Selective gas-phase cleavage at the peptide bond C-terminal to aspartic acid in fixed-charge derivatives of Asp-containing peptides

C. Gu, George Tsaprailis, L. Breci, V. H. Wysocki

Research output: Contribution to journalArticle

176 Citations (Scopus)

Abstract

This study focuses on the molecular level interpretation of the selective gas-phase cleavage at aspartic acid residues (Asp) in protonated peptides. A φ3P+CH2C(=O) group (φ = 2,4,6-trimethoxyphenyl) is attached to the N-terminal nitrogen of the selected peptides LDIFSDF and LDIFSDFR, via solid-phase synthesis, to 'mimic' the tightly held charge of a protonated arginine (Arg) residue. Collision-induced dissociation in a quadrupole ion trap instrument and surface-induced dissociation in a dual quadrupole instrument were performed for electrospray generated ions of the fixed-charge peptide derivatives. Selective cleavages at Asp-Xxx are observed for those ions with charge provided only by the fixed charge or for those with a fixed charge and one Arg plus one added proton. This supports a previously proposed mechanism which suggests that the cleavages at Asp-Xxx, initiated by the acidic hydrogen of the Asp residue, become significant when ionizing protons are strongly bound by Arg in the protonated peptides. It is clear that the fixed charge is indeed serving as a 'mimic' of protonated Arg and that a protonated Arg side chain is not required to interact with the Asp to induce cleavage at Asp-Xxx. When the number of protons exceeds the number of Arg in a peptide containing Arg and Asp, nonselective cleavages occur. The fragmentation efficiency of the peptides is consistent with the idea that these nonselective cleavages are promoted by a mobile proton. The peptide with a fixed charge and one added proton, [φ3P+CH2C(O)-LDIFSDF + H]2+, fragments much more efficiently than the corresponding peptide with a fixed charge, an Arg and one added proton, [φ3P+CH2C(=O)-LDIFSDFR + H]2+; both of these fragment more efficiently than the peptide with a fixed charge and no added proton, φ3P+CH2C(=O)-LDIFSDF. MS/MS/MS (i.e., MS3) experimental results for b(n) ions formed at Asp-Xxx from φ3P+CH2C(=O)-LDIFS DF and its H/D exchange derivative, φ3P+CH2C(=O)-LDIFSDF-d11, are consistent with the b(n) ions formed at Asp-Xxx having a succinic anhydride cyclic structure. MS/MS experiments were also carried out for φ3P+CH2C(=O)-AAAA, a peptide derivative containing active hydrogens only at amide nitrogens plus the C-terminus, and its active H/D exchange product, φ3P+CH2C(=O)-AAAA-d5. The results show that a hydrogen originally located at an amide nitrogen is transferred away in the formation of a cyclic charge remote b ion.

Original languageEnglish (US)
Pages (from-to)5804-5813
Number of pages10
JournalAnalytical Chemistry
Volume72
Issue number23
DOIs
StatePublished - Dec 1 2000

Fingerprint

Aspartic Acid
Gases
Arginine
Derivatives
Peptides
Protons
Ions
Hydrogen
Nitrogen
Amides

ASJC Scopus subject areas

  • Analytical Chemistry

Cite this

Selective gas-phase cleavage at the peptide bond C-terminal to aspartic acid in fixed-charge derivatives of Asp-containing peptides. / Gu, C.; Tsaprailis, George; Breci, L.; Wysocki, V. H.

In: Analytical Chemistry, Vol. 72, No. 23, 01.12.2000, p. 5804-5813.

