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Georgia Journal of Science

Article Title

OPTIMIZATION OF A WILD-TYPE HEMOGLOBIN CATALYZED CYCLOPROPANATION REACTION FOR UNDERGRADUATE LABORATORY COURSE**

Abstract

Biocatalysis is the use of enzymes/proteins as catalyst to perform chemical reactions. Protein/enzyme catalyzed reactions are chemo-selective, regioselective, and stereoselective. Proteins/enzymes are cost effective, environmentally friendly, and can be used under mild reaction conditions. The intent of this study is to design a practical Biocatalysis experiment that can be performed in an undergraduate, organic laboratory. In this study, wild-type hemoglobin was used as a biocatalyst to perform a cyclopropanation reaction between commercially available Styrene and Ethyl Diazoacetate (EDA). Various reaction conditions were optimized; the optimal enzyme concentration was found to be 40 μM, EDA concentration was 10 mM, and Styrene concentration was 30 mM, making the substrate ratio 1:3. The pH of the reaction medium and the time in which the reaction occurs will also be optimized. Another objective to be investigated is measuring the recyclability of the enzyme/protein. A Chiral Gas Chromatography (GC) was used to calculate the enzyme activity and stereoselectivity. Our results indicate that the trans diastereomer was formed in excess, and around 25% enantiomeric excess (%ee) for the trans (SS) product. A calibration curve was constructed and used to standardize the results. By optimizing various reaction conditions, the percent yield has been increased to be in the 86%-87% range. Later, the optimized reaction will be tested with first semester undergraduate organic laboratory students. This experiment is designed to be an inexpensive and sustainable way to incorporate biocatalysis in an organic undergraduate teaching lab.

Acknowledgements

VSU Dept. of Chemistry

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