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(Distance Å)

FIGURE 2-1 Distribution of physiologically productive single-electron tunneling distances (in angstroms or Å) in electron transfer and oxidoreductase proteins. More than 97 percent of the proteins have tunneling distances of less than 14 Å.

SOURCE: Adapted from Moser et al. (2010, Fig. 1A).

ologically productive electron reactions in these enzymes have tunneling distances within 4 to 14 Å (Figure 2-1; Moser et al., 2010). These distances appear to be ideal for burying and protecting redox centers so that they can maintain catalytic rates (on the millisecond timescale) found in most physiological enzymatic reactions.

Natural energy systems have evolved a general and simple engineering for electron transfer that can be used for understanding uncharacterized, naturally occurring oxidoreductases, and in constructing synthetic enzymes. Dutton talked about his ultimate goal to design artificial proteins, or what he calls “maquettes,” from scratch. He starts with a simple artificial protein scaffold, and then introduces function by progressive, iterative, and entirely reversible design steps. He tries to avoid mimicry of natural enzymes (examples shown in comparison to a maquette in



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