Research output: Contribution to journalArticle

@article{8082a60c3b3840bcb7b1bfa102415f43,
title = "Selective gas-phase cleavage at the peptide bond C-terminal to aspartic acid in fixed-charge derivatives of Asp-containing peptides",
abstract = "This study focuses on the molecular level interpretation of the selective gas-phase cleavage at aspartic acid residues (Asp) in protonated peptides. A φ3P+CH2C(=O) group (φ = 2,4,6-trimethoxyphenyl) is attached to the N-terminal nitrogen of the selected peptides LDIFSDF and LDIFSDFR, via solid-phase synthesis, to 'mimic' the tightly held charge of a protonated arginine (Arg) residue. Collision-induced dissociation in a quadrupole ion trap instrument and surface-induced dissociation in a dual quadrupole instrument were performed for electrospray generated ions of the fixed-charge peptide derivatives. Selective cleavages at Asp-Xxx are observed for those ions with charge provided only by the fixed charge or for those with a fixed charge and one Arg plus one added proton. This supports a previously proposed mechanism which suggests that the cleavages at Asp-Xxx, initiated by the acidic hydrogen of the Asp residue, become significant when ionizing protons are strongly bound by Arg in the protonated peptides. It is clear that the fixed charge is indeed serving as a 'mimic' of protonated Arg and that a protonated Arg side chain is not required to interact with the Asp to induce cleavage at Asp-Xxx. When the number of protons exceeds the number of Arg in a peptide containing Arg and Asp, nonselective cleavages occur. The fragmentation efficiency of the peptides is consistent with the idea that these nonselective cleavages are promoted by a mobile proton. The peptide with a fixed charge and one added proton, [φ3P+CH2C(O)-LDIFSDF + H]2+, fragments much more efficiently than the corresponding peptide with a fixed charge, an Arg and one added proton, [φ3P+CH2C(=O)-LDIFSDFR + H]2+; both of these fragment more efficiently than the peptide with a fixed charge and no added proton, φ3P+CH2C(=O)-LDIFSDF. MS/MS/MS (i.e., MS3) experimental results for b(n) ions formed at Asp-Xxx from φ3P+CH2C(=O)-LDIFS DF and its H/D exchange derivative, φ3P+CH2C(=O)-LDIFSDF-d11, are consistent with the b(n) ions formed at Asp-Xxx having a succinic anhydride cyclic structure. MS/MS experiments were also carried out for φ3P+CH2C(=O)-AAAA, a peptide derivative containing active hydrogens only at amide nitrogens plus the C-terminus, and its active H/D exchange product, φ3P+CH2C(=O)-AAAA-d5. The results show that a hydrogen originally located at an amide nitrogen is transferred away in the formation of a cyclic charge remote b ion.",
author = "C. Gu and George Tsaprailis and L. Breci and Wysocki, {V. H.}",
year = "2000",
month = "12",
day = "1",
doi = "10.1021/ac000555c",
language = "English (US)",
volume = "72",
pages = "5804--5813",
journal = "Analytical Chemistry",
issn = "0003-2700",
publisher = "American Chemical Society",
number = "23",

}

TY - JOUR

T1 - Selective gas-phase cleavage at the peptide bond C-terminal to aspartic acid in fixed-charge derivatives of Asp-containing peptides

AU - Gu, C.

AU - Tsaprailis, George

AU - Breci, L.

AU - Wysocki, V. H.

PY - 2000/12/1

Y1 - 2000/12/1

N2 - This study focuses on the molecular level interpretation of the selective gas-phase cleavage at aspartic acid residues (Asp) in protonated peptides. A φ3P+CH2C(=O) group (φ = 2,4,6-trimethoxyphenyl) is attached to the N-terminal nitrogen of the selected peptides LDIFSDF and LDIFSDFR, via solid-phase synthesis, to 'mimic' the tightly held charge of a protonated arginine (Arg) residue. Collision-induced dissociation in a quadrupole ion trap instrument and surface-induced dissociation in a dual quadrupole instrument were performed for electrospray generated ions of the fixed-charge peptide derivatives. Selective cleavages at Asp-Xxx are observed for those ions with charge provided only by the fixed charge or for those with a fixed charge and one Arg plus one added proton. This supports a previously proposed mechanism which suggests that the cleavages at Asp-Xxx, initiated by the acidic hydrogen of the Asp residue, become significant when ionizing protons are strongly bound by Arg in the protonated peptides. It is clear that the fixed charge is indeed serving as a 'mimic' of protonated Arg and that a protonated Arg side chain is not required to interact with the Asp to induce cleavage at Asp-Xxx. When the number of protons exceeds the number of Arg in a peptide containing Arg and Asp, nonselective cleavages occur. The fragmentation efficiency of the peptides is consistent with the idea that these nonselective cleavages are promoted by a mobile proton. The peptide with a fixed charge and one added proton, [φ3P+CH2C(O)-LDIFSDF + H]2+, fragments much more efficiently than the corresponding peptide with a fixed charge, an Arg and one added proton, [φ3P+CH2C(=O)-LDIFSDFR + H]2+; both of these fragment more efficiently than the peptide with a fixed charge and no added proton, φ3P+CH2C(=O)-LDIFSDF. MS/MS/MS (i.e., MS3) experimental results for b(n) ions formed at Asp-Xxx from φ3P+CH2C(=O)-LDIFS DF and its H/D exchange derivative, φ3P+CH2C(=O)-LDIFSDF-d11, are consistent with the b(n) ions formed at Asp-Xxx having a succinic anhydride cyclic structure. MS/MS experiments were also carried out for φ3P+CH2C(=O)-AAAA, a peptide derivative containing active hydrogens only at amide nitrogens plus the C-terminus, and its active H/D exchange product, φ3P+CH2C(=O)-AAAA-d5. The results show that a hydrogen originally located at an amide nitrogen is transferred away in the formation of a cyclic charge remote b ion.

