Microemulsion-controlled reaction sites in biocatalytic films for electrochemical reduction of vicinal dibromides.
We report herein the electrochemical dehalogenation of vicinal dibromides in microemulsions using cross-linked films of the redox protein myoglobin (Mb) and poly-l-lysine (PLL) covalently bonded to carbon electrodes. Catalytic reduction of the dibromides to olefins was more efficient in an SDS microemulsion than in a CTAB microemulsion. SDS shifts the Mb redox potential more negative, but a comparison to Mb-SDS films suggests that the activation free energy of the reduction is controlled by an inner-sphere mechanism. SDS also enters the positively charged Mb-PLL films and preconcentrates the dibromide reactants, enhancing catalytic efficiency in SDS microemulsions. Shifts in formal potential and Soret absorbance bands for Mb-PLL films suggested binding of trans-1,2-dibromocyclohexane in the iron heme distal pocket with little catalysis. Results are consistent with active catalytic reduction sites for reactant bound on the protein surface and less-reactive sites in the distal heme pocket. Preconcentration into catalytic PLL films using SDS incorporated from microemulsions may be a general way to improve catalytic efficiency for nonpolar reactants in microemulsions.
Vaze
Abhay
A
Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, USA.
Rusling
James F
JF
D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry; D001665:Binding Sites; D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D003510:Cyclohexanes / Q000737:chemistry*; D004563:Electrochemistry; D004566:Electrodes; D004655:Emulsions; D004980:Ethane / Q000031:analogs & derivatives* / Q000737:chemistry; D008567:Membranes, Artificial; D008958:Models, Molecular; D009211:Myoglobin / Q000737:chemistry; D010084:Oxidation-Reduction; D011107:Polylysine / Q000737:chemistry; D011791:Quartz; D013329:Structure-Activity Relationship; D013499:Surface Properties
C453159:1,2-dibromocyclohexane; D000475:Alkenes; D003510:Cyclohexanes; D004655:Emulsions; D008567:Membranes, Artificial; D009211:Myoglobin; D011791:Quartz; D011107:Polylysine; D002244:Carbon; D004980:Ethane