Term
| 1 letter abbrev. of Alanine |
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| 3 letter abbrev. of Alanine |
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Definition
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| Very abundant, very versatile. More stiff than glycine, but small enough to pose only small steric limits for the protein conformation. It behaves fairly neutrally, and can be located in both hydrophilic regions on the protein outside and the hydrophobic areas inside. |
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| 1 letter abbrev. of Arginine |
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| 3 letter abbrev. of Arginine |
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| Functionally similar to lysine. |
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| 1 letter abbrev. of Asparagine |
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| 3 letter abbrev. of Asparagine |
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| Similar to aspartic acid. Asn contains an amide group where Asp has a carboxyl. |
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| 1 letter abbrev. of Aspartic acid |
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| 3 letter abbrev. of Aspartic acid |
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| function of Aspartic acid |
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Definition
| Behaves similarly to glutamic acid. Carries a hydrophilic acidic group with strong negative charge. Usually is located on the outer surface of the protein, making it water-soluble. Binds to positively-charged molecules and ions, often used in enzymes to fix the metal ion. When located inside of the protein, aspartate and glutamate are usually paired with arginine and lysine. |
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Term
| structure of Aspartic acid |
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Definition
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Term
| polarity of Aspartic acid |
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Term
| 1 letter abbrev. of Cysteine |
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Definition
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Term
| 3 letter abbrev. of Cysteine |
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| The sulfur atom bonds readily to heavy metal ions. Under oxidizing conditions, two cysteines can join together in a disulfide bond to form the amino acid cystine. When cystines are part of a protein, insulin for example, the tertiary structure is stabilized, which makes the protein more resistant to denaturation; therefore, disulfide bonds are common in proteins that have to function in harsh environments including digestive enzymes (e.g., pepsin and chymotrypsin) and structural proteins (e.g., keratin). Disulfides are also found in peptides too small to hold a stable shape on their own (eg. insulin). |
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| 1 letter abbrev. of Glutamine |
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Term
| 3 letter abbrev. of Glutamine |
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| Similar to glutamic acid. Gln contains an amide group where Glu has a carboxyl. Used in proteins and as a storage for ammonia. The most abundant Amino Acid in the body. |
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Term
| structure of of Glutamine |
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| 1 letter abbrev. of Glutamic acid |
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| 3 letter abbrev. of Glutamic acid |
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| function of Glutamic acid |
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Definition
| Behaves similar to aspartic acid. Has longer, slightly more flexible side chain. |
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Term
| structure of Glutamic acid |
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Definition
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Term
| polarity of Glutamic acid |
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Term
| 1 letter abbrev. of Glycine |
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Definition
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Term
| 3 letter abbrev. of Glycine |
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| Because of the two hydrogen atoms at the α carbon, glycine is not optically active. It is the smallest amino acid, rotates easily, adds flexibility to the protein chain. It is able to fit into the tightest spaces, e.g., the triple helix of collagen. As too much flexibility is usually not desired, as a structural component it is less common than alanine. |
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| 1 letter abbrev. of Histidine |
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| 3 letter abbrev. of Histidine |
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| In even slightly acidic conditions protonation of the nitrogen occurs, changing the properties of histidine and the polypeptide as a whole. It is used by many proteins as a regulatory mechanism, changing the conformation and behavior of the polypeptide in acidic regions such as the late endosome or lysosome, enforcing conformation change in enzymes. However only a few histidines are needed for this, so it is comparatively scarce. |
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| 1 letter abbrev. of Isoleucine |
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| 3 letter abbrev. of Isoleucine |
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| Essential for humans. Isoleucine, leucine and valine have large aliphatic hydrophobic side chains. Their molecules are rigid, and their mutual hydrophobic interactions are important for the correct folding of proteins, as these chains tend to be located inside of the protein molecule. |
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| 1 letter abbrev. of Leucine |
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| 3 letter abbrev. of Leucine |
