Formula prediction

Description

This module attempts to calculate all possible molecular formulas for a peak, using given elemental and heuristic constraints. For a detailed description of the functionality and the embedded algorithms, please see the following publication:
Pluskal T. et al, Highly Accurate Chemical Formula Prediction Tool Utilizing High-Resolution Mass Spectra, MS/MS Fragmentation, Heuristic Rules, and Isotope Pattern Matching. Anal Chem (2012), 84(10):4396-403.

The module is invoked by selecting a single peak within a peak list:

List of formula candidates:

Method parameters

Neutral mass
The neutral mass is calculated from the peak m/z value, its charge and type of ionization adduct.
m/z tolerance
Tolerance of the neutral mass for searching the formula.
Elements
Elements allowed in the formula and their minimum and maximum counts.
Element count heuristics
Selection of heuristic restrictions on element counts.
RDBE restrictions
Selection of restrictions on RDBE (rings double bonds) values. .
Isotope pattern filter
If selected, only results which fit the required isotope pattern similarity score will be returned.
MS/MS filter
Restrict the formulas to those that can be interpreted in the peak's MS/MS pattern.