amino acid peptide and protein

amino acid peptide and protein

اسلاید 1: AMINO ACIDS

اسلاید 2: 2Amino Acids share common structural FeaturesProteins are polymers of amino acids, with each amino acid residue joined to its neighbor by a specific type of covalent bond.The additional carbons in an R group are designated b, g, d, e etc.Carbon atoms are numbered from one end, giving priority to carbons with substitutions. containing atoms with the highest atomic numbers.

اسلاید 3: 3EnantiomersThe a-carbon of AA is a chiral center. Molecules with a chiral center are optically active, they rotate plane-polarized light.Enantiomers : Nearly all biological compounds with a chiral center occur naturally in only one stereoisomeric form, either D or L. The amino acid residues in protein molecules are exclusively L-stereoisomers. D-Amino acid residues have been found only in a few, generally small peptides, including some peptides of bacterial cell walls and certain peptide antibiotics.

اسلاید 4: 4Amino acid can be classified by R group:20 Common Amino Acids

اسلاید 5: 5Nonpolar, Alipatic R GroupsGlycine has the simplest structure, its very small side chain makes no real contribution to hydrophobic interactionsMethionine, one of two sulfur containing amino acids. has a nonpolar thioether group. First AA residue in translation of proteinsAlanine, Valine, Leucine, and Isoleucine could contribute to hydrophobic interaction.The secondary amino (imino) group of Pro is held in a rigid conformation that reduces the structural flexibility of polypeptide regions containing proline.

اسلاید 6: 6indole ring

اسلاید 7: 7Absorbance of UV by Aromatic Amino acidsAll are relatively nonpolar (hydrophobic).-OH group of thyrosine can form hydrogen bonds and are important functional group. Can be phosphorylated as well.All can absorb UV light (280 nm), Tyrosine and Tryptophan are stronger than phenylalanine. Use for protein quantification.

اسلاید 8: 8گروه سولفور

اسلاید 9: 9Polar, Uncharged R GroupsThe R groups of these amino acids are more soluble in water, or more hydrophilic, than those of the nonpolar amino acids, because they contain functional groups that form hydrogen bonds with water.Serine and Threonine has –OH(Such as Tyr), which contribute to polarity, and could be phosophorelated.Asparagine and Glutamine are the amides of Aspartate, and Glutamate, and are easily hydrolyzed by acid or base.

اسلاید 10: 10Reversible Formation of Disulfide BondCysteine is readily oxidized to form a covalently linked dimeric AA called cystine (disulfide bond).The disulfide-linked residues are strongly hydrophobic (nonpolar). Disulfide bonds play a special role in the structures of many proteins by forming covalent links between parts of a protein molecule or between two different polypeptide chains.

اسلاید 11: 11