Mascot: The trusted reference standard for protein identification by mass spectrometry for 25 years

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Posted by Ville Koskinen (February 16, 2024)

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 [...]

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Posted by Richard Jacob (January 15, 2024)

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. [...]

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Posted by Richard Jacob (December 5, 2023)

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 [...]

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Posted by Patrick Emery (November 13, 2023)

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 [...]

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Posted by Patrick Emery (October 13, 2023)

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 [...]

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Posted by Ville Koskinen (September 18, 2023)

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 [...]

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Posted by Ville Koskinen (August 23, 2023)

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 [...]

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Posted by Ville Koskinen (July 13, 2023)

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 [...]

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Posted by Richard Jacob (June 16, 2023)

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 [...]

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Posted by Ville Koskinen (May 15, 2023)

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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Posted by Ville Koskinen (April 25, 2023)

Get more search speed with SplitNumberOfQueries

Mascot Server has several parameters and options that have an effect on database search duration. One of them is SplitNumberOfQueries, which specifies how many queries (MS/MS spectra) are searched at a time. The default is 1000 queries, which is reasonable, but like all defaults, it isn’t optimal. On most hardware, increasing it to 2000 will yield an immediate 10-20% performance [...]

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Posted by Patrick Emery (March 15, 2023)

Generating high quality spectral libraries for DIA-MS

Using Mascot Daemon, Mascot Distiller and Mascot Server A recent paper from Manda et al.[1] describes a pipeline to generate high quality spectral libraries from Data-Dependent Acquisition (DDA) experiments for use in searching Data-Independent Acquisition (DIA) data, starting from the raw data, through to generating the library from the search results. The pipeline uses a collection of different tools in [...]

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