METHOD AND APPARATUS FOR DETERMINING MOLECULAR WEIGHT OF LABILE MOLECULES

摘要

A mass spectrometer instrument for determining the molecular weight of labile molecules of biological importance, in particular heavy molecules, such as proteins, peptides or DNA oligomers, is disclosed. The instrument includes a MALDI ion source that is enclosed in a chamber with an inlet for admitting a gas and an ion sampling aperture for limiting gas flow from the chamber. The elevated pressure of the source in the range from 0.1 to 10 torr causes low energy collisions between the gas and the ions that can cause rapid collisional cooling of the excited ions, thereby improving the stability of the produced ions. The formation of clusters of ions (e.g., protein ions) with matrix material is broken without fragmenting the ions by increasing the downstream gas temperature to between 150 and 250 DEG C. Operating the source at laser energy at least two times higher than the threshold value of ion formation and using a high repetition rate laser significantly improve sensitivity of analysis and speed of data acquisition.