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Unformatted text preview: 766 AMINO ACIDS, PEPTIDES, AND PROTEINS. NUCLEIC ACIDS 27.29 Bradykinin is a nonapeptide but contains only ﬁve different amino acids. Three of the amino acid
residues are proline, two are arginine, and two are phenylalanine. Five peaks will appear on the strip
chart after amino acid analysis of bradykinin.
Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg 27.30 2Arg 3Pro Gly O H2NCCH2CHCO2 H2O NH3 HOCCH2CHCO2 NH3 NH3 Asparagine Water Ammonia O Aspartic acid O H2NCCH2CH2CHCO2 H2O NH3 HOCCH2CH2CHCO2 NH3 NH3 Glutamine (a) O F O NHCHCNHCH2CNHCHCO2H CH2OH hydrolysis O NHCHCNHCH2CNHCHCO2H
(CH3)2CHCH2 O (CH3)2CHCH2 CH2OH DNP-Leu-Gly-Ser Hydrolysis of the product in part (a) cleaves the peptide bonds. Leucine is isolated as its 2,4dinitrophenyl (DNP) derivative, but glycine and serine are isolated as the free amino acids. NO2 CH2OH Main Menu O2N NO2
O H3NCH2CO2 NHCHCOH H3NCHCO2
DNP-Leu DNP-Leu-Gly-Ser Forward O Leu-Gly-Ser (b) Glutamic acid NO2 H3NCHCNHCH2CNHCHCO2 1-Fluoro-2,4dinitrobenzene Back Ammonia O2N O (CH3)2CHCH2 O2N Water 1-Fluoro-2,4-dinitrobenzene reacts with the amino group of the N-terminal amino acid in a
nucleophilic aromatic substitution reaction of the addition– elimination type. NO2
O2N Ser Asparagine and glutamine each contain an amide function in their side chain. Under the conditions
of peptide bond hydrolysis that characterize amino acid analysis, the side-chain amide is also
hydrolyzed, giving ammonia. O 27.31 2Phe TOC Study Guide TOC Gly Student OLC Ser MHHE Website ...
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