FORMATION OF MULTIPLY-CHARGED IONS FROM LARGE MOLECULES USING MASSIVE-CLUSTER IMPACT

Massive-cluster impact is demonstrated to be an effective ionization t echnique for the mass analysis of proteins as large as 17 kDa. The des ign of the cluster source permits coupling to both magnetic-sector and quadrupole mass spectrometers. Mass spectra are characterized by the almost total absence of chemical background and a predominance of mult iply charged ions formed from 100% glycerol matrix. The number of char ge states produced by the technique is observed to range from +3 to +9 for chicken egg lysozyme (14 310 Da). The lower m/z values provided b y higher charge states increase the effective mass range of analyses p erformed with conventional ionization by fast-atom bombardment or liqu id secondary ion mass spectrometry.