title: Kemp Elimination in Cationic Micelles: Designed Enzyme-Like Rates Achieved through the Addition of Long-Chain Bases.
abstract: The Kemp elimination is prototypical reaction used to study proton abstraction from carbon. Several hydrophobic systems are known to accelerate this reaction, including two classes of computationally-designed enzymes. However, it is unclear whether these computationally-designed enzymes establish specific interactions with their substrates, as natural enzymes do, or if most of the rate acceleration is due to the hydrophobicity of the substrate. We used a simple system composed of cationic micelles and a long chain base (such as lauryl phosphate or lauric acid) to measure the rate acceleration for the Kemp elimination. Remarkably, we found that this simple system can accelerate the reaction by 4 orders of magnitude, approaching the rates of more complex designed systems. Use of different substrates suggests that the reaction takes place at the interface between the micellar head and water (the Stern layer) with the long-chain base embedded in the micelle and the substrate in the aqueous solution. Thus, we suggest that significant rate accelerations can be achieved regardless of the precise positioning of substrates. Because natural enzymes use specific interactions to position their substrates, we propose that acceleration of the Kemp elimination is not a suitable benchmark for the success of the design process, and we suggest that more complex reactions should be used.
authors.affiliation: Department of Chemistry and Biochemistry, College of Charleston, 202 Calhoun St, Charleston, SC 29424, U.S.A.
authors.forename: Enis
authors.initials: E
authors.lastname: Sanchez
authors.affiliation: Academic Magnet High School, 5109 W Enterprise St, North Charleston, SC 29405. U.S.A.
authors.forename: Steven
authors.initials: S
authors.lastname: Lu
authors.affiliation: Department of Chemistry and Biochemistry, College of Charleston, 202 Calhoun St, Charleston, SC 29424, U.S.A.
authors.forename: Carson
authors.initials: C
authors.lastname: Reed
authors.affiliation: Department of Chemistry and Biochemistry, College of Charleston, 202 Calhoun St, Charleston, SC 29424, U.S.A.
authors.forename: Joshua
authors.initials: J
authors.lastname: Schmidt
authors.affiliation: Department of Chemistry and Biochemistry, College of Charleston, 202 Calhoun St, Charleston, SC 29424, U.S.A.
authors.forename: Marcello
authors.initials: M
authors.lastname: Forconi
keywords: Kemp elimination; catalysis; enzyme design; hydrophobic interactions; micelles