AB - This study focuses on the molecular level interpretation of the selective gas-phase cleavage at aspartic acid residues (Asp) in protonated peptides. A φ3P+CH2C(=O) group (φ = 2,4,6-trimethoxyphenyl) is attached to the N-terminal nitrogen of the selected peptides LDIFSDF and LDIFSDFR, via solid-phase synthesis, to 'mimic' the tightly held charge of a protonated arginine (Arg) residue. Collision-induced dissociation in a quadrupole ion trap instrument and surface-induced dissociation in a dual quadrupole instrument were performed for electrospray generated ions of the fixed-charge peptide derivatives. Selective cleavages at Asp-Xxx are observed for those ions with charge provided only by the fixed charge or for those with a fixed charge and one Arg plus one added proton. This supports a previously proposed mechanism which suggests that the cleavages at Asp-Xxx, initiated by the acidic hydrogen of the Asp residue, become significant when ionizing protons are strongly bound by Arg in the protonated peptides. It is clear that the fixed charge is indeed serving as a 'mimic' of protonated Arg and that a protonated Arg side chain is not required to interact with the Asp to induce cleavage at Asp-Xxx. When the number of protons exceeds the number of Arg in a peptide containing Arg and Asp, nonselective cleavages occur. The fragmentation efficiency of the peptides is consistent with the idea that these nonselective cleavages are promoted by a mobile proton. The peptide with a fixed charge and one added proton, [φ3P+CH2C(O)-LDIFSDF + H]2+, fragments much more efficiently than the corresponding peptide with a fixed charge, an Arg and one added proton, [φ3P+CH2C(=O)-LDIFSDFR + H]2+; both of these fragment more efficiently than the peptide with a fixed charge and no added proton, φ3P+CH2C(=O)-LDIFSDF. MS/MS/MS (i.e., MS3) experimental results for b(n) ions formed at Asp-Xxx from φ3P+CH2C(=O)-LDIFS DF and its H/D exchange derivative, φ3P+CH2C(=O)-LDIFSDF-d11, are consistent with the b(n) ions formed at Asp-Xxx having a succinic anhydride cyclic structure. MS/MS experiments were also carried out for φ3P+CH2C(=O)-AAAA, a peptide derivative containing active hydrogens only at amide nitrogens plus the C-terminus, and its active H/D exchange product, φ3P+CH2C(=O)-AAAA-d5. The results show that a hydrogen originally located at an amide nitrogen is transferred away in the formation of a cyclic charge remote b ion.

UR - http://www.scopus.com/inward/record.url?scp=0034536341&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0034536341&partnerID=8YFLogxK

U2 - 10.1021/ac000555c

DO - 10.1021/ac000555c

M3 - Article

C2 - 11128940

AN - SCOPUS:0034536341

VL - 72

SP - 5804

EP - 5813

JO - Analytical Chemistry

JF - Analytical Chemistry

SN - 0003-2700

IS - 23

ER -