A LASER VAPORIZATION, LASER IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETER FOR THE PROBING OF FRAGILE BIOMOLECULES

We report the design and evaluation of a new spectrometer for probing fragile biomolecules in the gas phase. The spectrometer is based on a laser vaporization method to transfer biomolecules up to several hundr ed thousand dalton into the gas phase as intact, neutral species. This method requires the formation of a thin film containing a dye molecul e and the analyte of interest which is molecularly vaporized using a h igh energy, pulsed laser. The gas phase, neutral analyte molecules are laser vaporized directly into a laser ionization region without the n eed of a pulsed nozzle. The molecules are subsequently ionized using m ultiphoton ionization; two-color, two-photon laser ionization is repor ted here. The resulting ions are detected using time-of-flight mass sp ectrometry. The spectrometer employs a four grid extraction system whi ch both filters unwanted ions produced in the initial vaporization ste p and extracts the laser ionized species into the field free drift reg ion. A hybrid copper-beryllium dynode with a dual microchannel plate d etector is employed as the high mass ion detector and amplifier before external amplification. Anthracene-tagged nucleotides and some small test molecules are vaporized and ionized to evaluate the spectrometer.