In: Chemical Physics Letters, 2005, vol. 406, no. 4, p. 355-359
DFT investigations on the mechanism of Diels–Alder reactions of a hydroxy-ortho-quinodimethane with fumaric acid derivatives were performed to understand the origin of the syn or anti configuration of the adducts. The diene hydroxyl group and the dieneophile carboxyl group show hydrogen bonding in the transition state, significantly favouring the syn product. This reaction is poorly...
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In: Synlett, 2004, no. 13, p. 2268-2274
A major challenge in organic synthesis is the selective reaction of a functional group in the presence of others. This can be achieved by using an appropriate reagent, tuned to react exclusively at the desired center. An alternate approach would be to use a single reagent, and to transmit from the outside the information as to where it should react. This account describes the use of light as a...
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In: Tetrahedron Letters, 2005, vol. 46(2), p. 3793-3795
A simple spectroscopic method was applied to determine the geometry of tetrasubstituted alkenes. The observation of the ⁵J-coupling constants in proton NMR spectra on the ¹³C satellite signals could confirm the previous misassignment of 2,3-diphenylbutene. Hence, the (E)-isomer showed a 1.5 Hz coupling constant, whereas the (Z)-isomer showed a 1.1 Hz coupling constant. Based on this new...
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In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2005, vol. 38, p. 603
Absolute differential elastic and vibrational excitation cross sections have been measured for NO at 135° with resolution of the ²Π1/2 and ²Π3/2 spin-orbit components of the ground electronic term. The electronic fine structure excitation is dominated by the ³Σ⁻ and the ¹Δ resonances of NO⁻, the nonresonant contribution is very small. The cross section is very large, it has about the...
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In: Physical Review Letters, 2004, vol. 93, p. 063201-63204
The electron impact cross section for the transition between the ²Π₁͵₂ and ²Π₁͵₃ spin-orbit components of the ground electronic term of nitric oxide, separated by 15 meV, has been measured as a function of electron energy at a scattering angle of Θ= 135°. It is dominated by the ³Σ⁻ and the ¹Δ resonances. Its magnitude is very large, at peak about equal to that of the elastic...
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In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2005, vol. 38, p. 1679
Absolute differential elastic and vibrational excitation cross sections have been measured for CH₄ at 90° and from 0.1 to 1.5 eV, with the resolution of all four vibrational modes. Threshold peaks were observed in the excitation of the ν1, ν3 and ν4 modes, but not in the ν2 mode. These results are in good agreement with the recent calculation of Nishimura and Gianturco (2002 J. Phys. B:...
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Thèse de doctorat : Université de Fribourg, 2001 ; no 1341.
Le sujet de cette thèse est l’étude de différents facteurs influençant le transfert d’électron photoinduit ou la recombinaison des charges et qui ne sont pas liés à la force motrice thermodynamique. Un grand nombre de techniques expérimentales ont été utilisées, allant de la spectroscopie photoélectronique pour la mesure des potentiels d’ionisation à la spectroscopie des...
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Thèse de doctorat : Université de Fribourg, 2002 ; Nr. 1382.
Im Rahmen der vorliegenden Arbeit wurden neue enantiomerenreine 5’- und 6’- substituierte, mit Pinen annellierte Bipyridin- (Pinen-bpy Derivate) und N-Pyridin- Liganden (Pinen-N-py Derivate) hergestellt. Die 6’-Brom substituierten Pinen-bpy Derivate stellen dabei geeignete Zwischenstufen für die Synthese von weiteren 6’- substituierten Pinen-bpy Derivate dar. Tetradentate Liganden...
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Thèse de doctorat : Université de Fribourg, 2001 ; Nr. 1361.
Die Verankerung von bestimmten Proteinen an der Aussenseite der Plasmamembran mittels eines Glycosylphosphatidylinositol (GPI)-Ankers ist in eukaryontischen Zellen weit verbreitet. Es gibt Hinweise, dass GPI-Anker neben ihrer Funktion als stabiler Anker auch eine wichtige Rolle in der Uebertragung von Signalen und in der Sortierung von Proteinen spielen. Sowohl die Biosynthese des GPI-Ankers als...
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Thèse de doctorat : Université de Fribourg : 2003 ; no 1400.
Proper chromosome segregation is a crucial event for accurate cell division. Defects in chromosome segregation lead to genetic instability and aneuploidy and are correlated with cancer. The laboratory studies chromosome segregation in the budding yeast Saccharomyces cerevisiae. Since this process is highly conserved among eukaryotes, studies in yeast will provide fundamental understanding of this...
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