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Apomyoglobin undergoes a transition from the
native state to an acid intermediate at pH below 5
As explained in the introduction, apomyoglobin undergoes a transition to a compact acid intermediate with pKa = 5.5. This transition can be easily followed by tryptophan fluorescence emission and far UV circular dichroism. Fluorescence emission is a good probe of the interaction between helices
A and H since Trp14 is quenched by Met131 in the native
form (distance is approximately 0.66 nm), when the two helices are
close to each other. The formation of the intermediate leads to a
larger separation between the two helices and the quenching effect is accordingly
reduced.
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