A laser vaporization, laser ionization time-of-flight mass spectrometer for the probing of fragile biomolecules

Abstract

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 hundred thousand dalton into the gas phase as intact, neutral species. This method requires the formation of a thin film containing a dye molecule and the analyte of interest which is molecularly vaporized using a high energy, pulsed laser. The gas phase, neutral analyte molecules are laser vaporized directly into a laser ionization region without the need of a pulsed nozzle. The molecules are subsequently ionized using multiphoton ionization; two-color, two-photon laser ionization is reported here. The resulting ions are detected using time-of-flight mass spectrometry. The spectrometer employs a four grid extraction system which both filters unwanted ions produced in the initial vaporization step and extracts the laser ionized species into the field free drift region. A hybrid copper-beryllium dynode with a dual microchannel plate detector 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.