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CHEMISTRY 410 – NUCLEAR CHEMISTRY LABORATORY Lab #3 – Radioiodination of a protein Equipment: NaI(Tl) scintillation detector with associated electronics, PC-based Ortec multi- channel analyzer, I-131 iodide in 0.1 N NaOH, bovine serum albumin 50 mg/mL in PBS, pH 7.2, plastic columns, 10 µ L pipet, AG 1x8 ion exchange resin, Sephadex G25 coarse, presoaked in saline or pre-packed columns Purpose The purpose of this experiment is to carry out electrophilic radioiodination of a protein. The second objective is to compare chromatographic methods for chemical purification and electrophoretic analysis of the radiochemical purity of the labeled product. Theory of Protein Radioiodination The most common way to introduce a radioactive atom into a large biological molecule is through radioiodination. This technique is most commonly used for proteins, but can also be used for steroids, nucleic acids, and even some carbohydrates. The reactions start with radioactive iodide anion, which is then oxidized to a more reactive oxidation state. It does not have to be I + , but it must have some electropositive character, eg I δ + Cl δ - . The electrophilic I δ + will react with aromatic groups in proteins. It prefers the phenolic structure of tyrosine, resulting in the following chemistry: 131 I + R OH R OH 131 I In this experiment we will generate electropositive I through the decomposition in water of chloramine-T. The initial product of this decomposition is HOCl, which exchanges with I
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This note was uploaded on 01/24/2011 for the course CHEM 3011 taught by Professor Joe during the Winter '09 term at American College of Computer & Information Sciences.

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