Suzuki-Miyaura cross-coupling reactions of aryl tellurides with potassium aryltrifluoroborate salts

Palladium(O)-catalyzed cross-coupling between potassium aryltrifluoroborate salts and aryl tellurides proceeds readily to afford the desired biaryls in good to excellent yield. the reaction seems to be unaffected by the presence of electron-withdrawing or electron-donating substituents in both the potassium aryltrifluoroborate salts and aryl tellurides partners. Biaryls containing a variety of functional groups can be prepared. A chemoselectivity study was also carried out using aryl tellurides bearing halogen atoms in the same compound. in addition, this new version of the Suzuki-Miyaura cross-coupling reaction was monitored by electrospray ionization mass spectrometry where some reaction intermediates were detected and analyzed.Univ São Paulo, Inst Quim, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biofis, São Paulo, BrazilUniv São Paulo, Fac Ciencias Farmaceut, São Paulo, BrazilInst Butantan, CEPID, CAT, Lab Espectrometria Massas, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biofis, São Paulo, BrazilWeb of Scienc

Correction of Enhanced Na+-H+ Exchange of Rat Small Intestinal Brush-Border Membranes in Streptozotocin-induced Diabetes by Insulin or 1,25-Dihydroxycholecalciferol

Diabetes was induced in rats by administration of a single i.p. injection of streptozotocin (50 mg/kg body wt). After 7 d, diabetic rats were further treated with insulin or 1,25-dihydroxycholecalciferol [1,25(0H)2D3J for an additional 5-7 d. Control, diabetic, diabetic + insulin, and diabetic + 1,25(OH)2D3 rats were then killed, their proximal small intestines were removed, and villus-tip epithelial cells were isolated and used to prepare brush-border membrane vesicles. Preparations from each of these groups were then analyzed and compared with respect to their amiloride-sensitive, electroneutral Na+-H+ exchange activity, using 22Na uptake as well as acridine orange techniques. The results of these experiments demonstrated that (a) H+ gradient-dependent 22Na uptake as well as Na+ gradient-dependent transmembrane H+ fluxes were significantly increased in diabetic vesicles compared to their control counterparts, (b) kinetic studies demonstrated that this enhanced 'Na uptake in diabetes was a result of increased maximal velocity (V.,.) of this exchanger with no change in apparent affinity (K.) for Na+, (c) serum levels of 1,25(OH)2D3 were significantly lower in diabetic animals compared with their control counterparts; and (d) insulin or 1,25(OH)2D3 treatment restored the alterations to control values, without any significant changes in K., concomitant with significantly increasing the serum levels of 1,25(OH)2D3 in diabetic animals. These results indicate that Na+-H+ activity is significantly increased in proximal small intestinal luminal membranes of streptozotocin-induced diabetic rats. Moreover, alterations in the serum levels of 1,25(0H)2D3 may, at least in part, explain this enhanced antiporter activity and its correction by insulin. (J. Clin. Invest

Ultra-lightweight and flexible inverted metamorphic four junction solar cells for space applications

In this work an inverted metamorphic four junction (IMM4J) solar cell with 30.9% conversion efficiency in beginning of life conditions under the AM0 (1367 W/m2) spectrum is presented. Additionally, our newest improved IMM3J cell, consisting of Ga0.51In0.49P/GaAs/Ga0.73In0.27As subcells, with 30.6% efficiency is also shown. The IMM4J solar cells consist of Al0.05Ga0.46In0.49P/Al0.14Ga0.86As/Ga0.89In0.11As/Ga0.73In0.27As subcells and are epitaxially grown by metal organic vapor phase epitaxy (MOVPE) on a GaAs substrate. These IMM solar cells achieve power-to-mass ratios of 3 W/g or more, which is more than three times higher than standard germanium based triple or four junction space solar cells. The losses in comparison to the simulated near-term potential efficiency of 33.8% for the IMM4J are analyzed in detail. Furthermore, the irradiation behavior for 1 MeV electron fluences of 1 × 1014 e−/cm2 and 2.5 × 1014 e−/cm2 for the IMM4J cells was investigated. A roadmap to further develop this concept towards an IMM5J with a realistic begin of life (BOL) efficiency potential of 35.9% under AM0 is presented

Substrate phosphorylation affects degradation and interaction to endopeptidase 24.15, neurolysin, and angiotensin-converting enzyme

Recent findings from our laboratory suggest that intracellular peptides containing putative post-translational modification sites (i.e., phosphorylation) could regulate specific protein interactions. Here, we extend our previous observations showing that peptide phosphorylation changes the kinetic parameters of structurally related endopeptidase EP24.15 (EC 3.4.24.15), neurolysin (EC 3.4.24.16), and angiotensin-converting enzyme (EC 3.4.15.1). Phosphorylation of peptides that are degraded by these enzymes leads to reduced degradation, whereas phosphorylation of peptides that interacted as competitive inhibitors of these enzymes alters only the K-i's. These data suggest that substrate phosphorylation could be one of the mechanisms whereby some intracellular peptides would escape degradation and could be regulating protein interactions within cells. (c) 2005 Elsevier Inc. All rights reserved.Univ Cidade São Paulo, Neurociencias Lab, BR-03071000 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biofis, BR-04044020 São Paulo, SP, BrazilUniv São Paulo, Inst Ciencias Biomed, Programa Biol Celular, Dept Biol Celular & Desenvolvimento, BR-05508900 São Paulo, BrazilPtoteimax Biotecnol LTDA, BR-06700900 Cotia, SP, BrazilCEPID, CAT, Inst Butantan, Lab Especial Toxinol Aplicada, BR-05467010 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biofis, BR-04044020 São Paulo, SP, BrazilWeb of Scienc

Polyphase Magmatism During the Formation of the Northern East Greenland Continental Margin

New marine geophysical data acquired across the partly ice-covered northern East Greenland continental margin highlight a complex interaction between tectonic and magmatic events. Breakup-related lava flows are imaged in reflection seismic data as seaward dipping reflectors, which are found to decrease in size both northward and southward from a central point at 75°N. We provide evidence that the magnetic anomaly pattern in the shelf area is related to volcanic phases and not to the presence of oceanic crust. The remnant magnetization of the individual lava flows is used to deduce a relative timing of the emplacement of the volcanic wedges. We find that the seaward dipping reflectors have been emplaced over a period of 2–4 Ma progressively from north to south and from landward to seaward. The new data indicate a major post-middle Eocene magmatic phase around the landward termination of the West Jan Mayen Fracture Zone. This post-40-Ma volcanism likely was associated with the progressive separation of the Jan Mayen microcontinent from East Greenland. The breakup of the Greenland Sea started at several isolated seafloor spreading cells whose location was controlled by rift structures and led to the present-day segmentation of the margin. The original rift basins were subsequently connected by steady-state seafloor spreading that propagated southward, from the Greenland Fracture Zone to the Jan Mayen Fracture Zone