Tailor-Made Modification of a Gold Surface for the Chemical Binding of a High-Activity [FeFe] Hydrogenase

Hydrogenases are iron-sulfur proteins that catalyze hydrogen turnover in a wide range of microorganisms. Three different classes have been described, and among these [FeFe] hydrogenases are the most active in H-2 evolution. Hydrogenases are redox enzymes that have been shown to exchange electrons with graphite and modified noble metal electrodes. Making use of the latter, diffusible electron carriers are required to enable redox catalysis, as proteins do not specifically bind to the electrode surface. Diffusion-limited electron transfer can be replaced by electron injection into immobilized hydrogenase by binding the redox mediator to the electrode surface. Here, we present the synthesis and spectroelectrochemical characterization of 1-( 10-mercaptodecyl)-1'-benzyl-4,4'-bipyridinium dibromide (MBBP), which is used as redox-active linker. CrHydA1, the high-activity [FeFe] hydrogenase from Chlamydomonas reinhardtii, is immobilized on the linker-modified gold electrode. Each surface modification step is controlled in situ by surface-enhanced infrared absorption spectroscopy (SEIRAS). Functionality of the electrode-protein hybrid is demonstrated by recording the linker-supported current. The specific catalytic rate of hydrogen evolution by CrHydA1 (2.9 mu molH(2)min(-1)mg(-1) hydrogenase) promises a valuable approach for further optimization of this novel bioelectrical interface.