Pre-M Phase-promoting Factor Associates with Annulate Lamellae in Xenopus Oocytes and Egg Extracts

We have used complementary biochemical and in vivo approaches to study the compartmentalization of M phase-promoting factor (MPF) in prophase Xenopus eggs and oocytes. We first examined the distribution of MPF (Cdc2/CyclinB2) and membranous organelles in high-speed extracts of Xenopus eggs made during mitotic prophase. These extracts were found to lack mitochondria, Golgi membranes, and most endoplasmic reticulum (ER) but to contain the bulk of the pre-MPF pool. This pre-MPF could be pelleted by further centrifugation along with components necessary to activate it. On activation, Cdc2/CyclinB2 moved into the soluble fraction. Electron microscopy and Western blot analysis showed that the pre-MPF pellet contained a specific ER subdomain comprising "annulate lamellae" (AL): stacked ER membranes highly enriched in nuclear pores. Colocalization of pre-MPF with AL was demonstrated by anti-CyclinB2 immunofluorescence in prophase oocytes, in which AL are positioned close to the vegetal surface. Green fluorescent protein-CyclinB2 expressed in oocytes also localized at AL. These data suggest that inactive MPF associates with nuclear envelope components just before activation. This association may explain why nuclei and centrosomes stimulate MPF activation and provide a mechanism for targeting of MPF to some of its key substrates

Schuldiger Glückwunsch Dem WolEhrenvesten ... Herrn Samueli Movio, von Colberg aus Pommern SS. Theol. Studios. als Er den 13. Octobr. des 1659. Jahrs der Weltweißheit Magister erkläret ward

Außgeruffen ... Von Johann Detlaff/ von Colberg aus Pommern ..

Caffeine : properties and examples of use

1,3,7-trimethyloxanthine commonly known as caffeine is naturally occurring alkaloid inter alia in coffee beans. It is acquired mainly in decaffeination of coffee process. It can also be synthesized by subsequent chemical reactions from uracil or by using enzymatic reaction assuming transfer of methyl group on xanthine derivatives by methyltransferase obtained from tea leaves. This alkaloid is associated mainly with coffee however it can be also found in tea or chocolate. With increasing age more and more caffeine from coffee and tea is consumed. Both drinks are its main source in human diet. During metabolite biotransformation caffeine is converted into three main products: theobromine (3,7-dimethylxanthine), theophylline (1,3-dimethylxanthine) and paraxanthine (1,7-dimethylxanthine). Caffeine polycrystals have ability to emit photons in radiative transition during phosphorescence at low temperature while its methanol solutions show fluorescence at low concentration. Caffeine might be used in synthesis of N-heterocyclic complex compound. Properly bonded with gold, silver or platinum atom might have many important properties. One of the most important properties is the possibility of binding free radicals that can cause DNA damage. Other significant properties of caffeine include its influence on the cell cycle and multiplication of cancer cells. 1,3,7- trimethylxanthine is also commonly used to reduce fatigue caused by inhibition of excitatory neurotransmitter emission. In this work we have presented interesting examples of the use of caffeine as a substrate in selected chemical syntheses. We have also included selected chemical and physical properties. In addition, we presented examples of its impact on the human body and consumption statistics based on international reports

Carbon nanotube sheets for the use as artificial muscles

Low voltage artificial muscles are of great importance for an enormous variety of industrial applications. In 1999 a new material, carbon nanotube sheets also called bucky paper, was described with suitable electromechanical properties. We developed an experimental set-up which allows, for the first time, the analysis of actuation forces vertical to the sheet plane. Single walled carbon nanotubes (SWNT) from arc discharge or HiPco process as well as multi walled carbon nanotubes (MWNT) were used as received or after further purification steps to produce carbon nanotube sheets by the filtration technique. The fastest actuation time of three seconds could be, up to now, obtained with the HiPco-material, which is free of amorphous carbon particles. Several parameters influence the electromechanical properties like the sheet thickness, the used electrolyte, the applied voltage and so on. But also the nanotube material itself and the procedure for the bucky paper production must be considered intensively to avoid large differences between different batches and to produce indiscriminate and reproducible carbon nanotube sheets. We characterized the material, among others, by TGA, SEM/EDX, and BET analysis. (C) 2004 Elsevier Ltd. All rights reserved

Carbon nanotube sheets for the use as artificial muscles

Low voltage artificial muscles are of great importance for an enormous variety of industrial applications. In 1999 a new material, carbon nanotube sheets also called bucky paper, was described with suitable electromechanical properties. We developed an experimental set-up which allows, for the first time, the analysis of actuation forces vertical to the sheet plane. Single walled carbon nanotubes (SWNT) from arc discharge or HiPco process as well as multi walled carbon nanotubes (MWNT) were used as received or after further purification steps to produce carbon nanotube sheets by the filtration technique. The fastest actuation time of three seconds could be, up to now, obtained with the HiPco-material, which is free of amorphous carbon particles. Several parameters influence the electromechanical properties like the sheet thickness, the used electrolyte, the applied voltage and so on. But also the nanotube material itself and the procedure for the bucky paper production must be considered intensively to avoid large differences between different batches and to produce indiscriminate and reproducible carbon nanotube sheets. We characterized the material, among others, by TGA, SEM/EDX, and BET analysis. (C) 2004 Elsevier Ltd. All rights reserved

Carbon nanotubes for interconnects in VLSI integrated circuits

The paper reviews the requirements for carbon nanotubes to be used as interconnects in VLSI integrated circuits. It describes the production by chemical vapour deposition of high density arrays of nanotubes suitable for use as interconnects, and describes their characterisation by Raman and transmission electron microscopy. © 2008 Wiley-VCH Verlag GmbH and Co. KGaA