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Université de Fribourg

Zuschlag und Verfügung : Ein Beitrag zum öffentlichen Vergaberecht

Gauch, Peter (Universität Freiburg)

In: Mensch und Staat, Festgabe der Rechtswissenschaftlichen Fakultät der Universität Freiburg für Thomas Fleiner zum 65. Geburtstag, 2003, p. 595-618

Université de Neuchâtel

Inhibition of Escherichia coli porphobilinogen synthase using analogs of postulated intermediates

Jarret, Caroline ; Stauffer, Frédéric ; Henz, Matthias E ; Marty, Maurus ; Lüönd, Rainer M ; Bobálová, Janette ; Schürmann, Peter ; Neier, Reinhard

In: Chemistry & Biology, 2000, vol. 7, no. 3, p. 185-196

Background: Porphobilinogen synthase is the second enzyme involved in the biosynthesis of natural tetrapyrrolic compounds, and condenses two molecules of 5-aminolevulinic acid (ALA) through a nonsymmetrical pathway to form porphobilinogen. Each substrate is recognized individually at two different active site positions to be regioselectively introduced into the product. According to...

Université de Neuchâtel

Evaluation of dipeptide-derivatives of 5-aminolevulinic acid as precursors for photosensitizers in photodynamic therapy

Berger, Yann ; Ingrassia, Laurent ; Neier, Reinhard ; Juillerat-Jeanneret, Lucienne

In: Bioorganic & Medicinal Chemistry, 2003, vol. 11, no. 7, p. 1343-1351

N-terminal-blocked and N-terminal-free pseudotripeptide Gly-Gly and Gly-Pro derivatives of 5-aminolevulinic acid (ALA) esters were synthesized as potential specific substrates for cellular peptidases and precursors for the production of the photosensitizer protoporphyrin IX (PpIX). These precursors were evaluated using human cell lines of either carcinoma or endothelial origin. N-blocked or...

Université de Neuchâtel

On the formation of the mixed pyrrole catalysed by porphobilinogen synthase from Rhodobacter spheroides

Lüönd, Rainer Martin ; Neier, Reinhard

In: Biochimica et Biophysica Acta (BBA), 1996, vol. 1289, no. 1, p. 83-86

The enzyme porphobilinogen synthase (PBGS) catalyses the formation of porphobilinogen (PBG) from two molecules of 5-aminolevulinic acid (ALA). It has been claimed that the PBGS from Rhodobacter spheroides is able to form a mixed pyrrole, from one molecule of 5-aminolevulinic acid and one molecule of levulinic acid. The chemical synthesis of this mixed pyrrole allowed to show, that the...

Université de Neuchâtel

The X-ray structure of yeast 5-aminolaevulinic acid dehydratase complexed with two diacid inhibitors

Erskine, P. T. ; Coates, L. ; Newbold, R. ; Brindley, A. A. ; Stauffer, Frédéric ; Wood, S. P. ; Warren, M. J. ; Cooper, J. B. ; Shoolingin-Jordan, P. M. ; Neier, Reinhard

In: FEBS Letters, 2001, vol. 503, no. 2-3, p. 196-200

The structures of 5-aminolaevulinic acid dehydratase complexed with two irreversible inhibitors (4-oxosebacic acid and 4,7-dioxosebacic acid) have been solved at high resolution. Both inhibitors bind by forming a Schiff base link with Lys 263 at the active site. Previous inhibitor binding studies have defined the interactions made by only one of the two substrate moieties (P-side substrate) which...

Université de Neuchâtel

1-Methoxycarbonyl-substituiertes 2,3-Dihydropyridin-4(1H)-on (= Methyl-1,2,3,4-tetrahydro-4-oxopyridin-1-carboxylat) als Chromophor für die photochemische [2 + 2]-Cycloaddition = 1-Methoxycarbonyl-Substituted 2,3-Dihydropyridin-4(1H)-one(= Methyl 1,2,3,4-Tetrahydro-4-oxopyridine-1-carboxylate) as Chromophore for Photochemical [2 + 2]-Cycloadditions

Guerry, Philippe ; Blanco, Philippe ; Brodbeck, Heinz ; Pasteris, Olivier ; Neier, Reinhard

In: Helvetica Chimica Acta, 1991, vol. 74, no. 1, p. 163-178

With olefins having an electron-acceptor as well as with olefins having an electron-donor substituent, 1-methoxycarbonyl-substituted dihydropyridinone 12 undergoes [2 + 2] cycloaddition in good preparative yields. The photochemical cycloaddition is highly regioselective. For preparative purposes, the ring junction can be equilibrated to the thermodynamically more stable cis-junction. Only...

Université de Neuchâtel

Michael Reactions of α-Unsubstituted Trisubstituted 1/H-Pyrroles

Lüönd Rainer ; Neier, Reinhard

In: Helvetica Chimica Acta, 1991, vol. 74, no. 1, p. 91-102

To obtain stable derivatives of α-unsubstituted pyrroles, the reaction of the test pyrrole 9 with a series of chalcones 14a-h were studied. Michael adducts 16b-h could be isolated. In order to synthesize coloured derivatives, the reaction of different pyrroles 9, 21, 23, and 25 with diphenylpropynone 19 was investigated. In these cases,...

Université de Neuchâtel

Inhibition Studies of Porphobilinogen Synthase from Escherichia coli Differentiating between the Two Recognition Si

Stauffer, Frédéric ; Zizzari, Eleonora ; Engeloch-Jarret, Caroline ; Faurite, Jean-Philippe ; Bobálová, Janette ; Neier, Reinhard

In: ChemBioChem, 2001, vol. 2, no. 5, p. 343-354

Porphobilinogen synthase condenses two molecules of 5-aminolevulinate in an asymmetric way. This unusual transformation requires a selective recognition and differentiation between the substrates ending up in the A site or in the P site of porphobilinogen synthase. Studies of inhibitors based on the key intermediate first postulated by Jordan allowed differentiation of the two recognition sites....

Université de Neuchâtel

Tandem Nucleophilic Addition/Diels-Alder Reaction of N-Butadienyl N,O-Ketene Silyl Acetals with C60: Stereoselective Formation of Bicyclic Octahydroquinolino-1,2,3,4-Tetrahydrobuckminsterfullerenes and Combined NMR Spectroscopic and Computational Evaluation of the Functionalization Reactions

Rubin, Yves ; Ganapathi, Padma S. ; Franz, Andreas ; An, Yi-Zhong ; Qian, Wenyuan ; Neier, Reinhard

In: Chemistry - A European Journal, 1999, vol. 5, no. 11, p. 3162-3184

Abstract: We have studied the reactivity of the N,0-ketene N-l,3-butadienyl-N-alkyl-0-silyl acetals 1a-e with C60 proceeding through a tandem process to give the adducts 2a-e. The addition order of these tandem reactions has been evaluated. The initial nucleophilic Michael-like addition of the electron-rich N,O-ketene acetal moiety...