Ligand exchange reactions with η6-arene-η5-cyclopentadienyliron cations under thermal or photochemical conditions

Reactions of various η⁶-arene-η⁵-cyclopentadienyliron or substituted cyclopentadienyliron cations with trimethyl, triethyl or triphenyl phosphite under either thermal or photochemical conditions all resulted in the replacement of the arene ligand with three phosphite ligands to give η⁵-tris(trimethyl, triethyl or triphenyl phosphite)-η⁵-cyclopentadienyliron or substituted cyclopentadienyliron cations. The yields of the phosphite complexes were higher from photolysis than from the analogous thermolysis. Photolysis of the η⁶-chlorobenzene-η⁵-cyclopentadienyliron cation (IX) carried out in the presence of a more basic or more electron-rich aromatic ligand resulted in the exchange of the chlorobenzene of IX with the more basic arene, thus providing synthetic routes to cyclopentadienyliron complexes that may be difficult to prepare by other means. New complexes synthesized in this way are the η⁶-2-phenylethyl tosylate-η⁵-cyclopentadienyliron cation and the CpFe⁺ complexes of thiophene, 2-methylthiophene, 3-methylthiophene and 2,5-dimethylthiophene.     

Metastasis-suppressor KAI1/CD82 induces homotypic aggregation of human prostate cancer cells through Src-dependent pathway

To investigate the functional role of KAI1/CD82, a metastasis suppressor for human prostate cancer, in the regulation of homotypic cell adhesion, we transfected KAI1 cDNA into DU 145 human prostate cancer cells and established stable transfectant clones with high KAI1/CD82 expression. The KAI1 transfectant cells exhibited significantly increased homotypic cell aggregation in comparison with the control transfectant cells. This aggregation of the KAI1 transfectants was further enhanced upon exposure to anti-CD82 antibody, suggesting that KAI1/CD82 may be involved in the intracellular signaling for the cell adhesion. Among several signal pathway inhibitors tested, PP1, an inhibitor of Src family kinases, significantly suppressed homotypic aggregation of the KAI1 transfectant cells. Ligation of KAI1/CD82 with anti-CD82 antibody increased endogenous Src kinase activity of the KAI1 transfectant cells. When different types of src expression constructs were retransfected into the KAI1-transfected DU 145 cells, kinase-negative mutant src transfectant cells exhibited much lower homotypic aggregation than the mock cells transfected with an empty vector. Moreover, homotypic aggregation of the mutant src transfectant cells was not enhanced by KAI1/CD82 ligation with anti- CD82 antibody. These results suggest that Src mediates the intracellular signaling pathway of KAI1/CD82 for the induction of homotypic adhesion of human prostate cancer cells.     

The nonlinear shear gradient effect on the shear viscosity of a ternary system near a plait point

We have studied the shear viscosity of a ternary liquid mixture (water-ethanol-chloroform) near a plait point by the capillary method and found an apparently strong levelling-off as we approach the critical point. This levelling-off cannot be explained simply in terms of a strong cusp. It is found that the nonlinear shear gradient effect suggested by Oxtoby can be used to explain this behavior.     

Study of the major fragmentation pathways of cypermethrin and related synthetic insecticides using tandem mass spectrometry

Fragmentation pathways of the synthetic pyrethroid cypermethrin and four structurally related insecticides were investigated using a tandem quadrupole mass spectrometer incorporating a hexapole collision cell under positive-ion electron impact ionization conditions. Conventional mass spectrometry using the first quadrupole analyser only and tandem mass spectrometry on selected precursor ions and product ions, and also constant neutral loss scan experiments, were used. Mechanisms and fragmentation pathways are proposed to explain the inherent stability of ions associated with the benzylphenoxy portion of this class of insecticide.     

Enantioselective Addition of Iodine Azide to α,β-Unsaturated Carboxylic Acid Derivatives

The addition of iodine azide to chiral conjugated N-enoyl-sultam or α,β-unsaturated N-acyloxazolidinones generated two asymmetric centers at C(α) and C(β) with high π-face differentiation and regioselectivity. The diastereomerically pure product was easily obtained by crystallization with purity up to 94% de. The structure of 2a was determined by X-ray diffraction analysis which also indicated that B and 4 are reactive conformations.     

