isotopic_information: Get useful isotopic information

In RuggeroFerrazza/IsotopicLabelling: A package for the analysis of MS isotopic patterns in labelling experiments

Description

This function gathers essential isotopic information required by the other functions of the IsotopicLabelling package.

Usage

isotopic_information(compound, charge = 1, labelling)

Arguments

compound	Character vector specifying the chemical formula of the compound of interest, with X being the element with unknown isotopic distribution (to be fitted)
charge	Natural number, denoting the charge state of the target adduct (1,2,3,...). If not provided, it is 1 by default
labelling	Character, either "H" or "C", specifying the labelling element

Details

The specified compound is not the neutral molecular species of interest, but the adduct observed by ESI-MS (such as protonated or sodiated species). In the chemical formula, the element with unknown abundance should be denoted by X. For example, the proton adduct of TAG 52:2, C55H103O6, should be written X55H103O6 for ^13C labelling experiments, and C55X102HO6 for ^2H labelling experiments. Note that in this last case only 102 hydrogen atoms have unknown isotopic distribution, since the one giving rise to the adduct comes from the solvent, and is considered to have fixed natural abundance.

Value

A list with the following elements:

compound	The same as input
target	Named vector with the exact masses of all the possible isotopologues arising from the labelling isotope. M+0 is the monoisotopic mass (sum of the masses of the atoms using the lightest isotope for each element, X included); in M+1 one light isotope is replaced by its heaviest counterpart, and so forth
isotopes	Table containing the natural isotopic abundances of the elements present in compound (numbers between 0 and 1). The two isotopes of element X are given NA value
nX	The number of X atoms. In other words, the number of atoms with unknown isotopic distribution
nTOT	The total number of atoms of the labelling element (either H+X or C+X)

Author(s)

Ruggero Ferrazza

Examples

info <- isotopic_information(compound="X40H77NO8P", charge=1, labelling="C") 
# This is the case for [PC 32:2+H]+ in a ^13C-labelling experiment 

RuggeroFerrazza/IsotopicLabelling documentation built on May 9, 2019, 10:36 a.m.