![]() ![]() The aromatic groups of these amino acids can be involved in non-covalent cation – π interactions with different cationic species. Aromatic amino acids may, besides interaction through their polar heads, also interfere via their aromatic part of the molecule. The effect of water molecules on the stability of the zwitterionic structure of phenylalanine, tyrosine and tryptophan was also investigated. In order to investigate the nature of the interaction between metal cations and aromatic amino acids, a number of theoretical and experimental studies have been conducted. The zwitterionic form of amino acids ( +H 3N–CH(R)–COO –) can be stabilized by the presence of counter ions and/or water molecules. However, in aqueous solution the zwitterions are the predominant species. All three aromatic amino acids can also be administered as nutraceuticals.īoth experimental and theoretical studies demonstrate that amino acids exist in the gas phase in the neutral form. Tryptophan is an essential amino acid that is necessary for normal growth in infants and for nitrogen balance in adults. A shortage of either of these two aromatic amino acids could cause mental disorders, including anxienty, depression, low libido, and chronic fatigue. The body needs the essential amino acid L-phenylalanine (and L-tyrosine) to make melanine, dopamine, noradrenaline, adrenaline and thyroxine. The phenolic hydroxyl group of this amino acid is substantially more acidic than are the hydroxyls of aliphatic amino acids (serine, threonine) and its acidity vary depending on its environment. L-tyrosine is a hydroxylated derivative of L-phenylalanine. The indole functional group of L-tryptophan contains the N-H hydrogen bonding group, which can interact with solvent in folded proteins. Due to its hydrophobicity L-phenylalanine is nearly always found buried within a protein. Phenylalanine and tryptophan contain phenyl and indole rings and are classified as non-polar. Aromatic amino acids (AAA) are essential to higher animals including humans. ![]()
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