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High-definition differential ion mobility spectrometry with resolving power up to 500.

ABSTRACT: As the resolution of analytical methods improves, further progress tends to be increasingly limited by instrumental parameter instabilities that were previously inconsequential. This is now the case with differential ion mobility spectrometry (FAIMS), where fluctuations of the voltages and gas pressure have become critical. A new high-definition generator for FAIMS compensation voltage reported here provides a stable and accurate output than can be scanned with negligible steps. This reduces the spectral drift and peak width, thus improving the resolving power (R) and resolution. The gain for multiply-charged peptides that have narrowest peaks is up to ~40%, and R ~400-500 is achievable using He/N(2) or H(2)/N(2) gas mixtures.

SUBMITTER: Shvartsburg AA

PROVIDER: S-EPMC3581339 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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High-definition differential ion mobility spectrometry with resolving power up to 500.

Shvartsburg Alexandre A AA Seim Tom A TA Danielson William F WF Norheim Randy R Moore Ronald J RJ Anderson Gordon A GA Smith Richard D RD

Journal of the American Society for Mass Spectrometry 20121220 1

As the resolution of analytical methods improves, further progress tends to be increasingly limited by instrumental parameter instabilities that were previously inconsequential. This is now the case with differential ion mobility spectrometry (FAIMS), where fluctuations of the voltages and gas pressure have become critical. A new high-definition generator for FAIMS compensation voltage reported here provides a stable and accurate output than can be scanned with negligible steps. This reduces the ...[more]

PMID: 23345059

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Project description:Detection of arrival time shifts between ion mobility spectrometry (IMS) separations can limit achievable resolving power (Rp), particularly when multiple separations are summed or averaged, as commonly practiced in IMS. Such variations can be apparent in higher Rp measurements and are particularly evident in long path length traveling wave structures for lossless ion manipulations (SLIM) IMS due to their typically much longer separation times. Here, we explore data processing approaches employing single value alignment (SVA) and nonlinear dynamic time warping (DTW) to correct for variations between IMS separations, such as due to pressure fluctuations, to enable more effective spectrum summation for improving Rp and detection of low-intensity species. For multipass SLIM IMS separations, where narrow mobility range measurements have arrival times that can extend to several seconds, the SVA approach effectively corrected for such variations and significantly improved Rp for summed separations. However, SVA was much less effective for broad mobility range separations, such as obtained with multilevel SLIM IMS. Changes in ions' arrival times were observed to be correlated with small pressure changes, with approximately 0.6% relative arrival time shifts being common, sufficient to result in a loss of Rp for summed separations. Comparison of the approaches showed that DTW alignment performed similarly to SVA when used over a narrow mobility range but was significantly better (providing narrower peaks and higher signal intensities) for wide mobility range data. We found that the DTW approach increased Rp by as much as 115% for measurements in which 50 IMS separations over 2 s were summed. We conclude that DTW is superior to SVA for ultra-high-resolution broad mobility range SLIM IMS separations and leads to a large improvement in effective Rp, correcting for ion arrival time shifts regardless of the cause, as well as improving the detectability of low-abundance species. Our tool is publicly available for use with universal ion mobility format (.UIMF) and text (.txt) files.

Project description:In this report, we explored the benefits of cyclic ion mobility (cIM) mass spectrometry in the analysis of isomeric post-transcriptional modifications of RNA. Standard methyl-cytidine samples were initially utilized to test the ability to correctly distinguish different structures sharing the same elemental composition and thus molecular mass. Analyzed individually, the analytes displayed characteristic arrival times (tD ) determined by the different positions of the modifying methyl groups onto the common cytidine scaffold. Analyzed in mixture, the widths of the respective signals resulted in significant overlap that initially prevented their resolution on the tD scale. The separation of the four isomers was achieved by increasing the number of passes through the cIM device, which enabled to fully differentiate the characteristic ion mobility behaviors associated with very subtle structural variations. The placement of the cIM device between the mass-selective quadrupole and the time-of-flight analyzer allowed us to perform gas-phase activation of each of these ion populations, which had been first isolated according to a common mass-to-charge ratio and then separated on the basis of different ion mobility behaviors. The observed fragmentation patterns confirmed the structures of the various isomers thus substantiating the benefits of complementing unique tD information with specific fragmentation data to reach more stringent analyte identification. These capabilities were further tested by analyzing natural mono-nucleotide mixtures obtained by exonuclease digestion of total RNA extracts. In particular, the combination of cIM separation and post-mobility dissociation allowed us to establish the composition of methyl-cytidine and methyl-adenine components present in the entire transcriptome of HeLa cells. For this reason, we expect that this technique will benefit not only epitranscriptomic studies requiring the determination of identity and expression levels of RNA modifications, but also metabolomics investigations involving the analysis of natural extracts that may possibly contain subsets of isomeric/isobaric species.

Dataset Information

High-definition differential ion mobility spectrometry with resolving power up to 500.

Publications

High-definition differential ion mobility spectrometry with resolving power up to 500.

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