Amino acid Abbreviations  Structure of R group shown in Figure 1 Alanine Ala A -CH3 Arginine Arg R -(CH2)3-NH-C(NH2)=NH Asparagine Asn N -CH2-CO-NH2 Aspartic acid Asp D -CH2-COOH Cysteine Cys C -CH2-SH Glutamine Gln Q -(CH2)2-CO-NH2 Glutamic Acid Glu E -(CH2)2-COOH Glycine Gly G -H Histidine His H -CH2C3H3N2 Isoleucine Ile I -CH(CH3)-CH2-CH3 Leucine Leu L -CH2-CH-(CH3)2 Lysine Lys K -(CH2)4NH2 Methionine Met M -(CH2)2-S-CH3 Phenylalanine Phe F -CH2-C6H5 Proline Pro P -CH(CH2)3NH Serine Ser S -CH2-OH Threonine Thr T -CH(OH)-CH3 Tryptophan Trp W -CH2-C8H6N Tyrosine Tyr Y -CH2-C6H5-OH Valine Val V -CH-(CH3)2

Table 1: Structure of R groups of amino acids.