Fourier-transform ion cyclotron resonance FT ICR mass spectrometry

Decarboxylation of 1,3-dimethylorotic acid in the presence of benzyl bromide yields 6-benzyl-1,3-dimethyluracil and presumably involves a C(6) centered nucleophilic intermediate which could nonetheless have either a carbene or ylide structure. Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry has been used to explore the gas-phase reactions of methyl nitrate with anions from active methylene compounds anions of aliphatic ketones and nitriles react by the 5n2 mechanism and Fco reactions yielding N02 ions are also observed nitronate ions are formed on reaction with the carbanions derived from toluenes and methylpyridines. 

The gas-phase ionization of 2,4,6-tribromobenzene in the presence of m-fluoropyridine afforded the A -aryI -m-fluoropyridinc adduct from which the biradical cation was generated by loss of two bromine radicals.232 This biradical species was isolated and characterized using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and its chemical properties are discussed. FT-ICR was also used to isolate and characterize the products of electron ionization of fluorinated acetyl compounds, which included a biradical anion.233... 

Fornarini, Matire, and co-workers110 have recently used Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry assaying the multiphoton dissociation behavior (IR-MPD) of the C3H7+ ion. This study has confirmed the conclusions of the computational results discussed above. The IR spectra recorded in solution and in a solid matrix display close resemblance to the spectral characteristics found by the IR-MPD study. Theoretical studies also indicated that the virtually free methyl rotation allows the interconversion of the two enantiomers of the isopropyl cation. 

The analytically important features of Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometry (1) have recently been reviewed (2-9) ultrahigh mass resolution (>1,000,000 at m/z. < 200) with accurate mass measurement even 1n gas chromatography/mass spectrometry experiments sensitive detection of low-volatility samples due to 1,000-fold lower source pressure than in other mass spectrometers versatile Ion sources (electron impact (El), self-chemical ionization (self-Cl), laser desorption (LD), secondary ionization (e.g., Cs+-bombardment), fast atom bombardment (FAB), and plasma desorption (e.g., 252cf fission) trapped-ion capability for study of ion-molecule reaction connectivities, kinetics, equilibria, and energetics and mass spectrometry/mass spectrometry (MS/MS) with a single mass analyzer and dual collision chamber. 

The only stable binary fluoride of krypton is the difluoride, KrF2, and all the known chemistry derives from this molecule. Early reports of the preparation of KrF4 have not been substantiated, and no simple stable oxides or oxide fluorides have been isolated. However, small amounts of the violet free radical, KrF, have been observed following y-irradiation of KrF2 (.2—4). There has also now been direct observation of [KrO ]+ (n = 1, 2) and [KrOH]+ by Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry, for which ab initio theoretical calculations suggest that the two species are covalently bonded with bond dissociation enthalpies of 237.7 and 169.5 kJ mol1 respectively (21). 

Features of Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry... 

Structural characterization of proteins and peptides using quadrupole ion trap mass spectrometry, Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry, and traveling wave ion mobility mass spectrometry... 

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. 

Radiative Association Reactions The study of radiative association reactions, (Eq. 2.2), has been of considerable interest [6-8] in chemical kinetics, planetary and interstellar chemistry, flames, and a variety of other areas. The kinetic study makes it possible to model the formation of complex molecular species in the interstellar science. At the very low molecular number densities in interstellar environments, the probability of formation of the products of association reactions by collisional stabilization is very low. Therefore, the radiative association process becomes an extremely important one for the production of the complex molecular species observed by astronomical physicist. The methodology is either flowing afterglow (FA) or Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. For the study of the apparent bimolecular rate constant for formation of association products as a function of pressme of a third body (N), the pressure should be set up to be sufficiently high in order to release the energy in the associated complex. Under the high pressure conditions collisional stabilization has competed with and usually dominated over radiative associatioiL As a result, the radiative association rate was then extrapolated from the intercept of a plot of apparent rate constant versus pressure of a third body, N. 

The gas-phase chemistry of [Fe(olefin)] complexes with CH3X (X = OH, F, Cl, Br, I) was investigated by means of Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry. C-C bond formation between the alkene and CFIsX occurs via initial insertion of Fe into the C-X bond of [FeX(CH3)] (Scheme 33). A combination of subsequent /3-H shift and reductive elimination of HX completes the reaction. 

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