Doubly-charged precursor

Figure 6.15. Product ion spectrum of the doubly-charged precursor (550.1 Th) of the same peptide as shown in Fig. 6.14.

Figure 6.18. Annotated product ion spectra, doubly charged precursor.

Fig. 1.45 Example of a 2D nano LC-MS/MS analysis of a C elegans extract. (A) Fraction 2, 4 mM KCI salt elution on the strong cation exchange column. (B) Full scan MS spectrum of the peak eluting at RT 26.3 min in (A). (C) product ion spectrum of the doubly charged precursor of (B) at m/z 784.8. Y fragments are typical for C-terminal fragments while b ions are typical for N-terminal fragments.

Approximately 80 pL of the remaining diluted HPLC fraction was subsequently subjected to mPC-CE-MS/MS. The doubly charged precursor ion at m/z 503.6 was subjected to collision induced dissociation and the resulting product ion spectrum (Figure 4) revealed a series of y and b ions. Interpretation of these ion series indicated a sequence of XSFKFDHX (where X is either 1 or L). The spectral data was also searched and interpreted using the Sequest database routine developed by Yates (17),... 

Fig. 6. (A) Low-energy CID spectrum (obtained by means of a nano-ESI-QIT instrument) of the doubly charged precursor ion (m/z 859.07) of the peptide with the amino acid sequence lANNVQPILTSrV. (B) Low-energy CID spectrum (obtained by means of a MALDI-QIT/RTOF instrument) of the singly charged precursor ion (m/z 1717.15) of the above-mentioned peptide.

A final category of gas-phase ion-electron reactions as activation methods for tandem mass spectrometry involves interactions between singly charged precursor ions and free electrons (note that ECD, hot ECD, ETD, and EDD require at least doubly charged precursor ions). The first reaction of this type, involving singly protonated peptides, was reported by Zubarev... 

Figure 5.17 ESI product ion mass spectrum of the doubly charged precursor ion [M+2H] of m/z 592 of Inteinizing hormone releasing hormone (LHRH, mol wtmonoisotopic = 1181.6Da), measured on an LTQ system.

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