| dual Cs;The reflecting time-of-flight mass spectrometer (Manitoba TOF II) has been modified for matrix-assisted laser desorption (MALD) mass spectrometry. The performance of the MALD TOF mass spectrometer has been examined, including sensitivity, mass range and resolution. The MALD mass spectrometric analysis of IcIR protein, including its molecular weight and the verification of its sequence, is particularly described.;Measurements of kinetic energy distributions of molecular ions ejected into an electric field by matrix-assisted laser desorption were performed in a reflecting time-of-flight mass spectrometer by measuring the reflected molecular ion signal as a function of the difference between the accelerating voltage and mirror voltage. The molecular ions were found to have less kinetic energy than expected from the accelerating potential, i.e., an energy deficit was observed. Under conditions typical for a matrix-assisted laser desorption experiment, the deficit is about 24 eV for positive molecular ions of insulin. The energy deficit increases with the intensity of molecular ion signal, and the molecular weight of the protein; it is also larger for negative molecular ions than for positive molecular ions of insulin. Singly and doubly charged positive molecular ions have similar energy deficits.;The metastable decay of insulin produced by matrix-assisted laser desorption has been examined in a reflecting time-of-flight mass spectrometer. The (M-H)... |
