Abstract:Ion mobility spectrometry (IMS) is a widespread separation technique used in various research fields. It can be coupled to liquid chromatography–mass spectrometry (LC–MS/MS) methods providing an additional separation dimension. During IMS, ions are subjected to multiple collisions with buffer gas, which may cause significant ion heating. The present project addresses this phenomenon from the bottom‐up proteomics point of view. We performed LC–MS/MS measurements on a cyclic ion mobility mass spectrometer with v… Show more
“…It is important to note that the applied collision energy has a profound impact on the information content of the obtained MS/MS spectra 24 (Supplementary Fig. S1).…”
Section: Resultsmentioning
confidence: 99%
“…It is important to note that the applied collision energy has a profound impact on the information content of the obtained MS/MS spectra 24 . Thus, collision energy calibration is needed for accurate fragment ion intensity predictions.…”
Section: Discussionmentioning
confidence: 99%
“…This kinetic energy can be transferred to internal energy, similarly to what takes place during the activation of ions in collision-induced dissociation. Because IMS energizes the peptides significantly, the use of lower collision energies is advised 24 . Similarly to what has been observed for retention time alignment 42 , we expect a benefit from collision energy alignment to account for the run-to-run fluctuations.…”
Immunopeptidomics plays a crucial role in identifying targets for immunotherapy and vaccine development. Because the generation of immunopeptides from their parent proteins does not adhere to clear-cut rules, rather than being able to use known digestion patterns, every possible protein subsequence within HLA class-specific length restrictions needs to be considered. This leads to an inflation of the search space and results in lower spectrum annotation rates. Rescoring is a powerful enhancement of standard sequence database searching that boosts the spectrum annotation performance. In the field of immunopeptidomics low abundant peptides often occur, which is why the highly sensitive timsTOF instruments are increasingly gaining popularity. To improve rescoring for immunopeptides measured using timsTOF instruments, we trained a deep learning-based fragment ion intensity prediction model. Over 300,000 synthesized non-tryptic peptides from the ProteomeTools project were analyzed on a timsTOF-Pro to generate a dataset that was used to fine-tune an existing Prosit model. By applying our fragment ion intensity prediction model, we demonstrate up to 3-fold improvement in the identification of immunopeptides. Furthermore, our approach increased detection of immunopeptides even from low input samples.
“…It is important to note that the applied collision energy has a profound impact on the information content of the obtained MS/MS spectra 24 (Supplementary Fig. S1).…”
Section: Resultsmentioning
confidence: 99%
“…It is important to note that the applied collision energy has a profound impact on the information content of the obtained MS/MS spectra 24 . Thus, collision energy calibration is needed for accurate fragment ion intensity predictions.…”
Section: Discussionmentioning
confidence: 99%
“…This kinetic energy can be transferred to internal energy, similarly to what takes place during the activation of ions in collision-induced dissociation. Because IMS energizes the peptides significantly, the use of lower collision energies is advised 24 . Similarly to what has been observed for retention time alignment 42 , we expect a benefit from collision energy alignment to account for the run-to-run fluctuations.…”
Immunopeptidomics plays a crucial role in identifying targets for immunotherapy and vaccine development. Because the generation of immunopeptides from their parent proteins does not adhere to clear-cut rules, rather than being able to use known digestion patterns, every possible protein subsequence within HLA class-specific length restrictions needs to be considered. This leads to an inflation of the search space and results in lower spectrum annotation rates. Rescoring is a powerful enhancement of standard sequence database searching that boosts the spectrum annotation performance. In the field of immunopeptidomics low abundant peptides often occur, which is why the highly sensitive timsTOF instruments are increasingly gaining popularity. To improve rescoring for immunopeptides measured using timsTOF instruments, we trained a deep learning-based fragment ion intensity prediction model. Over 300,000 synthesized non-tryptic peptides from the ProteomeTools project were analyzed on a timsTOF-Pro to generate a dataset that was used to fine-tune an existing Prosit model. By applying our fragment ion intensity prediction model, we demonstrate up to 3-fold improvement in the identification of immunopeptides. Furthermore, our approach increased detection of immunopeptides even from low input samples.
“…Thus, via extended IM separations, cIM has potential to offer improved LC-MS peak capacity in bottom-up LC-MS applications such as HDX-MS. The design, operation, and multifunctional capabilities of cIM have been described in detail. , A handful of publications have now used the SELECT SERIES Cyclic IMS with cIM technology for the purpose of increasing LC-MS peak capacity during peptide mapping and other omics applications. − Despite this, to date, no systematic evaluation of cIM in HDX-MS has been performed nor has its multipass functionality been utilized online in any bottom-up LC-MS or omics application; only one-pass routines have previously been reported.…”
Hydrogen/deuterium exchange-mass spectrometry (HDX-MS) has emerged as a powerful tool to probe protein dynamics. As a bottom-up technique, HDX-MS provides information at peptide-level resolution, allowing structural localization of dynamic changes. Consequently, the HDX-MS data quality is largely determined by the number of peptides that are identified and monitored after deuteration. Integration of ion mobility (IM) into HDX-MS workflows has been shown to increase the data quality by providing an orthogonal mode of peptide ion separation in the gas phase. This is of critical importance for challenging targets such as integral membrane proteins (IMPs), which often suffer from low sequence coverage or redundancy in HDX-MS analyses. The increasing complexity of samples being investigated by HDX-MS, such as membrane mimetic reconstituted and in vivo IMPs, has generated need for instrumentation with greater resolving power. Recently, Giles et al. developed cyclic ion mobility (cIM), an IM device with racetrack geometry that enables scalable, multipass IM separations. Using one-pass and multipass cIM routines, we use the recently commercialized SELECT SERIES Cyclic IM spectrometer for HDX-MS analyses of four detergent solubilized IMP samples and report its enhanced performance. Furthermore, we develop a novel processing strategy capable of better handling multipass cIM data. Interestingly, use of one-pass and multipass cIM routines produced unique peptide populations, with their combined peptide output being 31 to 222% higher than previous generation SYNAPT G2-Si instrumentation. Thus, we propose a novel HDX-MS workflow with integrated cIM that has the potential to enable the analysis of more complex systems with greater accuracy and speed.
Immunopeptidomics is a key technology in the discovery of targets for immunotherapy and vaccine development. However, identifying immunopeptides remains challenging due to their non‐tryptic nature, which results in distinct spectral characteristics. Moreover, the absence of strict digestion rules leads to extensive search spaces, further amplified by the incorporation of somatic mutations, pathogen genomes, unannotated open reading frames, and post‐translational modifications. This inflation in search space leads to an increase in random high‐scoring matches, resulting in fewer identifications at a given false discovery rate. Peptide‐spectrum match rescoring has emerged as a machine learning‐based solution to address challenges in mass spectrometry‐based immunopeptidomics data analysis. It involves post‐processing unfiltered spectrum annotations to better distinguish between correct and incorrect peptide‐spectrum matches. Recently, features based on predicted peptidoform properties, including fragment ion intensities, retention time, and collisional cross section, have been used to improve the accuracy and sensitivity of immunopeptide identification. In this review, we describe the diverse bioinformatics pipelines that are currently available for peptide‐spectrum match rescoring and discuss how they can be used for the analysis of immunopeptidomics data. Finally, we provide insights into current and future machine learning solutions to boost immunopeptide identification.
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