Amino Acids

From Proteopedia

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For a general introduction to amino acids, please see Amino Acids in Wikipedia.

Here are the names of the twenty standard amino acids, with their three and one-letter abbreviations. Mnemonic names may help you to remember the one-letter codes, but are not the correct names.

Ala A Alanine Arg R Arginine Asn N Asparagine Asp D Aspartic acid  (mnemonic: asparDic) Cys C Cysteine

Gln Q Glutamine  (mnemonic: Quetamine) Glu E Glutamic acid  (mnemonic: gluEtamic) Gly G Glycine His H Histidine Ile I Isoleucine

Leu L Leucine Lys K Lysine  (mnemonic: liKesine) Met M Methionine Phe F Phenylalanine  (mnemonic: Fenylalanine) Pro P Proline

Ser S Serine Thr T Threonine Trp W Tryptophan  (mnemonic: tWyptophan) Tyr Y Tyrosine Val V Valine

Angel Herráez has provided a tutorial introduction to amino acid structure in which each of the 20 amino acids may be visualized in 3D using Jmol.

The list below will gradually be expanded to include all 20 amino acids.

Histidine His H

Charged: Basic, Aromatic, Bulky

See Histidine in Wikipedia, where the structure is shown. The sidechain of His can be positively charged (protonated), in which case both of the nitrogens in the sidechain imidazole ring have hydrogens, and the charge is delocalized between them. The pKa for protonation is 6.1. This means that, on average at any moment, half of the His sidechains are protonated when the pH is 6.1. At the pH of blood, 7.4 ±0.05, more than 90% of the His sidechains are positively charged.

Tyrosine Tyr Y

Neutral, Polar, Aromatic, Bulky

See Tyrosine in Wikipedia, where the structure is shown.

See Also

• Non-Standard Residues.
• Standard Residues