Blog
Mascot workflow for LC-MS/MS data
Data analysis in mass spectrometry proteomics is complex and, nowadays, almost entirely software driven. Processing a raw file, peptide identification by database searching, protein inference and protein quantitation all have many steps and built-in assumptions, not to mention a huge number of parameters. Software continues to evolve as does best practice. Whether you are new to mass spectrometry proteomics or [...]
Tutorial: Creating custom reports in Mascot Distiller
Mascot Distiller 2.8 reports are written in Python, a commonly used programming language, and use Mascot Parser to access the search and quantitation results. We supply a range of standard reports, including reports for quality, clustering and statistical analysis, which we took a look at in an earlier blog article. In addition to these, you can develop your own reports [...]
How to run the public Mascot service
The public Mascot service running on this website recently had its 25th birthday: the service was launched in November 1998. The purpose is to let you evaluate the product before buying, but it’s also useful for small data sets and proteomics training courses. We’re a small company and our main activity is software development. The secrets to running the public [...]
Mascot security – guest users and administrators
Mascot Security is a role-based access system that allows administrators to control different aspects of privacy and priority access. It integrates with authentication systems like Microsoft Active Directory (AD) and various single sign-on systems. It can also be configured for a core lab, where search results can be shared with collaborators without them having access to the results of other groups. [...]
ABRF iPRG 2023 crosslinking study
One of the great things about the Association of Biomolecular Resource Facilities (ABRF) is their technical studies involving real samples and data. The three proteomics research groups, Proteomics (PRG), Proteome Informatics (iPRG) and Proteomics Standards (sPRG), have all held interesting studies over the years. This year the iPRG group has put together a crosslinking study. The goal is to teach [...]
Finding unsuspected modifications in narrow-window DIA data using the Mascot Error Tolerant Search
Mascot’s spectrum-centric approach doesn’t have the constraints on variable modifications, missed cleavages and protein sequences that are required by peptide-centric DIA tools. In fact, it’s nearly trivial to identify unsuspected variable modifications in narrow-window DIA data using the Mascot Error Tolerant Search. There can be many reasons for failing to get a significant sequence match to an MS/MS spectrum. Three [...]
Spectrum-centric searching of narrow window DIA data with Mascot Server
Data-independent acquisition (DIA) can be broadly separated into narrow window and wide window strategies depending on the size of the isolation window. There are also two data analysis strategies – peptide-centric and spectrum-centric. Wide window DIA typically requires a peptide-centric approach, but narrow window DIA data can be analysed either way. Mascot Server is spectrum-centric, and it’s possible to run [...]
Mascot Distiller 20th anniversary
This year is the 25th anniversary of Matrix Science and 25 years of Mascot Server, but it’s also the 20th birthday of Mascot Distiller! Mascot Distiller 1.0 was released in June 2003 and it’s still under active development today. Distiller started as a GUI application for browsing and peak picking native (raw, binary) mass spectrometry data files. Let’s have a [...]
Identifying peptides from chimeric spectra (DDA, DIA)
Many traditional search engines assume the MS/MS spectrum of a peptide is produced by a single precursor. This is often true when you run a single-species tryptic digest in data dependent acquisition (DDA) mode with a narrow isolation window. Once you change the acquisition strategy or analyse a complex mixture, like an environmental sample, it’s possible for two or more [...]
Get better HCD results by matching internal fragments
Mascot ships with several instrument definitions, which define the fragment ion series used for matching and scoring. All of them enable b ions and most enable y ions, and a few like ETD-TRAP also enable c and z+1. Mascot can also match internal fragments, which are formed by double backbone cleavage, a combination of a/b type and y type. Of [...]
Mascot Daemon Export Extender
Mascot Daemon has two features to help with automation and creating pipelines. The first is the AutoExport feature that allows you to configure and export a report into a CSV file, mzIdentML file or other format that Mascot Server supports with the options you choose. This happens once the search is complete. The lesser known but more powerful feature is [...]
How old is the software in that publication?
Most proteomics data analysis requires complex and sophisticated software. When you read the methods section of a journal article, it should state the software name and version number, as this is the minimum required for reproducibility of the data analysis. Often it is useful to also know how old the software package is. If it’s Mascot Server, there is now [...]
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