The activation of Hageman factor (factor XII) by ellagic acid may involve a conformational change in which at least some of its hydrophobic regions, previously buried, are exposed to the surrounding environment. The fluorescent probe, l,6-diphenyl-l,3,5-hexatriene (DPH), when added to a solution of ellagic acid-activated Hageman factor, displayed substantially more fluorescence compared to solutions of the probe and the unactivated form of the protein. These studies imply that the hydrophobic regions of activated Hageman factor are exposed in such a way that the DPH probe has easy access to the hy-drophobic environment to which it binds.
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Fair et al. (1977) studied this question.