Gold(I)- and gold(III)-catalyzed cycloisomerization of allenynes: a remarkable halide effect.
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Journal Article↗
Biomedical subjects
Jean-Philippe Goddard
Publications and source records attributed to Jean-Philippe Goddard.
Boron-mediated polymerization of ylides derived from allylic arsonium salts: influence of the double bond substitution on the outcome.
New oligomers or polymers are prepared by polymerization of arsonium ylides in the presence of boron compounds.
Allyl Compounds↗
Enzyme activity fingerprinting with substrate cocktails.
In the postgenomic era, emphasis is shifting from protein identification to protein functional analysis. Enzyme function can be characterized by measuring activity across series of substrates, which generates an activity profile or fingerprint. Activity fingerprinting is particularly useful to differentiate closely related enzymes. Previously reported fingerprinting methods use series of parallel measurements, which are complex and difficult to reproduce. Here we report a new method for fingerprinting enzyme activities based on using mixtures of substrates, or substrate cocktails, in a single reaction that is then analyzed by HPLC. The fingerprints produced are highly reproducible and allow functional differentiation and classification of closely related enzymes, as demonstrated for a series of lipases and esterases. The method is practical, general, and flexible in terms of reaction conditions and can be adapted to any reaction type.
Enzymes↗
Expression improvement and mechanistic study of the retro-Diels-Alderase catalytic antibody 10F11 by site-directed mutagenesis.
Antibody 10F11 catalyzes the retro-Diels-Alder reaction of the bicyclic prodrug 1 releasing HNO and anthracene 4 (kcat/kuncat=2500). Earlier X-ray crystal structures of Fab 10F11 showed that tryptophan H104 at the bottom of the binding pocket interacts by pi-stacking with the aromatic ring of the substrate. Antibody 10F11 was expressed as a chimeric Fab and subjected to site-directed mutagenesis. Expression was improved by substituting a serine for a phenylalanine residue on the Fv-domain surface. Nine active-site mutants were then prepared including replacements at TrpH104, PheH101 and SerH100. Catalysis depends mainly on TrpH104 and PheH101. Catalysis is most likely caused by a combination of shape complementarity and specific electronic interactions between transition state and the aromatic residue H104. Medium and de-solvation effects have no effect on the reaction rate. Catalysis was improved to (kcat/kuncat=6300) by substituting phenylalanine for LeuL101 to indirectly enhance pi-stacking between transition state and TrpH104.
Antibodies, Catalytic↗
Enzyme assays for high-throughput screening.
Assaying enzyme-catalyzed transformations in high-throughput is crucial to enzyme discovery, enzyme engineering and the drug discovery process. In enzyme assays, catalytic activity is detected using labelled substrates or indirect sensor systems that produce a detectable spectroscopic signal upon reaction. Recent advances in the development of high-throughput enzyme assays have identified new labels and chromophores to detect a wide range of enzymes activities. Enzyme activity profiling and fingerprinting have also been used as tools for identification and classification, while microarray formats have been devised to increase throughput.
Catalysis↗
Recent advances in enzyme assays.
Enzyme assays for high-throughput screening and enzyme engineering, which are often based on derivatives of coumarin, nitrophenol, fluorescein, nitrobenzofurazane or rhodamine dyes, can be divided into two categories: those that depend on labelled substrates, and those that depend on sensing the reactions of unmodified substrates. Labelled substrates include, for example, fluorogenic and chromogenic substrates that generate a reporter molecule by beta-elimination, fluorescence resonance energy transfer (FRET) substrates and isotopic labels for enantioselectivity screening. By contrast, endpoint sensing can be done using amine reagents, fluorescent affinity labels for phosphorylated proteins, or synthetic multifunctional pores. Sensing assays can also be done in real time by using, for example, aldehyde trapping to follow vinyl ester acylation in organic solvent or calcein-copper fluorescence for sensing amino acids. The current trend is to assemble many such assays in parallel for enzyme profiling and enzyme fingerprinting.
Biochemistry↗
Chain elongations by three carbon atoms at a time in the boron-catalyzed polymerization of methallyltriphenylarsonium ylide.
Methallyltriphenylarsonium ylide polymerized in the presence of catalytic amounts of trialkylboranes. Linear polymers containing a terminal alcohol function were obtained after alkaline hydrogen peroxide oxidation. The chain of these polymers is constituted of methyl-substituted double bonds, separated by one methylene group. Their structure is related to that of natural rubber, in which the double bonds are separated by two methylene groups. These polymers arise from successive chain elongations of three carbon atoms at a time. A cyclic, polymeric ketone was also prepared from a cyclic trialkylborane. The mechanism, which involves a boratropic rearrangement after every insertion of a monomer, is discussed.
Journal Article↗