Method and device for irradiating ions in an ion cyclotron resonance trap with photons and electrons

The present invention relates to a method and a device for irradiating ions in a ion cyclotron resonance (ICR) trap with photons and/or electrons. For electron irradn. a hollow electron emitter is used, through the hole of which a light beam can be sent into the ICR trap. The emitter generates a hollow, tubular electron beam. In a special application low energy ions within the tubular electron beam are irradiated with photons. The ions can be cyclotron-excited mass selectively, by which they enter the electron beam and interact with electrons. [on SciFinder (R)

Peptide and protein characterization by high-rate electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry

A review. The anal. utility of the electron capture dissocn. (ECD) technique, developed by McLafferty and co-workers, has substantially improved peptide and protein characterization using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The limitations of the first ECD implementations on com. instruments were eliminated by the employment of low-energy electron-injection systems based on indirectly heated dispenser cathodes. In particular, the ECD rate and reliability were greatly increased, enabling the combination of ECD/FTICR-MS with online liq. sepn. techniques. Further technique development allowed the combination of two rapid fragmentation techniques, high-rate ECD and IR multiphoton dissocn. (IRMPD), in a single exptl. configuration. Simultaneous and consecutive irradiations of trapped ions with electrons and photons extended the possibilities for ion activation/dissocn. and led to improved peptide and protein characterization. The application of high-rate ECD/FTICR-MS has demonstrated its power and unique capabilities in top-down sequencing of peptides and proteins, including characterization of post-translational modifications, improved sequencing of peptides with multiple disulfide bridges and secondary fragmentation (w-ion formation). Anal. of peptide mixts. has been accomplished using high-rate ECD in bottom-up mass spectrometry based on mixt. sepn. by liq. chromatog. and capillary electrophoresis. This paper summarizes the current impact of high-rate ECD/FTICR-MS for top-down and bottom-up mass spectrometry of peptides and proteins. [on SciFinder (R)

Liquid chromatography and electron-capture dissociation in Fourier transform ion cyclotron resonance mass spectrometry

Liq. sepn. methods in combination with electrospray mass spectrometry as well as the recently introduced fragmentation method electron capture dissocn. (ECD) have become powerful tools in proteomics research. This paper presents the results of the first successful attempts to combine liq. chromatog. (LC) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) with ECD in the anal. of a mixt. of std. peptides and of a bovine serum albumin tryptic digest. A novel electron injection system provided conditions for ECD sufficient to yield extensive sequence information for the most abundant peptides in the mixts. on the time-scale of the chromatog. sepn. The results suggest that LC/ECD-FTICRMS can be employed in the characterization of peptides in enzymic digests of proteins or protein mixts. and identify and localize posttranslational modifications. [on SciFinder (R)

Combined infrared multiphoton dissociation and electron capture dissociation with a hollow electron beam in Fourier transform ion cyclotron resonance mass spectrometry

An electron injection system based on an indirectly heated ring-shaped dispenser cathode was developed and installed in a 7 T Fourier transform ICR (FTICR) mass spectrometer. This new hardware design allows high-rate electron capture dissocn. (ECD) to be carried out by a hollow electron beam coaxial with the ICR trap. IR multiphoton dissocn. (IRMPD) can also be performed with an on-axis IR-laser beam passing through a hole at the center of the dispenser cathode. Electron and photon irradn. times of the order of 100 ms are required for efficient ECD and IRMPD, resp. As ECD and IRMPD generate fragments of different types (mostly c, z and b, y, resp.), complementary structural information that improves the characterization of peptides and proteins by FTICR mass spectrometry can be obtained. The developed technique enables the consecutive or simultaneous use of the ECD and IRMPD methods within a single FTICR exptl. sequence and on the same ensemble of trapped ions in multistage tandem (MS/MS/MS or MSn) mass spectrometry. Flexible changing between ECD and IRMPD should present advantages for the anal. of protein digests sepd. by liq. chromatog. prior to FTICRMS. Also, ion activation by either electron or laser irradn. prior to, as well as after, dissocn. by IRMPD or ECD increases the efficiency of ion fragmentation, including the w-type fragment ion formation, and improves sequencing of peptides with multiple disulfide bridges. The developed instrumental configuration is essential for combined ECD and IRMPD on FTICR mass spectrometers with limited access into the ICR trap. [on SciFinder (R)

Ionization energies of multiply protonated polypeptides obtained by tandem ionization in Fourier transform mass spectrometers

Ionization energies (IE) of [M + zH]z+ (z+) electrospray-produced polypeptides were detd. by electron ionization in a Penning cell of 4.7 and 9.4 .T Fourier transform mass spectrometers. For z = 1+ and substance P, the found IE value of 11.0+-0.4 eV is in agreement with that obtained earlier for ions generated with matrix-assisted laser desorption/ionization. For higher z, the following values were found: 11.7+-0.3 eV for 2+ of [Arg-8]-vasopressin, 11.1+-0.6 eV for 2+ of substance P, 12.2+-0.7 eV for 2+ of renin substrate, 13.3+-0.4 eV for 3+ of B-chain of insulin and 14.6+-0.6 eV for 4+ and 15.1+-0.4 eV for 5+ of melittin. It was found that 90% of existing IE data on polypeptides in the 1.0-3.5 kDa mass range are described with ? 0.5 eV uncertainty by the empirical equation IE(z) = 9.8+1.1z. The av. IE increase of 1.1 eV/charge is attributed to Coulombic repulsion. The deduced ionization energy of a neutral polypeptide mol., 9.8+-0.3 eV, is consistent with literature expectations. [on SciFinder (R)

Peptide and protein characterization by high-rate electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry. [Erratum to document cited in CA142:280385]

A review. On page 723, the equation should read: [M + zH](z-1)+.bul.: [M + zH]Z+ + e -> [M + zH](z-1)+.bul. (+6 eV) -> [M + (z - 1)H](z-1)+ + H.* -> fragments. [on SciFinder (R)

Capillary electrophoresis and electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry for peptide mixture and protein digest analysis

Recent advances in peptide fragmentation techniques and mass spectrometry have opened up the possibility of combining peptide sepn. techniques, such as capillary electrophoresis (CE) and capillary liq. chromatog., with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and electron capture dissocn. (ECD) in order to characterize peptide mixts. and protein digests. The results presented in this study show that CE/ECD-FT-ICR MS can be employed for peptide characterization in mixts. of std. peptides and in peptides resulting from the enzymic digestion of proteins. Furthermore, the technique has potential for the identification and localization of post-translational modifications in peptides and proteins. [on SciFinder (R)

Shifted-basis technique improves accuracy of peak position determination in Fourier transform mass spectrometry

A new algorithm is suggested for estn. of peak positions in FTMS spectra. Theor. and exptl. the new technique yields superior results compared to the currently applied techniques, when the noise level is high and/or the peaks are located close to each other. Cases are presented where the deviation from the true mass could be mistaken for space charge effect, while the shift is in fact solely due to the shortcomings of the current techniques and can be cor. by applying the shifted-basis technique. In 2 out of 3 cases, this technique gave more accurate (>5 times) result compared to the conventional anal. In the 3rd case, where the signal was high compared to the noise, the results were comparable. The new technique can be used to achieve better mass accuracy for noisy and not well resolved spectra, and to further study the features of the space charge effect. [on SciFinder (R)