Mass spectra of peptides

P. Roepstorff and J. Fohlman, Proposal for a Common Nomenclature for Sequence Ions in Mass Spectra of Peptides. Biomed. Mass Spectrom., 11(1984) 601. 

Roepstorff P. and Fohlman J. (1984), Proposal for a common nomenclature of sequence ions in mass spectra of peptides, Biomed. Mass Spectrom. 11, 601. 

Papayannopoulos I.A. (1995), The interpretation of collision-induced dissociation tandem mass spectra of peptides, Mass Spectrom. Rev. 14, 49-73. 

Example The significant increase in sensitivity and the improvements of sig-nal-to-background ratio (Chap. 5.2.4) in CF-FAB spectra are demonstrated by comparison of the standard FAB and CF-FAB mass spectra of peptides. [108,116] In case of 10 pmol of the peptide des(gln)-substance P (Fig. 9.16) solely CF-FAB reveals the low-intensity signals due to some loss of side chain groups and several a-type fragments. 

The amount of sequence information available in the positive and negative ion FAB mass spectra of peptides varies considerably. 

Most of the sequence ions observed in the positive ion (+) mode are cationised by NA+. The base peaks in the positive ion FAB mass spectra of peptides that lack basic functional groups as in CB-1 often correspond to the M of peptides cationised by the formation of adducts with Na+ and/or K+, traces of which are usually present in the matrix. 

RC-MS stems from the observation that mass spectra of peptides and proteins can be generated by laser activation of chromatographic surfaces placed on MALDI targets. The product application of RC-MS, called surface-enhanced laser desorption ionization-time of fiight (SELDI-TOF), refers to a mass spectrometry method for measuring native proteins adsorbed (retained) on various chemical or biochemical surfaces (Figure 4.11). Although the concept of laser desorption of intact proteins is well established, it has been commercially exploited only recently as a means... 

Figure 13 Mass spectra of peptide mixture [Ang I, ACTH clip 1-17, ACTH clip 18-39, and ACTH clip 7-38 with a level of 2 fmol/ftL (2 nM), respectively] enriched on and eluted from the weir- (left) and grid-SMEC (right), respectively. Each spectrum, A-D, corresponds to 30-s collection of the eluent from each SMEC at intervals 0-30, 30-60, 60-90, and 90-120 s, respectively, using a peptide mixture.

FIGURE 7.8. Mass spectra of peptide fraction of human blood plasma control (left) and after in vitro incubation of whole blood with RVX 0.1 mg/ml at 37°C for 1 h (right). 

FIGURE 7.9. Mass spectra of peptide fraction of blood plasma of control rats (left) and that of rats after suhchronic exposure to RVX (right). Lack of peptide with MH+ 1452.77 Da is demonstrated on the spectrum of control rats (C). 

MacCoss, M.J., Wu, C.C., Matthews, D.E. and Yates, J.R., 3rd (2005) Measurement of the isotope enrichment of stable isotope-labeled proteins using high-resolution mass spectra of peptides. Anal. Chem. 77,7646-7653. 

U.A. Mirza, B.T. Chait, Effects of anions on the positive ion ESI mass spectra of peptides and proteins. Anal. Chem., 66 (1994) 2898. 

After a substantial range of examples of EIMS mass spectra of peptides had accumulated, it became clear that difficulties and ambiguities of interpretation could be expected (Anderegg et al., 1976). Applications of EIMS methods declined, as softer ionisation methods - such as fast-atom bombardment (FAB) MS - became established (Biemann and Martin, 1987 Biemann, 1989). These methods create less-energetic molecular ions and the ensuing fragmentation is therefore less extensive (this usually ensures the presence of an intense molecular ion peak in the spectrum) and spectra are therefore more easily interpreted. 

Why was MS slow to gain favour in peptide structure determination After all, by 1965, when the early mass spectra of peptides were being collected and assessed, sophisticated examples of structure determination by MS were commonplace in other areas of the organic chemistry of natural products. 

T Solouki, L Pas-a-Tolis, GS Jackson, S Guan, AG Marshall. High resolution multistage MS, MS2 and MS3 matrix-assisted laser desorption/ionization FT-ICR mass spectra of peptides from a single laser shot. Anal Chem 68(21) 3718-3725, 1996. 

FIGURE 47.14 Time-of-flight mass spectra of peptides prepared via tryptic digestion of bovine hemoglobin. (Reprinted with permission from Lazar, I. M., et al., Electrophoresis, 24, 3655, 2003. Copyright 2003 Elsevier B.V.) (a) Peptides separated in the CEC system with monolithic column shown in Figure 47.13, (b) unseparated... 

Figure 7.11 Mass spectra of peptide LI 31-LI 38 (with seven backbone amide hydrogens) from the light chain of antistreptavidin IgCI antibody, after the antibody was labeled for different lengths of time under 4 M guanidine [16]. The deuterated peptide exhibits a bimodal isotope distribution, indicating hydrogen exchange with an EXI mechanism...

Palmblad, M., Buijs, J., Hakansson, P. (2001) Automatic aneilysis of hydrogen/deuterium exchange mass spectra of peptides and proteins using calculations of isotopic distributions. J Am Soc Mass Spectrom, 12(11), 1153-1162. 

W. Heerma and W. KuUk, Identification of amino acids in the fast atom bombardment mass spectra of peptides, Biomed. Environ. Mass Spectrom. 16, 155-159 (1988). 

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