TANDEM MASS-SPECTROMETRY OF PEPTIDES USING A MAGNETIC-SECTOR QUADRUPOLE HYBRID - THE CASE FOR HIGHER COLLISION ENERGY AND HIGHER RADIOFREQUENCY POWER

Using a magnetic sector/quadrupole hybrid tandem mass spectrometer designed for high transmission at high ion energies (400-500 eV), it has been possible to obtain tandem mass spectra results for high-mass ions (m/z 1000-2500) which resemble those achieved with four-sector tandem instruments. With a number of peptide ions, the high laboratory collision energies (at 400-500 eV compared to 30 eV) led to the observation of fragmentations which were not present at lower energies. At constant center-of-mass collision energy, changing the collision gas from Ar to He and at the same time changing laboratory collision energies from 400 to 4000 eV, resulted in more high-energy fragmentation pathways. This implies a greater uptake of internal energy with He collision gas. In the case of dynorphin A fragment 1-g, a tandem mass spectrum was obtained with the hybrid instrument using 500 pmol of sample whereas a previous attempt had failed to obtain useful fragmentation by collisional activation in a hybrid instrument.