THE ASSIGNMENT OF CHARGE STATES IN COMPLEX ELECTROSPRAY MASS-SPECTRA

In the present paper a new approach to the assignment of charge states in complex electrospray ionisation (ESI) mass spectra, entitled the M assProb procedure, is presented and discussed. This new procedure is a multisolution method in which probabilities for all possible solution s within prespecified ranges of mass and charge are assessed and the m ost probable in the mass range is selected, In each successive step, p robabilities are recalculated and the most probable charge state assig nment is selected, Following the assignment of charge states to the io n peaks, the molecular masses of the components of the mixture are cal culated in the normal manner. The paper compares the results obtained using the MassProb procedure to determine the molecular masses (M(r)s) of the components of three complex mixtures of proteins and glycoprot eins with those found using two commercially available procedures, nam ely MaxEnt and VGtrans, The overall conclusion reached from this compa rative study is that a fully comprehensive solution has yet to be foun d to the problem of disentangling the raw complex ESI mass spectra of differing quality produced by such multicomponent mixtures, The paper is concluded with a brief survey of the approaches to the problem adop ted by others in order to place in context the characteristic features of the MassProb procedure.