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排序方式: 共有260条查询结果,搜索用时 31 毫秒
221.
Open‐Circuit Voltage in Organic Solar Cells: The Impacts of Donor Semicrystallinity and Coexistence of Multiple Interfacial Charge‐Transfer Bands
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Guy O. Ngongang Ndjawa Kenneth R. Graham Sonya Mollinger Di M. Wu David Hanifi Rohit Prasanna Bradley D. Rose Sukumar Dey Liyang Yu Jean‐Luc Brédas Michael D. McGehee Alberto Salleo Aram Amassian 《Liver Transplantation》2017,7(12)
In organic solar cells (OSCs), the energy of the charge‐transfer (CT) complexes at the donor–acceptor interface, E CT, determines the maximum open‐circuit voltage (V OC). The coexistence of phases with different degrees of order in the donor or the acceptor, as in blends of semi‐crystalline donors and fullerenes in bulk heterojunction layers, influences the distribution of CT states and the V OC enormously. Yet, the question of how structural heterogeneities alter CT states and the V OC is seldom addressed systematically. In this work, we combine experimental measurements of vacuum‐deposited rubrene/C60 bilayer OSCs, with varying microstructure and texture, with density functional theory calculations to determine how relative molecular orientations and extents of structural order influence E CT and V OC. We find that varying the microstructure of rubrene gives rise to CT bands with varying energies. The CT band that originates from crystalline rubrene lies up to ≈0.4 eV lower in energy compared to the one that arises from amorphous rubrene. These low‐lying CT states contribute strongly to V OC losses and result mainly from hole delocalization in aggregated rubrene. This work points to the importance of realizing interfacial structural control that prevents the formation of low E CT configurations and maximizes V OC. 相似文献
222.
Aydar Y Sukumar S Szakal AK Tew JG 《Journal of immunology (Baltimore, Md. : 1950)》2005,174(9):5358-5366
It is believed that Ag in immune complexes (ICs) on follicular dendritic cells (FDCs) selects high affinity B cells and promotes affinity maturation. However, selection has been documented in the absence of readily detectable ICs on FDCs, suggesting that FDC-ICs may not be important. These results prompted experiments to test the hypothesis that IC-bearing murine FDCs can promote high affinity IgG responses by selecting B cells after stimulating naive IgM(+) cells to mature and class switch. Coculturing naive lambda(+) B cells, FDCs, (4-hydroxy-3-nitrophenyl)acetyl-chicken gamma-globulin (CGG) + anti-CGG ICs, and CGG-primed T cells resulted in FDC-lymphocyte clusters and production of anti-4-hydroxy-5-iodo-3-nitrophenyl acetyl. Class switching was indicated by a shift from IgM to IgG, and affinity maturation was indicated by a change from mostly low affinity IgM and IgG in the first week to virtually all high affinity IgG anti-4-hydroxy-5-iodo-3-nitrophenyl acetyl in the second week. Class switching and affinity maturation were easily detectable in the presence of FDCs bearing appropriate ICs, but not in the absence of FDCs. Free Ag plus FDCs resulted in low affinity IgG, but affinity maturation was only apparent when FDCs bore ICs. Class switching is activation-induced cytidine deaminase (AID) dependent, and blocking FDC-CD21 ligand-B cell CD21 interactions inhibited FDC-IC-mediated enhancement of AID production and the IgG response. In short, these data support the concept that ICs on FDCs can promote AID production, class switching, and maturation of naive IgM(+) B cells, and further suggest that the IC-bearing FDCs help select high affinity B cells that produce high affinity IgG. 相似文献
223.
Nicotinic receptor signaling in nonexcitable cells 总被引:6,自引:0,他引:6
The finding that neuronal nicotinic acetylcholine receptors (nAChRs) are present in non-neuronal cells both within and outside the nervous system raises some interesting issues. The mechanisms underlying receptor signaling and its downstream consequences in these cells remain to be elucidated. Factors controlling the release of acetylcholine and the extent of its diffusion are likely to be different for these cells than for traditional neuronal synapses. Recent advances on the physiologic functions of some of these cell types have provided a better insight into possible functional roles for nAChRs in nonexcitable cells. The presence of nAChRs on these cells also implies a broader scope for the actions of nicotine that needs to be considered from a clinical viewpoint. Revealing the potential physiologic roles for nAChRs on nonexcitable cells is likely to provide a more complete understanding of cholinergic signaling. 相似文献
224.
Enyedy IJ Sakamuri S Zaman WA Johnson KM Wang S 《Bioorganic & medicinal chemistry letters》2003,13(3):513-517
Abnormal dopamine signaling in brain has been implicated in several conditions such as cocaine abuse, Parkinson's disease and depression. Potent and selective dopamine transporter inhibitors may be useful as pharmacological tools and therapeutic agents. Simple substituted pyridines were discovered as novel dopamine transporter (DAT) inhibitors through pharmacophore-based 3D-database search. The most potent compound 18 has a K(i) value of 79 nM in inhibition of WIN35,248 binding to dopamine transporter and 255 nM in inhibition of dopamine reuptake, respectively, as potent as cocaine. Preliminary structure-activity relationship studies show that the geometry and the nature of the substituents on the pyridine ring determine the inhibitory activity and selectivity toward the three monoamine transporters. The substituted pyridines described herein represent a class of novel DAT inhibitors with simple chemical structures and their discovery provides additional insights into the binding site of DAT. 相似文献
225.
