In silico fragmentation for computer assisted identification of metabolite mass spectra

BMC Bioinformatics

Table 1 Neutral loss rules

Ion Mode^a	Exact Mass^b	Topological Fragment^c	Neutral Loss^d	Maximum Distance^e
+ -	18.0106	OH	H2O	3
+ -	27.0109	CN	HCN	3
+ -	17.0266	NH2	NH3	3
+ -	30.0106	COH	CH2O	3
+	46.0055	COOH	HCOOH	3

These rules are applied to the initial candidate structures to account for rearrangements during the tandem MS fragmentation, i.e. neutral losses of unconnected fragments: ^aionisation mode where this rule can be applied, ^bexact mass in Da of the neutral loss, ^cmolecular formula of the characteristic fragment, ^dall atoms that are removed, e maximum number of bonds traversed to match neutral loss.