PubChem searches
A search submits a neutral mass to the public PubChem server.
The neutral mass for a search is computed from the entered experimental m/z,
charge carrier and any neutral adducts or losses.
Results from the search are displayed in a table
for review. Either summary of unique formulas within the allowed mass range,
or a longer list of all the compounds is the database are shown.
Each matched formula is scored and color coded by a score based on the mass error and isotopic pattern fit.
Select a compound in the table from the Info button to show more details,
including common names and the structure. Select the PubChem ID link to open a new page
within PubChem for full information on that compound.
If fragment ion details are included in the search, possible formulas are calculated for each
fragment mass, based on the elements in the formula of the parent.
The formulas for each fragment, and for the corresponding neutral losses,
are shown.
Isotopic pattern calculations
MZanswers uses established concepts to calculate isotopic patterns for a given formula.
Reference
Molecular Isotopic Distribution Analysis (MIDAs) with Adjustable Mass Accuracy
Gelio Alves, Aleksy Y. Ogurtsov, and Yi-Kuo Yu
J. Am. Soc. Mass Spectrom. (2014) 25:57-70
DOI: 10.1007/s13361-013-0733-7
Formula calculations
Formula calculations find all possible elemental combinations in a given mass range for the selected elements.
Formulas are then filtered with basic chemistry principles, such as C/H ratios and Nitrogen rule, and allowed formulas displayed.