Heuristic charge assignment for deconvolution of electrospray ionization mass spectra

We propose a new algorithm for deconvolution of electrospray ionization mass spectra based on direct assignment of charge to the measured signal at each mass‐to‐charge ratio (m/z). We investigate two heuristics for charge assignment: the entropy‐based heuristic is adapted from a deconvolution algorithm by Reinhold and Reinhold;10 the multiplicative‐correlation heuristic is adapted from the multiplicative‐correlation deconvolution algorithm of Hagen and Monnig.6 The entropy‐based heuristic is insensitive to overestimates of zmax, the maximum ion charge. We test the deconvolution algorithm on two single‐component samples: the measured spectrum of human beta‐endorphin has two prominent and one very weak line whereas myoglobin has a well‐developed quasi‐gaussian envelope of 17 peaks. In both cases, the deconvolution algorithm gives a clean deconvoluted spectrum with one dominant peak and very few artefacts. The relative heights of the peaks due to the parent molecules in the deconvoluted spectrum of a mixture of two peptides, which are expected to ionize with equal efficiency, give an accurate measure of their relative concentration in the sample. Copyright © 2003 John Wiley & Sons, Ltd.