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851.
Actin-binding marine macrolides exhibit significant structural and functional diversity. In this issue, Perrins et al. demonstrate that a long stereochemically conserved aliphatic side chain, known as the "tail", found in many of these compounds is the functional determinant of cytotoxicity (Perrins et al., 2008). 相似文献
852.
Prof. Yasuhiro Morisaki Shizue Ueno Prof. Akinori Saeki Atsushi Asano Prof. Shu Seki Prof. Yoshiki Chujo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4216-4224
[2.2]Paracyclophane‐based through‐space conjugated oligomers and polymers were prepared, in which poly(p‐arylene–ethynylene) (PAE) units were partially π‐stacked and layered, and their properties in the ground state and excited state were investigated in detail. Electronic interactions among PAE units were effective through at least ten units in the ground state. Photoexcited energy transfer occurred from the stacked PAE units to the end‐capping PAE moieties. The electrical conductivity of the polymers was estimated using the flash‐photolysis time‐resolved microwave conductivity (FP‐TRMC) method and investigated together with time‐dependent density functional theory (TD‐DFT) calculations, showing that intramolecular charge carrier mobility through the stacked PAE units was a few tens of percentage larger than through the twisted PAE units. 相似文献
853.
Prof. Dr. Shiki Yagai Keisuke Ohta Marina Gushiken Kazunori Iwai Atsushi Asano Prof. Dr. Shu Seki Dr. Yoshihiro Kikkawa Prof. Dr. Masakazu Morimoto Prof. Dr. Akihide Kitamura Prof. Dr. Takashi Karatsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(8):2244-2253
Diarylethene 1 equipped with two monotopic melamine hydrogen‐bonding sites and oligothiophene‐functionalized ditopic cyanurate (OTCA) were mixed in a nonpolar solvent to form AA‐BB‐type supramolecular co‐polymers (SCPs) bearing photoswitchable moieties in their main chains and extended π systems as side chains. UV/Vis, fluorescence, dynamic light scattering (DLS), TEM, and AFM studies revealed that the two functional co‐monomers formed flexible quasi‐one‐dimensional SCPs in solution that hierarchically self‐organized into helical nanofibers through H‐aggregation of the oligothiophene side chains. Upon irradiating the SCPs with UV light, a transition occurred from the H‐aggregated state to non‐aggregated monomeric oligothiophene side chains, as shown by spectroscopic studies, which indicates the formation of small oligomeric species held together only by hydrogen‐bonding interactions. TEM and AFM visualized unfolded fibrils corresponding to elongated single SCP chains formed upon removal of solvent. The helical nanofibers were regenerated upon irradiating the UVirradiated solution with visible light. These results demonstrated that the supramolecular polymerisation followed by hierarchical organization can be effectively controlled by proper supramolecular designs using diarylethenes and π‐conjugated oligomers. 相似文献
854.
Saigusa D Shiba K Inoue A Hama K Okutani M Iida N Saito M Suzuki K Kaneko T Suzuki N Yamaguchi H Mano N Goto J Hishinuma T Aoki J Tomioka Y 《Analytical and bioanalytical chemistry》2012,403(7):1897-1905
We developed a liquid chromatography/electrospray ionization tandem mass spectrometry method for the simultaneous quantitative determination of C18 sphingosine (Sph), C18 dihydrosphingosine (dhSph), C18 phytosphingosine (pSph), C18 sphingosine-1-phosphate (S1P), C18 dihydrosphingosine-1-phosphate (dhS1P), and C18 phytosphingosine-1-phosphate (pS1P). Samples were prepared by simple methanol deproteinization and analyzed in selected reaction monitoring modes. No peak tailing was observed on the chromatograms using a Capcell Pak ACR column (1.5 mm i.d. × 250 mm, 3 μm, Shiseido). The calibration curves of the sphingoids showed good linearity (r > 0.996) over the range of 0.050-5.00 pmol per injection. The accuracy and precision of this method were demonstrated using four representative biological samples (serum, brain, liver, and spleen) from mice that contained known amounts of the sphingoids. Samples of mice tissue such as plasma, brain, eye, testis, liver, kidney, lung, spleen, lymph node, and thymus were examined for their Sph, dhSph, pSph, S1P, dhS1P, and pS1P composition. The results confirmed the usefulness of this method for the physiological and pathological analysis of the composition of important sphingoids. 相似文献
855.
