Title

Peptide Fragmentation: Proton Vs. Metal as charge carrier.

Poster Number

11

Lead Author Affiliation

Chemistry

Introduction

Collision induced dissociation (CID) is a widely used technique to gain sequence coverage of peptides. The main fragment ions in CID of peptide are b-ions and y-ions. It is attributed to the position of basic side chain group to determine if the b-ion or the y-ion will be major fragment.

Purpose

To find the effect of basic side chain in peptide CID by varying the position of basic side chain in the peptide from N-terminus through C-terminus. We also aim to gain insight into the reaction mechanism of the CID fragmentation process by using different charge carriers (proton and metal).

Method

Samples were prepared using 100x diluted 1 mg/ml peptide solution in 50:50 water-methanol solvent. An electrospray ionization (ESI) source was used to generate the positive ions in a Varian 320L triple quadrupole LC/MS spectrometer. CID was performed in the second quadruple using Ar gas at a pressure of ~1.2 mTorr at a collision energy of ~35 V. For the metaled positive ions, a Thermo Finnigan LCQ Duo ion trap LC/MS spectrometer fitted with an ESI source was used. Data acquisition and data analysis were done using respective proprietary softwares.

Results

Protonated peptides showed more extensive CID fragmentation compared to the metaled peptides. Presence of N-terminal basic side chain in protonated peptide induces ammonia and/or water loss from fragmented ions. For metalated peptides, metal cations are the charge carrier in both b-ions and y-ions.

Significance

Fragmentation ions indicate basic side chain taking part in CID process. Incorporation of metal in both y-ion and b-ion indicates a dynamic metal bound heterodimer as intermediate instead of conventional proton bound heterodimer.

Location

DeRosa University Center, Stockton campus, University of the Pacific

Format

Poster Presentation

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Peptide Fragmentation: Proton Vs. Metal as charge carrier.

DeRosa University Center, Stockton campus, University of the Pacific

Collision induced dissociation (CID) is a widely used technique to gain sequence coverage of peptides. The main fragment ions in CID of peptide are b-ions and y-ions. It is attributed to the position of basic side chain group to determine if the b-ion or the y-ion will be major fragment.