Magnetooptical Properties of Chiral [Co2Ln] Clusters.

Two pairs of enantiomeric 3d-4f metal clusters, [Co2Ln[( R )/( S )-L]4]·Cl5·(H2O)2·CH3OH·CH3CH2OH [ Co 2 Ln ; Ln = Gd ( 1S and 1R ), Dy ( 2S and 2R )], were synthesized by the reaction of chiral Schiff-base ligand ( R )/( S )-3-[(2-hydroxybenzylidene) amino]propane-1,2-diol [( R )/( S )-HL] with CoCl2·6H2O and LnCl3·6H2O. The circular dichroism spectra of ( S )/( R )-Co 2 Ln display a mirror-symmetry effect with seven peaks at 210-800 nm, which can be ascribed to π-π* transitions, exciton coupling, charge-transfer transitions between ligands and Co3+, and characteristic d-d transitions of Co3+ ions. Interestingly, the chiral Co 2 Ln metal clusters display strong magnetic circular dichroism signals at room temperature. This work suggests that the chiromagnetic metal cluster is expected to show a strong magnetooptical response

Identification of Antifreeze Proteins and Their Functional Residues by Support Vector Machine and Genetic Algorithms based on n-Peptide Compositions

For the first time, multiple sets of n-peptide compositions from antifreeze protein (AFP) sequences of various cold-adapted fish and insects were analyzed using support vector machine and genetic algorithms. The identification of AFPs is difficult because they exist as evolutionarily divergent types, and because their sequences and structures are present in limited numbers in currently available databases. Our results reveal that it is feasible to identify the shared sequential features among the various structural types of AFPs. Moreover, we were able to identify residues involved in ice binding without requiring knowledge of the three-dimensional structures of these AFPs. This approach should be useful for genomic and proteomic studies involving cold-adapted organisms

An Updated Search of Steady TeV γ−\gamma-Ray Point Sources in Northern Hemisphere Using the Tibet Air Shower Array

Using the data taken from Tibet II High Density (HD) Array (1997 February-1999 September) and Tibet-III array (1999 November-2005 November), our previous northern sky survey for TeV $\gamma-$ray point sources has now been updated by a factor of 2.8 improved statistics. From $0.0^{\circ}$ to $60.0^{\circ}$ in declination (Dec) range, no new TeV $\gamma-$ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV $\gamma-$ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.Comment: This paper has been accepted by hepn

Electron quantum metamaterials in van der Waals heterostructures

In recent decades, scientists have developed the means to engineer synthetic periodic arrays with feature sizes below the wavelength of light. When such features are appropriately structured, electromagnetic radiation can be manipulated in unusual ways, resulting in optical metamaterials whose function is directly controlled through nanoscale structure. Nature, too, has adopted such techniques -- for example in the unique coloring of butterfly wings -- to manipulate photons as they propagate through nanoscale periodic assemblies. In this Perspective, we highlight the intriguing potential of designer sub-electron wavelength (as well as wavelength-scale) structuring of electronic matter, which affords a new range of synthetic quantum metamaterials with unconventional responses. Driven by experimental developments in stacking atomically layered heterostructures -- e.g., mechanical pick-up/transfer assembly -- atomic scale registrations and structures can be readily tuned over distances smaller than characteristic electronic length-scales (such as electron wavelength, screening length, and electron mean free path). Yet electronic metamaterials promise far richer categories of behavior than those found in conventional optical metamaterial technologies. This is because unlike photons that scarcely interact with each other, electrons in subwavelength structured metamaterials are charged, and strongly interact. As a result, an enormous variety of emergent phenomena can be expected, and radically new classes of interacting quantum metamaterials designed

Targeting cholesterol-rich microdomains to circumvent tamoxifen-resistant breast cancer

Adjuvant treatment with tamoxifen substantially improves survival of women with estrogen-receptor positive (ER+) tumors. Tamoxifen resistance (TAMR) limits clinical benefit. RRR alpha tocopherol ether-linked acetic acid analogue (alpha-TEA) is a small bioactive lipid with potent anticancer activity. We evaluated the ability of alpha-TEA in the presence of tamoxifen to circumvent TAMR in human breast cancer cell lines. Methods: Two genotypically matched sets of TAM-sensitive (TAMS) and TAM-resistant (TAMR) human breast cancer cell lines were assessed for signal-transduction events with Western blotting, apoptosis induction with Annexin V-FITC/PI assays, and characterization of cholesterol-rich microdomains with fluorescence staining. Critical involvement of selected mediators was determined by using RNA interference and chemical inhibitors. Results: Growth-factor receptors (total and phosphorylated forms of HER-1 and HER-2), their downstream prosurvival mediators pAkt, pmTOR, and pERK1/2, phosphorylated form of estrogen receptor-alpha (pER-alpha at Ser-167 and Ser-118, and cholesterol-rich lipid microdomains were highly amplified in TAMR cell lines and enhanced by treatment with TAM. alpha-TEA disrupted cholesterol-rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators, and induced DR5-mediated mitochondria-dependent apoptosis via an endoplasmic reticulum stress-triggered pro-death pJNK/CHOP/DR5 amplification loop. Furthermore, methyl-beta-cyclodextrin (M beta CD), a chemical disruptor of cholesterol rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators and to induce apoptosis. Conclusions: Data for the first time document that targeting cholesterol-rich lipid microdomains is a potential strategy to circumvent TAMR, and the combination of alpha-TEA + TAM can circumvent TAMR by suppression of prosurvival signaling via disruption of cholesterol-rich lipid microdomains and activation of apoptotic pathways via induction of endoplasmic reticulum stress.Clayton Foundation for ResearchCenter for Molecular and Cellular Toxicology at the University of TexasNIEHS/NIH T32 ES07247Nutritional Science

Formation of buckminsterfullerene and its perchlorinated fragments by laser ablation of perchloroacenaphthylene

通讯作者地址: Zheng, LS (通讯作者), Xiamen Univ, Dept Chem, State Key Lab Phys Chem Solid Surface, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, Dept Chem, State Key Lab Phys Chem Solid Surface, Xiamen 361005, Peoples R China 学科类别: Chemistry, Physical; Physics, Atomic, Molecular & Chemical IDS 号: 343CF ISSN: 1089-5639 DOI: 10.1021/jp0012395Perchloroacenaphthylene(C12Cl8), a perchlorinated polycyclic hydrocarbon composed of two hexagons and a pentagon, was ablated by a pulsed laser beam in a vacuum. The products created from the laser ablation were characterized by high-performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry and rapid-scan ultraviolet spectrophotometric detection. Buckminsterfullerene C-60 and various perchlorinated carbon clusters have been observed among the products. The observation is helpful for understanding the formation mechanisms of fullerenes and suggests that the Pentagon Road scheme is feasible with the involvement of chlorines

Microwave synthesis of fullerenes from chloroform

Zheng, LS (通讯作者), Xiamen Univ, Dept Chem, State Key Lab Phys Chem Solid Surface, Xiamen 361005, Peoples R ChinaFullerenes C-60 and C-70 were synthesized continuously via microwave plasma from chloroform at low pressure argon atmosphere, and identified in toluene extracts of soot, using high-performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry and diode-array spectrophotometric detection. Yield of C-60 (0.3%-1.3%) and C-70 (0.1%-0.3%) and their ratio depend on the temperature gradient and the collision probability. Besides fullerenes, a series of perchlorinated carbon clusters were found in the synthesis products. Since frameworks of the products are fragments of fullerenes, the further investigation of this process may lead to a better knowledge of the formation mechanisms of fullerenes. (C) 1999 American Institute of Physics. [S0003-6951(99)03944-3]