A technique for radioactively labeling proteins is electrophilic radioiodination, in which an aromatic substitution of 131 I onto a tyrosine residue is performed as follows Using the activity of 131 I, one can measure protein lifetimes in a variety of biological processes 131 I undergoes beta decay...

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A technique for radioactively labeling proteins is electrophilic radioiodination, in which an aromatic substitution of 131 I

Question:

A technique for radioactively labeling proteins is electrophilic radioiodination, in which an aromatic substitution of¹³¹I onto a tyrosine residue is performed as follows:

R 131 1311 OH ОН

Using the activity of ¹³¹I, one can measure protein lifetimes in a variety of biological processes. ¹³¹I undergoes beta decay with a half-life of 8.02 days. Initially a protein labeled with ¹³¹I has a specific activity of 1.0Î¼Ci, which corresponds to 37,000 decay events every second. The protein is suspended in aqueous solution and exposed to oxygen for 5 days. After isolating the protein from solution, the protein sample is found to have a specific activity of 0.32 Î¼Ci. Is oxygen reacting with the tyrosine residues of the protein resulting in the loss of ¹³¹I?