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. 2002 Oct;76(19):10000–10008. doi: 10.1128/JVI.76.19.10000-10008.2002

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Copyright © 2002, American Society for Microbiology

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FIG. 3. — Spectra of N-terminal tryptic peptides derived from CyPA and corresponding to spots 7, 8, and 25; postsource decay spectrum; and N-acylamino acid-releasing enzyme treatment of an N-terminal tryptic peptide derived from the spot 8 protein, N-acetyl-VNPTVFFDIAVDGEPLGR. (A) MALDI-TOF mass spectra of N-terminal tryptic peptides derived from CyPA and corresponding to spots 7, 8, and 25. As shown in the top and bottom spectra, the peaks of (M + H)⁺ at m/z 1,946.30 and 1,945.70 represent N-terminal tryptic peptide Val₁-Arg₁₈ of CyPA. As shown in the middle spectrum, the peak of (M + H)⁺ at m/z 1,988.26 could be assigned to the acetylated form of N-terminal tryptic peptide Val₁-Arg₁₈. The fragment with a molecular mass of 41.96 and corresponding to the acetyl group was deleted. a.i., absolute intensity. (B) MS determination of the partial peptide sequence of the N-terminal tryptic peptide derived from the spot 8 protein. y" series ions were defined according to the nomenclature of Biemann (2) (C) Liberation of N-acetylated Val₁ from the N-terminal peptide derived from the spot 8 protein. As shown in the lower spectrum, the peak at m/z 1,847.18 and corresponding to the peptide Asn₂-Arg₁₈ (theoretical mass, m/z 1,846.93) was detected after N-acylamino acid-releasing enzyme treatment. The peak at m/z 1,847.18 was not found before N-acylamino acid-releasing enzyme treatment (upper spectrum). The unknown peaks of (M + H)⁺ at m/z 1,956.74 and 1,973.01 were also found in control experiments under identical conditions, except for the omission of tryptic peptides derived from the spot 8 protein.

FIG. 3. — Spectra of N-terminal tryptic peptides derived from CyPA and corresponding to spots 7, 8, and 25; postsource decay spectrum; and N-acylamino acid-releasing enzyme treatment of an N-terminal tryptic peptide derived from the spot 8 protein, N-acetyl-VNPTVFFDIAVDGEPLGR. (A) MALDI-TOF mass spectra of N-terminal tryptic peptides derived from CyPA and corresponding to spots 7, 8, and 25. As shown in the top and bottom spectra, the peaks of (M + H)⁺ at m/z 1,946.30 and 1,945.70 represent N-terminal tryptic peptide Val₁-Arg₁₈ of CyPA. As shown in the middle spectrum, the peak of (M + H)⁺ at m/z 1,988.26 could be assigned to the acetylated form of N-terminal tryptic peptide Val₁-Arg₁₈. The fragment with a molecular mass of 41.96 and corresponding to the acetyl group was deleted. a.i., absolute intensity. (B) MS determination of the partial peptide sequence of the N-terminal tryptic peptide derived from the spot 8 protein. y" series ions were defined according to the nomenclature of Biemann (2) (C) Liberation of N-acetylated Val₁ from the N-terminal peptide derived from the spot 8 protein. As shown in the lower spectrum, the peak at m/z 1,847.18 and corresponding to the peptide Asn₂-Arg₁₈ (theoretical mass, m/z 1,846.93) was detected after N-acylamino acid-releasing enzyme treatment. The peak at m/z 1,847.18 was not found before N-acylamino acid-releasing enzyme treatment (upper spectrum). The unknown peaks of (M + H)⁺ at m/z 1,956.74 and 1,973.01 were also found in control experiments under identical conditions, except for the omission of tryptic peptides derived from the spot 8 protein.