Amino Acid Structures

The following amino acid structures are listed in alphabetical order. Ionizable groups are shown in their neutral form - this implies absolutely nothing about the predominant form at any particular pH.

The following table gives the pKa values for the a-carboxylic acid group, the a-amino group, and any ionizable side chains.


Amino Acid pKa Values

Amino Acida-carboxylic acida-aminoSide chain
Alanine2.359.87
Arginine2.019.0412.48
Asparagine2.028.80
Aspartic Acid2.109.823.86
Cysteine2.0510.258.00
Glutamic Acid2.109.474.07
Glutamine2.179.13
Glycine2.359.78
Histidine1.779.186.10
Isoleucine2.329.76
Leucine2.339.74
Lysine2.188.9510.53
Methionine2.289.21
Phenylalanine2.589.24
Proline2.0010.60
Serine2.219.15
Threonine2.099.10
Tryptophan2.389.39
Tyrosine2.209.1110.07
Valine2.299.72
Last modified 2/4/97


Abby Parrill
Department of Chemistry
Michigan State University

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