Zhang XD Jenkins JN Callahan FE Creech RG Si Y McCarty JC Saha S Ma DP 《Biochimica et biophysica acta》2003,1625(3):269-279
226.
Population differentiation within and among Asian elephant (Elephas maximus) populations in southern India 总被引:1,自引:0,他引:1
Southern India, one of the last strongholds of the endangered Asian elephant (Elephas maximus), harbours about one-fifth of the global population. We present here the first population genetic study of free-ranging Asian elephants, examining within- and among-population differentiation by analysing mitochondrial DNA (mtDNA) and nuclear microsatellite DNA differentiation across the Nilgiris-Eastern Ghats, Anamalai, and Periyar elephant reserves of southern India. Low mtDNA diversity and 'normal' microsatellite diversity were observed. Surprisingly, the Nilgiri population, which is the world's single largest Asian elephant population, had only one mtDNA haplotype and lower microsatellite diversity than the two other smaller populations examined. There was almost no mtDNA or microsatellite differentiation among localities within the Nilgiris, an area of about 15,000 km2. This suggests extensive gene flow in the past, which is compatible with the home ranges of several hundred square kilometres of elephants in southern India. Conversely, the Nilgiri population is genetically distinct at both mitochondrial and microsatellite markers from the two more southerly populations, Anamalai and Periyar, which in turn are not genetically differentiated from each other. The more southerly populations are separated from the Nilgiris by only a 40-km-wide stretch across a gap in the Western Ghats mountain range. These results variably indicate the importance of population bottlenecks, social organization, and biogeographic barriers in shaping the distribution of genetic variation among Asian elephant populations in southern India. 相似文献
227.
de Garavilla L Greco MN Sukumar N Chen ZW Pineda AO Mathews FS Di Cera E Giardino EC Wells GI Haertlein BJ Kauffman JA Corcoran TW Derian CK Eckardt AJ Damiano BP Andrade-Gordon P Maryanoff BE 《The Journal of biological chemistry》2005,280(18):18001-18007
Certain leukocytes release serine proteases that sustain inflammatory processes and cause disease conditions, such as asthma and chronic obstructive pulmonary disease. We identified beta-ketophosphonate 1 (JNJ-10311795; RWJ-355871) as a novel, potent dual inhibitor of neutrophil cathepsin G (K(i) = 38 nm) and mast cell chymase (K(i) = 2.3 nm). The x-ray crystal structures of 1 complexed with human cathepsin G (1.85 A) and human chymase (1.90 A) reveal the molecular basis of the dual inhibition. Ligand 1 occupies the S(1) and S(2) subsites of cathepsin G and chymase similarly, with the 2-naphthyl in S(1), the 1-naphthyl in S(2), and the phosphonate group in a complex network of hydrogen bonds. Surprisingly, however, the carboxamido-N-(naphthalene-2-carboxyl)piperidine group is found to bind in two distinct conformations. In cathepsin G, this group occupies the hydrophobic S(3)/S(4) subsites, whereas in chymase, it does not; rather, it folds onto the 1-naphthyl group of the inhibitor itself. Compound 1 exhibited noteworthy anti-inflammatory activity in rats for glycogen-induced peritonitis and lipopolysaccharide-induced airway inflammation. In addition to a marked reduction in neutrophil influx, 1 reversed increases in inflammatory mediators interleukin-1alpha, interleukin-1beta, tissue necrosis factor-alpha, and monocyte chemotactic protein-1 in the glycogen model and reversed increases in airway nitric oxide levels in the lipopolysaccharide model. These findings demonstrate that it is possible to inhibit both cathepsin G and chymase with a single molecule and suggest an exciting opportunity in the treatment of asthma and chronic obstructive pulmonary disease. 相似文献
228.
The levels of seven elements determined in the hair were compared between male controls and industrial workers from Madras
(South India). Particularly, the concentrations of Cd, Cr, Cu, Mn, and Ni in the foundry workers and Cu, Mn, and Ni in the
workers of a workshop and match factory were observed to be higher than that of controls working in the office. In addition,
the occupation, age, and period of service of workers had an influence, but diet, smoking habits, income of family, and hair
color had no influence on the element levels in the hair. 相似文献
229.
The conformational analysis of a protected homodipeptide of 1-aminocyclopentanecarboxylic acid (Acc5) has been carried out. 1H-nmr studies establish a β-turn conformation for Boc-Acc5-Acc5-NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X-ray diffraction studies reveal a type III β-turn conformation in the solid state stabilized by a 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The ?,ψ values for both Acc5 residues are close to those expected for an ideal 310-helical conformation (?? ± 60°, ψ~ ±30°). 相似文献
230.