Amidination of Lysine Side Chains
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Perhaps the largest variety of modifications available is that for ε-amino group of lysine (1-4). The amino side chain can be acylated (using e.g., acetic anhydride) or alkylated by trinitrobenzenesulfonic acid (TNBS); these reactions alter both the size and the charge of the amino group. Other modifications, using anhydrides of dicarboxylic acids (e.g., succinic anhydride), replace the positively charged amino group with a negatively charged carboxyl group. Amidinations (5-6) and reductive alkylations (see ref. 7) offer an opportunity to modify the structure of the ε-amino group of lysines, while maintaining the positive charge. Modifications that usually do not disrupt the overall structure of the protein are preferred, particularly in those cases when one wishes to identify the specific role of lysine in the active site of the protein being studied.
KeywordsDicarboxylic Acid Acetic Anhydride Succinic Anhydride Charge Amino Group Ammonium Hydroxide Solution
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