Dolbier HW Solutions 660

Dolbier HW Solutions 660 - 754 AMINO ACIDS PEPTIDES AND...

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