Mass-to-charge ratio deserts. Figure 5 illustrates the mass-to-charge ratio deserts. There are subsets of the mass-to-charge ratio dimension not occupied by any peptide features. We term these subsets mass-to-charge ratio “deserts” and utilize them to split the data for parallelization. The deserts are empirically determined using all datasets in the alignment. Shown is a histogram of measured m/z values for E. coli lysate data, the empirical m/z deserts are indicated with vertical red lines.