Detection of single macromolecules using a cryogenic particle detector coupled to a biopolymer mass spectrometer

Macromolecules with masses up to 50 kDa have been detected with a cryogenic particle detector in a MALDI time-of-flight biopolymer mass spectrometer. The cryogenic particle detector was a Sn/Sn-ox/Sn tunnel junction operated at a temperature of 0.4 K. A calibration with 6 keV single photons inferred that the delayed detector pulses corresponded to the absorption of the kinetic energy of a single macromolecule. Time-of-flight spectra of lysozyme proteins are presented. The mass resolution is 100 Da at 14 300 Da. The energy sensitive detection mechanism suggests that cryogenic particle detectors have a high and mass independent detection efficiency for macromolecules. (C) 1996 American Institute of Physics.