A novel surface-induced dissociation instrument for ion mobility-time-of-flight mass spectrometry

doi:10.1016/j.ijms.2006.09.005

International Journal of Mass Spectrometry

Volume 259, Issues 1–3, 1 January 2007, Pages 79-86

https://doi.org/10.1016/j.ijms.2006.09.005 Get rights and content

Abstract

A surface-normal surface-induced dissociation (SID) configuration specifically designed for coupling ion mobility spectrometry (IMS) and orthogonal time-of-flight (TOF) mass spectrometer is described. The instrument configuration and the effects of various operating parameters are critically evaluated using ion trajectory calculations (SIMION) and SID spectra of a series of model peptides. The utility of the instrument configuration for simultaneous acquisition of MS and MS–MS spectra in both data-dependent and non-data-dependent modes are also discussed.

Introduction

Mass spectrometry (MS) has become an unrivaled technique for proteomics owing to high sample throughput and high mass measurement accuracy. The minimal amount of fragmentation observed by electrospray ionization (ESI) [1] and matrix-assisted laser desorption/ionization (MALDI) [2], [3] greatly reduces spectral complexity. Furthermore, combining these ionization sources with tandem mass spectrometry allows for further characterization of analyte ions in terms of amino acid sequence of peptides and/or post-translational modifications (PTM) [4], [5], [6]. A variety of tandem mass spectrometry techniques have been developed for sequencing and PTM studies of peptides, the most frequently used being collision-induced dissociation (CID) [7], [8], [9]; however, surface-induced dissociation (SID) [10], [11], photodissociation (PD) [12], [13], [14], electron capture dissociation (ECD) [15], and electron transfer dissociation (ETD) [16] have all demonstrated specific advantages over CID. In some cases SID is preferred over CID, because SID can be performed without the addition of a collision gas [11], [28], [29], which greatly simplifies the experiments, especially for high resolution TOF-MS and Fourier transform ion cyclotron resonance (FT-ICR)-MS, which require ultra-high vacuum for high resolution and accurate mass measurements.

SID was first introduced by Cooks in 1975 [10] and since that time a number of instrument configurations have been evaluated and the fundamentals of ion–surface collisions have been investigated. Especially relevant to SID are issues related to energy uptake by the ion–surface collisions [17], [18], [19], [20], [21], [22]. Cooks recently published an excellent review that covers the fundamentals of SID and our current level of understanding of the SID process [23]. Of particular relevance for our work are the effects of surface-normal ion–surface interactions on energy uptake as well as the angle and kinetic energy distributions of the scattered ions.[24], [25] Surface-normal SID has been previously performed by Laskin et al. using ion detection by FT-ICR-MS [24] and Zare and co-workers at the back of a reflector in a reflectron TOF-MS [26], [27].

We previously described a MALDI-IM-SID-TOF instrument and discussed the advantages of coupling SID to IM-MS [30], [31]. In this paper we describe a new SID instrument configuration, which greatly facilitates IM-SID-TOF-MS. This instrument has an SID region (a stainless steel ring electrode) that is positioned within the TOF ion source and SID is performed using a surface-normal incident angle. This design overcomes many of the limitations of the previous SID configurations, viz. low conversion efficiency of primary to secondary ions and inefficient collection of fragment ions, which significantly facilitates the coupling of IMS with TOF while maintaining highly efficient energy deposition and subsequent fragment ion collection.

Section snippets

Experimental

The MALDI-IM-TOF instrument (Fig. 1) has been described previously [32]. Briefly, the MALDI ion source is equipped with a 20 Hz cartridge type nitrogen laser (337 nm, Thermo Laser Science), and a 30.5 cm length periodic focusing IMS drift cell. The drift cell is operated at a pressure of ∼1 torr, using helium as the buffer gas. A non-uniform electric field is established along the length of the drift cell by applying a voltage (1900 V) across a chain of 1 MΩ resistors [32]. Ions exiting the drift

Results and discussion

A complete understanding of SID processes, i.e., energy uptake as a result of ion–surface collisions and how chemical and physical properties of the surface affect such processes, requires precise control of many experimental parameters (e.g., the incident angle and incident energy of the ions), whereas the analytical utility of SID is directly dependent upon the efficiency of precursor and fragment ion sampling. Consequently, we have focused our efforts on designing an SID apparatus that will

Conclusions

The new SID/TOF source configuration discussed here provides three primary functions: (i) it provides a surface for the normal incident collision, (ii) by pulsing the ring electrode simultaneously with the TOF extraction plates, it maintains linearity of the field in a large collection space to accommodate the diverged scattered ions, and (iii) it helps confine the scattered ions by establishing an electrostatic potential well within the ring electrode. This new in-line SID source provides a

Acknowledgements

Financial support for this work was provided by U.S. Department of Energy, Division of Chemical Sciences (BES DE-FG02-04ER15520) and the Robert A. Welch Foundation (A-1176).

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A novel surface-induced dissociation instrument for ion mobility-time-of-flight mass spectrometry

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgements

Int. J. Mass Spectrom. Ion Process.

Meth. Enzymol.

Int. J. Mass Spectrom. Ion Phys.

J. Am. Soc. Mass Spectrom.

Int. J. Mass Spectrom. Ion Process.

Int. J. Mass Spectrom. Ion Process.

Surf. Sci.

Int. J. Mass Spectrom. Ion Process.

Int. J. Mass Spectrom. Ion Process.

Int. J. Mass Spectrom. Ion Process.

Int. J. Mass Spectrom. Ion Process.

J. Am. Soc. Mass Spectrom.

Int. J. Mass Spectrom. Ion Process.

Int. J. Mass Spectrom.

Int. J. Mass Spectrom.

Meth. Enzymol.

Anal. Chem.

Rapid Commun. Mass Spectrom.

Proc. Natl. Acad. Sci. USA

Electrophoresis