The two enantiomers of each amino acid defined by the a-carbon are designated D-and L-forms(d for Dextrorotary右旋, Lfor Levorotary左旋) COO coo C00 CO0 H3N-C-H H--c-NH3H3 N-C-H H--C-NHs CH3 CH CH3 CH3 L-Alanine D-Alanine L-Alanine D-Alanine (c) The horizontal bonds project out of the plane of the paper, the vertical behind
The horizontal bonds project out of the plane of the paper, the vertical behind. The two enantiomers of each amino acid defined by the -carbon are designated D- and L- forms (D for Dextrorotary右旋, L for Levorotary左旋)
The d-and L-forms of amino acids are named in reference to the absolute configuration of D-and L glyceraldehydes(whose structure was originally assumed and confirmed by x-ray crystallography later). ICHO CHO HO-C-H H-C-OH BCHOOH CHOH L-Glyceraldehyde D-Glyceraldehyde CoO CoO H—C=NH3 CH3 CH3 L-Alanine D-Alanine Lined up by similarity: chiral to chiral, Coo to CHO
Lined up by similarity: chiral to chiral, COO to CHO The D- and L-forms of amino acids are named in reference to the absolute configuration of D- and Lglyceraldehydes (whose structure was originally assumed and confirmed by X-ray crystallography later)
about aa chirality Normally, the a-carbon is the only chiral center with several exceptions. There are ways to determine the d-and L-forms of amino acids .Only the L-amino acids have been found in proteins D-isomers have been found only in small peptides of bacteria cell walls and in some peptide antibiotics). The correlation of structure(or configuration) with optical rotation is very complex and has not been successful to date!(i.e, the D- and L-signs do not tell anything about their optical rotation!)
About AA chirality： •Normally, the -carbon is the only chiral center with several exceptions. •There are ways to determine the D- and L-forms of amino acids. •Only the L-amino acids have been found in proteins (D-isomers have been found only in small peptides of bacteria cell walls and in some peptide antibiotics). •The correlation of structure (or configuration) with optical rotation is very complex and has not been successful to date! (i.e., the D- and L-signs do not tell anything about their optical rotation!)
1.2 Each amino acid is given a three-letter abbreviation and a one-letter symbol. They often use the first three letter and the first letter. When there is confusion an alternative is used. These must be remembered 1.3 All proteins in all species(from bacteria to human) are constructed from the same set of 20 amino acids All proteins, no matter how different they are in structure and function are made from the 20 standard amino acids This fundamental alphabet of the protein language is at least two billion years old
1.2 Each amino acid is given a three-letter abbreviation and a one-letter symbol. They often use the first three letter and the first letter. When there is confusion, an alternative is used. These must be remembered. 1.3 All proteins in all species (from bacteria to human) are constructed from the same set of 20 amino acids. •All proteins, no matter how different they are in structure and function, are made from the 20 standard amino acids. •This fundamental alphabet of the protein language is at least two billion years old
List of amino acids and their abbreviations Nonpolar Amino Acids (hydrophobic) Polar (hydrophilic) amino acid three letter code single letter code Gly alanine A serine valine Val threonine Thr cysteine C C euc ine isoleuc ine lle tyrosine methionine Met asparagine phenylalanine Phe F glutamine GIn tryptophan Ir proline Pro Electrically Charged(positive Electrically Charged (negative and and hydrophilic) hydrophilic aspartic acid D arginine Arg R glutamic acid histidine Yellow amino acids contain sulfur. Blue amino acids can be phosphorylated
List of Amino Acids and Their Abbreviations amino acid three letter code single letter code glycine Gly G alanine Ala A valine Val V leucine Leu L isoleucine Ile I methionine Met M phenylalanine Phe F tryptophan Trp W proline Pro P Polar (hydrophilic) serine Ser S threonine Thr T cysteine Cys C tyrosine Tyr Y asparagine Asn N glutamine Gln Q Electrically Charged (negative and hydrophilic) aspartic acid Asp D glutamic acid Glu E Electrically Charged (positive and hydrophilic) lysine Lys K arginine Arg R histidine His H Nonpolar Amino Acids (hydrophobic) Yellow amino acids contain sulfur. Blue amino acids can be phosphorylated