When the ligating histidine the Rieske protein is modified with diethylpyrocarbonate (DEPC), one of the iron atoms in the [2Fe-2S] cluster becomes reduced from Fe(III) to Fe(II). This reduction is hypothesized to be caused by the strong electron withdrawing characteristics of the adduct. Furthermore, when modified by methylbromoacetate, which provides an adduct that is less able to withdraw electron density, there is no reduction of the [2Fe-2S] cluster. To further investigate how the electron-withdrawing capability of the adduct influences the reduction potential of the [2Fe-2S] cluster, a new compound, phenyl chloroformate, was synthesized to modify the protein. Test reactions with imidazole showed the expected modification. If reaction with protein is successful, this compound could then be synthesized with additional functional groups of varying electron-withdrawing capabilities to finely adjust the reduction potential of the cluster. To date, limited modification of the protein by phenyl chloroformate has been observed and more soluble modifiers, 4-sulfophenyl chloroformate and 4-carboxyphenyl chloroformate, are being synthesized to optimize modification of the Rieske protein.

Synthesis of chloroformate modifiers for the <i>Thermus thermophilus</i> Rieske protein

247th National Meeting (2014)

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Synthesis of chloroformate modifiers for the Thermus thermophilus Rieske protein