DISENTANGLING ELECTROSPRAY SPECTRA WITH MAXIMUM-ENTROPY

Software using maximum entropy (MaxEnt) analysis has been developed, and used to deconvolute complete electrospray spectra of protein mixtures. It automatically produces zero-charge mass spectra on a molecular mass scale, along with probabilistic quantification so that the reliability of features in the spectrum can be ascertained. Because maximum entropy is faithful to the experimental data, the results tend to have improved resolution and signal-to-noise ratio. This improved performance, particularly regarding resolution, is demonstrated on a haemoglobin containing two beta-globins separated by 12 Da at m/z 15 867 (0.08%). A separation of 12 Da was previously the closest at which mass measurement of two globins was practicable. Also, two hitherto unresolved beta-globins from a second haemoglobin, separated by 9 Da (0.06%) were resolved by MaxEnt and their masses accurately measured. These are the first results using rigorous MaxEnt analysis in electrospray mass spectrometry.