The crystal structure and absolute configuration of the antitumor platinum complex trans(OH)-Pt(OH)2(malonato)(1R,2R-cyclohexanediamine).

The absolute configuration of the anti-tumor complex trans(OH)-Pt(OH)2(malonato)(1R,2R-cyclohexanediamine) was determined by X-ray anomalous scattering technique. The final unit cell was monoclinic, space group P2(1) with a = 9.142 A, b = 7.788 A, c = 11.946 A, beta = 96.48 degrees, Z = 2. The crystal structure was determined by direct method and difference Fourier synthesis, and refined to R = 0.025 and Rw = 0.033 based on 2768 independent reflections. The platinum atom has roughly octahedral coordination. The cyclohexane ring has the expected chair configuration, with two amino groups in equatorial positions while the malonato ligand, in contrast, shows a boat conformation for six membered Pt O-C-C-C-O ring.     

Isomerization ofn-hexane overplatinum loaded zeolites

The effect of the calcination temperature of bifunctional Pt/zeolites on the isomerization ofn-hexane has been investigated. The catalyst calcined at 350°C showed the highest metal dispersity and the best activity. The higher selectivity of dimethylbutanes over Pt/H- than over Pt/H-MOR might be attributed to the combined effect of acidity, channel structure and pore size of zeolites.     

Impaired phosphorylation and mis-localization of Bub1 and BubR1 are responsible for the defective mitotic checkpoint function in Brca2-mutant thymic lymphomas

Breast cancer susceptibility gene, BRCA2, is a tumor suppressor and individuals who inherit one defected copy of BRCA2 allele experience early onset breast cancer or ovarian cancer accompanied by the loss of the wild type allele. Mouse model for Brca2 mutation shows growth retardation and paradoxical occurrence of thymic lymphomas. Thymic lymphomas from Brca2-mutant mice harbor mutations in p53, Bub1, and BubR1, which function as mitotic checkpoint proteins. Therefore, interplay between Brca2 and mitotic checkpoint has been suggested in the maintenance of genetic fidelity, although it has not been assessed whether the unique mutations in Bub1 and BubR1 found in Brca2-mutant mice are responsible for the abolishment of mitotic checkpoint function. This report demonstrates that Bub1 and BubR1 mutant proteins from Brca2-/- thymic lymphomas have defects in the phosphorylation and kinetochore localization after spindle damage. Thus, the mutations of Bub1 and BubR1 found in Brca2- mutant mice indeed are responsible for the chromosome instability in Brca2-mutated tumors.     

Indo study of some cyclic carbenes

INDO calculations, with geometry optimization, have been performed on the cyclic carbenes cyclopropenylidene (I) cyclopropylidene (II), and cyclopentadienylidene (III). It is found that all three systems have a singlet ground state and, due to aromaticity, the triplet-singlet energy separations for I and III are particularly large. In addition, for each system, the electronic structure and its influences on geometry and reactivity are discussed.     

Thermosonimetry of the phase II/III transition of hexachloroethane

A thermosonimetric study has shown that the Phase II/III polymorphic transition of hexachloroethane emits acoustic signals. This solid-solid phase transition is known to occur by a nucleation-growth process during which a nucleus of the new phase, once formed, grows at the expense of the mother phase to form a complete crystal without fracture. Acoustic emissions from a conditioned multi-crystal sample have been used to study the transition. Acoustic activity correlated well with dilatometric measurements. Frequency analysis on waveforms of many hundreds of individual acoustic emissions revealed marked differences between individual signals. Principal-components analysis on 24 signal features revealed a single dispersed cluster with a highly non-uniform distribution of signals. These experiments provided highly reproducible average power spectra. Time-resolved acoustic power spectra were also generated. These additional types of information cannot be obtained by other techniques.