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The pKA of histidine in a protein active site where it is next to an aspartate or glutamate would be____________ the pKa of free histidine solution

higher, lower, no different

Is it higher??

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To answer this question, we need to know what pKa means.

pKa = -log Ka

So, what does that tell us? What is Ka? That is the dissociation or ionization constant for an acid.

HA + H2O <------> A- + H3O+

Ka = [A-][H3O+]/[HA]

Therefore, the more that the acid dissociates in water, the larger the Ka. The Ka is a measure of the degree of ionization of an acid in water. A ...