At physiological ph conjugate base of asparac acid

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Unformatted text preview: Aroma=c (3) Polar, uncharged (5) Posi=vely charged (3) Nega=vely charged (2) ring à༎ rigid more carbons, more hydrophobic Absorbance Spectra of Aroma=c Amino Acids •  Tryptophan and tyrosine absorb ultraviolet light –  (also phenylalanine but weaker) •  Used to characterize proteins thiol à༎ disulfide bond not very polar Disulfide Bond Forma=on •  The oxida=on of two cysteines à༎ Disulfide bond •  Stabilize the structures of many proteins Both neutral and protonated forms present at physiological pH conjugate base of Aspara+c Acid, Glutamic Acid Glutamine Greek nomenclature for Carbon atoms in amino acids •  The carbon atoms are assigned sequen=al le]ers in the Greek alphabet. Stereochemistry of Amino Acids •  α- carbon is a chiral center (asymmetric C, 4 different subs=tuents) – except Glycine •  2 possible stereoisomers that are nonsuperimposable mirror images (enan+omers), D and L •  L- amino acids = the naturally occurring enan=omers found in all proteins. •  Naturally occurring D- amino acids exist in some bacterial cell wall pep=de structures, in some pep=de an=bio=cs, etc., but not in proteins. •  Only right- handed helices observed in proteins Life is Asymmetric Biosynthe=c processes produce pure stereoisomers Biomolecules are asymmetric •  Ordinary chemical synthesis produces racemic mixture (equal amounts of each enan=omer) •  Many drugs are chemically synthesized as racemic mixture, but only one enan=omer has biological ac=vity (ex. ibuprofen, thalidomide) Amino Acid Names are abbreviated alanyltyrosylaspartylglycine – never used 3 le]er code 1 le]er code AYDG Full name Cysteine His=dine Isoleucine Methionine Serine Valine Alanine Glycine Leucine Proline Threonine Arginine Phenylalanine Tyrosine Tryptophan Aspa...
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