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Stephen MT Hoke Gaoyang Liang A Irina Mutiu Julie Genereaux Christopher J Brandl 《BMC biochemistry》2007,8(1):16
Background
Spt7 is an integral component of the multi-subunit SAGA complex that is required for the expression of ~10% of yeast genes. Two forms of Spt7 have been identified, the second of which is truncated at its C-terminus and found in the SAGA-like (SLIK) complex. 相似文献2.
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Dr. Agnese Amati Dr. Mirco Natali Prof. Dr. Maria Teresa Indelli Prof. Dr. Elisabetta Iengo Prof. Dr. Frank Würthner 《Chemphyschem》2019,20(17):2195-2203
A side-to-face array DPy-gPBI[Ru(4-tBuTPP)(CO)]2, based on a “green” perylene bisimide chromophore sandwiched between two RuII-porphyrins, has been prepared by self-assembly. Its photophysical properties have been characterized in detail by a combination of steady-state and time-resolved techniques upon selective excitation of the two different components. Different photoinduced processes are observed as a function of the excitation wavelength. Electron transfer quenching is attained upon “red light” excitation of the perylene unit, whilst an energy transfer pathway is followed upon “green light” excitation of the metallo-porphyrin moiety. Regardless of the excitation wavelength efficient population of the triplet excited state of the perylene chromophore is achieved. The photophysical results are discussed within the framework of classical electron transfer theory and compared with those of a previously reported system. 相似文献
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A series of binuclear Ru(II)-Rh(III) complexes of general formula (ttpy)Ru-tpy-(ph)(n)-tpy-Rh(ttpy)(5+) (n = 0-2) have been synthesized, where ttpy = 4'-p-tolyl-2,2':6,2"-terpyridine and tpy-(ph)(n)-tpy represents a bridging ligand where two 2,2':6',2"-terpyridine units are either directly linked together (n = 0) or connected through one (n = 1) or two (n = 2) phenyl spacers in the 4'-position. This series of complexes is characterized by (i) rigid bridge structures and (ii) variable metal-metal distances (11 ? for n = 0, 15.5 ? for n = 1, 20 ? for n = 2). The photophysics of these binuclear complexes has been investigated in 4:1 methanol/ethanol at 77 K (rigid glass) and 150 K (fluid solution) and compared with that of mononuclear [Ru(ttpy)(2)(2+) and Rh(ttpy)(2)(3+)] or binuclear [(ttpy)Ru-tpy-tpy-Ru(ttpy)(4+)] model compounds. At 77 K, no quenching of the Ru(II)-based excited state is observed, whereas energy transfer from excited Rh(III) to Ru(II) is observed for all complexes. At 150 K, energy transfer from excited Rh(III) to Ru(II) is again observed for all complexes, while quenching of excited Ru(II) by electron transfer to Rh(III) is observed, but only in the complex with n = 0. The reasons for the observed behavior can be qualitatively understood in terms of standard electron and energy transfer theory. The different behavior between n = 0 and n = 1, 2 can be rationalized in terms of better electronic factors and smaller reorganizational energies for the former species. The freezing of electron transfer quenching but not of energy transfer, in rigid glasses reflects the different reorganizational energies involved in the two processes. Unusual results arising from multiphotonic and conformational effects have also been observed with these systems. 相似文献
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Indelli MT Orlandi M Chiorboli C Ravaglia M Scandola F Lafolet F Welter S De Cola L 《The journal of physical chemistry. A》2012,116(1):119-131
A series of dyads of general formula Ru(bpy)(2)(bpy-ph(n)-DQ)(4+) (n = 1-5), based on a Ru(II) polypyridine unit as photoexcitable donor, a set of oligo-p-phenylene bridges with 1-5 modular units, and a cyclo-diquaternarized 2,2'-bipyridine (DQ(2+)) as electron acceptor unit, have been synthesized. Their spectroscopic and photophysical properties have been investigated in CH(3)CN and CH(2)Cl(2) by time-resolved emission and absorption spectroscopy in the nanosecond and picosecond time scale. The experimental study has also been complemented with a computational investigation carried out on the whole series of dyads. The absorption spectra of the dyads show new spectroscopic transitions, in addition to those characteristic of the donor, bridge, and acceptor fragments. DFT calculations suggest the assignment of such bands as bridge-to-acceptor (π ph(n)) → (π* DQ) charge-transfer transitions. This assignment is consistent with the solvatochromic and spectroelectrochemical behavior of the new bands. For all the dyads at room temperature in fluid solution, the typical (3)MLCT luminescence of the Ru(II) polypyridine unit is strongly (>90%) quenched, supporting the occurrence of an efficient intramolecular photoinduced electron transfer. The study has revealed, however, that the photophysical mechanism is actually more complex than presumed on the basis of a simple photoinduced electron-transfer scheme. For n = 1, very fast (few picoseconds) photoinduced electron transfer from the MLCT state localized on the substituted bpy ligand to the DQ unit has been observed, followed by slower interligand hopping and charge recombination. For n = 2-5, MLCT excited-state quenching takes place without transient detection of charge-separated product, indicating that charge recombination is faster than charge separation. This behavior can be rationalized in terms of the superexchange couplings expected through this type of bridges for the two processes. The kinetics of MLCT quenching in the dyads with n = 1-5 does not follow the usual exponential falloff with bridge length: after a regular decrease for n = 1-3, the rate constants become almost insensitive to bridge length for n = 3-5. The rationale of this uncommon behavior, as suggested by DFT calculations, lies in a switch in the MLCT quenching mechanism with increasing bridge length, from oxidative quenching by the DQ acceptor to reductive quenching by the bridge. 相似文献
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Iengo E Gatti T Zangrando E Indelli MT Scandola F Alessio E 《Chemical communications (Cambridge, England)》2011,47(5):1616-1618
According to NMR evidence the metal-mediated sandwich assemblies of porphyrins 2 and 3 undergo in solution a thermally driven motion that resembles that of a stepper: the spontaneous rotational motion of the pyridyl rings is converted into a reciprocating linear motion of the porphyrins. 相似文献
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C A Bignozzi R Argazzi M T Indelli F Scandola J R Schoonover G J Meyer 《Journal of Chemical Sciences》1997,109(6):397-409
A series of polynuclear complexes based on RuII, OsII, ReI and RhIII polypyridine moieties have been prepared in the context of intramolecular energy and electron transfer studies and of interfacial
electron transfer with nanocrystalline TiO2. The polynuclear complexes allow for the occurrence of vectorial intramolecular energy and electron transfer and have been
proven to be efficient sensitizers of the wide band-gap semiconductor. The performance of photoregenerative cells based on
these systems and the dynamics of the excited state intramolecular processes and of the interfacial electron transfer processes
are discussed. 相似文献