Patent ID: 7396686

Claim:
Method for the acquisition of a mass spectrum containing information about sequences of a biopolymer, in a tandem mass spectrometer with an ion source for the ionization of the biopolymer by means of matrix-assisted laser desorption, the method comprising: (a) preparing the biopolymer together with a matrix substance as a sample on a sample support; (b) placing the sample support in the ion source; (c) bombarding the sample on the sample support with light pulses from a pulsed laser with such a high energy density that it causes spontaneous fragmentations of a part of the biopolymer molecules whereby different species of in-source decay ISD fragment ions are formed; (d) accelerating the ions and injecting them into a first mass spectrometer of the tandem mass spectrometer; (e) selecting one species of the ISD fragment ions in the first mass spectrometer of the tandem mass spectrometer; (f) fragmenting the selected ISD fragment ions at least partially to granddaughter ions by means of gas collisions (CID), surface collisions (SID) photon collisions (PID) or metastable decay (LID); and (g) measuring the granddaughter ions in a second mass spectrometer of the tandem mass spectrometer to form a granddaughter mass spectrum.