Blog
Single sign-on (SSO) and Mascot
Mascot Server has a role-based security system called Mascot Security. Common use cases are restricting access to configuration files or specific sequence databases, or imposing limits on search size or duration for specific users or groups. These were discussed in earlier blog articles Mascot Security: priority settings and Mascot Security: privacy settings. Mascot Security isn’t designed to have super secure [...]
Solving a puzzle with Mascot Distiller de novo
Have you tried either of the MS/MS interpretation challenges organised by EUPA and LBMSDG? Maybe you are expert enough to read off the peptide sequence, directly. If so, you can stop reading right here! If your interpretation skills and mental arithmetic are a bit rusty, we thought it might be useful to walk through how Mascot Distiller plus a bit [...]
The minutiae of database management
The two major inputs into a database search are sequence databases and mass spectrometry data. Management of the databases in Mascot Server has evolved and improved over the years and newer versions. There are still a few issues that come up regularly and I am going to cover them in this article. Common error messages When you activate a new [...]
Validating intact crosslinked peptide matches
Intact crosslinked search results are more complex than conventional (non-crosslinked) searches, because there are many more degrees of freedom. The precursor mass could be within tolerance of a looplinked sequence, a linear sequence with monolink and several different alpha-beta candidates. Each possibility is multiplied if you also consider variable modifications like oxidation of methionine. Mascot 2.7 uses the same scoring [...]
Variable Modifications in Mascot 2.7
Most protein samples will exhibit some degree of modification which needs to be considered when carrying out a database search In this article we’ll take a look at some important changes we introduced in Mascot 2.7 in how Mascot handles variable modifications. Variable modification permutation in Mascot 2.6 and earlier In Mascot 2.6 or earlier, variable modification permutation is handled [...]
Using the Quantitation Summary to create reports and charts
An earlier article described how to create a Quantitation Summary in Mascot Daemon. This is a spreadsheet-like text file, where the rows correspond to proteins and the columns contain expression data for various samples in the form of abundances or ratios of abundances. A Quantitation Summary can be opened and manipulated in a spreadsheet program such as Excel, and it [...]
Tabulate expression data from multiple analyses with Mascot Daemon
Studies that use mass spectrometry-based quantitation often contain large numbers of individual analyses: samples from different sources or treatments or time points, possibly fractionated, with replicates and so forth. Using statistical methods to combine the analyses, extract meaningful information, and report it as charts and tables is a complex task that usually requires custom scripting in a language such as [...]
Human Proteome Project data interpretation guidelines
The Human Proteome Project (HPP) data interpretation guidelines were recently updated. Many of the guidelines are good practice and common sense in any proteomics study where reliable protein identification is critical, not just when studying the human proteome. The guidelines are easy to meet using Mascot Server 2.7. Core guidelines The full list consists of 9 guidelines. The first one [...]
How to set up remote working
There are times when you unexpectedly find yourself having to work from home. Fear not: data analysis doesn’t need to stop when you’re away from the lab. Mascot Server has a client-server architecture, and the client PC can be located anywhere. Distiller and Daemon can also be used remotely, or they can be run on a remote client PC and [...]
Disulfide bond characterisation
Support for matching crosslinked peptides is a new feature in Mascot Server 2.7. The following linkage types can be detected: intralinks – the linked peptides are from the same protein interlinks – the linked peptides are from two different proteins looplinks – connecting two amino acids within a single peptide monolinks – a linker with one end attached and the [...]
The Third Column: MS/MS fragment ion decharging in Mascot Server 2.7
In the Mascot Generic (mgf) peak list format, MS/MS fragment ions are typically defined as pairs of values. The first value is the m/z of the fragment ion peak and the second the intensity of the peak. However, a third value can also be supplied – the charge state of the fragment ion. In Mascot 2.6 or earlier, the fragment [...]
Protein FDR in Mascot Server 2.7
One of the new features in Mascot Server 2.7, now running on this web site, is an estimate of protein FDR. This is displayed in the Protein Family Summary for Fasta searches whenever automatic decoy is selected. The basis is the number of proteins inferred in the target database compared with the number in the decoy database. Conceptually, this is [...]
RSS feed