754AMINO ACIDS, PEPTIDES, AND PROTEINS. NUCLEIC ACIDS(d)On further treatment with base, both the monoanions in part (c) yield the same dianion.27.4At pH 1 the carboxylate oxygen and both nitrogens of lysine are protonated.As the pH is raised, the carboxyl proton is removed frst.The pKavalue for the frst ionization of lysine is 2.18 (from Table 27.3), and so this process isvirtually complete when the pH is greater than this value.The second pKavalue for lysine is 8.95. This is a fairly typical value for the second pKaof aminoacids and likely corresponds to proton removal from the nitrogen on the acarbon. The species thatresults is the predominant one at pH 9.The pKavalue for the third ionization of lysine is 10.53. This value is fairly high compared withthose of most of the amino acids in Tables 27.1 to 27.3 and suggests that this proton is removed fromthe nitrogen of the side chain. The species that results is the major species present at pH values
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