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951.
Ki-Young Choi Seung-Man Yang Kyu-Chul Lee Haiil Ryu Chan Hee Lee Jungho Seo Mancheol Suh 《Transition Metal Chemistry》2008,33(1):99-105
The tridentate ligand 2-Oximino-3-thiosemicarbazone-2,3-butanedione (Hotsb) reacts with MCl2 (M = Ni2+ or Cu2+) to give rise to the mononuclear complexes [Ni(Hotsb)2]Cl2 · H2O (1) and [Cu(Hotsb)Cl2] · H2O (2). These complexes have been characterized by X-ray crystallography, spectroscopy, and cyclic voltammetry. The nickel(II) ion
in (1) is in a six-coordinate octahedral environment being bonded to the two protonated tridentate ligands which occupy mer positions. The copper(II) ion in (2) is in a five-coordinate square-pyramidal geometry, in which the basal plane is made up the two nitrogens, sulfur, and chloride
atom, while the other chloride atom is coordinated at the axial position. The cyclic voltammogram of the complexes displays
two one-electron waves corresponding to MII/MIII and MII/MI processes. The electronic as well as infrared spectral properties of the title complexes are reported and discussed. 相似文献
952.
Jae Hee Song Jong Ryoung Park Yeong-Joon Kim 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,324(1-3):155-158
We describe a synthetic route for the high yield production of Au nanomaterials via a simple one step reduction process. Thenoyltrifluoroacetone was used as a reducing and stabilizing agent as well for the synthesis of gold nanoparticles. The reaction rate for the formation of Au nanoparticles using thenoyltrifluoroacetone was much faster than that of any other β-diketones such as acetylacetone. By simply varying the reaction temperature and the concentration, the shape and size of the resulting Au nanocrystals were easily controlled. The colloidal state of the Au nanocrystals in water lasts several weeks without any spectral changes. 相似文献
953.
Poulsen A William A Lee A Blanchard S Teo E Deng W Tu N Tan E Sun E Goh KL Ong WC Ng CP Goh KC Bonday Z 《Journal of computer-aided molecular design》2008,22(12):897-906
The Aurora family of serine/threonine kinases are mitotic regulators involved in centrosome duplication, formation of the
bipolar mitotic spindle and the alignment of the chromosomes along the spindle. These proteins are frequently overexpressed
in tumor cells as compared to normal cells and are therefore potential therapeutic oncology targets. An Aurora A high throughput
screen revealed a promising sub-micromolar indazole-benzimidazole lead. Modification of the benzimidazole portion of the lead
to a C2 linker with a phenyl ring was proposed to achieve novelty. Docking revealed that a conjugated linker was optimal and
the resulting compounds were equipotent with the lead. Further structure-guided optimization of substituents on the 5 & 6
position of the indazole led to single digit nanomolar potency. The homology between the Aurora A & Aurora B kinase domains
is 71% but their binding sites only differ at residues 212 & 217 (Aurora A numbering). However interactions with only the
latter residue may be used for obtaining selectivity. An analysis of published Aurora A and Aurora B X-ray structures reveals
subtle differences in the shape of the binding sites. This was exploited by introduction of appropriately sized substituents
in the 4 & 6 position of the indazole leading to Aurora B selective inhibitors. Finally we calculate the conformational energy
penalty of the putative bioactive conformation of our inhibitors and show that this property correlates well with the Aurora
A binding affinity. 相似文献
954.
M. S. Balathanigaimani Min-Joo Lee Wang-Geun Shim Jae-Wook Lee Hee Moon 《Adsorption》2008,14(4-5):525-532
Methane adsorptions on various synthesized and commercial activated carbons were assessed in a volumetric apparatus for the design of an efficient adsorbed natural gas storage system. Based on the methane adsorption equilibrium results from different carbon based materials, a monolith was also produced from RP-20. Dynamic studies were also performed for the prepared monolith and the pelletized commercial Norit-B4 activated carbon. The temperature variation in RP-20 monolith was analyzed and compared with those of Norit-B4 and a blank test, which consisted of a run without a sample. The temperature variation in RP-20 monolith was quite high compared to that observed with Norit-B4 and the blank test because of a higher isosteric heat of adsorption and a high packing density. 相似文献
955.
Kim HM Kim BR An MJ Hong JH Lee KJ Cho BR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(7):2075-2083
2-Acetyl-6-(dimethylamino)naphthalene-derived two-photon fluorescent Ca2+ probes (ACa1-ACa3) are reported. They can be excited by a 780 nm laser beam, show 23-50-fold enhancement in one- and two-photon excited fluorescence in response to Ca2+, emit fourfold stronger two-photon excited fluorescence than Oregon Green 488 BAPTA-1 upon complexation with Ca2+, and can selectively detect intracellular free Ca2+ ions in live cells and living tissues with minimum interference from other metal ions and membrane-bound probes. Moreover, these probes are capable of monitoring calcium waves at a depth of 120-170 microm in live tissues for 1100-4000 s using two-photon microscopy with no artifacts of photobleaching. 相似文献
956.
