Applications of fast atom bombardment-tandem mass spectrometry and Fourier transform mass spectrometry for amino acids, peptides, and chlorophylls

In Part I, the application of fast atom bombardment (FAB) combined with tandem mass spectrometry (MS/MS) for biomolecules is discussed in general (Chapter 1), and applied to specific studies of peptides (Chapters 2, 3) and chlorophylls (Chapters 4, 5). Problems facing Fourier transform mass spectrometry (FTMS) and applications of FTMS for analysis of amino acids and peptides are investigated in Part II (Chapters 6-8). The gas-phase interactions of alkali metal ions and peptides have analogies with transition metal ion-peptide interactions in solution. In the gas phase, alkali metal ions bind to peptides at the C-terminus, promoting loss of the C-terminal residue. Upon collisional activation (CA), the peptide-metal ion complex can isomerize so that the metal ion is coordinated to deprotonated amide nitrogens at specific residues. Decompositions of lithiated dipeptides are explained in terms of lithium coordination with the C-terminal carboxylate anion and the relative proton affinities of the amino acid side chains. FAB and FAB/MS/MS was also used to study chlorophyll $a$ and $b$, bacteriochlorophyll $a$, chlorophyll allomers, and the corresponding pheophytins. The FAB-matrix modifies the strong solid-phase aggregation of chlorophyll; thus, FAB-desorbed molecular ions are formed with less internal energy than those desorbed from thin films. Decompositions of chlorophyll M$\sp{+}\cdot$ ions are informative of modifications of ring V. MS/MS is also useful for investigating reactivities of chlorophyll with alkali metal ions and chlorophyll dimerization. The application of a UV-laser with FTMS for multiphoton ionization (MPI) and electron capture ionization (ECI) of amino acids is investigated in Chapter 6. Incorporation of naphthalene moieties into amino acids provide chromophores for MPI. A strategy for sequencing combines degradation of small peptides by reaction with $o$-naphthoquinone and detection of the resulting amino acid derivatives by MPI-FTMS and ECI-FTMS. FTMS offers advantages for biomolecule analysis; however, current implementations are limited by various problems. A strategy for identifying causes and implementing solutions to problems facing FTMS is proposed (Chapter 7, 8)