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Artificial Enzymes (artificial + enzyme)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

From Theozymes to Artificial Enzymes: Enzyme-Like Receptors for Michael Additions with Oxyanion Holes and Active Amino Groups

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2007
Luis Simón
Abstract Different artificial enzymes, based on the theozyme concept, have been designed for Michael additions of pyrrolidine to ,,,-unsaturated lactams. These molecules each have skeleton able to mimic a structure called an "oxyanion hole", as is present in many enzymes. Amine groups are also responsible for the catalytic activities of these receptors, since they support the important proton-transport step. The requirement for the amine groups was established from the reaction mechanism and from theoretical calculations. The catalytic activities of the receptors are discussed, taking into account their relative association constants with the substrate: kcat/kuncat values of up to 104 were obtained. The catalytic activities of the receptors are compared with those found in natural enzymes and catalytic antibodies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Synthesis of Some Trifluoromethylated Cyclodextrin Derivatives and Analysis of Their Properties as Artificial Glycosidases and Oxidases

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2007
Jeannette Bjerre
Abstract Cyclodextrin derivatives containing trifluoromethyl groups at C6 of the A and D rings were synthesized for the purpose of creating artificial enzymes. The compounds were synthesized by perbenzylation of ,-cyclodextrin followed by selective A,D-debenzylation according to Sina˙. Subsequent oxidation to dialdehyde with Dess,Martin periodinane followed by addition of CF3 by using Arduengo carbene and TMSCF3 led to the C6 -bistrifluoromethylated alcohols. These were either deprotected by hydrogenolysis or subjected to another round of oxidation to provide the corresponding ketones that were deprotected. The trifluoromethylated alcohols were found to be weak artificial enzymes catalysing hydrolysis of nitrophenyl glycosides at neutral pH with a kcat/kuncat of up to 56. It is proposed that this catalysis is analogues to the catalysis performed by related cyanohydrins. The trifluoro ketones were likewise weak articial enzymes catalysing oxidation of amines to nitro derivatives or alcohols to ketones with a kcat/kuncat of up to 133. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Water Exclusion and Enantioselectivity in Catalysis,

CHEMBIOCHEM, Issue 10 2006
Ronald Breslow Prof. Dr.
High and dry. Enzymes perform catalyses in the interior of the protein, which is not aqueous in character. Polyethylenimine enzyme mimics with a hydrophobic core also achieve high rates by excluding water. Two different approaches to the synthesis of such artificial enzymes with chirally attached side chains are described, as well as the use of these enzymes in performing biomimetic transaminations with chiral selectivity [source]

Noncovalent Modulation of pH-Dependent Reactivity of a Mn,Salen Cofactor in Myoglobin with Hydrogen Peroxide

CHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2009
Jun-Long Zhang Dr.
Abstract To demonstrate protein modulation of metal-cofactor reactivity through noncovalent interactions, pH-dependent sulfoxidation and 2,2,-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) oxidation reactivity of a designed myoglobin (Mb) containing non-native Mn,salen complex (1) was investigated using H2O2 as the oxidant. Incorporation of 1 inside the Mb resulted in an increase in the turnover numbers through exclusion of water from the metal complex and prevention of Mn,salen dimer formation. Interestingly, the presence of protein in itself is not enough to confer the increase activity as mutation of the distal His64 in Mb to Phe to remove hydrogen-bonding interactions resulted in no increase in the turnover numbers, while mutation His64 to Arg, another residue with ability to hydrogen-bond interactions, resulted in an increase in reactivity. These results strongly suggest that the distal ligand His64, through its hydrogen-bonding interaction, plays important roles in enhancing and fine-tuning reactivity of the Mn,salen complex. Nonlinear least-squares fitting of rate versus pH plots demonstrates that 1,Mb(H64X) (X=H, R and F) and the control Mn,salen 1 exhibit pKa values varying from pH,6.4 to 8.3, and that the lower pKa of the distal ligand in 1,Mb(H64X), the higher the reactivity it achieves. Moreover, in addition to the pKa at high pH, 1,Mb displays another pKa at low pH, with pKa of 5.0±0.08. A comparison of the effect of different pH on sulfoxidation and ABTS oxidation indicates that, while the intermediate produced at low pH conditions could only perform sulfoxidation, the intermediate at high pH could oxidize both sulfoxides and ABTS. Such a fine-control of reactivity through hydrogen-bonding interactions by the distal ligand to bind, orient and activate H2O2 is very important for designing artificial enzymes with dramatic different and tunable reactivity from catalysts without protein scaffolds. [source]