排序方式: 共有179条查询结果,搜索用时 15 毫秒
161.
Tsuda R Kaino S Kokubo H Imabayashi S Watanabe M 《Colloids and surfaces. B, Biointerfaces》2007,56(1-2):255-259
Redox properties of phenothiazine-labeled poly(ethyl glycidy ether)-block-poly(ethylene oxide) (PT-EGEn-b-EOm) are reversibly changed by core-shell micelle formation. In the temperature range higher than the critical micellization temperature (cmt), the anodic potential of PT group positively shifts and concomitantly its anodic current decrease, or levels off compared to those of the reference polymer PT-EOm without the thermo-responsive EGEn segment. The former alteration is caused by incorporation of hydrophobic PT groups into a core of the micelle and the latter by the decrease in the diffusion coefficient of PT groups due to formation of the core-shell micelles. The cmt value and the temperature-dependent alteration in the redox properties strongly depend on the polymer structure, especially the length of thermo-responsive EGEn segment. The electrochemically determined hydrodynamic radii of the polymer aggregates seem to be overestimated, compared to the values reported for the aggregates of other thermo-responsive polymers with similar molecular weights, implying the presence of electrochemically inactive PT groups in the copolymers having longer thermo-responsive segments. 相似文献
162.
Shibata S Zhang Z Korotkov KV Delarosa J Napuli A Kelley AM Mueller N Ross J Zucker FH Buckner FS Merritt EA Verlinde CL Van Voorhis WC Hol WG Fan E 《Analytical and bioanalytical chemistry》2011,401(5):1585-1591
Ultrafiltration provides a generic method to discover ligands for protein drug targets with millimolar to micromolar K(d), the typical range of fragment-based drug discovery. This method was tailored to a 96-well format, and cocktails of fragment-sized molecules, with molecular masses between 150 and 300 Da, were screened against medical structural genomics target proteins. The validity of the method was confirmed through competitive binding assays in the presence of ligands known to bind the target proteins. 相似文献
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164.
Akine S Hotate S Matsumoto T Nabeshima T 《Chemical communications (Cambridge, England)》2011,47(10):2925-2927
The left-handed isomer of the helical complex [LZn(3)La(OAc)(3)] was spontaneously enriched from 50 : 50 to 87 : 13 when the quasiracemate crystals were dissolved. The invertible helicity of [LZn(3)La(OAc)(3)] (global chirality) helps the quasiracemate formation and the fixed point chirality of the R,R-cyclohexanediamine moiety (local chirality) effectively controls the global chirality in solution. 相似文献
165.
Dr. Tomohiro Seki Sayaka Kurenuma Prof. Dr. Hajime Ito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16214-16220
We report the luminescent color tuning of a new complex, 2‐benzothiophenyl(4‐methoxyphenyl isocyanide)gold(I) ( 1 ), by using a new “polymorph doping” approach. The slow crystallization of the complex 1 afforded three different pure polymorphic crystals with blue, green, and orange emission under UV‐light irradiation. The crystal structures of pure polymorphs of 1 were investigated in detail by means of single‐crystal X‐ray analyses. Theoretical calculations based on the single‐crystal structures provided qualitative explanation of the difference in the excited energy‐levels of the three polymorphs of 1 . In sharp contrast, the rapid precipitation of 1 , with the optimized conditions reproducibly afforded homogeneous powder materials showing solid‐state white‐emission with Commission Internationale de l’Éclairage (CIE) 1931 chromaticity coordinates of (0.33, 0.35), which is similar to pure white. New “polymorphic doping” has been revealed to be critical to this white emission through spectroscopic and X‐ray diffraction analyses. The coexistence of the multiple polymorphs of 1 within the homogeneous powder materials and the ideal mixing of multiple luminescent colors gave its white emission accompanied with energy transfer from the predominant green‐emitting polymorph to the minor orange‐emitting polymorph. 相似文献
166.
