Electron tunneling, reaction center proteins

A eomparison of the calculated vs. experimental AG optimized tunneling rates for the productive charge separating electron transfers in two bacterial photosynthetic reaction centers shows that rate estimates have a standard deviation of 0.5 log units, or about a factor of 3 (Figure 5). Considering the experimental errors of determining AG and especially X, or even the uneertainties in R of a dynamic protein, it is not clear that a calculation any more involved than the one we have just described is usually justified. 

Figure 4B shows the set of 31 produetive and 21 unproductive electron transfer reactions in multi-redox center oxidoreduetases with structures available in the Protein Data Bank (PDB). Both productive and unpro-duetive reactions have statistically indistinguishable distributions, which are in turn indistinguishable from the arbitrary protein paeking distribution. Thus Nature has not generally selected protein heterogeneity to assist pro-duetive and hinder counterproductive eleetron tunneling. 

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