Ultraviolet Laser Desorption/Ionization Mass Spectrometry of Proteins above 100 000 Daltons by Pulsed Ion Extraction Time-of-Flight Analysis

UV laser desorption mass spectra of large proteins (up to 116 kDa) have been obtained on a Wiley-McLaren type time-offlight Instrument with pulsed ion extraction. Intense ion signals could be observed following delay times of several microseconds prior to ion acceleration and extraction. Initial kinetic energy distributions of ions could be determined from the drift time between the probe tip and the ion optical axis and were found to be about 1 eV, in contrast to measurements by retarding potential techniques at the detector site.