The influence and utility of varying field strength for the separation of tryptic peptides by ion mobility-mass spectrometry

Abstract

The influence of field strength on the separation of tryptic peptides by drift tube-based ion mobility-mass spectrometry is reported. Operating the ion mobility drift tube at elevated field strengths (expressed in V cm Ϫ1 torr Ϫ1 ) reduces separation times and increases ion transmission efficiencies. Several accounts in the literature suggest that performing ion mobility separation at elevated field strength can change the selectivity of ion separation. To evaluate the field strength dependant selectivity of ion mobility separation, we examined a data set of 65 singly charged tryptic peptide ion signals (mass range 500 -2500 m/z) at six different field strengths and four different drift gas compositions (He, N 2 , Ar, and CH 4 ). Our results clearly illustrate that changing the field strength from low field (15 V cm Ϫ1 torr Ϫ1) to high field (66 V cm Ϫ1 torr Ϫ1 ) does not significantly alter the selectivity or peak capacity of IM-MS. The implications of these results are discussed in the context of separation methodologies that rely on the field strength dependence of ion mobility for separation selectivity, e.g., high-field asymmetric ion mobility spectrometry ( H ybrid mass spectrometry techniques have emerged as powerful tools for complex mixture analysis. For example, several groups have used liquid chromatography-mass spectrometry (LC-MS) for identification of components of simple proteomes, and have reported enhanced sequence coverage, limit-of-detection, dynamic range, and peak capacity relative to MS-only methods of analysis [1,2]. Prior to the development of LC-MS techniques for proteomics, mass spectrometry of 2-D gel-separated proteins was the method of choice for large-scale protein identification, because the method provides both excellent peak capacity and modestly improved dynamic range [3,4]. However, both LC and 2-D gel separations inefficiently utilize MS detection, because separations can take 5 to 10 orders of magnitude longer than necessary for mass spectrometry detection (i.e., Ͻ100 s for time-of-flight (TOF) MS) [5].Ion mobility (IM) separation (based on ion collision cross-section) coupled with mass spectrometry possesses many of the same advantages of LC-MS approaches, i.e., enhanced dynamic range and increased peak capacity when compared with MS-only analysis [6,7]. Further, IM separations require only milliseconds (typically 500 s to 2 ms for tryptic peptides), which is better suited to MS timescales [8]. For example, both Russell (using matrix assisted laser desorption ionization -MALDI) and Clemmer (using electrospray ionization -ESI) have utilized IM-MS for the analysis of complex protein mixtures [9,10]. In the case of MALDI-IM-MS protein mixture analysis, the hybrid separation technique provided enhanced percent amino acid sequence coverage through the increased dynamic range relative to MS-only analysis [9]. Clemmer and coworkers used LC-ESI-IM-MS to analyze biologically derived complex mixtures, and demonstrated that the combination of LC and IM provides complementary separation...

A Novel Differential Ion Mobility Device Expands the Depth of Proteome Coverage and the Sensitivity of Multiplex Proteomic Measurements

“…IMS can be divide into two broad categories that regroup drift-tube ion mobility spectrometry (DTIMS) and differential mobility spectrometry (DMS), the latter being mostly represented by high-field asymmetric waveform ion mobility spectrometry (FAIMS). In DTIMS, ions are separated in a drift tube filled with an inert background gas based on their mobilities in a low but constant electric field (E) (22). For appropriate separation, ions are introduced as a narrow pulse into the drift tube, and resolution up to 200 can be achieved using DTIMS (23).…”

Optimum waveforms for differential ion mobility spectrometry (FAIMS)

“…For EIN allowed by the electrical breakdown limitations of gases at standard temperature and pressure (STP), typical Ia I are~1O-2 (except for the smallest ions) [37]. That is close to the accuracy of existing DT IMS systems, and K(EIN) for sizable ions such as peptides appear flat [38].…”

Modern Methodologies to Assess the Olive Oil Quality

“…ESI and MALDI ion sources have both been coupled to IM-MS instrument. 19,20 Latter consists of a MALDI source, an ion mobility cell, a CID cell, and a TOF mass analyzer. Ions exit the drift tube when the axial field strength of the ion mobility cell is ramped up, and enter the source region of a -TOF instrument, where the ions are detected intact in the usual manner.…”