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Université de Neuchâtel

Supramolecular cluster catalysis : facts and problems

Süss-Fink, Georg ; Therrien, Bruno ; Vieille-Petit, Ludovic ; Tschan, Mathieu J.-L. ; Romakh, Vladimir B. ; Ward, Thomas R. ; Dadras, Massoud ; Laurenczy, Gabor

In: Journal of Organometallic Chemistry, 2004, vol. 689, p. 1362-1369

By checking the chemistry underlying the concept of "supramolecular cluster catalysis" we identified two major errors in our publications related to this topic, which are essentially due to contamination problems. (1) The conversion of the "closed" cluster cation [H3Ru3(C6H6)(C6Me6)2(O)]+ (1) into the...

Université de Neuchâtel

Isolation and single-crystal X-ray structure analysis of the catalyst–substrate host–guest complexes [C6H6⊂H3Ru3{C6H5(CH2) nOH}(C6Me6)2(O)]+ (n = 2, 3)

Vieille-Petit, Ludovic ; Therrien, Bruno ; Süss-Fink, Georg ; Ward, Thomas R.

In: Journal of Organometallic Chemistry, 2003, vol. 684, p. 117-123

The trinuclear arene-ruthenium cluster cations [H3Ru3{C6H5 (CH2)nOH}(C6Me6)2 (O)]+ (3: n=2, 4: n=3) have been synthesised from the dinuclear precursor [H3Ru2 (C6Me6)2]+ and the mononuclear...

Université de Neuchâtel

Electrophoretic behavior of streptavidin complexed to a biotinylated probe : A functional screening assay for biotin-binding proteins

Humbert, Nicolas ; Zocchi, Andrea ; Ward, Thomas R.

In: Electrophoresis, 2004, vol. 26, p. 47-52

The biotin-binding protein streptavidin exhibits a high stability against thermal denaturation, especially when complexed to biotin. Herein we show that, in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), streptavidin is stabilized at high temperature in the presence of biotinylated fluorescent probes, such as biotin-4-fluorescein, which is incorporated within the binding...

Université de Neuchâtel

Expression and purification of a recombinant avidin with a lowered isoelectric point in Pichia pastoris

Zocchi, Andrea ; Jobé, Anna Marya ; Neuhaus, Jean-Marc ; Ward, Thomas R.

In: Protein Expression and Purification, 2003, vol. 32, p. 167-174

A recombinant glycosylated avidin (recGAvi) with an acidic isoelectric point was expressed and secreted by the methylotrophic yeast Pichia pastoris. The coding sequence for recGAvi was de novo synthesized based on the codon usage of P. pastoris. RecGAvi is secreted at approximately 330 mg/L of culture supernatant. RecGAvi monomer displays a molecular weight of 16.5 kDa, as assessed...

Université de Neuchâtel

Aqueous oxidation of alcohols catalyzed by artificial metalloenzymes based on the biotin–avidin technology

Thomas, Christophe M. ; Letondor, Christophe ; Humbert, Nicolas ; Ward, Thomas R.

In: Journal of Organometallic Chemistry, 2005, vol. 690, p. 4488-4491

Based on the incorporation of biotinylated organometallic catalyst precursors within (strept)avidin, we have developed artificial metalloenzymes for the oxidation of secondary alcohols using tert-butylhydroperoxide as oxidizing agent. In the presence of avidin as host protein, the biotinylated aminosulfonamide ruthenium piano stool complex 1 (0.4 mol%) catalyzes the oxidation of...

Université de Neuchâtel

Artificial metalloenzymes for enantioselective catalysis : the phenomenon of protein accelerated catalysis

Collot, Jérôme ; Humbert, Nicolas ; Skander, Myriem ; Klein, Gérard ; Ward, Thomas R.

In: Journal of Organometallic Chemistry, 2005, vol. 689, p. 4868-4871

We report on the phenomenon of protein-accelerated catalysis in the field of artificial metalloenzymes based on the non-covalent incorporation of biotinylated rhodium–diphosphine complexes in (strept)avidin as host proteins. By incrementally varying the [Rh(COD)(Biot-1)]+ vs. (strept)avidin ratio, we show that the enantiomeric excess of the produced acetamidoalanine decreases slowly....

Université de Neuchâtel

Artificial metalloenzymes based on biotin-avidin technology for the enantioselective reduction of ketones by transfer hydrogenation

Letondor, Christophe ; Humbert, Nicolas ; Ward, Thomas R.

In: Proceedings of the National Academy of Sciences of the USA (PNAS), 2005, vol. 102, p. 4683-4687

Most physiological and biotechnological processes rely on molecular recognition between chiral (handed) molecules. Manmade homogeneous catalysts and enzymes offer complementary means for producing enantiopure (single-handed) compounds. As the subtle details that govern chiral discrimination are difficult to predict, improving the performance of such catalysts often relies on trial-and-error...

Université de Neuchâtel

Artificial metalloenzymes : proteins as hosts for enantioselective catalysis

Ward, Thomas R. ; Thomas, Christophe M.

In: Chemical Society Reviews, 2005, vol. 34, p. 337-346

Enantioselective catalysis is one of the most efficient ways to synthesize high-added-value enantiomerically pure organic compounds. As the subtle details which govern enantioselection cannot be reliably predicted or computed, catalysis relies more and more on a combinatorial approach. Biocatalysis offers an attractive, and often complementary, alternative for the synthesis of enantiopure...

Université de Neuchâtel

Artificial Metalloenzymes for Enantioselective Catalysis Based on the Noncovalent Incorporation of Organometallic Moieties in a Host Protein

Ward, Thomas R.

In: Chemistry - A European Journal, 2005, vol. 11, p. 3798-3803

Enzymatic and homogeneous catalysis offer complementary means to produce enantiopure products. Incorporation of achiral, biotinylated aminodiphosphine-rhodium complexes in (strept)avidin affords enantioselective hydrogenation catalysts. A combined chemogenetic procedure allows the optimization of the activity and the selectivity of such artificial metalloenzymes: the reduction of...