Correcting mass isotopomer distributions for naturally occurring isotopes

TLDR

Metabolic flux analysis often fits simulated mass spectrometry data to measured mass distributions of metabolites isolated from cultures fed with (13)C‑labeled substrates. The study demonstrates that all isotopes of each element should be corrected in a single step. Existing correction methods apply consecutive steps for each isotope of each element, but the authors propose a single‑step correction approach. The authors find that a single‑step correction is required and that the choice of isotopic composition data must be made carefully.

Abstract

In one method of metabolic flux analysis, simulated mass spectrometry data is fitted to measured mass distributions of metabolites that are isolated from cultures with defined feeding of (13)C-labeled substrates. Doing so, simulated mass distributions must be corrected for the presence of naturally occurring isotopes. A method that was recently introduced for this purpose consists of consecutive correction steps for each isotope of each element in the considered compound. Here we show that all isotopes of each individual element must, however, be corrected in one single step. Furthermore, it is shown that the source of information with respect to isotopic compositions of the elements needs to be chosen with care.