Principles of Biochemistry Volume 1 - A. Lehninger 1985

Biomolecules
Water
Three amino acids contain positively charged (basic) R groups

Amino Acids with R-groups that carry a net positive charge at pH 7.0 include Lysine, which contains a second amino group attached to the aliphatic chain at the ε-position; Arginine, which features a positively charged guanidino group; and Histidine, which contains a weakly ionized imidazole group (Fig. 5–6).



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