IRMPD, principles

Chapter 5 provides an overview of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and its applications in the structural characterization of peptides and proteins. The principles of FT-ICR, that is, ion motion, ion excitation/ detection, and instrumental considerations, are discussed and an explanation of the features of FT-ICR that make it so suitable for peptide/protein analysis is presented. New methods for the fragmentation of peptide and protein ions in FT-ICR mass spectrometry, such as sustained off-resonance irradiation collision-induced dissociation (SORI-CID), infrared multiphoton dissociation (IRMPD), blackbody infrared radiative dissociation (BIRD), surface-induced dissociation (SID), and electron capture dissociation (BCD), are described in detail. Innovative hybrid FT-ICR instruments, which have recently become available, are reviewed. In conclusion, the chapter discusses the applications of FT-ICR in bottom-up and top-down proteomics. 

Time-resolved BIRD measurements provide an opportunity to precisely measure the kinetics of dissociation for isolated gaseous ions. The BIRD technique can, in principle, be used to study the dissociation kinetics of gaseous ions of any size. However, interpretation of the kinetic data depends on the size of the ions (or more accurately, the relative rates of absorption, emission, and dissociation). The general kinetic scheme for unimolecular reactions initiated by photon absorption at zero pressure is analogous to that described for IRMPD [see Eq. (16.3) in Section 16.3.1.1). Application of the steady-state approximation (i.e., the assumption that apparent rate constant ( mi) for unimolecular dissociation ... 

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