Harpers

Table 3–1.L- α-Amino acids present in proteins.Name Symbol Structural Formula pK 1 pK 2 pK 3With Aliphatic Side Chains -COOH -NH + 3 R GroupGlycine Gly [G]H CH COO –2.4 9.8+NH 3Alanine Ala [A]CH 3 CH COO –2.4 9.9+NH 3H 3 CValine Val [V]CH CH COO –H 3 C+NH 32.2 9.7H 3 CLeucine Leu [L]CH CH COO –2 CHH 3 C+NH 32.3 9.7CH 3CH 2Isoleucine Ile [I] CH CH COO –2.3 9.8CH 3+NH 3With Side Chains Containing Hydroxylic (OH) GroupsSerine Ser [S]CH 2 CH COO –2.2 9.2 about 13OH+NH 3Threonine Thr [T]CH 3 CH CH COO –2.1 9.1 about 13OH+NH 3Tyrosine Tyr [Y] See below.With Side Chains Containing Sulfur AtomsCysteine Cys [C] CH 2 CH COO –1.9 10.8 8.3SH+NH 3Methionine Met [M] CH CH COO –2 CH 22.1 9.3+S CH 3 NH 3With Side Chains Containing Acidic Groups or Their AmidesAspartic acid Asp [D] – OOC CH 2 CH COO –2.0 9.9 3.9+NH 3Asparagine Asn [N]H 2 N C CH 2 CH COO –2.1 8.8O+NH 3Glutamic acid Glu [E] – OOC CH 2 CH 2 CH COO –2.1 9.5 4.1+NH 3Glutamine Gln [Q]C CH 2CH COO –2.2 9.1O+NH 3H 2 N CH 215(continued)