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Reference


Amino Acids



Standard Amino Acid Abbreviations and Side Chain Properties

Amino Acid   3-Letter   1-Letter   Side chain polarity   Side chain acidity or basicity   Hydropathy index  
Alanine Ala A nonpolar neutral 1.8
Arginine Arg R polar basic (strongly) -4.5
Asparagine Asn N polar neutral -3.5
Aspartic acid Asp D polar acidic -3.5
Cysteine Cys C polar neutral 2.5
Glutamic acid Glu E polar acidic -3.5
Glutamine Gln Q polar neutral -3.5
Glycine Gly G nonpolar neutral -0.4
Histidine His H polar basic (weakly) -3.2
Isoleucine Ile I nonpolar neutral 4.5
Leucine Leu L nonpolar neutral 3.8
Lysine Lys K polar basic -3.9
Methionine Met M nonpolar neutral 1.9
Phenylalanine Phe F nonpolar neutral 2.8
Proline Pro P nonpolar neutral -1.6
Serine Ser S polar neutral -0.8
Threonine Thr T polar neutral -0.7
Tryptophan Trp W nonpolar neutral -0.9
Tyrosine Tyr Y polar neutral -1.3
Valine Val V nonpolar neutral 4.2

Nutritional Importance

Of the 20 standard proteinogenic amino acids, 8 are called essential amino acids because the human body cannot synthesize them from other compounds at the level needed for normal growth, and they therefore must be obtained from food.Cysteine, tyrosine, histidine and arginine are considered as semiessential amino acids in children, because the metabolic pathways that synthesize these amino acids are not fully developed.

Essential & Nonessential Amino Acids

Essential Nonessential
Isoleucine Alanine
Leucine Asparagine
Lysine Aspartate
Methionine Cysteine*
Phenylalanine Glutamate
Threonine Glutamine*
Tryptophan Glycine*
Valine Proline*
Arginine* Serine*
Histidine* Tyrosine*

(*) Essential only in certain cases.

General Chemical Properties

Amino Acid   Short   Abbrev.   Avg. Mass (Da)   pI   pK1
(α-COOH)  		 pK2
(α-+NH3)  
Alanine A Ala 89.09404 6.01 2.35 9.87
Cysteine C Cys 121.15404 5.05 1.92 10.70
Aspartic acid D Asp 133.10384 2.85 1.99 9.90
Glutamic acid E Glu 147.13074 3.15 2.10 9.47
Phenylalanine F Phe 165.19184 5.49 2.20 9.31
Glycine G Gly 75.06714 6.06 2.35 9.78
Histidine H His 155.15634 7.60 1.80 9.33
Isoleucine I Ile 131.17464 6.05 2.32 9.76
Lysine K Lys 146.18934 9.60 2.16 9.06
Leucine L Leu 131.17464 6.01 2.33 9.74
Methionine M Met 149.20784 5.74 2.13 9.28
Asparagine N Asn 132.11904 5.41 2.14 8.72
Proline P Pro 115.13194 6.30 1.95 10.64
Glutamine Q Gln 146.14594 5.65 2.17 9.13
Arginine R Arg 174.20274 10.76 1.82 8.99
Serine S Ser 105.09344 5.68 2.19 9.21
Threonine T Thr 119.12034 5.60 2.09 9.10
Selenocysteine U Sec 169.06      
Valine V Val 117.14784 6.00 2.39 9.74
Tryptophan W Trp 204.22844 5.89 2.46 9.41
Tyrosine Y Tyr 181.19124 5.64 2.20 9.21

Side Chain Properties

Amino Acid   Short   Abbrev.   Side chain   Hydro-
phobic  		 pKa   Polar   pH   Small   Tiny   Aromatic
or Aliphatic  		 van der Waals
volume  
Alanine A Ala -CH3 X - - - X X - 67
Cysteine C Cys -CH2SH X 8.18 - acidic X - - 86
Aspartic acid D Asp -CH2COOH - 3.90 X acidic X - - 91
Glutamic acid E Glu -CH2CH2COOH - 4.07 X acidic - - - 109
Phenylalanine F Phe -CH2C6H5 X - - - - - Aromatic 135
Glycine G Gly -H - - - - X X - 48
Histidine H His -CH2-C3H3N2 - 6.04 X weak basic - - Aromatic 118
Isoleucine I Ile -CH(CH3)CH2CH3 X - - - - - Aliphatic 124
Lysine K Lys -(CH2)4NH2 - 10.54 X basic - - - 135
Leucine L Leu -CH2CH(CH3)2 X - - - - - Aliphatic 124
Methionine M Met -CH2CH2SCH3 X - - - - - - 124
Asparagine N Asn -CH2CONH2 - - X - X - - 96
Proline P Pro -CH2CH2CH2- X - - - X - - 90
Glutamine Q Gln -CH2CH2CONH2 - - X - - - - 114
Arginine R Arg -(CH2)3NH-C(NH)NH2 - 12.48 X strongly basic - - - 148
Serine S Ser -CH2OH - - X - X X - 73
Threonine T Thr -CH(OH)CH3 - - X weak acidic X - - 93
Selenocysteine U Sec -CH2SeH X 5.73 - - X - -  
Valine V Val -CH(CH3)2 X - - - X - Aliphatic 105
Tryptophan W Trp -CH2C8H6N X - - - - - Aromatic 163
Tyrosine Y Tyr -CH2-C6H4OH - 10.46 X - - - Aromatic 141

Note: The pKa values of amino acids are typically slightly different when the amino acid is inside a protein. Protein pKa calculations are sometimes used to calculate the change in the pKa value of an amino acid in this situation.

Gene Expression and Biochemistry

Amino Acid   Short   Abbrev.   Codon(s)   Occurrence
in proteins
(%)  		 Essential in humans  
Alanine A Ala GCU, GCC, GCA, GCG 7.8 -
Cysteine C Cys UGU, UGC 1.9 -
Aspartic acid D Asp GAU, GAC 5.3 -
Glutamate E Glu GAA, GAG 6.3 -
Phenylalanine F Phe UUU, UUC 3.9 X
Glycine G Gly GGU, GGC, GGA, GGG 7.2 -
Histidine H His CAU, CAC 2.3 -
Isoleucine I Ile AUU, AUC, AUA 5.3 X
Lysine K Lys AAA, AAG 5.9 X
Leucine L Leu UUA, UUG, CUU, CUC, CUA, CUG 9.1 X
Methionine M Met AUG 2.3 X
Asparagine N Asn AAU, AAC 4.3 -
Proline P Pro CCU, CCC, CCA, CCG 5.2 -
Glutamine Q Gln CAA, CAG 4.2 -
Arginine R Arg CGU, CGC, CGA, CGG, AGA, AGG 5.1 -
Serine S Ser UCU, UCC, UCA, UCG, AGU, AGC 6.8 -
Threonine T Thr ACU, ACC, ACA, ACG 5.9 X
Selenocysteine U Sec UGA*   -
Valine V Val GUU, GUC, GUA, GUG 6.6 X
Tryptophan W Trp UGG 1.4 X
Tyrosine Y Tyr UAU, UAC 3.2 -
Stop codon† - Term UAA, UAG, UGA - -

* UGA is normally a stop codon, but encodes selenocysteine if a SECIS element is present.
† The stop codon is not an amino acid, but is included for completeness.

Source: Wikipedia article Amino Acid


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