Nonpolar Aliphatic Amino Acids CH3 CH3 H CH3 -CH3 HO cooe Cooe H,N Isoleucine (le; I) HạN coo H,N Alanıne (Ala; A) H3N Glyclne (Gly; G) Valline (Val; V) Leudine (Leu; L) Nonpolar Aromatic Amino Acids но Nonpolar Amino Acids CH3 HN HgN H,N HN COo Co Prolline (Pro; P) Methlonine (Met; M) Phenylalanlne (Phe; F) Tyroslne (Tyr; Y) Tryptophan (Trp; w) Polar Amino Acids NH2 - NH2 но HS Но CH COoe cooe C00 e co0e Serine (Ser; S) Cystelne (Cys; C) Threonine (Thr; T) Asparaglne (Asn; N) Glutamine (Gin; Q) Positively Charged Polar Amino Acids Negatively Charged Polar Amino Acids H,N NH2 HN HN: e COoe cooe coo cooe HIstidine (Hls; H) Lysine (Lys; K) Arginine (Arg; R) Aspartic Acld (Asp; D) Glutamlc Acld (Glu; E) A FIGURE 5.3 The 20 common amino acids found in proteins. The chemical structures of the 20 common a-amino acids that are incorporated into proteins are shown and arranged here in the order in which they are discussed in the text. The "side chain" or "R group" of each amino acid is highlighted in green. Below each amino acid are its name, its three-letter abbreviation, and its one-letter abbreviation. TABLE 5.1 Properties of the common amino acids found in proteins Abbreviations: 1- pK, of a-COOH and 3-letter codes pKg of a-NHj Group pKg of lonizing Side Chain Residue Mass (daltons) Occurrence in Name Group Proteins (mol %) Alanine А, Ala 2.3 9.7 71.08 8.7 Arginine R, Arg 2.2 9.0 12.5 156.20 5.0 Asparagine Aspartic acid N, Asn 2.0 8.8 114.11 4.2 D, Asp 2.1 9.8 3.9 115.09 5.9 C, Cys Q, Gln Cysteine 1.8 10.8 8.3 103.14 1.3 Glutamine 2.2 9.1 128.14 3.7 Glutamic acid E, Glu 2.2 9.7 4.2 129.12 6.6 Glycine G, Gly 2.3 9.6 57.06 7.9 Histidine H, His 1.8 9.2 6.0 137.15 2.4 I, lle L, Leu Isoleucine 2.4 9.7 113.17 5.5 Leucine 2.4 9.6 113.17 8.9 К, Lys М, Met F, Phe P, Pro S, Ser Lysine 2.2 9.0 10.0 128.18 5.5 Methionine 2.3 9.2 131.21 2.0 Phenylalanine 1.8 9.1 147.18 4.0 Proline 2.0 10.6 97.12 4.7 Serine 2.2 9.2 87.08 5.8 Threonine T, Thr 2.6 10.4 101.11 5.6 W, Trp Y, Tyr V, Val Tryptophan 2.4 9.4 186.21 1.5 Tyrosine 2.2 9.1 10.1 163.18 3.5 Valine 2.3 9.6 99.14 7.2