Enzyme Immobilization and Self-Assembly

An important consideration in the design of a BFC is the method for retaining enzymes in a device, in most cases in close proximity to the eleetrode surface. A BFC that requires constant addition of soluble enzyme would be prohibitively costly to operate, and the rate of electron transfer between the enzymes and electrode surface would likely be poor. Instead, enzymes are commonly immobilized in a BFC through adsorption [50], covalent attachment [51], confinement within a polymer matrix (such as Nafion [52], chitosan [53], or other synthetic polymers) [54], or other means [55]. The method of immobilization used can have a profound effect on enzyme activity through denaturation or inactivation of the enzyme, steric hindrance (blocking) of the active site, imposing mass transport limitations on substrate and/or cofactor diffusion, or significant modification of the local environment of the enzyme. Immobilization 

Leucine zipper domains from lelrameric coiled-coil bundles 

Domains genetically fused to the termini of a protein bifunctionalize the construct for self-assembly 

Under mild conditions, leucine zipper domains form non-covalent cross-links between protein monomers, resulting in a macromolecular bioactive hydrogel 

FIGURE 7.3 Schematic of leucine zipper fusions to enable self-assembly of various proteins of interest into a robust macromolecular hydrogel. 

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