An Imidazoline–Aminophenol (IAP) Nickel Catalyst: Structure and Catalytic Activity in the Enantioselective 1,4‐Addition of 3′‐Indolyl‐3‐Oxindoles to Nitroethylene 下载免费PDF全文
Atsuko Awata Makiko Wasai Prof. Dr. Hyuma Masu Sayaka Kado Prof. Dr. Takayoshi Arai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2470-2477
The structure of a nickel complex of imidazoline–aminophenol (IAP) prepared from IAP with Ni(OAc)2 was elucidated as cis‐bis(imidazolineaminophenoxide) [Ni(IAP)2]. The [Ni(IAP)2] complex smoothly promoted catalytic asymmetric 1,4‐addition of 3′‐indolyl‐3‐oxindole to nitroethylene to provide chiral mixed 3,3′‐bisindoles with high enantioselectivities. Mechanistic studies using ESI‐MS analyses suggest that one IAP ligand dissociated from [Ni(IAP)2] to generate the Ni–enolate of 3′‐indolyl‐3‐oxindole. From the optically active 3,3′‐mixed indole adduct, biologically important 3′‐indolyl‐3‐pyrrolidinoindoline was successfully synthesized in a three‐step reaction sequence. 相似文献
167.
Hiroaki Sato Sayaka Nakamura Kanae Teramoto Takafumi Sato 《Journal of the American Society for Mass Spectrometry》2014,25(8):1346-1355
High-resolution mass spectrometry (HRMS) continues to play an important role in the compositional characterization of larger organic molecules. In the field of polymer characterization, however, the application of HRMS has made only slow progress because of lower compatibility between matrix-assisted laser desorption/ionization (MALDI) and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS). In this study, a newly developed type of MALDI high-resolution time-of-flight mass spectrometry (TOFMS) with a spiral ion trajectory (MALDI spiral-TOFMS) was applied to the structural and compositional characterization of polymers. To create a graphical distribution of polymer components on a two-dimensional plot converted from complex mass spectra, we adopted a slightly modified Kendrick mass defect (KMD) analysis based on accurate masses determined using spiral-TOFMS. By setting the Kendrick mass scale based on the mass of the repeating units of a given polymer, components with common repeat units lined up in the horizontal direction on the KMD plot, whereas those components with different structures were shifted vertically. This combination of MALDI spiral-TOFMS measurement and KMD analysis enabled the successful discrimination of the polymer components in a blend of poly(alkylene oxide)s, the compositional analysis of poly(ethylene oxide)/poly(propylene oxide) block copolymers, and profiling of the end-group distribution of poly(ε-caprolactone)s synthesized under different conditions.
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168.
Sayaka Yoshiwaka Kosuke Sasagawa Keiichi Noguchi Noriyuki Yonezawa Akiko Okamoto 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(12):1096-1100
The title molecule, C40H32O6, possesses crystallographically imposed twofold symmetry, with the central two C atoms of the naphthalene unit sited on the rotation axis. The two 4‐phenoxybenzoyl groups in the molecule are twisted away from the attached naphthalene unit, with a torsion angle of 66.76 (15)° between the naphthalene unit and the carbonyl group (C—C—C=O), and are oriented in mutually opposing directions (anti orientation). There is an apparent difference in the conformations of the 4‐phenoxybenzoyl groups at the 1‐ and 8‐positions of the naphthalene ring between the title molecule and its methoxy‐bearing homologue [Hijikata et al. (2010). Acta Cryst. E 66 , o2902–o2903]. Whilst the 4‐phenoxybenzoyl groups in 2,7‐diisopropoxy‐1,8‐bis(4‐phenoxybenzoyl)naphthalene [Yoshiwaka et al. (2013). Acta Cryst. E 69 , o242] are situated in the same anti orientation as the title molecule, those of 2,7‐dimethoxy‐1,8‐bis(4‐phenoxybenzoyl)naphthalene are oriented in the same direction with respect to the naphthalene ring system, i.e. in a syn orientation. 相似文献
169.
Nohara T Okamoto K Matsushita S Fujiwara Y Ikeda T Miyashita H Ono M Yoshimitsu H Kansui H Kunieda T 《Chemical & pharmaceutical bulletin》2008,56(7):1015-1017
Previously, we reported an interesting reaction by which esculeogenin A [(5alpha,22S,23S,25S)-3beta,23,27-trihydroxyspirosolane], a sapogenol of tomato-saponin, esculeoside A, was easily converted into a pregnane derivative, 5alpha-pregn-16-en-3beta-ol-20-one, merely by refluxing with pyridine and water. Its chemical mechanism including air oxidation is here described. 相似文献
170.
A combinatorial synthesis of 24-member RGD models was accomplished on polymer-support. Ortho-, meta-, and para-iodobenzylamines loaded on an aldehyde linker by reductive amination were coupled with RGD sequences and various omega-amino acids by a split-and-pool method. Palladium-catalyzed carbonylative macrolactamization of the polymer-supported cyclization precursors, followed by acid cleavage, provided conformationally restricted RGD model cyclic peptides. 相似文献