Ronald C. Beavis1, Brian T. Chait1, Kenneth G. Standing2
1Rockefeller University, New York, NY 10021 USA
2University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
Tóm tắt
AbstractThe production of high‐mass quasimolecular ions from proteins by matrix‐assisted ultraviolet laser desorption is described. A simple time‐of‐fight system using a Q‐switched frequency‐quadrupled Nd‐YAG laser to desorb protein molecules is shown to have a mass range of up to 116 000 u by the observation of intact, singly charged quasimolecular ions from 700 fmol of β‐galactosidase subunit (mol.wt = 116 336 Da). Both positive‐ and negative‐ion spectra of proteins are shown. Four new matrix materials, with properties as good as or better than nicotinic acid, are described. A mass resolution of approximately 500 (full width at half maximum definition) is demonstrated for proteins with mol.wt < 20 000 Da. Product species, formed by fast photochemical reactions in the matrix, are observed to form adduct ions with protein molecules. These adduct ions are a significant cause of the observed broadness of protein quasimolecular ion peaks. The practical physical considerations in detection of large‐mass quasimolecular ions from laser desorption, such as detector overloading, are discussed.