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| Essential for humans. Behaves similar to isoleucine and valine. See isoleucine. |
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| 1 letter abbrev. of Lysine |
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| 3 letter abbrev. of Lysine |
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| Essential for humans. Behaves similarly to arginine. Contains a long flexible side-chain with a positively-charged end. The flexibility of the chain makes lysine and arginine suitable for binding to molecules with many negative charges on their surfaces. E.g., DNA-binding proteins have their active regions rich with arginine and lysine. The strong charge makes these two amino acids prone to be located on the outer hydrophilic surfaces of the proteins; when they are found inside, they are usually paired with a corresponding negatively-charged amino acid, e.g., aspartate or glutamate. |
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| 1 letter abbrev. of Methionine |
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| 3 letter abbrev. of Methionine |
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| Essential for humans. Behaves similarly to arginine. Contains a long flexible side-chain with a positively-charged end. The flexibility of the chain makes lysine and arginine suitable for binding to molecules with many negative charges on their surfaces. E.g., DNA-binding proteins have their active regions rich with arginine and lysine. The strong charge makes these two amino acids prone to be located on the outer hydrophilic surfaces of the proteins; when they are found inside, they are usually paired with a corresponding negatively-charged amino acid, e.g., aspartate or glutamate. |
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| 1 letter abbrev. of Phenylalanine |
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| 3 letter abbrev. of Phenylalanine |
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Term
| function of Phenylalanine |
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Definition
| Essential for humans. Phenylalanine, tyrosine, and tryptophan contain large rigid aromatic group on the side-chain. These are the biggest amino acids. Like isoleucine, leucine and valine, these are hydrophobic and tend to orient towards the interior of the folded protein molecule. Phenylalanine can be converted into Tyrosine. |
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Term
| structure of Phenylalanine |
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Definition
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Term
| polarity of Phenylalanine |
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Term
| 1 letter abbrev. of Proline |
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| 3 letter abbrev. of Proline |
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| Contains an unusual ring to the N-end amine group, which forces the CO-NH amide sequence into a fixed conformation. Can disrupt protein folding structures like α helix or β sheet, forcing the desired kink in the protein chain. Common in collagen, where it often undergoes a posttranslational modification to hydroxyproline. |
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| 1 letter abbrev. of Serine |
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| 3 letter abbrev. of Serine |
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| Serine and threonine have a short group ended with a hydroxyl group. Its hydrogen is easy to remove, so serine and threonine often act as hydrogen donors in enzymes. Both are very hydrophilic, therefore the outer regions of soluble proteins tend to be rich with them. |
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| 1 letter abbrev. of Threonine |
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| 3 letter abbrev. of Threonine |
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| Essential for humans. Behaves similarly to serine. |
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| 1 letter abbrev. of Tryptophan |
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| 3 letter abbrev. of Tryptophan |
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| Essential for humans. Behaves similarly to phenylalanine and tyrosine (see phenylalanine). Precursor of serotonin. Naturally fluorescent. |
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| 1 letter abbrev. of Tyrosine |
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| 3 letter abbrev. of Tyrosine |
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| Behaves similarly to phenylalanine (precursor to Tyrosine) and tryptophan (see phenylalanine). Precursor of melanin, epinephrine, and thyroid hormones. Naturally fluorescent, although fluorescence is usually quenched by energy transfer to tryptophans. |
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| 1 letter abbrev. of Valine |
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| 3 letter abbrev. of Valine |
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| Essential for humans. Behaves similarly to isoleucine and leucine. See isoleucine. |
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| 1 letter abbrev. of Selenocysteine |
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| 3 letter abbrev. of Selenocysteine |
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Term
| function of Selenocysteine |
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Definition
| Selenated form of cysteine, which replaces sulfur. |
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Term
| structure of Selenocysteine |
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Definition
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Term
| polarity of Selenocysteine |
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Term
| 1 letter abbrev. of Pyrrolysine |
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| 3 letter abbrev. of Pyrrolysine |
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| Similar to lysine, with a pyrroline ring attached. |
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