Sang S Lee MJ Yang I Buckley B Yang CS 《Rapid communications in mass spectrometry : RCM》2008,22(10):1567-1578
Tea is rich in polyphenols and has a variety of biological activities. In order to better understand the biological effects of tea constituents on human health, markers for their exposure and their metabolic fates are needed. Previously, we have characterized several catechin metabolites in the blood and urine, but more information on the metabolite profile of tea polyphenols is needed. In the present study, the human urinary metabolite profile of tea polyphenols was investigated using liquid chromatography/electrospray ionization tandem mass spectrometry with data-dependent acquisition. With data-dependent MS/MS analysis by collecting the MS2 and MS3 spectra of the most intense ions in the sample, we identified more than twenty metabolites of tea polyphenols from human urine samples. (-)-Epigallocatechin (EGC) glucuronide, methylated EGC glucuronide, methylated EGC sulfate, (-)-epicatechin (EC) glucruronide, EC sulfate, methylated EC sulfate, as well as the glucuronide and sulfate metabolites of the ring-fission metabolites of tea catechins, 5-(3',4',5'-trihydroxyphenyl)-gamma-valerolactone (M4), 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone (M6) and 5-(3',5'-dihydroxyphenyl)-gamma-valerolactone (M6'), were the major human urinary metabolites of tea polyphenols. To our knowledge, this is the first report of the direct simultaneous analysis of the human urinary metabolite profile of tea polyphenols using single sample analysis. This method can also be used for thorough investigations of the metabolite profiles of many other dietary constituents. 相似文献
957.
Ohira S Rudra I Schmidt K Barlow S Chung SJ Zhang Q Matichak J Marder SR Brédas JL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(35):11082-11091
Many squaraines have been observed to exhibit two-photon absorption at transition energies close to those of the lowest energy one-photon electronic transitions. Here, the electronic and vibronic contributions to these low-energy two-photon absorptions are elucidated by performing correlated quantum-chemical calculations on model chromophores that differ in their terminal donor groups (diarylaminothienyl, indolenylidenemethyl, dimethylaminopolyenyl, or 4-(dimethylamino)phenylpolyenyl). For squaraines with diarylaminothienyl and dimethylaminopolyenyl donors and for the longer examples of 4-(dimethylamino)phenylpolyenyl donors, the calculated energies of the lowest two-photon active states approach those of the lowest energy one-photon active (1B(u)) states. This is consistent with the existence of purely electronic channels for low-energy two-photon absorption (TPA) in these types of chromophores. On the other hand, for all squaraines containing indolinylidenemethyl donors, the calculations indicate that there are no low-lying electronic states of appropriate symmetry for TPA. Actually, we find that the lowest energy TPA transitions can be explained through coupling of the one-photon absorption (OPA) active 1B(u) state with b(u) vibrational modes. Through implementation of Herzberg-Teller theory, we are able to identify the vibrational modes responsible for the low-energy TPA peak and to reproduce, at least qualitatively, the experimental TPA spectra of several squaraines of this type. 相似文献
958.
Chung MK Hebling CM Jorgenson JW Severin K Lee SJ Gagné MR 《Journal of the American Chemical Society》2008,130(35):11819-11827
A dynamic combinatorial library composed of racemic hydrazone-based dipeptides becomes deracemized on binding to the chiral analytes (-)-cytidine and (-)-2-thiocytidine through the amplification of two receptors, (SS)-dimer and (RRRR)-tetramer. The deracemization phenomenon was investigated by laser polarimetry, mass-tagged pseudo-enantiomers in conjunction with electrospray ionization mass spectrometry, HPLC/UV-MS, UPLC/UV-MS, rapid-resolution LC-MS, collision-induced dissociation MS/MS, and numerical simulations. These data were consistent with a phenomenon where (SS)-dimer and (RRRR)-tetramer selectively bind the chiral analyte in preference to their enantiomeric counterparts, which ultimately causes them to be amplified and the library to become deracemized. 相似文献
959.
Baik JM Shon Y Lee SJ Jeong YH Kang TW Lee JL 《Journal of the American Chemical Society》2008,130(41):13522-13523
We report the room-temperature ferromagnetism in transition metals (Co, Ni)-doped 8-hydroxy-quinoline aluminum (Alq3) by thermal coevaporation of high purity metal and Alq3 powders. For 5% Co-doped Alq3, a maximum magnetization of approximately 0.33 microB/Co at 10 K was obtained and ferromagnetic behavior was observed up to 300 K. The Co atoms interact chemically with O atoms and provide electrons to Alq3, forming new states acting as electron trap sites. From this, it is suggested that ferromagnetism may be associated with the strong chemical interaction of Co atoms and Alq3 molecules. 相似文献
960.
Chung LW Hayashi S Lundberg M Nakatsu T Kato H Morokuma K 《Journal of the American Chemical Society》2008,130(39):12880-12881
Firefly emission is a well-known efficient bioluminescence. However, the mystery of the efficient thermal generation of electronic excited states in firefly still remains unsolved, particularly at the atomic and molecular levels. We performed SA-CASSCF(12,12)/6-31G* and CASPT2(12,12)/6-31G*//SA-CASSCF(12,12)/6-31G* calculations to elucidate the reaction mechanism of bioluminescence from the firefly dioxetanone in the gas phase. Adiabatic transition state (TS) for the O-O bond cleavage and the minimum energy conical intersection (MECI) were located and characterized. The unique topology of MECI featuring a seam of a sloped conical intersection for the firefly dioxetanone, which was uncovered for the first time, emerges along the reaction pathway to provide a widely extended channel to diabatically access the excited-state from the ground state. 相似文献