Amino Acid    3- & 1- letter codes    Side Chain
----------    --------------------    ----------



alanine             ala   A            -CH3
                                           

                                                         +
arginine            arg   R            -CH2-CH2-CH2-NH-C=NH2
                                                       |  
                                                       NH2


asparagine          asn   N            -CH2-CO-NH2


                                               _
aspartic acid       asp   D            -CH2-COO


cysteine            cys   C            -CH2-SH


glutamine           gln   Q            -CH2-CH2-CO-NH2


glutamic acid       glu   E            -CH2-CH2-COOH


glycine             gly   G            -H


histidine           his   H            -CH2-C = CH
                                            |   |
                                           +N=C-NH
                                            H 


isoleucine          ile   I            -CH-CH2-CH3
                                        |
                                        CH3


leucine             leu   L            -CH2-CH-CH3
                                            |
                                            CH3

                                                    +
lysine              lys   K            -CH2-CH2-CH2-NH3


methionine          met   M            -CH2-CH2-S-CH3


phenylalanine       phe   F            -CH2-Ph


proline             pro   P            -CH2-CH2-CH2-
                                       (the terminus is bonded to the 
                                        main chain amine nitrogen to 
                                        form a ring)


serine              ser   S            -CH2-OH


threonine           thr   T            -CH-CH3
                                        |
                                        OH


tryptophan          trp   W            -CH2-C = CH
                                            |   |
                                            Ph -NH
                                       (the phenyl group is bonded at 
                                        carbons 1 and 2 ie 'ortho' 
                                        positions)


tyrosine            tyr   W            -CH2-Ph-OH
                                       (the phenyl group is bonded at 
                                        carbons 1 and 4 ie 'para' 
                                        positions)


valine              val   V            -CH2-CH3
                                        |
                                        CH3