Organometallic Compounds of the Lanthanoides. LXVI. Synthesis and X-ray crystal structure of [O(CH2CH2C5H4)2Y(μ-OH]2 and (MeC5H4)3Ho(H2O), two unusual products of the hydrolysis of organolanthanoide compounds

The partial hydrolysis of [O(CH₂CH₂C₅H₄)₂]Y(C₅H₄CH₃) 1 , [O(CH₂CH₂C₅H₄)₂]Y(C₅H₅) 3 , and [O(CH₂CH₂C₅H₄)₂]Ho(C₅H₄CH₃) 5 results in the formation of [O(CH₂CH₂CH₂C₅H₄)₂Y(μ-OH)₂]₂ 2 , (C₅H₅)₃Y(OH₂) 9 and (MeC₅H₄)₃Ho(OH₂) 11 . The new compounds have been characterized by elemental analyses, IR and NMR spectra. The X-ray structural analyses shows 2 to be monoclinic, space group P2₁/n with a = 1146.0(3), b= 1046.6(3), c = 1514.9(3) pm, β = 94.83(2)°. The molecular structure shows bridging hydroxyl groups with a mean distance Y? O = 223.8(3) pm. 11 crystallizes in the cubic space group 14 3d with a = 1847.9(3)pm with Z = 16 molecules per unit cell. The molecules posses symmetry C₃-3, the coordination is trigonal pyramidal with three methylcyclopentadienyl anions and one water molecule as ligands. The distance Ho? O is 231 pm.     

Direct observation of C2 hydrocarbon-oxygen complexes on Ag(110) with a variable-low-temperature scanning tunneling microscope

A variable-low-temperature scanning tunneling microscope (STM) was used to observe oxygen (O2), ethylene (C2H4), and acetylene (C2H2) molecules on a Ag(110) surface and the various complexes that were formed between these two hydrocarbons and oxygen at 13 K. Ethylene molecule(s) were moved to the vicinity of O2 either by STM tunneling electrons at 13 K or thermally at 45 K to form (C2H4)x-O2 (x = 1-4) complexes stabilized by C-H...O hydrogen bonding. Acetylene-oxygen complexes involving one or two acetylene molecules were observed.     

Nachweis der Keimwirkung bei der katalytischen Goldreaktion

Zusammenfassung Eisen(II)sulfat reduziert in saurer Lösung Silbernitrat zu metallischem Silber; diese Reaktion wird durch Goldspuren katalysiert. Bei Abwesenheit von Trägerkeimen liegt die molare Grenzkonzentration für Gold bei etwa 10^–8, bei Gegenwart von Keimen dagegen bei 10^–11 bis 10^–12. Eine geregelte Keimzahl wird durch Zusatz kleinster Bariummengen erhalten, die eine an sich kaum wahrnehmbare Bariumsulfattrübung bilden. Zur praktischen Anwendung geeignet dürfte eine Abänderung der Reaktion sein, bei der als Reduktor Hydrazin in alkalischer, Tartrat und Ammoniak enthaltender Lösung benutzt wird.

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Summary In acid solution, iron(II) sulfate reduces silver nitrate to metallic silver. This reaction is catalyzed by traces of gold. In the absence of carrier nuclei, the molar limiting concentration for gold is about 10^–8, but in the presence of nuclei this limit is 10^–11 to 10^–12. A controlled number of nuclei is obtained by adding very small amounts of barium, which produce a barely visible turbidity of barium sulfate. — For practical application, it may be possible to use a modified form of the reaction, in which the reductant is hydrazine acting in an alcaline solution containing tartrate and ammonia.

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Résumé En solution acide le sulfate de fer (II) réduit le nitrate d'argent à l'état d'argent métallique; cette réaction est catalysée par des traces d'or. En l'absence des germes, la concentration limite pour l'or est environ 10^–8, mais en présence des germes cette limite est 10^–11 à 10^–12. On peut obtenir un nombre connu de germes par addition d'une très petite quantité de baryum qui produira un trouble àpeine visible dû au sulfate de baryum formé. En pratique on peut employer une forme de réaction différente, l'agent réducteur étant l'hydrazine agissant en milieu alcalin en présence de tartrate et d'ammoniaque.

     

Functional involvement of src and focal adhesion kinase in a CD99 splice variant-induced motility of human breast cancer cells

Earlier report showed that expression of a splice variant of CD99 transmembrane protein increases invasive ability of human breast cancer cells. Cell motility was also significantly enhanced by the CD99 splice variant expression. In an effort to identify the cellular components that mediate a signal transduction pathway triggered by the CD99 splice variant, known signal path inhibitors were examined for their effects on the motility of the CD99 splice variant-transfected MDA-MB-231 breast cancer cells. Phenylarsine oxide, an inhibitor of phosphatase specific for focal adhesion kinase, and PP1, an inhibitor of src kinase family, significantly suppressed motility of the cells. Among different types of src transfectant clones generated, kinase-negative mutant src transfectant cells were 80% less motile than the mock cells transfected with an empty-vector, while v-src and c-src transfectants exhibited cell motility levels at or slightly above the mock transfectant. These results suggest that src and focal adhesion kinase mediate the intracellular signaling pathway of a CD99 splice variant for the induction of motility of human breast cancer cells.     

Generation of new landomycins by combinatorial biosynthetic manipulation of the LndGT4 gene of the landomycin E cluster in S. globisporus

A 3 kb DNA fragment from the Streptomyces globisporus 1912 landomycin E (LaE) biosynthetic gene cluster (lnd) was completely sequenced. Three open reading frames were identified, lndGT4, lndZ4, and lndZ5, whose probable translation products resemble a glycosyltransferase, a reductase, and a hydroxylase, respectively. Studies of generated mutants from disruption and complementation experiments involving the lndGT4 gene allowed us to determine that LndGT4 controls the terminal L-rhodinose sugar attachment during LaE biosynthesis and that LndZ4/LndZ5 are responsible for the unique C11-hydroxylation of the landomycins. Generation of the novel landomycins F, G, and H in the course of these studies provided evidence for the flexibility of lnd glycosyltransferases toward their acceptor substrates and a basis for initial structure-activity relationships within the landomycin family of antibiotics.     

Cycloadditionsreaktionen der aminofluorsilane

Aminofluorsilanes are obtained by the reaction of fluorosilanes with the lithium salts of the corresponding amines. The reaction of aminofluorosilanes with butyllithium in a (2 + 2)cyclo addition reaction leads to the formation of fourmembered silicon-nitrogen ring compounds. The mechanism of the reaction is discussed, the mass, ¹H and ¹⁹F NMR spectra of the compounds are reported.     

Exact convergence rates for the bounded law of the iterated logarithm in Hilbert space

Summary In a previous paper we obtained upper and lower class type results refining the bounded LIL for sums of iid Hilbert space valued mean zero random variables, whose covariance operators satisfy certain regularity assumptions. We now establish precise convergence rates for the bounded LIL in the non-regular case. It turns out that the almost sure behavior in this case is entirely different from the behavior in the previous situation.Supported in part by NSF Grant DMS 90-05804