Isotope pattern finder¶
Description¶
Feature list methods → Isotopes → Isotope pattern finder.
The module searches isotope patterns for each feature in selected feature lists by going back to the mass spectra. Starting from the feature m/z the algorithm will first backtrack any possible preceding isotope signals using a list of delta masses created from elements, their stable isotopes, and an m/z tolerance. For example, a -2 signal might be detected when searching for Br isotopes. In a second step, all picked potential isotope m/z values are used to search next isotope (with higher m/z). This is done for each charge state.
Parameters¶
Chemical elements¶
All stable isotopes of the chosen elements are used to create a list of mass differences to search. Signals with this mass difference (m/z difference with different charge states) are then considered as potential isotope signals.
m/z tolerance¶
Maximum allowed difference between two features' m/z values in order for them to be considered the same. The value is specified both as absolute tolerance (in m/z) and relative tolerance (in ppm). The tolerance range is calculated using maximum of the absolute and relative tolerances.
Maximum charge of isotope m/z¶
Maximum possible charge of isotope m/z distributions. All present m/z values obtained by dividing isotope masses with 1,2 ...,maxCharge values will be considered. The default value is 1, but insert an integer greater than 1 if you want to consider ions of higher charge states.
Search in scans¶
Currently, the supported option is "Single most intense", which means the search for isotopes will happen in the single most intense MS scan of each feature.