Project description:In this project we want to compare ovarian cell cancer treated or non treated with cis-platinum. As acquisition strategy we have used a Real Time Search MS3 method in an Orbitrap Eclipse. The acquisition cycle began with an MS1 scanwhere the most intense ions were selected for fragmentation in the ion trap using CID. MS2 spectra were searched in real time with data acquisition using the sp-human database. MS2 spectra with an Xcorr greater than or equal to 1 and less than 10 ppm precursor mas error, triggered the submission of an MS3 spectrum to the instrument. MS3 spectrum, were collected using the multinotch MS3-based TMT method, in a way were ten MS2 fragment ions were captured in the MS3 precursor population using isolation waveforms with multiple frequency notches
Project description:Over the past few decades cross-linking mass spectrometry (XLMS) has become a powerful tool for identification of protein-protein interactions and for gaining insight into the structures of proteins in living cells, tissues, and organelles. The development of new crosslinkers, enrichment strategies and data acquisition methods led to the establishment of numerous new software tools specifically for the analysis and interpretation of cross-linking data. We previously published one of these tools called MS Annika, a cross-linking search engine which can accurately identify cross-linked peptides in MS2 spectra from a variety of different MS-cleavable crosslinkers. In this publication we present an updated MS Annika and a new search algorithm that additionally supports processing of data from MS2-MS3-based approaches and identification of peptides from MS3 spectra. In the new MS2-MS3 search algorithm, MS3 spectra are matched to their corresponding precursor doublet peak in the MS2 scan to identify the crosslink modification and the monoisotopic peptide mass. This information is then used to adjust the MS3 spectra for search with MS Amanda, our in-house developed peptide search engine, to identify the cross-linked peptides. Peptides that are identified in the MS2 scan and one or more of the associated product MS3 scans are re-scored with a novel scoring function to reflect the increased confidence. Finally, the detected cross-links are validated by estimating the false discovery rate (FDR) using a target-decoy approach. We evaluated the MS3-search-capabilities of MS Annika on five different datasets covering a variety of experimental approaches and compared it to XlinkX and MaXLinker, two other cross-linking search engines that support MS3 crosslink identification. Three of the datasets were benchmark datasets of synthetic peptides that allow calculation of an experimentally validated FDR, and we show that MS Annika detects up to 4 times more true unique crosslinks than MaXLinker and up to 35% more than XlinkX while simultaneously yielding less false positive hits and therefore a more accurate FDR than the other two search engines. Additionally, for the other two datasets we could show that MS Annika finds between 74% to 2.5 times more crosslinks at 1% estimated FDR and reveals protein-protein interactions that are not detected by either XlinkX or MaXLinker.
Project description:The rise of sample multiplexing in quantitative proteomics for the dissection of complex phenotypic comparisons has been advanced by the development of ever more sensitive and robust instrumentation. Here, we evaluated the utility of the Orbitrap Eclipse Tribrid mass spectrometer (advanced quadrupole filter, optimized FTMS scan overhead) and new instrument control software features (Precursor Fit filtering, TurboTMT and Real-time Peptide Search filtering). Multidimensional comparisons of these novel features increased total peptide identifications by 20% for SPS-MS3 methods and 14% for HRMS2 methods. Importantly Real-time Peptide Search filtering enabled a ~2X throughput improvement for quantification. Across the board, these sensitivity increases were attained without sacrificing quantitative accuracy. New hardware and software features enable more efficient characterization in pursuit of comparative whole proteome insights.
Project description:A tetrameric CID-cleavable cross-linker was synthesized and applied to BSA and isolated mitochondria from mouse hearts. A real-time instrument method was developed to dynamically target released peptides from cross-linked species, enabling their characterization through a series of ms3 scans.
Project description:Multiplexed quantitative analyses of complex proteomes enable deep biological insight. While a multitude of workflows have been developed for multiplexed analyses, the most quantitatively accurate method (SPS-MS3) suffers from long acquisition duty cycles. We built a new, real-time database search (RTS) platform, Orbiter, to combat the SPS-MS3 method’s longer duty cycles. RTS with Orbiter eliminates SPS-MS3 scans if no peptide matches to a given spectrum. With Orbiter’s online proteomic analytical pipeline, which includes RTS and false discovery rate analysis, it was possible to process a single spectrum database search in less than 10 milliseconds. The result is a fast, functional means to identify peptide spectral matches using Comet, filter these matches, and more efficiently quantify proteins of interest. Importantly, the use of Comet for peptide spectral matching allowed for a fully featured search, including analysis of post-translational modifications, with well-known and extensively validated scoring. These data could then be used to trigger subsequent scans in an adaptive and flexible manner. In this work we tested the utility of this adaptive data acquisition platform to improve the efficiency and accuracy of multiplexed quantitative experiments. We found that RTS enabled a two-fold increase in mass spectrometric data acquisition efficiency. Orbiter’s RTS quantified more than 8000 proteins across 10 proteomes in half the time of an SPS-MS3 analysis (18 hours for RTS, 36 hours for SPS-MS3).
Project description:We use palaeoproteomic analysis to obtain the taxonomic identification of an exceptional bone tool from a Bronze Age site near Heiloo, the Netherlands. ZooMS, SPIN and a conventional MaxQuant database search were employed to narrow down the species the tool belonged to. Here, only the LC-MS/MS raw data and MaxQuant analysis are stored. For the accompanying ZooMS and SPIn data see the associated publication.
Project description:Purpose: The aim of this study was to determine the DNA methylation state of wildtype female mouse embryonic fibroblasts with nonsilencing shRNA mediated knockdown and Setdb1 geneTrap heterozygous cells with Setdb1 shRNA mediated knockdown. Methods: Enhanced Reduced Representation Bisulfite Libraries (eRRBS) were produced as previously descirbed (Akalin et al. 2012). Libraries were pooled and sequenced on the Illumina HiSeq 2000 platform for 100 bp single-end reads with dark cycle parameters (Boyle et al. 2012). Image analysis was performed in real time by the HiSeq Control Software (HCS) v1.4.8 and Real Time Analysis (RTA) v1.12.4.2, running on the instrument computer. Real-time base calling on the HiSeq instrument computer was performed with the RTA software. Illumina CASAVA1.8 pipeline was used to generate the sequence data.