Yagai S Usui M Seki T Murayama H Kikkawa Y Uemura S Karatsu T Kitamura A Asano A Seki S 《Journal of the American Chemical Society》2012,134(18):7983-7994
Perylene 3,4:9,10-tetracarboxylic acid bisimide (PBI) was functionalized with ditopic cyanuric acid to organize it into complex columnar architectures through the formation of hydrogen-bonded supermacrocycles (rosette) by complexing with ditopic melamines possessing solubilizing alkoxyphenyl substituents. The aggregation study in solution using UV-vis and NMR spectroscopies showed the formation of extended aggregates through hydrogen-bonding and π-π stacking interactions. The cylindrical fibrillar nanostructures were visualized by microscopic techniques (AFM, TEM), and the formation of lyotropic mesophase was confirmed by polarized optical microscopy and SEM. X-ray diffraction study revealed that a well-defined hexagonal columnar (Col(h)) structure was formed by solution-casting of fibrillar assemblies. All of these results are consistent with the formation of hydrogen-bonded PBI rosettes that spontaneously organize into the Col(h) structure. Upon heating the Col(h) structure in the bulk state, a structural transition to a highly ordered lamellar (Lam) structure was observed by variable-temperature X-ray diffraction, differential scanning calorimetry, and AFM studies. IR study showed that the rearrangement of the hydrogen-bonding motifs occurs during the structural transition. These results suggest that such a striking structural transition is aided by the reorganization in the lowest level of self-organization, i.e., the rearrangement of hydrogen-bonded motifs from rosette to linear tape. A remarkable increase in the transient photoconductivity was observed by the flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements upon converting the Col(h) structure to the Lam structure. Transient absorption spectroscopy revealed that electron transfer from electron-donating alkoxyphenyl groups of melamine components to electron-deficient PBI moieties takes place, resulting in a higher probability of charge carrier generation in the Lam structure compared to the Col(h) structure. 相似文献
856.
A new kaempferol glycoside, kaempferol 3-O-alpha-rhamnopyranosyl-(1 --> 2)-[alpha-rhamnopyranosyl-(1 --> 6)-beta-glucopyranoside]-7-O-beta-glucopyranoside (2) was isolated from the flowers of Clematis cultivar "Jackmanii Superba", together with a known kaempferol 3-O-alpha-rhamnopyranosyl-(1 --> 6)-beta-glucopyranoside-7-O-beta-glucopyranoside (1). The chemical structures of the isolated glycosides were established by UV, LC-MS, characterization of acid hydrolysates, and 1H and 13C NMR spectroscopy. 相似文献
857.
Yoshinori Kohashi Takuya Sato Keitaro Ikejiri Katsuhiro Tomioka Shinjiroh Hara Junichi Motohisa 《Journal of Crystal Growth》2012,338(1):47-51
Indium-rich InGaAs nanowires were grown on an InP (111)B substrate by catalyst-free selective-area metal–organic vapor phase epitaxy, and the growth-temperature dependence of growth rate and composition was studied. In particular, nanowire growth rate rapidly decreases as growth temperature increases. This tendency is opposite (for a similar temperature range) to that found in a previous study on selective-area growth of gallium-rich InGaAs nanowires. This difference between indium-rich and gallium-rich nanowires suggests that the influence of growth temperature on the growth of InGaAs nanowires is dependent on the group-III supply ratio. On the basis of previous experimental observations in InAs and GaAs nanowires, temperature dependence of nanowire growth rate and its dependence on group-III supply ratio are predicted. A guideline to determine the optimum growth conditions of InGaAs nanowires is also discussed. 相似文献
858.
859.
Moriya M Tominaga S Hashimoto T Tanifuji K Matsumoto T Ohki Y Tatsumi K Kaneshiro J Uesu Y Sakamoto W Yogo T 《Inorganic chemistry》2012,51(8):4689-4693
A novel chiral coordination polymer, [Cu(C(6)H(5)CH(OH)COO)(μ-C(6)H(5)CH(OH)COO)] (1-L and 1-D), was synthesized through a reaction of copper acetate with L-mandelic acid at room temperature. Although previously reported copper mandelate prepared by hydrothermal reaction was a centrosymmetric coordination polymer because of the racemization of mandelic acid, the current coordination polymer shows noncentrosymmetry and a completely different structure from that previously reported. The X-ray crystallography for 1-L revealed that the copper center of the compound showed a highly distorted octahedral structure bridged by a chiral mandelate ligand in the unusual coordination mode to construct a one-dimensional (1D) zigzag chain structure. These 1D chains interdigitated each other to give a layered structure as a result of the formation of multiple aromatic interactions and hydrogen bonds between hydroxyl and carboxylate moieties at mandelate ligands. The coordination polymer 1-L belongs to the noncentrosymmetric space group of C2 to show piezoelectric properties and second harmonic generation (SHG) activity. 相似文献
860.
Suzuki–Miyaura cross-coupling reaction with 2-heteroarylboronic acids is generally challenging due to these acids easy decomposition. To overcome this problem, we developed a coupling method that uses 2-heteroaryl pinacol boronates in the presence of 1.0 mol % Pd(OAc)2 and 2.0 mol % S-Phos with 4 equiv amount of LiOH in dioxane and H2O at 80 °C for 30 min. This developed method allowed for the synthesis of a wide variety of 2-heteroaryl pyrimidines from 2-chloropyrimidyl derivatives in high yields, and is also useful in the preparation of various biaryl derivatives from heteroaryl chlorides. 相似文献