties of DCs, gene-modified DCs represent a particularly attractive approach for immunotherapy of diseases such as cancer. Methods Gene-modified DCs were obtained by a receptor-mediated gene delivery system using adenovirus (Ad) particles as ligand and RNA or DNA condensed by polyethylenimine (PEI). In vitro transcribed polyadenylated or non-polyadenylated RNA was used. RNA-transduced DCs were generated expressing chicken ovalbumin (OVA) or chimeric constructs thereof, and compared with DNA-transduced DCs. Results Ad/PEI transfection complexes efficiently delivered RNA into DCs. Such RNA-transduced DCs induced OVA-specific T cell responses more effectively than DNA-transduced DCs. Furthermore, DCs transduced with polyadenylated RNA were more potent in stimulating CD4+ and CD8+ T cell responses than DCs transduced with non-polyadenylated RNA and this was particularly important for CD4+ T cell responses. Conclusions Ad/PEI/RNA transfection is an efficient means for generating RNA-transduced DCs and for stimulating antigen-specific T cell responses. Polyadenylation of RNA enhances CD8+ T cell responses and is essential for CD4+ T cell responses. Copyright © 2004 John Wiley & Sons, Ltd. [source] Spectroscopic studies of charge transfer complexes of meso -tetra- p -tolylporphyrin and its zinc complex with some aromatic nitro acceptors in different organic solventsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2007Mohamed E. El-Zaria Abstract The charge transfer complex (CTC) formation of 5,10,15,20-tetra(p -tolyl)porphyrin (TTP) and zinc 5,10,15,20-tetra(p -tolyl)porphyrin with some aromatic nitro acceptors such as 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, 3,5-dinitrobenzoic acid (DNB) and 2,4-dinitrophenol (DNP) was studied spectrophotometrically in different organic solvents at different temperatures. The spectrophotometric titration, Job's and straight line methods indicated the formation of 1:1 CTCs. The values of the equilibrium constant (KCT) and molar extinction coefficient (,CT) were calculated for each complex. The ionization potential of the donors and the dissociation energy of the charge transfer excited state for the CTC in different solvents was also determined and was found to be constant. The spectroscopic and thermodynamic properties were observed to be sensitive to the electron affinity of the acceptors and the nature of the solvent. No CT band was observed between Zn-TTP as donor and DNP or DNB as acceptors in various organic solvents at different temperature. Bimolecular reactions between singlet excited TTP (1TTP*) and the acceptors were investigated in solvents with various polarities. A new emission band was observed. The fluorescence intensity of the donor band decreased with increasing the concentration of the acceptor accompanied by an increase in the intensity of the new emission. The new emission of the CTCs can be interpreted as a CT excited complex (exciplex). Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||