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591.
Wolak MA Melinger JS Lane PA Palilis LC Landis CA Anthony JE Kafafi ZH 《The journal of physical chemistry. B》2006,110(22):10606-10611
We examine the steady-state and time-resolved photoluminescence of guest-host films featuring a dioxolane-substituted pentacene derivative (2,2,10,10-tetraethyl-6,14-bis(triisopropylsilylethynyl)-1,3,9,11-tetraoxadicyclopenta[b,m]pentacene, EtTP-5) dispersed in the hole transporting material (4,4-bis[N-1-naphthyl-N-phenylamino]biphenyl, alpha-NPD). The films show bright red emission (lambda(max) = 640 nm) as a result of efficient F?rster energy transfer from alpha-NPD host molecules to EtTP-5 guest molecules. High absolute photoluminescence (PL) quantum yield (phi(PL) = 76% +/- 4%) and fluorescence lifetime (tau = 18.6 +/- 0.8 ns) were measured at low concentration (0.28 mol % EtTP-5), with moderate PL quenching observed upon increasing the EtTP-5 concentration. The concentrated films (> or = 1.50 mol % EtTP-5) show less evidence of aggregation than previously seen when EtTP-5 was dispersed in tris(quinolin-8-olato)aluminum(III), making alpha-NPD a superior host for the red-emitting EtTP-5. 相似文献
592.
Payne EK Shuford KL Park S Schatz GC Mirkin CA 《The journal of physical chemistry. B》2006,110(5):2150-2154
The optical properties of gold rods electrochemically deposited in anodic aluminum oxide templates have been investigated. Homogeneous suspensions of rods with an average diameter of 85 nm and varying lengths of 96, 186, 321, 465, 495, 578, 641, 735, and 1175 nm were fabricated. The purity and dimensions of these rod nanostructures allowed us to observe higher-order multipole resonances for the first time in a colloidal suspension. The experimental optical spectra agree with discrete dipole approximation calculations that have been modeled from the dimensions of the gold nanorods. 相似文献
593.
Tsefrikas VM Arns S Merner PM Warford CC Merner BL Scott LT Bodwell GJ 《Organic letters》2006,8(23):5195-5198
[Structure: see text] Flash vacuum pyrolysis of 7,10-bis(2-bromophenyl)acenaphtho[1,2-d]pyridazine (C26H14Br2N2) has resulted in a surprising transformation, including dinitrogen loss, to give benzo[a]acecorannulene, a novel C26H12 bowl-shaped fullerene fragment. 相似文献
594.
Oliveri CG Gianneschi NC Nguyen ST Mirkin CA Stern CL Wawrzak Z Pink M 《Journal of the American Chemical Society》2006,128(50):16286-16296
Nature routinely uses cooperative interactions to regulate cellular activity. For years, chemists have designed synthetic systems that aim toward harnessing the reactivity common to natural biological systems. By learning how to control these interactions in situ, one begins to allow for the preparation of man-made biomimetic systems that can efficiently mimic the interactions found in Nature. To this end, we have designed a synthetic protocol for the preparation of flexible metal-directed supramolecular cofacial porphyrin complexes which are readily obtained in greater than 90% yield through the use of new hemilabile porphyrin ligands with bifunctional ether-phosphine or thioether-phosphine substituents at the 5 and 15 positions on the porphyrin ring. The resulting architectures contain two hemilabile ligand-metal domains (RhI or CuI sites) and two cofacially aligned porphyrins (ZnII sites), offering orthogonal functionalities and allowing these multimetallic complexes to exist in two states, "condensed" or "open". Combining the ether-phosphine ligand with the appropriate RhI or CuI transition-metal precursors results in "open" macrocyclic products. In contrast, reacting the thioether-phosphine ligand with RhI or CuI precursors yields condensed structures that can be converted into their "open" macrocyclic forms via introduction of additional ancillary ligands. The change in cavity size that occurs allows these structures to function as allosteric catalysts for the acyl transfer reaction between X-pyridylcarbinol (where X = 2, 3, or 4) and 1-acetylimidazole. For 3- and 4-pyridylcarbinol, the "open" macrocycle accelerates the acyl transfer reaction more than the condensed analogue and significantly more than the porphyrin monomer. In contrast, an allosteric effect was not observed for 2-pyridylcarbinol, which is expected to be a weaker binder and is unfavorably constrained inside the macrocyclic cavity. 相似文献
595.
Chen L Olsen RA Elliott DW Boettcher JM Zhou DH Rienstra CM Mueller LJ 《Journal of the American Chemical Society》2006,128(31):9992-9993
Even as available magnetic fields for NMR continue to increase, resolution remains one of the most critical limitations in assigning and solving structures of larger biomolecules. Here we present a novel constant-time through-bond correlation spectroscopy for solids that offers superior resolution for 13C chemical shift assignments in proteins. In this experiment, the indirect evolution and transfer periods are combined into a single constant time interval, offering increased resolution while not sacrificing sensitivity. In GB1, this allows us to resolve peaks that are otherwise unresolved and to make assignments in the absence of multibond transfers. 相似文献
596.
Stoeva SI Lee JS Smith JE Rosen ST Mirkin CA 《Journal of the American Chemical Society》2006,128(26):8378-8379
We have developed the chemistry for preparing a universal probe and the appropriate nano- and microparticle labels that can be used to do highly selective multiplexed detection of three protein cancer markers at low-femtomolar concentration in buffer and serum media. The approach relies on a new multiplexed version of the biobarcode amplification method and offers new opportunities for studying multiple protein markers in a single sample. This could lead to new forms of disease diagnosis and monitoring disease recurrence in a variety of settings. 相似文献
597.
A two-point set is a subset of the plane which meets every line in exactly two points. We discuss previous work on the topological symmetries of a two-point set, and show that there exist subgroups of S1 which do not leave any two-point set invariant. Further, we show that two-point sets may be chosen to be topological groups, in which case they are also homogeneous. 相似文献
598.
Vamshikrishna Reddy Sammeta Brian M. Anderson John D. Norris Chad D. Torrice Carstyn Joiner Shubin Liu Haoxi Li Konstantin I. Popov Sean W. Fanning Donald P. McDonnell Timothy M. Willson 《Helvetica chimica acta》2023,106(9):e202300097
Synthetic, structural, and computational approaches were used to solve the puzzle as to how a phenolic nonsteroidal estrogen 1 with only a single H-bond to its receptor was more potent than an isomer 2 which formed an intricate network of H-bonds. Synthesis of a series of substituted phenols revealed that pKa was not a determinant of estrogenic activity. First-principles calculation also failed to explain the difference in activity of 1 and 2 . Molecular dynamics revealed that 1 formed a more stable receptor complex compared to 2 , which may explain its increased activity despite forming fewer apparent H-bonds with the protein. 相似文献
599.
A theory is presented for the flow-induced fiber orientation and stress in fiber-reinforced polymer composites with planar fiber orientation. The rate of change of fiber orientation is given as a function of the strain rate in the continuum and the probabilistic effects of physical inter-fiber contacts. The continuum stress is calculated from the stress in the fluid and fibers, where fiber stress is a result of the local disturbance in the fluid velocity field and of the inter-fiber contact forces. Fiber orientation is described via a probability density function whose transport equation has the form of a standard advection-diffusion equation with an orientation-dependent rotary diffusion. This equation is solved using a finite difference scheme and the results are presented. 相似文献