Number of different amino acids that make up all proteins

List of the 20 Amino Acids

Amino Acid 3-Letter Abbreviation 1-Letter Abbreviation Class of Amino Acid (Side Chain) Hydrophobicity Index (100 being extremely hydrophobic, 0 being neutral, and - 55 being hydrophilic) Structure pKa of COOH group pKa of NH3 + group pKa of R group Molecular Weight [g/mol] alpha helix beta sheet Reverse turn

Glycine Gly G Aliphatic, nonpolar Neutral (0 at pH = 2; 0 at pH = 7)

2.4 9.8 - - 75.07 0.43 0.58 1.77

Alanine Ala A Aliphatic, nonpolar Hydrophobic (47 at pH = 2; 41 at pH = 7)

2.4 9.9 - - 89.1 1.41 0.72 0.82

Valine Val V Aliphatic, nonpolar Very Hydrophobic (79 at pH = 2; 76 at pH = 7)

2.3 9.7 - - 117.15 0.90 1.87 0.41

Leucine Leu L Aliphatic, nonpolar Very Hydrophobic (100 at pH = 2; 97 at pH = 7)

2.3 9.7 - - 131.18 1.34 1.22 0.57

Isoleucine Ile I Aliphatic, nonpolar Very Hydrophobic (100 at pH = 2; 99 at pH = 7)

2.3 9.8 - - 131.18 1.09 1.67 0.47

Methionine Met M Hydroxyl or Sulfur-Containing, nonpolar Very Hydrophobic (74 at pH = 2; 74 at pH = 7)

2.1 9.3 - - 149.21 1.30 1.14 0.52

Serine Ser S Hydroxyl or Sulfur-Containing, polar Neutral (-7 at pH = 2; - 5 at pH = 7)

2.2 9.2 - - 105.09 0.57 0.96 1.22

Cysteine Cys C Hydroxyl or Sulfur-Containing, polar Hydrophobic (52 at pH = 2; 49 at pH = 7)

1.9 10.7 8.4 121.16 0.66 2.40 0.54

Threonine Thr T Hydroxyl or Sulfur-Containing, polar Neutral (13 at pH = 2; 13 at pH = 7)

2.1 9.1 - - 119.12 0.76 1.17 0.96

Proline Pro P Cyclic Hydrophilic (-46 at pH = 2; - 46 at pH = 7)

2.0 9.6 - - 115.13 0.34 0.31 1.32

Phenylalanine Phe F Aromatic Very Hydrophobic (92 at pH = 2; 100 at pH = 7)

2.2 9.3 - - 165.19 1.16 1.33 0.59

Tyrosine Tyr Y Aromatic Hydrophobic (49 at pH = 2; 63 at pH = 7)

2.2 9.2 10.5 181.19 0.74 1.45 0.76

Tryptophan Trp W Aromatic Very Hydrophobic (84 at pH = 2; 97 at pH = 7)

2.5 9.4 - - 204.25 1.02 1.35 0.65

Histidine His H Basic Hydrophilic at pH=2 (-42), Neutral at pH=7 (8)

1.8 9.3 6.0 155.16 1.05 0.80 0.81

Lysine Lys K Basic Hydrophilic (-37 at pH = 2; - 23 at pH = 7)

2.2 9.1 10.5 146.188 1.23 0.69 1.07

Arginine Arg R Basic Hydrophilic (-26 at pH = 2; - 14 at pH = 7)

1.8 9.0 12.5 174.2 1.21 0.84 0.90

Aspartate Asp D Acidic Neutral at pH=2 (-18), Hydrophilic at pH=7 (-55)

2.0 9.9 3.9 133.10 0.99 0.39 1.24

Glutamate Glu E Acidic Neutral at ph=2 (8), Hydrophilic at pH=7 (-31)

2.1 9.5 4.1 147.13 1.59 0.52 1.01

Asparagine Asn N Acidic, polar Hydrophilic (-41 at pH = 2; - 28 at pH = 7)

2.1 8.7 - - 132.118 0.76 0.48 1.34

Glutamine Gln