This table gives selected properties of some important amino acids and closely related compounds. Compounds are listed by name in alphabetical order. The three-letter symbol is included for the 20 “standard” amino acids that are the basic constituents of proteins. Structures are given in the following table. Column definitions for the table are as follows.
Column heading | Definition |
Symbol | Three-letter symbol for standard amino acids; table lists amino acids alphabetically by this symbol |
Name | Amino acid name |
Mol. form. | Molecular formula of amino acid |
Mol. wt. | Molecular weight |
tmp/°C | Melting point, in °C |
pKa, pKb, pKc, pKd | Negative of the logarithm of the acid dissociation constants for the COOH and NH2 groups (and, in some cases, other groups) in the molecule (at 25 °C) |
pI | pH at the isoelectric point |
Sol./g kg-1 | Solubility in water, in units of grams of compound per kilogram of water; a temperature of 25 °C is understood unless otherwise stated; when quantitative data are not available, a qualitative indication is given |
2/ cm3 mol-1 |
Partial molar volume in aqueous solution at infinite dilution at 25 °C |
Data on the enthalpy of formation of many of these compounds are included in the table “Standard Thermodynamic Properties of Chemical Substances” in Section 5 of this CRC Handbook. Absorption spectra and optical rotation data can be found in Ref. 3. Partial molar volume is taken from Ref. 5; other thermodynamic properties, including solubility as a function of temperature, are given in Refs. 3 and 5. Most of the pK values come from Refs. 1, 6, and 7.
Symbol | Name | Synonym | Mol. form. | CAS Reg. No. | Mol. wt. | tmp/ºC | pKa | pKb | pKc | pKd | pI | Sol./g kg-1 | 2/ cm3 mol-1 |
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Standard amino acids | |||||||||||||
Ala | L-Alanine | 2-Aminopropanoic acid, (S)- | C3H7NO2 | 56-41-7 | 89.094 | 297 dec | 2.33 | 9.71 | 6.00 | 166.9 | 60.54 | ||
Arg | L-Arginine | C6H14N4O2 | 74-79-3 | 174.201 | 260 | 2.03 | 9.00 | 12.10 | 10.76 | 182.6 | 127.42 | ||
Asn | L-Asparagine | α-Aminosuccinamic acid | C4H8N2O3 | 70-47-3 | 132.118 | 235 | 2.16 | 8.73 | 5.41 | 25.1 | 78.0 | ||
Asp | L-Aspartic acid | L-Aminosuccinic acid | C4H7NO4 | 56-84-8 | 133.104 | 270 | 1.95 | 9.66 | 3.71 | 2.77 | 5.04 | 74.8 | |
Cys | L-Cysteine | 2-Amino-3-mercaptopropanoic acid, (R)- | C3H7NO2S | 52-90-4 | 121.159 | 240 dec | 1.91 | 10.28 | 8.14 | 5.07 | vs | 73.45 | |
Gln | L-Glutamine | 2-Aminoglutaramic acid | C5H10N2O3 | 56-85-9 | 146.144 | 182 | 2.18 | 9.00 | 5.65 | 42 | |||
Glu | L-Glutamic acid | (S)-2-Aminopentanedioic acid | C5H9NO4 | 56-86-0 | 147.130 | 160 dec | 2.16 | 9.58 | 4.15 | 3.22 | 8.6 | 89.85 | |
Gly | Glycine | Aminoacetic acid | C2H5NO2 | 56-40-6 | 75.067 | 290 dec | 2.34 | 9.58 | 5.97 | 239 | 43.26 | ||
His | L-Histidine | Glyoxaline-5-alanine | C6H9N3O2 | 71-00-1 | 155.154 | 287 dec | 1.70 | 9.09 | 6.04 | 7.59 | 43.5 | 98.3 | |
Ile | L-Isoleucine | 2-Amino-3-methylpentanoic acid | C6H13NO2 | 73-32-5 | 131.173 | 284 dec | 2.26 | 9.60 | 6.02 | 34.2 | 105.80 | ||
Leu | L-Leucine | 2-Amino-4-methylpentanoic acid | C6H13NO2 | 61-90-5 | 131.173 | 293 | 2.32 | 9.58 | 5.98 | 23.8 | 107.77 | ||
Lys | L-Lysine | 2,6-Diaminohexanoic acid, (L)- | C6H14N2O2 | 56-87-1 | 146.187 | 224 dec | 2.15 | 9.16 | 10.67 | 9.74 | 5.8 | 108.5 | |
Met | L-Methionine | C5H11NO2S | 63-68-3 | 149.212 | 281 dec | 2.16 | 9.08 | 5.74 | 56 | 105.57 | |||
Phe | L-Phenylalanine | α-Aminobenzenepropanoic acid, (S)- | C9H11NO2 | 63-91-2 | 165.189 | 283 dec | 2.18 | 9.09 | 5.48 | 27.9 | 121.5 | ||
Pro | L-Proline | 2-Pyrrolidinecarboxylic acid | C5H9NO2 | 147-85-3 | 115.131 | 221 dec | 1.95 | 10.47 | 6.30 | 1625 | 82.76 | ||
Ser | L-Serine | 2-Amino-3-hydroxypropanoic acid, (S)- | C3H7NO3 | 56-45-1 | 105.093 | 228 dec | 2.13 | 9.05 | 5.68 | 250 | 60.62 | ||
Thr | L-Threonine | 2-Amino-3-hydroxybutanoic acid, [R-(R*,S*)] | C4H9NO3 | 72-19-5 | 119.119 | 256 dec | 2.20 | 8.96 | 5.60 | 90.6 | 76.90 | ||
Trp | L-Tryptophan | α-Aminoindole-3-propanoic acid, (l)- | C11H12N2O2 | 73-22-3 | 204.225 | 289 dec | 2.38 | 9.34 | 5.89 | 13.2 | 143.8 | ||
Tyr | L-Tyrosine | 4-Hydroxy-L-phenylalanine | C9H11NO3 | 60-18-4 | 181.188 | 343 dec | 2.24 | 9.04 | 10.10 | 5.66 | 0.51 |
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